Prepared for
Chula Vista Energy Center 2, LLC
Chula Vista, California
Prepared by
Ramboll Americas Engineering Solutions, Inc.
Los Angeles, California
Project Number
1690003784
Date
June 2025
HAZARDS ANALYSIS
CHULA VISTA ENERGY CENTER 2
CHULA VISTA, CALIFORNIA
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Prepared By Ramboll
PREPARED BY ___________________________________ Yasmine Stutz Senior Managing Consultant ___________________________________ M. Scott Weaver Principal & Practice Leader, Air & Climate
Ramboll Americas Engineering Solutions, Inc.
350 South Grand Avenue
Suite 2800
Los Angeles, California 90071
(213) 943-6300
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
i
Contents Ramboll
CONTENTS
Page
1. EXECUTIVE SUMMARY 1
2. INTRODUCTION 2
3. PROJECT DESCRIPTION 3
3.1 Project Background 3
3.2 Project Location 3
3.3 Existing Environment 4
3.4 Project Purpose 6
4. LITHIUM-ION BATTERIES AND PROPOSED TECHNOLOGY 7
4.1 Lithium-ion Batteries 7
4.2 Proposed Battery Technology 8
5. POTENTIAL RISKS 11
6. REGULATORY AND HEALTH PROTECTION REQUIREMENTS 14
6.1 Battery Testing Requirements and Regulations 14
6.2 Health Protective Regulations 17
6.3 Emergency Response and Emergency Action Plan 18
7. DESIGN MEASURES 19
7.1 Passive Design Measures 19
7.2 Active Design Measures 20
8. OFF-SITE CONSEQUENCE ANALYSIS 22
8.1 Thermal Runaway Scenarios Based on UL 9540A Testing 23
8.2 Particulates and Metals 25
8.3 Toxic Pollutants 26
8.4 Flammable Components 31
8.5 Health Risk Screening 32
8.6 Off-Site Consequence Analysis Modeling 32
8.6.1 Local Surroundings 33
8.6.2 Meteorological Conditions 33
8.6.3 Selection of Dispersion Models Used for Off-Site Consequence Analysis 35
8.6.4 Assessment Model 36
9. OFF-SITE CONSEQUENCE ANALYSIS RESULTS 39
9.1 Screening of Toxic Impacts 39
9.2 Modeling Results 39
10. SUMMARY OF IMPACTS AND CONCLUSIONS 41
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
ii
Contents Ramboll
CONTENTS (Continued)
TABLES
Table 1: Chemical Compounds Identified During UL9540A Cell Level Testing 23 Table 2: Potential Toxic Pollutants Released from Battery Malfunction 26 Table 3: Definitions of Acute Exposure Guideline Levels 27 Table 4: AEGL Values for Potential Pollutants which could be released from Battery Manufacturing and/or Malfunction (60-minute exposure) 27 Table 5: Definitions of Emergency Response Planning Guidelines 29 Table 6: Definitions of Temporary Emergency Exposure Limits 29 Table 7: Definitions of Protective Action Criteria 30
Table 8: Potential Flammable Components from Battery Malfunction 31 Table 9: Facility Designation Based on Total Score 32
Table 10: Dispersion Models 35
Table 11: CAPCOA Risk Prioritization Results 39
FIGURES
Figure 1: Project Location 4
Figure 2: Local Surrounding Area of BESS and Distances to Sensitive Receptors 5 Figure 3: Zoning Map 6
Figure 4: Scheme of Li+ Ion Transport in LiB 8
Figure 5: Tesla MegaPack 2 XL Components 10
Figure 6: Global Grid-Scale BESS Deployment and Failure Statistics 13 Figure 7: Wind Rose for Meteorological Data at the Imperial Beach Airport (2021-2023) 34
APPENDICES
Appendix A: Emission Calculations
Appendix B: Battery Emergency Response Guide
Appendix C: Prioritization Score Calculations
Appendix D: Modeling Results
Appendix E: Toxic and Flammable Vapor Extents
Appendix F: Model Output Files
\\wclaofps1\projects\W\Wellhead Electric\Chula Vista BES\Public Health Risk Assessment\CVEC2 Hazards Analysis_LIVE.docx Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
iii
Acronyms and Abbreviations Ramboll
ACRONYMS AND ABBREVIATIONS
AEGL Acute Exposure Guideline Level
ALOHA Area Locations of Hazardous Atmospheres
BESS Battery energy storage system
CAISO California Independent System Operator
CAPCOA California Air Pollution Control Officers Association CVEC2 Chula Vista Energy Center 2
EES Electrical energy storage
EPA Environmental Protection Agency
EPRI Electric Power Research Institute
ERPG Emergency Response Planning Guidelines
GW Gigawatts
ICC International Code Council
IDLH Immediately dangerous to life or health
IEEE Institute of Electrical and Electronics Engineers
IFC International Fire Code
KNRS Imperial Beach Airport
KSDM Brown Field Municipal Airport
kV Kilovolt
LEL Lower Explosive Limit
LFP Lithium Iron Phosphate
Li+ Lithium ions
LiB Lithium-ion battery
LMO Lithium Manganese Oxide
LOC Level of Concern
µg/m3 Microgram per cubic meter
mg/m3 Milligram per cubic meter
mi Miles
NCA Lithium Nickel Cobalt Aluminum Oxide
NCM Nickel Cobalt Manganese
NESC National Electric Safety Code
NFPA National Fire Protection Association
NIOSH National Institute for Occupational Safety and Health Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
iv
Acronyms and Abbreviations Ramboll
ACRONYMS AND ABBREVIATIONS (Continued)
NMC Lithium Nickel Manganese Cobalt Oxide
NWS National Weather Service
OCA Off-Site Consequence Analysis
OEHHA Office of Environmental Health Hazard Assessment
PAC Protective Action Criteria
PG Pasquill-Gifford
ppm Parts per million
REL Reference exposure levels
RMP Risk Management Program
SCICHEM Second Order Closure Integrated Puff Model with Chemistry SDG&E San Diego Gas & Electric
TEEL Temporary Emergency Exposure Limits
TS Total Score
USEPA United States Environmental Protection Agency
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
1 Executive Summary Ramboll
1. EXECUTIVE SUMMARY
This technical report evaluates the potential off-site consequences and localized health risk impacts of an unlikely thermal runaway event at the Chula Vista Energy Center 2 (CVEC2) Project (Project), a battery energy storage system proposed to be located in Chula Vista, California. This report provides a detailed description of the proposed project, its surroundings, technology, and potential risks such as an exothermic reaction and thermal runaway of the batteries that could result in a battery fire. This report lists regulatory and health protection requirements applicable to the Project, and how the Project meets these requirements. The Project’s robust design measures are intended to ensure effective mitigation against rare hazards such as thermal runaway.
This report includes an off-site consequence analysis in which the dispersion of pollutants from various worst-case scenarios of a thermal runaway event at the CVEC2 were modeled.
The projected distances for the reasonable worst-case scenarios and the alternative case scenario were found to be limited to areas immediately adjacent to the Project fence line and the predicted threat zones are <10 m from the perimeter of the land on which the Tesla MP2XL units would be located. Additionally, the facility’s emergency response plan will include signage and alarm systems to ensure immediate evacuation of bystander areas in the case of a thermal runaway event. Therefore, the potential impacts for the Project would not pose a public health threat.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
2 Introduction Ramboll
2. INTRODUCTION
Wellhead Power Solutions, LLC is proposing a new battery energy storage system (BESS), the CVEC2 Project (Project) to be located in the City of Chula Vista. The Project is proposed to be a 72 MW BESS facility with service into a nearby San Diego Gas & Electric (SDG&E) substation. The CVEC2 Project would consist of arrays of interconnected lithium-ion batteries within fully-enclosed, purpose-built containers that are temperature controlled and constructed in compliance with California Fire Code requirements. The batteries will be charged from the SDG&E regional grid, primarily during high-renewables-supply/low-demand hours (i.e., daytime) and will discharge back to the grid during low-renewables-supply/ high-demand hours (i.e., evening and overnight). CVEC2 will also discharge as-needed to stabilize renewables-based grid voltage.
This technical report evaluates the potential off-site consequences and localized health risk impacts which might result from an unlikely event in which an exothermic reaction and thermal runaway of the batteries occurs (i.e., “battery fire”). This report is intended to provide focused technical information related only to an exothermic reaction and thermal runaway event and is not an evaluation of the Project for California Environmental Quality Act impact significance. Potential off-site receptors considered by this analysis would include employees of nearby businesses, including agricultural workforces, residences, commercial businesses, or schools. Any consequences to emergency response units and on-site employees are not included in this report as they are outside the scope of this analysis.
The CVEC2 Project intends to utilize the Tesla MegaPack 2 XL (MP2XL) BESS product. The MP2XL product uses Lithium Iron Phosphate (LFP) cells (157.2 amp hour with a nominal voltage of 3.22 volts) which are individually hermetically sealed. Given this product design, this Hazards Analysis is specific to the MP2XL product.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
3 Project Description Ramboll
3. PROJECT DESCRIPTION
3.1 Project Background
The Project, along with other utility-scale battery storage facilities throughout California, is a critical public utility facility necessary to store excess renewable energy generated by wind and solar generators, especially during peak solar generation periods in California, for use during evening and overnight hours when renewable sources are no longer sufficient to meet demand, and to generally aide in reliability of the electric grid. The Project is intended to be responsive to State goals to integrate more renewable energy into the state power supply.
On February 10, 2022, the California Public Utilities Commission approved procurement of 15,000 MW of new energy storage and demand response resources by 2032.
The CVEC2 Project is proposed to be a 72 MW BESS that will discharge as-needed to stabilize renewables-based grid voltage and will be available to SDG&E and the California Independent System Operator (CAISO) to energize local distribution and transmission circuits for improved local reliability or system emergencies that might otherwise result in de-energized SDG&E transmission lines supplying energy to the City of Chula Vista and adjacent cities. The Project will be operated as a stand-alone resource, with dispatch instructions provided by the CAISO.
3.2 Project Location
The Project site is a 1.9-acre portion of an approximately 3.82-acre parcel located at 3497 Main Street, Chula Vista, California, 91911, over 800 feet south of Main Street (Figure 1). The southern portion of the parcel is developed with the Chula Vista Energy Center, LLC (CVEC), an electricity generating power plant. CVEC2 LLC seeks to develop CVEC2 on the northern, undeveloped portion of the parcel, and CVEC2 will be operated independently from the existing CVEC. The site is located in an area zoned as Limited Industrial (I-L) under the City General Plan and is surrounded by limited industrial land uses on the west, north, and east sides, and by the Otay Valley Regional Park on the south side.1 The Project will be connected to the SDG&E transmission system by an existing 69 kilovolt (kV) transmission line connected to the SDG&E Otay 69 kV substation, located within 1,300 feet north of the Project site.
1 City of Chula Vista General Plan Diagram. Available at:
https://www.chulavistaca.gov/home/showpublisheddocument/9345/637866426996330000.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
4 Project Description Ramboll
Figure 1: Project Location
3.3 Existing Environment
The site is adjacent to a meat processing facility on the west side; a printing business and metalworking business on the east side; and an auto dealership, towing business, and recycling center on the north side; which are all limited industrial uses. The SDG&E Otay 69 kV substation is located 0.25 miles (mi) north of the site. The Otay Valley Regional Park immediately south of the parcel is a major urban park and open space area. Otay Elementary School is located approximately 0.25 miles to the north. The closest residential neighborhood is 0.07 miles west of the site.
The nearest wetland is a freshwater pond 0.22 miles southeast of the Project site.2 Immediately south of the site is the floodplain of the Otay River Preserve. The Project site is located approximately 3.36 miles northeast of the Naval Outlying Landing Field Imperial Beach and 4 miles northwest of Brown Field Municipal Airport, and no impacts on flight paths or noise conflicts are expected. The nearest hospital is Oasis of Hope Hospital, located approximately 2.20 miles east of the Project site. The nearest daycare is Elgrillitonet Daycare, located approximately 0.45 mi northwest of the Project site. The nearest adult care facility is Glenner Alzheimer’s Family Centers, located approximately 0.83 mi west of the Project site. See Figure 2 for an overview of nearby sensitive receptors (i.e., residences or schools) and Figure 3 for a map of the zoning in the area surrounding the Project site. 2 National Wetlands Inventory Wetlands Mapper. Available at:
https://fwsprimary.wim.usgs.gov/wetlands/apps/wetlands-mapper/.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
5 Project Description Ramboll
Figure 2: Local Surrounding Area of BESS and Distances to Sensitive Receptors Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
6 Project Description Ramboll
Figure 3: Zoning Map3
3.4 Project Purpose
The Project is designed to receive energy from an interconnection point with SDG&E during high-renewables-supply/low-demand hours (typically between 9 a.m. and 3 p.m.), store this energy in batteries, and later discharge the energy back to the grid during periods of low-renewables-supply/high-demand, typically between 6 and 10 PM. The Project, along with other utility-scale battery energy facilities throughout California, is a critical public utility facility necessary to store solar-generated daytime power for overnight use, stabilize voltage from fluctuating renewable power generation sources, and provide local generation capacity in the event regional SDG&E transmission lines are inoperative or de-energized during a Public Safety Power Shutdown high-wind period.
3 City of Chula Vista General Plan Diagram. Available at:
https://www.chulavistaca.gov/home/showpublisheddocument/9345/637866426996330000.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
7 Lithium-ion Batteries and Proposed Technology Ramboll
4. LITHIUM-ION BATTERIES AND PROPOSED
TECHNOLOGY
4.1 Lithium-ion Batteries
A lithium-ion battery (LiB) is a rechargeable battery which uses the reversible reduction of lithium ions to store energy. A LiB consists of an anode, cathode, separator, electrolyte, and two (positive and negative) current collectors. The anode and cathode materials store and release lithium ions. The separator is permeable to positively charged lithium ions (Li+) which are transported between the anode and cathode through the electrolyte. The separator blocks the transport of electrons inside the battery, thereby preventing short-circuiting.4The anode of a conventional LiB cell is typically graphite made from carbon. The cathode is typically a metal oxide such as Lithium Nickel Manganese Cobalt Oxide (NMC) or Lithium Iron Phosphate (LFP).5
The electrolyte is typically a lithium salt dissolved in an organic solvent.6 Figure 4 provides a schematic of lithium-ion transport within the battery. Li+ ions initially stored at the cathode dissolve when a LiB is discharged. The ions are released into the electrolyte and flow to the anode. This process creates a potential difference between the two electrodes which is maintained by the separator, which blocks the flow of ions and associated electrons inside the battery. When a load is connected to the battery, it draws the electric current, resulting in a battery discharge as the electrons to which the Li+ ions were tied at the anode are released. The anode simultaneously releases Li+ ions through the electrolyte and separator to the cathode.7
4 Li-ion batteries: basics, progress, and challenges. Energy Science and Engineering, 2015, 3, 5, 385-418.
Available at: https://doi.org/10.1002/ese3.95. 5 A Review of Cathode and Anode Materials for Lithium-Ion Batteries. SoutheastCon 2016, 2016, 1-6. Available at: https://doi.org/10.1109/SECON.2016.7506639v. 6 Progress in electrolytes for rechargeable Li-based batteries and beyond. Green Energy & Environment, 2016, 1, 1, 18-42. Available at: http://dx.doi.org/10.1016/j.gee.2016.04.006.. 7 A review of recent developments in membrane separators for rechargeable lithium-ion batteries. Energy & Environmental Science, 2014, 7, 12, 3857-3886. Available at: https://doi.org/10.1039/C4EE01432D.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
8 Lithium-ion Batteries and Proposed Technology Ramboll Figure 4: Scheme of Li+ Ion Transport in LiB8
LiBs are the preferred battery technology for many commercial and industrial uses because they store more energy in a smaller unit due to high energy density. This high energy density is a function of lithium’s small atomic weight and radius, which allows for more ions, and ultimately more electricity, to be generated per unit of mass. LiBs also have lower self-discharge rates and typically do not contain toxic materials commonly found in other batteries, such as lead or cadmium.9In general, LiBs are stable under normal operations and conditions.
4.2 Proposed Battery Technology
Numerous LiB cell types have been under evaluation for the Project, which include but are not limited to the following:
• LFP (Lithium Iron Phosphate);
• NCA (Lithium Nickel Cobalt Aluminum Oxide);
• NMC (Lithium Nickel Manganese Cobalt Oxide); and
• Prismatic, NCA (Lithium Nickel Cobalt Aluminum Oxide) + NCM Oxide) + LMO (Lithium Manganese Oxide). 8
Ibid. 9
Lithium-Ion Battery, University of Washington Clean Energy Institute. Available at:
https://www.cei.washington.edu/research/energy-storage/lithium-ion-battery/.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
9 Lithium-ion Batteries and Proposed Technology Ramboll The CVEC2 Project is now intending to utilize the Tesla MegaPack 2 XL (MP2XL) BESS product, which uses LFP cells.
NMC and LFP battery technologies are used widely and well understood. The LFP battery cathode material has higher thermal and chemical stability than other LiBs. The crystalline structure of the cathode is made stable due to the high covalent feature of the P–O bonds in the tetrahedral (PO3-4) units which in turn slows the oxygen release from the cathode during the charge cycle or malfunction.10 This minimizes the risk of thermal runaways (detailed in Section 5 of this report) and self-propagation, reducing the risks of battery fire and explosion. Thermal runaway of an LFP battery releases a very low level of energy and intrinsically impossible to trigger under normal operations.11 LFP has a relatively high thermal runaway temperature of 518°F (270°C).12 For batteries, the higher the thermal runaway temperature, the less likely thermal runaway is to occur.
NMC batteries have high energy density and a lower thermal runaway temperature of 410°F (210°C).13 Scientific experiments have demonstrated that the maximum total internal heat generated by fully charged LFP batteries is a third of that generated by NMC batteries, which is attributable to their lower energy density.14 LFP batteries also exhibit low flammability due to their stable chemistry. In addition to being considered one of the safest battery types, LFPs have a long cycle and calendar life and they can operate over a wider temperature range than other LiBs without damage to the battery or power degradation.15 The Tesla manufactured MegaPack 2 XL (MP2XL), an LFP cell product, was selected for the Project. As such, this analysis is based on the MP2XL.
Figure 5 depicts the components of the Tesla MegaPack 2 XL. Each enclosure cabinet is comprised of a customer interface bay in the center, and four bays on either side of the center. Each of the eight bays can be populated with up to three battery modules. Each battery module contains three battery trays, which are arrays of prismatic LFP cells.
Prismatic LFP cells are batteries that encapsulate Lithium Iron Phosphate in a rigid, prismatic shell. Each battery tray contains 112 cells. 10 Typical cathode materials for lithium-ion and sodium-ion batteries: From structural design to performance optimization, Carbon Neutralization, 2023, 2, 3, 339-377. Available at: https://doi.org/10.1002/cnl2.62. 11 Safety of Lithium-Ion batteries, PowerTech. Available at: https://www.powertechsystems.eu/home/techcorner/safety-of-lithium-ion-batteries/. 12 New Tests Prove: LFP Lithium Batteries Live Longer than NMC. Available at:
https://www.onecharge.biz/blog/lfp-lithium-batteries-live-longer-than-nmc/. Accessed: September 2024. 13 Cell-to-pack LFP Lithium Batteries Outperform NMC. Available at: https://www.onecharge.biz/blog/cell-to-packlfp-lithium-batteries-outperform-nmc/. Accessed: September 2024. 14 Heat release during thermally-induced failure of a lithium ion battery: Impact of cathode composition, Fire Safety Journal, 2016, 85, 10-22. Available at: https://doi.org/10.1016/j.firesaf.2016.08.001. 15 New Tests Prove: LFP Lithium Batteries Live Longer than NMC. Available at:
https://www.onecharge.biz/blog/lfp-lithium-batteries-live-longer-than-nmc/.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
10 Lithium-ion Batteries and Proposed Technology Ramboll Figure 5: Tesla MegaPack 2 XL Components
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
11 Potential Risks Ramboll
5. POTENTIAL RISKS
Potential hazards from the use of lithium-ion batteries include overheating, smoke, swelling, electrolyte leakage, venting, fires, thermal runaway, and explosions from the release and ignition of flammable gases.16 Thermal runaway is a situation in which the temperature of a material increases uncontrollably and rapidly through a self-reinforcing process due to internal failure such as internal defects, or due to external mechanical, thermal, or electrical stress, and can occur when the heat generated by a system surpasses its ability to remove or dissipate heat.17,18 Examples of unusual conditions leading to thermal runaway include direct exposure to prolonged heat, overcharge, over-discharge, external and internal short circuits, and severe physical impact. Thermal runaway involves conversion of stored chemical energy to thermal energy within the batteries, which can lead to increased temperatures, cell rupture, and release of toxic or flammable gases.19 Gases produced as a result of thermal runaway can accumulate to a combustible level and cause a fire if ignited, or an explosion if ignited and contained within a structure that then undergoes rapid pressure increase.20 Battery failures can be caused by thermal abuse, mechanical abuse, electrical abuse, poor cell electrochemical design, or internal cell faults associated with cell manufacturing defaults.21
Other types of industrial fires, such as Class C fires involving electrical equipment, combustible dust fires, and combustion fires, are also caused by unpredictable internal defects or external stresses or malfunctions, although thermal runaway fires specifically are characterized by a positive feedback loop of heat buildup prior to the fire. Similar to combustion fires, thermal runaway fires are caused by the combustion of flammable gases released by a failing cell, which causes the release of smoke.
Thermal runaway or fire events of a BESS with lithium-ion batteries can, depending on battery cell chemistry, result in chemical release of hydrogen chloride, hydrogen fluoride, hydrogen cyanide, and/or carbon monoxide. Inhalation would be the primary pathway by which such air pollutants could potentially cause public health impacts. Such releases at certain levels and exposure periods could cause health effects such as damage to the heart, 16 Battery Hazards for Large Energy Storage Systems, ACS Energy Lett, 2022, 7, 8, 2725-2733. Available at:
https://pubs.acs.org/doi/10.1021/acsenergylett.2c01400. 17 Large-Scale Energy Storage System: Safety and Risk Assessment. Springer, Sustainability Energy Research 10, Article number 13 (2023). Available at: https://sustainenergyres.springeropen.com/articles/10.1186/s40807- 023-00082-z. 18 Review—Meta-Review of Fire Safety of Lithium-Ion Batteries: Industry Challenges and Research Contributions.
J. Electrochem. Soc., 2020, 167. Available at: https://doi.org/10.1149/1945-7111/aba8b9. 19 Managing Lithium-Ion Battery Energy Storage System (BESS) Hazards, Jensen Hughes, 2023, Available at:
https://www.jensenhughes.com/insights/mitigating-lithium-ion-battery-energy-storage-systems-bess-hazards. 20 Battery Hazards for Large Energy Storage Systems, ACS Energy Lett, 2022, 7, 8, 2725-2733. Available at:
https://pubs.acs.org/doi/10.1021/acsenergylett.2c01400. 21 Lithium-Ion Batteries Hazard and Use Assessment Final Report, The Fire Protection Research Foundation.
Available at: https://www.nfpa.org/education-and-research/research/fire-protection-researchfoundation/projects-and-reports/lithium-ion-batteries-hazard-and-use-assessment.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
12 Potential Risks Ramboll
lungs, circulatory system, skin, and central nervous system.22,23,24,25 While chemical release of acids from LiB fires is possible, the UL 9540A testing performed on the Tesla MP2XL technology reported that no acids were detected during the thermal runaway test events.26 Therefore acid releases are not expected with this technology. Additional off-site and natural hazards that could impact a BESS might include wind, seismic activity, flooding, and extreme temperatures.
Despite the potential risks of battery fires, incidents are rare when proper measures are taken to assure the quality of BESS engineering, construction, maintenance, and the design and manufacture of the battery modules themselves. In recent years, government regulation and increased industry knowledge of best practices has greatly reduced the occurrence of hazardous incidents from these types of systems. To monitor these events, the Electric Power Research Institute (EPRI) initiated the BESS Failure Incident Database in 2021.27 As shown in Figure 6, between 2018 and 2023, the global installed BESS capacity increased from approximately 2 Gigawatts to at least 52 Gigawatts (GW); an increase of 26 times over the 5-year period. During that same period, the reported failure rate per installed GW decreased by 97% (i.e., from nine incidents/GW down to 0.3 incidents/GW as lessons learned from early failures were progressively incorporated into the latest BESS designs).
While the actual probability of a battery fire event depends on multiple variables and can change over time, these global statistics demonstrate that battery fire rates are rapidly declining as the technology improves and applicable standards are developed. EPRI notes that battery industry R&D activities continue to improve incident prevention and mitigation technology. 22 Carbon Monoxide, National Institute for Occupational Safety and Health (NIOSH), 2018, Available at:
https://www.cdc.gov/niosh/topics/co-comp/default.html. 23 Hydrogen Cyanide (AC), National Institute for Occupational Safety and Health (NIOSH), 2011, Available at:
https://www.cdc.gov/niosh/ershdb/emergencyresponsecard_29750038.html#:~:text=Source%3A%20National %20Institute%20for%20Occupational%20Safety%20and%20Health,oxygen%20by%20nearly%20every%20org an%20of%20the%20body. 24 Hydrogen Fluoride, National Institute for Occupational Safety and Health (NIOSH), 2019, Available at:
https://www.cdc.gov/niosh/npg/npgd0334.html. 25 Hydrogen Chloride, National Institute for Occupational Safety and Health (NIOSH), 2019, Available at:
https://archive.cdc.gov/#/details?url=https://www.cdc.gov/niosh/topics/hydrogen-chloride/default.html. 26 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C). 27 Insights from EPRI’s Battery Energy Storage Systems (BESS) Failure Incident Database: Analysis of Failure Root Cause, Electric Power Research Institute (EPRI), Inc. (2024), Available at:
https://www.epri.com/research/products/000000003002030360.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
13 Potential Risks Ramboll
Figure 6: Global Grid-Scale BESS Deployment and Failure Statistics28 For LFP chemistry batteries specifically, thermal runaway releases a very low level of energy and has been reported as intrinsically impossible to trigger under normal operations.29 As described in Section 4.2, the LFP battery uses a cathode material with higher thermal and chemical stability than other LiBs, and has low energy density and flammability, rendering it one of the safest battery types. Out of the 87 failure incidents from the EPRI BESS Failure Incident Database, only six were specified to be at LFP BESS facilities, from 2020 to 2023. 28 Ibid. 29 Safety of Lithium-Ion batteries, PowerTech. Available at: https://www.powertechsystems.eu/home/techcorner/safety-of-lithium-ion-batteries/.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
14 Regulatory and Health Protection Requirements Ramboll
6. REGULATORY AND HEALTH PROTECTION
REQUIREMENTS
Rigorous requirements exist for energy storage systems and lithium-ion batteries, including codes for the installation, operation, and maintenance of energy storage facilities, fire preparedness, emergency response, product and design safety standards, and corresponding certifications. Health protection requirements also determine the scientific analyses and communications required for a BESS project. The City of Chula Vista also has specific requirements for BESS facilities. These requirements are listed in the following sections.
6.1 Battery Testing Requirements and Regulations
Applicable requirements and regulations on batteries are described below. The CVEC2 Project will comply with these requirements and regulations to minimize the potential for fire-related hazards through both passive and active design measures, as detailed in Section 7.
Institute of Electrical and Electronics Engineers (IEEE) C2-2023, 2023 National Electric Safety Code (NESC): The purpose of the NESC is the practical safeguarding of persons and utility facilities during the installation, operation, and maintenance of electric supply and communication facilities, under specified conditions. This Code covers basic provisions for safeguarding of persons from hazards arising from the installation, operation, or maintenance of (1) conductors and equipment in electric supply stations, and (2) overhead and underground electric supply and communication lines. The Code is applicable to the systems and equipment operated by utilities, or similar systems and equipment, of an industrial establishment or complex under the control of qualified persons.30 International Code Council (ICC) International Fire Code (IFC) 2021: The 2021 IFC contains regulations to safeguard life and property from fires and explosion hazards. Topics include general precautions, emergency planning and preparedness, fire department access and water supplies, fire alarm systems, special hazards, and the storage and use of hazardous materials.31 A Tesla UL9540A large-scale fire protection analysis for the MP2XL product (detailed in Section 8.1) concluded that the MP2XL can meet or exceed the installation codes and standards, such as the IFC and National Fire Protection Association (NFPA 855), required for outdoor, ground mounted BESS installations when installed in accordance with the MP2XL Design and Installation Manual.32
National Fire Protection Association 1, Fire Code: NFPA 1 provides a comprehensive, integrated approach to fire code regulation and hazard management, including fire alarms, building process hazards, and life safety issues.33
30 IEEE C2-2023. Available at: https://ieeexplore.ieee.org/document/9825487. 31 ICC IFC 2021. Available at:
https://webstore.ansi.org/standards/icc/iccifc2021?source=blog&_gl=1*q95kfh*_gcl_au*MTkxNzExODYyNC4xN zA3MzY0MjU5. 32 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C). 33 NFPA 1, Fire Code. Available at: https://www.nfpa.org/codes-and-standards/nfpa-1-standard-development/1.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
15 Regulatory and Health Protection Requirements Ramboll NFPA 68, Standard on Explosion Protection by Deflagration Venting: NFPA 68 applies to the design, location, installation, maintenance and use of systems that vent combustion gases and pressures resulting from a deflagration within an enclosure so that structural and mechanical damage is minimized.34
NFPA 69, Standard on Explosion Prevention Systems: NFPA 69 provides requirements for installing systems for the prevention and control of explosions in enclosures that contain flammable concentrations of flammable gases, vapors, mists, dusts, or hybrid mixtures.35 NFPA 70, National Electrical Code: NFPA 70 is the benchmark for safe electrical design, installation, and inspection to protect from electrical hazards.36 NFPA 550, Guide to Fire Safety Concepts Tree: NFPA 550 describes the structure, application, and limitations of the Fire Safety Concepts Tree, which provides an overall structure with which to analyze the potential impact of fire safety strategies.37 NFPA 855, Standard for the Installation of Stationary Energy Storage Systems: NFPA 855 provides minimum requirements for mitigating the hazards associated with Energy Storage Systems.38
International Electrotechnical Commission (IEC) 62619, Secondary cells and batteries containing alkaline or other non-acid electrolytes – Safety requirements for secondary lithium cells and batteries, for use in industrial applications: This safety standard specifies requirements and tests to ensure the safe operation of secondary (rechargeable) lithium-ion cells and batteries used in BESS and other industrial applications. Clause 8 of the standard requires the completion of a risk analysis to determine specific electrical safety issues associated with the intended use of a given battery system or device.39 The lithium-ion batteries used in the MP2XL are certified and listed to IEC 62619.40 IEC 62933-5-2, Electrical energy storage (EES) systems – Part 5-2: Safety requirements for grid-integrated EES systems - Electrochemical-based systems: This safety standard addresses safety requirements for grid-integrated aspects of BESS, including the 34 NFPA 68, Standard on Explosion Protection by Deflagration Venting. Available at: https://www.nfpa.org/codesand-standards/6/8/nfpa-68. 35 NFPA 69, Standard on Explosion Prevention Systems. Available at: https://www.nfpa.org/codes-andstandards/6/9/nfpa-69. 36 NFPA 70, National Electrical Code. Available at: https://www.nfpa.org/codes-and-standards/7/0/nfpa-70. 37 NFPA 550, Guide to the Fire Safety Concepts Tree. Available at: https://www.nfpa.org/codes-andstandards/5/5/0/550. 38 NFPA 855, Standard for the Installation of Stationary Energy Storage Systems. Available at:
https://www.nfpa.org/codes-and-standards/8/5/5/nfpa-855. 39 IEC 62619, Secondary cells and batteries containing alkaline or other non-acid electrolytes – Safety requirements for secondary lithium cells and batteries, for use in industrial applications. Available at:
https://webstore.iec.ch/en/publication/64073. 40 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C).
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
16 Regulatory and Health Protection Requirements Ramboll requirements for grid-integrated BESS.41 The MP2XL, as an entire cabinet, is certified, tested, and listed to IEC 62933-5-2.
UL1973, Standard, Standard for Batteries for Use in Stationary, Vehicle Auxiliary Power and Light Electric Rail Applications: UL1973 includes construction parameters with requirement for electrical spacing and separation of circuits, insulation and protective grounding, battery cell construction and system safety analyses. UL1973 also outlines a series of safety performance tests, including a test for failure of the cooling and thermal stability system and internal and external fire exposure tests.42 The standard evaluates the battery system's ability to safely withstand simulated abuse conditions. The lithium-ion batteries used in the MP2XL are certified and listed to UL1973.43
UL9540, Standard for Safety of Energy Storage Systems and Equipment: This standard covers energy storage systems (including lithium-ion BESS) for stationary indoor and outdoor installations and establishes system-level certification.44 The MP2XL, as an entire cabinet, is certified, tested, and listed to UL9540.
UL9540A Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems: The requirements of UL9540A were designed to evaluate the fire characteristics of a BESS that undergoes thermal runaway. The data generated can be used to determine the fire and explosion protection required for an installation of a battery energy storage system.45 This test is specifically referenced by the IFC, NFPA 1, NFPA 855, and California Fire Code Section 1207 to demonstrate the performance of the BESS fire protection features during large-scale fire testing.46 The MP2XL, as an entire cabinet, is certified, tested, and listed to UL9540A, and the results of a UL9540A large-scale fire protection analysis for the MP2XL product are detailed in Section 8.1.
Chula Vista Municipal Fire Code: The City of Chula Vista adopted by reference the 2022 California Fire Code.47 California Fire Code and International Fire Code: Specifies minimum size requiring permits (Lithium, all types, 20 kWh), specifies maximum limits on sizing for battery systems (Lithium all type, 50 kWh each array), seismic and structural design, spacing (minimum 3 feet separation of arrays), vehicle impact protection, testing, maintenance and repairs, maximum quantities within a building (lithium of 600 kWh), battery management systems 41 IEC 62933-5-2, Electrical energy storage (EES) systems - Part 5-2: Safety requirements for grid-integrated EES systems - Electrochemical-based systems. Available at: https://webstore.iec.ch/en/publication/32177. 42 UL1973. Available at: https://www.everexceed.com/overview-of-lithium-battery-safety-testing-ul-1973_n433. 43 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C). 44 UL9540. Available at: https://www.ul.com/news/ul-9540-energy-storage-system-ess-requirements-evolvingmeet-industry-and-regulatory-needs. 45 UL9540A. Available at: https://www.ul.com/news/ul-9540a-battery-energy-storage-system-ess-test-method. 46 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C). 47 Chula Vista Municipal Code, Title 15, Chapter 15.36. Available at:
https://chulavista.municipal.codes/CVMC/15.36.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
17 Regulatory and Health Protection Requirements Ramboll suppression and detection systems, and ventilation specifications.48 The CVEC2 Project will comply with all requirements of Section 1207 of the California Fire Code for EES systems.
6.2 Health Protective Regulations
The California Air Pollution Control Officers Association (CAPCOA), California Air Resources Board, and Office of Environmental Health Hazard Assessment (OEHHA) developed the Air Toxics “Hot Spots” Information and Assessment Act of 1987 (AB 2588) program which seeks to identify and evaluate risk from air toxics sources. AB 2588 does not reduce the quantity of air toxics emissions. Instead, under AB 2588, toxic air contaminant emissions from individual facilities are quantified and prioritized. “High priority” facilities are required to perform a health risk assessment that evaluates estimated cancer risk, non-cancer chronic hazard index, and non-cancer acute hazard index. If specific thresholds defined by OEHHA’s reference exposure levels (REL) are exceeded, facilities are required to communicate the results to the public in the form of notices and public meetings.49 In this Hazards Analysis, only the non-cancer acute RELs are used, as a release event would be a non-routine hazard event, to determine if the facility will be designated as high priority. Non-cancer acute RELs are the concentration levels at or below which no adverse non-cancer health effects are anticipated for an exposure duration of 1 hour.50
The California Public Utilities Commission’s Safety and Enforcement Division developed guidelines for inspectors of energy storage devices.51 The guidelines include a review of:
• Whether there is an overall safety plan in place;
• Whether the facility is inspected regularly by the company or utility per manufacturers recommendations;
• Interconnection equipment;
• Storage facility;
• Battery enclosures;
• Battery modules; and
• Hazardous materials policy and management program, if applicable. 48 California Fire Code. Available at: https://up.codes/viewer/california/ca-fire-code-2022/chapter/12/energysystems#1207. 49 CAPCOA. 2016. Air Toxics “Hot Spots” Program Facility Prioritization Guidelines. August. Available at:
http://www.vcapcd.org/pubs/Engineering/AirToxics/CAPCOA-Prioritization-Guidelines-August-2016-FINAL.pdf. 50 Air Toxics Hot Spots Program Risk Assessment Guidelines: Guidance Manual for Preparation of Health Risk Assessments. Air, Community, and Environmental Research Branch, Office of Environmental Health Hazard Assessment, 2015. Available at: https://oehha.ca.gov/media/downloads/crnr/2015guidancemanual.pdf. 51 CPUC. 2017. SED Safety Inspection Items for Energy Storage. Available at: https://www.cpuc.ca.gov/- /media/cpuc-website/divisions/safety-policy-division/documents/sed-safety-inspection-checklist-final042717.pdf.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
18 Regulatory and Health Protection Requirements Ramboll
6.3 Emergency Response and Emergency Action Plan
Wellhead Power Solutions will develop an emergency response and emergency action plan, as required by California Senate Bill 38.52
1. This emergency response and emergency action plan will:
a. Establish response procedures for an equipment malfunction or failure. b. Include procedures to ensure the safety of surrounding residents, neighboring properties, emergency responders, and the environment. These procedures will be established in consultation with local emergency management agencies. c. Establish notification and communication procedures between the facility and local emergency management agencies.
2. In developing the emergency response and emergency action plan, CVEC2 will coordinate with local emergency management agencies, unified program agencies, and local first response agencies.
3. CVEC2 will submit the emergency response and emergency action plan to the County.
The California Public Utilities Commission is in the process of amending General Order No. 167-B, Enforcement of Maintenance and Operation Standards for Electric Generating Facilities, to implement the requirements of Senate Bill 38. The emergency response and emergency action plan will be consistent with the final amended language of this order. The emergency response and emergency action plan will be prepared prior to the BESS becoming operational.
Specific to this Project, safety signs will be placed around the site and there will be a siren system for warning neighboring passersby of an incident. The Chula Vista Fire Department is designated as the first responder.
52 California Senate Bill 38. Available at: https://legiscan.com/CA/text/SB38/id/2844405.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
19 Design Measures Ramboll
7. DESIGN MEASURES
7.1 Passive Design Measures
The application of the requirements of the California Fire Code and industry standards will ensure that passive design measures are incorporated into the Project to prevent and slow the spread of any thermal runaway or fire event.
As stated in Section 6.1, the Tesla MP2XL is certified to IEC 62619, IEC 62933-5-2, UL1973, UL9540, and UL9540A. The rigorous testing performed on the MP2XL limits the likelihood of a thermal event due to an internal product failure. Each cell is individually inspected and tested prior to module assembly.53 Flawed cells are discarded and used to drive further cell manufacturing improvements. To create a significant fire, the enclosures need to be subject to an extreme external event, such as direct exposure to a large, long-lasting fire, or physical impact. In the event of a fire, full-scale fire testing has shown that the products perform in a safe and controlled manner without explosive bursts, unexpected hazards, or propagation to neighboring enclosure units.54 Additional protection and suppression will be provided by active design measures described in Section 7.2.
Each MP2XL module includes individually fused cells and dedicated power electronics that electrically and galvanically isolate the batteries from the common DC bus. These modules arrive pre-installed without the need to connect live high-voltage DC elements on-site and include a built-in isolated DC-DC converter and active fuse for additional protection. A parallel battery module architecture provides redundant safety control that reduces the risk of cascading failures such as electrical fault propagation, arc flash, or thermal runaway.55 Modules are sealed to prevent touch access to the battery cells, power electronics, and terminals. The Tesla MP2XL also features inverter DC and AC protection. The inverter modules installed at each of the battery modules have a high-speed pyrotechnic fuse that can isolate a battery module actively or passively during an event. Further, the MP2XL is equipped with a ground fault detection system which looks for excessive leakage current during operation.56 Each enclosure would be encased within a non-combustible casing, as required by Section 1207.3.5 of the California Fire Code.57 The Project proponent has designed the Project layout to ensure that there is spacing between enclosures and IFC clearance 53 Megapack Safety Overview: Enhanced Safety Architecture. Tesla. Available at:
https://www.greenburghny.com/DocumentCenter/View/7245/PB-20-18-Eagle-Energy---Tesla-Safety-DataSheet. 54 Megapack 2 XL Safety Overview. Tesla, 2022. Available at:
https://static1.squarespace.com/static/64c6f98a774661536ae7a362/t/65a8536a5741473e1cec1727/170553021 9747/Megapack_2_XL_Safety_Overview+%283%29.pdf. 55 Megapack Safety Overview: Enhanced Safety Architecture. Tesla. Available at:
https://www.greenburghny.com/DocumentCenter/View/7245/PB-20-18-Eagle-Energy---Tesla-Safety-DataSheet. 56 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C). 57 California Fire Code. Available at: https://up.codes/viewer/california/ca-fire-code-2022/chapter/12/energysystems#12.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
20 Design Measures Ramboll
requirements are followed.58 This spacing, along with each enclosures’ fire protection and safety systems, reduces the likelihood of a fire spreading to another enclosure. Analyses performed of past fire events show this sort of passive design measure is effective in limiting the spread of BESS fires.59
In accordance with NFPA 68 and NFPA 855, the MP2XL is designed with overpressure vents built into the roof that mitigate the deflagration hazards in case of accumulation of flammable gases due to thermal runaways or arc flash events.60 These pressure-sensitive vents are designed to direct all gases, smoke, and flame out of the top of the MP2XL, which results in minimized risk and exposures to nearby response personnel.
In accordance with NFPA 855, multi-spectrum radiant cameras for fire detection will be installed at the site to capture early signs of thermal runaway and other non-battery equipment fires.61
The MP2XL installations be remotely monitored by CVEC2 24 hours a day, 7 days a week, allowing for early detection, diagnosis and troubleshooting of system errors. Site operations personnel will be the primary contacts for first responders and will follow the procedures of the emergency response and emergency action plan.62
7.2 Active Design Measures
The BESS facility will include active design measures intended to prevent or limit any fire incident. In accordance with the IFC, the MegaPack 2 XL design includes a battery management system, thermal management system, and an explosion control system.63 The battery management system provides information on performance, voltage, current, and state of charge. It reacts to fault conditions such as over-temperature and over-voltage, which can prevent thermal runaway from occurring in the cell or prohibit propagation of thermal runaway to adjacent cells. The battery management system can isolate an affected battery module temporarily or permanently disconnect the module, and will transmit an alarm signal if fault conditions are detected.64 The thermal management system contains a closed-loop liquid cooling system that circulates coolant throughout the power electronics and battery modules to maintain an optimum operating temperature.65 It works 58 Fire Detection for ESS Outdoor Installations – Required. Kern County Fire Department. Available at:
https://kerncountyfire.org/wp-content/uploads/Fire-Detection-for-ESS-Outdoor-Installations-2021-IFC-2020- NFPA-855.cleaned-1.pdf. 59 Energy Storage in Local Zoning Ordinances. Pacific Northwest National Laboratory, October 2023. Available at:
https://www.pnnl.gov/main/publications/external/technical_reports/PNNL-34462.pdf. 60 Megapack 2 XL Safety Overview, Tesla, 2022. Available at:
https://static1.squarespace.com/static/64c6f98a774661536ae7a362/t/65a8536a5741473e1cec1727/170553021 9747/Megapack_2_XL_Safety_Overview+%283%29.pdf. 61 Megapack Safety Overview: Enhanced Safety Architecture. Tesla. Available at:
https://www.greenburghny.com/DocumentCenter/View/7245/PB-20-18-Eagle-Energy---Tesla-Safety-DataSheet. 62 Megapack: Safe by Design. Tesla. 63 Fire & Risk Alliance, Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report, Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C). 64 Ibid. 65 Ibid.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
21 Design Measures Ramboll
autonomously and does not require user feedback or controls to turn the system on when needed or to adjust temperature settings. In accordance with NFPA 69, the explosion control system includes sparkers which are designed to ignite flammable gases during an unlikely thermal runaway event before they accumulate within the enclosure, thus mitigating an explosion hazard.66
66 Ibid.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
22 Off-Site Consequence Analysis Ramboll
8. OFF-SITE CONSEQUENCE ANALYSIS
The batteries used in the CVEC2 Project will not release emissions to the atmosphere during normal operations. In the unlikely event of uncontrolled chemical reactions within battery cells, emissions could potentially be released to the atmosphere. Such an event could result in a potential fire, thermal runaway or explosion. Additionally, physical impacts to the batteries could rupture the exterior of a battery module and result in a similar fire or explosion. Although numerous possibilities and scale of releases may be theorized, this Hazards Analysis considers a worst-case scenario based on reasonable battery malfunction scenario, such as a control system failure, that might lead to a highly exothermic runaway chemical reaction.
Different battery energy storage technology manufacturers have developed various technical studies examining the potential scenarios related to possible battery malfunctions, including scenarios involving uncontrolled chemical reactions causing elevated system temperatures and/or combustion. Some studies have been independently performed for agencies, including studies by Det Norske Veritas, Inc. conducted on behalf of the New York State Energy Research & Development Authority and Consolidated Edison.67 Many other studies have been performed to evaluate off-gases when batteries are exposed to external heat sources.68,69,70 Impacts of battery malfunctions to public health and the environment are crucial for assessing the viability of BESS, and such impacts have been studied to inform both proprietors and regulators. The thermal runaway scenario evaluated is a reflection of battery malfunctions previously studied.
The technical analyses presented herein are based on the Tesla manufactured MegaPack 2 XL, whose physical and chemical properties were used to evaluate the potential environmental impacts are based on the results of the Tesla UL9540A fire protection analysis for the MP2XL product.71 For this analysis, releases are assumed to occur over the course of one to two hours as described in Section 7.1. This assumption serves as a conservative representation of the reasonable worst-case scenario because receptors are assumed to be exposed to a greater concentration of releases within an acute impact timeframe (i.e., one hour). 67 Consideration for ESS Fire Safety, Det Norske Veritas, Inc., February 9, 2017. Available at:
https://www.nyserda.ny.gov/-/media/Project/Nyserda/files/Publications/Research/Energy-Storage/20170118- ConEd-NYSERDA-Battery-Testing-Report.pdf. 68 Investigation of fire emissions from Li-Ion Batteries, Andersson, 2013. Available at: https://www.divaportal.org/smash/get/diva2:962743/FULLTEXT01.pdf. 69 Fire Hazard Assessment of Lithium Ion Battery Energy Storage Systems, Blum, 2016. Available at:
https://link.springer.com/book/10.1007/978-1-4939-6556-4. 70 Toxic fluoride gas emissions from lithium-ion battery fires., Larsson, 2017. August. Available at:
https://www.nature.com/articles/s41598-017-09784-z. 71 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024. Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C).
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
23 Off-Site Consequence Analysis Ramboll
8.1 Thermal Runaway Scenarios Based on UL 9540A Testing Because the proposed BESS will be comprised of numerous battery modules that each contain multiple battery cells, it is prudent to evaluate the quantity of battery cells that could malfunction in a reasonable worst-case scenario. UL1973 requires the control of battery systems to prevent a single battery cell failure from cascading into a numerous battery cell failure.72
A fire protection engineering analysis was conducted for Tesla’s Megapack 2XL BESS in accordance with the UL9540A standard. In that testing, a MP2XL product was forced to initiate thermal runaway under a contrived condition where all “active” design measures were defeated (i.e., not functional). As described in Section 7.2, the Tesla MP2XL product includes a number of active design measures which are intended to mitigate the possibility of a thermal runaway condition. Given that these systems were defeated for the UL9540A testing, the results of that test should be considered conservative.
In performing the UL9540A test, Tesla’s contractor simultaneously forcibly heated six interior battery cells until it propagated to a 7th cell. However, the induced thermal runaway was unable to propagate beyond that 7th cell, representing 2 percent of cells within one module (i.e., 7 of 336 cells). According to the test contractor, no flaming or other signs of distress were observed in the initiating battery module. Thermal runway did not propagate beyond the seven cells to other cells within the tray, nor did it spread to other trays within the module. On this basis, the 7-cell thermal runaway is considered a reasonable worst-case scenario.
Thermal runaway of a battery cell can occur in one of two stages. In an initial stage, a battery cell starts off-gassing chemical emissions which may be toxic and/or flammable in nature. A thermal runaway event can eventually generate enough heat to ignite such flammable emissions, causing combustion of the off-gases. The UL9540A test protocol requires characterization of both a “non-flaming” condition (i.e., off-gassing occurs, no combustion) and a “flaming” condition (i.e., combustion occurs).
Table 1 presents a summary of the chemical compounds identified for the non-flaming and flaming cell level thermal runaway conditions under the UL9540A tests for the Tesla MP2XL BESS product.73
Table 1: Chemical Compounds Identified During UL9540A Cell Level Testing Pollutant
Present in
Non-Flaming
Scenario
Present in Flaming
Scenario
Hydrogen (H2) X X
Carbon Monoxide (CO) X X
Carbon Dioxide (CO2) X X
Methane (CH4) X X 72 UL1973. Available at: https://www.everexceed.com/overview-of-lithium-battery-safety-testing-ul-1973_n433. 73 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C).
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
24 Off-Site Consequence Analysis Ramboll
Table 1: Chemical Compounds Identified During UL9540A Cell Level Testing Pollutant
Present in
Non-Flaming
Scenario
Present in Flaming
Scenario
Acetylene (C2H2) X X
Ethylene (C2H4) X
Ethane (C2H6) X
Propylene (C3H6) X
Propane (C3H8) X
Butanes (C4) X
Pentanes (C5) X
Hexanes (C6) X
Benzene (C6H6) X X
Toluene (C7H8) X
Dimethyl Carbonate (C3H6O3) X
Ethyl Methyl Carbonate (C4H8O3) X
For the reasonable worst-case scenario, we considered releases for both the non-flaming and flaming thermal runaway stages. The UL9540A test was performed over a period of
2.5 hours. However, for the reasonable worst-case scenario off-gassing was conservatively assumed to occur over the period of one hour.
A further alternative scenario was considered to understand the potential releases and health risk impacts if, somehow, 100% of cells within one MP2XL module was involved in thermal runaway. For the alternative scenario, it is assumed that the period of off-gassing/flaming would occur over a period of two hours, consistent with the test performance. The UL9540A testing showed that the concentration of hydrogen on the cell vent gas composition was significantly higher than its lower flammability limit, indicating that the gas would likely ignite during off-gassing. Additionally, as noted in Section 6.2, the Tesla MP2XL product is equipped with an explosion control system. The system includes sparkers designed to ignite flammable gases early in a thermal runaway event before they accumulate within the enclosure and become an explosion hazard. Therefore, the alternative scenario modeling was performed for flaming conditions. This alternative scenario is significantly more conservative than any outcome identified under the UL9540A testing for the Tesla MP2XL product.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
25 Off-Site Consequence Analysis Ramboll
Each scenario presented assumed that the chemical composition identified in the cell level testing would also be present during module thermal runaway. To summarize, the following scenarios were analyzed for this technical report:
1. Reasonable Worst-Case Scenario
1a: Failure of seven cells under non-flaming conditions consistent with UL9540A report 1b: Failure of seven cells under flaming conditions consistent with UL9540A report
2. Alternative Scenario (One Module): Failure of an entire Tesla MP2XL module (336 cells) under flaming conditions
These potential thermal runaway scenarios were modeled using a United States Environmental Protection Agency (USEPA) approved air dispersion model to understand potential threat zone distances. 74 Health risk screening and modeling results are presented in Section 9.
8.2 Particulates and Metals
Particulates and metals may also be released from a LiB BESS fire. However, for LFP batteries specifically, there may be health risks due to particulate matter releases, but not toxic metals releases, according to the following studies:
• A research study by the Centers of Disease Control and Prevention characterized aerosol particles emitted from thermal runaway of NMC, Lithium Titanium Oxide, and LFP batteries.75 Thermal runaway was initiated using an accelerating rate calorimeter, and the resulting explosion caused continuous emission of smoke. The LFP aerosols produced were comprised of homogeneous carbonaceous cenospheres (hollow spheres) that contained carbon, silicon, and fluorine, which suggests aerosol formation by the decomposition of organics within molten microspheres. The study notes that no transition metals are present in LFP aerosols. Thus, LFP explosion aerosols may be the least hazardous of the three battery types evaluated.
• A study conducted by Southwest Research Institute characterized particle emissions from LiB fires triggered by thermal runaway.76 Thermal runaway was initiated by either nail penetration or overcharging of a 0.864 kWh LFP module. For the nail penetration test, only cells in the path of the nail experienced thermal runaway. PM2.5 emission rates from the nail penetration initiation method ranged from 0 to 1.81 grams per hour. For the overcharge test, all cells in the module experienced thermal runaway and smoke and fire was observed. PM2.5 emission rates from the overcharge initiation method ranged from 375.97 to 386.09 grams per hour. Speciation of the particles was not provided in the study. 74 Risk Management Program Guidance for Offsite Consequence Analysis. USEPA. Available at:
https://www.epa.gov/sites/default/files/2013-11/documents/oca-chps.pdf. 75 Lithium-ion battery explosion aerosols: Morphology and elemental composition, Centers for Disease Control and Prevention, Aerosol Sci Technol., 2021, 55, 10, 1183–1201. Available at:
https://doi.org/10.1080/02786826.2021.1938966. 76 Detailed Characterization of Particle Emissions from Battery Fires. Aerosol Science and Technology. https://www.tandfonline.com/doi/full/10.1080/02786826.2021.2018399#d1e1136.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
26 Off-Site Consequence Analysis Ramboll
By comparison, the thermal runaway tests conducted on the Tesla MP2XL product under UL 9540A were not shown to propagate to all cells within a single module. Rather, a thermal runaway of six cells (forced by an external electrical feed) was demonstrated as unable to propagate to more than one additional cell (i.e., 7 out of 336 cells in a single module).
8.3 Toxic Pollutants
Table 2 provides a list of toxic pollutants that can be released from a thermal runaway in descending order of toxicity based on the acute REL as determined by the California OEHHA.
These acute REL values are used to evaluate the potential exposure consequences in Section 9 of this report.77 Table 2: Potential Toxic Pollutants Released from Battery Malfunction Pollutant
OEHHA Acute Reference Exposure Level
(µg/m3)
Carbon Monoxide (CO) 23,000
Toluene (C7H8) 5,000
Benzene (C6H6) 27
Hydrogen (H2) --
Carbon Dioxide (CO2) --
Methane (CH4) --
Acetylene (C2H2) --
Ethylene (C2H4) --
Ethane (C2H6) --
Propylene (C3H6) --
Propane (C3H8) --
Butanes (C4) --
Pentanes (C5) --
Hexanes (C6) --
Notes:
µg/m3
– microgram per cubic meter
USEPA Acute Exposure Guideline Levels (AEGLs) are commonly used worldwide by emergency planners and first responders as guidance in dealing with accidental releases of chemicals into the air and were originally developed by the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances.78 AEGLs describe the human 77 OEHHA. 2023. OEHHA Acute, 8-hour and Chronic Reference Exposure Level (REL) Summary. October. Available at: https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-relsummary. 78 History of Acute Exposure Guideline Levels (AEGLs). USEPA. Available at: https://www.epa.gov/aegl/historyacute-exposure-guideline-levels-aegls.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
27 Off-Site Consequence Analysis Ramboll
health effects from once-in-a-lifetime, or rare, exposure to airborne chemicals. These thresholds are expressed as specific ambient concentrations (in parts per million [ppm] or milligrams per cubic meter [mg/m3]) of a given airborne contaminant at which the described health effects would occur if a human is exposed to that concentration for a certain duration (e.g., 10 minutes, 60 minutes, 8 hours).79 The AEGLs are designed to protect sensitive receptors, such as the elderly and children, as well as other individuals who may be more susceptible to health effects from chemical exposure.
AEGL values (concentration levels) for different exposure periods differ because the same health effect could be a result of a prolonged exposure to a lower concentration of a contaminant or a brief exposure to a very high concentration. AEGLs may have three values for a given exposure duration (e.g., 1 hour), with each describing different health effects from mild (or transient), moderate, to serious (irreversible), represented by AEGL 1, AEGL 2, and AEGL 3, respectively (Table 3).
Table 3: Definitions of Acute Exposure Guideline Levels AEGL-1
AEGL-1 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic non-sensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.
AEGL-2
AEGL-2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.
AEGL-3
AEGL-3 is the airborne concentration, (expressed as ppm or mg/m3), of a substance above which it is predicted that the general population, including susceptible individuals, could experience life-threatening health effects or death.
Table 4 provides a list of the USEPA AEGLs (60-minute basis) for the toxic pollutants potentially found within lithium-ion batteries or potentially released during a battery malfunction event.
Table 4: AEGL Values for Potential Pollutants which could be released from Battery Manufacturing and/or Malfunction (60-minute exposure) Pollutant
AEGL 1
(ppm)
AEGL 2
(ppm)
AEGL 3
(ppm)
Hydrogen (H2) NA NA NA
Carbon Monoxide (CO) NR 83 330
Carbon Dioxide (CO2) NA NA NA
Methane (CH4) NA NA NA
Acetylene (C2H2) NA NA NA 79 EPA. 2024. Acute Exposure Guideline Levels. Available at: https://www.epa.gov/aegl/access-acute-exposureguideline-levels-aegls-values.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
28 Off-Site Consequence Analysis Ramboll
Table 4: AEGL Values for Potential Pollutants which could be released from Battery Manufacturing and/or Malfunction (60-minute exposure) Pollutant
AEGL 1
(ppm)
AEGL 2
(ppm)
AEGL 3
(ppm)
Ethylene (C2H4) NA NA NA
Ethane (C2H6) NA NA NA
Propylene (C3H6) NA NA NA
Propane (C3H8) 5,500* 17,000** 33,000***
Butanes (C4)1 5,500* 17,000** 53,000***
Pentanes (C5) NA NA NA
Hexanes (C6) NR 2,900* 8,600**
Benzene (C6H6) 52 800 4,000*
Toluene (C7H8) 67 560 3,700*
Dimethyl Carbonate (C3H6O3) NA NA NA
Notes:
NA – not applicable
NR – not recommended due to insufficient data
* Value exceeds 10% of the Lower Explosive Limit (LEL) of the compound ** Value exceeds 50% of the LEL of the compound
*** Value exceeds 100% of the LEL of the compound 1
Butane is used as a proxy for Butanes.
Emergency Response Planning Guidelines (ERPGs) were developed by the Emergency Response Planning committee of the American Industrial Hygiene Association.80 ERPGs identify the concentration levels at which people will begin to experience health effects if exposed to a hazardous chemical for 1 hour.81,82 ERPGs may have three values, with each describing different health effects from mild, moderate, to serious – represented by ERPG 1, ERPG 2, and ERPG 3, respectively (Table 5).83
80 ERPGs (Emergency Response Planning Guidelines™). American Industrial Hygiene Association. Available at:
https://www.aiha.org/get-involved/aiha-guideline-foundation/erpgs. 81 Ibid. 82 Emergency Response Planning Guidelines (ERPGs). National Oceanic and Atmospheric Administration. Available at: https://response.restoration.noaa.gov/oil-and-chemical-spills/chemical-spills/resources/emergencyresponse-planning-guidelines-erpgs.html. 83 DOE Handbook, Temporary Emergency Exposure Limits for Chemicals: Methods and Practice. U.S. Department of Energy. Available at: https://www.standards.doe.gov/standards-documents/1000/1046-Bhdbk-2016-reaff2022/@@images/file.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
29 Off-Site Consequence Analysis Ramboll
Table 5: Definitions of Emergency Response Planning Guidelines ERPG-1
ERPG-1 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 60 minutes without experiencing other than mild transient adverse health effects or perceiving a clearly defined, objectionable odor.
ERPG-2
ERPG-2 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 60 minutes without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual’s ability to take protective action.
ERPG-3
ERPG-3 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 60 minutes without experiencing or developing life-threatening health effects.
The AEGL values for the pollutants in Table 4 are lower and thus more conservative than the respective ERPGs, except for benzene and toluene.
Temporary Emergency Exposure Limits (TEELs) estimate the concentrations at which most people will begin to experience health effects if they are exposed to a hazardous airborne chemical for that given duration.84 A chemical may have up to three TEEL values corresponding to a variety of health effects (Table 6):85 Table 6: Definitions of Temporary Emergency Exposure Limits TEEL-1
TEEL-1 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, when exposed for more than one hour, could experience notable discomfort, irritation, or certain asymptomatic, non-sensory effects. However, these effects are not disabling and are transient and reversible upon cessation of exposure.
TEEL-2
TEEL-2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, when exposed for more than one hour, could experience irreversible or other serious, long-lasting, adverse health effects or an impaired ability to escape.
TEEL-3
TEEL-3 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, when exposed for more than one hour, could experience life-threatening adverse health effects or death.
Protective Action Criteria (PACs) combine all three common public exposure guideline systems (AEGLs, ERPGs, and TEELs). There are three level of PAC values (Table 7). PAC values represent the concentrations of airborne materials at which action is required to ensure the health and safety of workers or the public. 84 Temporary Emergency Exposure Limits (TEELs). National Oceanic and Atmospheric Administration. Available at:
https://response.restoration.noaa.gov/oil-and-chemical-spills/chemical-spills/resources/temporary-emergencyexposure-limits-teels.html. 85 DOE Handbook, Temporary Emergency Exposure Limits for Chemicals: Methods and Practice. U.S. Department of Energy. Available at: https://www.standards.doe.gov/standards-documents/1000/1046-Bhdbk-2016-reaff2022/@@images/file.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
30 Off-Site Consequence Analysis Ramboll
Table 7: Definitions of Protective Action Criteria
PAC-1 PAC-1 is the threshold exposure limit at which those affected could experience mild, transient health effects, including discomfort and irritation.
PAC-2
PAC-2 is the threshold exposure limit at which those affected could experience irreversible or other serious long-lasting health effects that could impair the ability to take protective action.
PAC-3 PAC-3 is the threshold exposure limit at which those affected could experience lifethreatening health effects.
Immediately dangerous to life or health (IDLH) pollutant air concentrations have been defined by the National Institute for Occupational Safety and Health to identify exposure in the workplace that could result in immediate or delayed undesirable health outcomes.86 The Area Locations of Hazardous Atmospheres (ALOHA) model used for the Off-site Consequence Analysis Modeling analysis determines its default standards based on the following hierarchy:
1. AEGLs are used preferentially because they are the best public exposure Levels of Concern (LOCs) available to date. They undergo a rigorous review process, have multiple exposure durations, and are designed as guidelines for nearly all members of the general public – including sensitive individuals. As part of the review process, interim AEGL values are established and then evaluated thoroughly (sometimes over several years) before the final AEGL values are approved. However, because the AEGL development process is so exhaustive, relatively few AEGLs have been finalized (about 175 as of mid-2016), and there are also about 80 interim AEGLs. ALOHA only includes the AEGLs with a 60-minute exposure duration.
2. ERPGs are used next. They are based on experimental data too, but – unlike AEGLs – they are only available for a 60-minute exposure duration and they are not designed as guidelines for sensitive individuals.
3. PACs are used next.87 This dataset combines all three common public exposure guideline systems (AEGLs, ERPGs, and temporary emergency exposure limits).
4. TEELs are used when AEGLs or ERPGs are not available and there has been a chemical release that is short term in duration. TEELs estimate the concentrations at which most people will begin to experience health effects if they are exposed to a hazardous airborne chemical for a given duration. In this case, the PAC values will be the TEEL values.
5. IDLH are used next.88 IDLH limits are used when no public exposure guidelines are defined for a given chemical. An IDLH limit is a workplace exposure limit that is used primarily for making decisions regarding respirator use. Unlike the three-tiered public exposure guidelines, only a single IDLH value is defined for applicable chemicals. 86 NIOSH. Documentation for Immediately Dangerous to Life or Health Concentrations (IDLHs). Available at:
https://www.cdc.gov/niosh/idlh/intridl4.html. 87 Protective Action Criteria. Available at: https://edms3.energy.gov/pac#/. 88 NIOSH Immediately Dangerous to Life or Health (IDLH) Values were used for modeling the threat zone distance for Carbon Dioxide, for which there are no AEGL, ERPG, or PAC values.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
31 Off-Site Consequence Analysis Ramboll
ALOHA implements a hierarchy-based system. (AEGLs are used preferentially, followed by ERPGs, and then TEELs.) If ALOHA is defaulting to the PAC values, it means that there are no AEGL or ERPG values in the ALOHA chemical library for that substance. In this case, the PAC values will be the TEEL values. Thus, the AEGLs in Table 4 were used to evaluate potential off-site exposure consequences as presented in Section 9 of this report.
8.4 Flammable Components
Compounds released during a battery malfunction scenario may be flammable. Table 8 presents flammable components which could potentially be released during a malfunction scenario.89 Table 8: Potential Flammable Components from Battery Malfunction Component
Lower Flammability Limit1
(vol%)
Acetylene (C2H2) 2.5
Benzene (C6H6) 1.2
Butanes (C4) 1.9
Carbon Monoxide (CO) 12.0
Ethane (C2H6) 3.0
Ethylene (C2H4) 2.8
Hexane (C6H14) 1.1
Hydrogen (H2) 4.0
Methane (CH4) 4.4
Pentanes (C5) 1.4
Propane (C3H8) 2.1
Propylene (C3H6) 2.0
Toluene (C7H8) 1.1
Notes:
Vol% – percent volume 1
The Engineering Toolbox. Gases – Explosion and Flammability Concentration Limits. Available at:
https://www.engineeringtoolbox.com/explosive-concentration-limits-d_423.html. Accessed:
February 2024. 89 Tesla Megapack 2 XL Fire Protection Engineering and UL 9540A Interpretation Report. Fire & Risk Alliance, 2024.
Available at: https://efiling.energy.ca.gov/GetDocument.aspx?tn=258490&DocumentContentId=94521 (Appendix C).
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
32 Off-Site Consequence Analysis Ramboll
8.5 Health Risk Screening
The estimated impacts of a reasonable worst-case scenario and an alternative scenario were evaluated using the San Diego County Air Pollution Control District screening approach for air toxics, which utilizes guidelines developed in accordance with the CAPCOA Guidelines.90 The purpose of the CAPCOA Guidelines is to provide air pollution control and air quality management districts with suggested procedures for use in prioritizing facilities into high, intermediate, and low priority categories as required by the State of California’s Air Toxics “Hot Spots” Information and Assessment Act of 1987. The screening approach assigns a Total Score (TS) to the Project as presented in Table 9.
Table 9: Facility Designation Based on Total Score
Total Score Facility Designation
>10 High priority
1 – <10 Intermediate priority
<1 Low priority
Per the CAPCOA Guidelines, because the threshold for high priority is based on a conservative modeling scenario, it is possible that facilities with higher scores than the threshold may not significantly impact off-site receptors.91 Facilities with TSs below 1 are expected to represent the lower end of the spectrum risk in terms of off-site receptor impacts.92 Facilities with a TS between 1 and 10 may impact off-site receptors. It is therefore necessary to consider other factors for prioritization, including population density near the facility, proximity of sensitive receptors, and presence of fugitive emissions.93
8.6 Off-Site Consequence Analysis Modeling
Ramboll also conducted an off-site consequence analysis for the defined battery cell failure scenarios using an agency approved model for estimation of potential health hazards which might occur if a thermal runaway incident caused a release of toxic and flammable vapors.
The purpose of an Off-Site Consequence Analysis (OCA) is to identify the hazards and risks associated with releases of hazardous chemicals, including unplanned or accidental releases associated with handling and storing of hazardous chemicals or otherwise using materials that may release hazardous chemicals.
In the case of BESS projects, an OCA can be used to identify the potential hazards associated with release of airborne toxics during a fire event. This report relies on guidance from the USEPA (“Risk Management Program Guidance for Off-Site Consequence Analysis”) which requires that the modeled scenarios represent “the release of the largest quantity of a regulated substance from a vessel or process line failure, and the release that results in the 90 SDAPCD Air Toxics “Hot Spots” Program Prioritization Procedures, June 2023. Available at:
https://www.sdapcd.org/content/dam/sdapcd/documents/permits/air-toxics/Prioritization-Procedures.pdf. 91 Ibid. 92 Ibid. 93 Ibid.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
33 Off-Site Consequence Analysis Ramboll
greatest distance to the endpoint for the regulated toxic or flammable substance.”94 The USEPA guidance document assumes the worst-case scenario of atmospheric stability Class F (stable atmosphere), wind speeds of 1.5 meters per second (3.4 miles per hour), and ambient temperature of 25°C (77°F).95
An OCA does not consider the probability of a release event or the probability of worst-case conditions occurring. Rather, it assumes that a release event occurs under such conditions and evaluates the resulting reasonably anticipated consequences. An OCA is intended to evaluate the hazards and risks associated with a specific facility in a specific location.
Therefore, it is necessary to consider several site-specific factors, including local surroundings and local meteorological conditions.
8.6.1 Local Surroundings
The CVEC2 Project is adjacent to a meat processing facility on the west side, a printing business and metalworking business on the east side, and an auto dealership, towing business, and recycling center on the north side. The Otay Valley Regional Park immediately south of the parcel is a major urban park and open space area. As shown in Figure 2, Otay Elementary School is located approximately 0.25 miles to the north, and the closest residential neighborhood is 0.07 miles west of the site. The nearest hospital is Oasis of Hope Hospital, located approximately 2.20 miles east of the Project site. The nearest daycare is Elgrillitonet Daycare, located approximately 0.45 mi northwest of the Project site. The nearest adult care facility is Glenner Alzheimer’s Family Centers, located approximately
0.83 mi west of the Project site.
8.6.2 Meteorological Conditions
Meteorological conditions can affect the location and concentration of airborne releases and, therefore, how such releases impact human health and safety. This section describes the meteorological conditions and phenomena considered in this OCA.
The closest meteorological stations are the National Weather Service (NWS) stations at the nearby Imperial Beach Airport (KNRS), roughly 3.6 miles southwest from the CVEC2 Project site, and Brown Field Municipal Airport (KSDM), roughly 4.3 miles southeast from the CVEC2 Project site. KNRS is at an elevation of 7.1 meters whereas KSDM is at an elevation of 160.4 meters. The CVEC2 Project site is at an elevation of 16.8 meters. Because of similar elevation and terrain as the Project site, KNRS was determined to be more representative of the range of potential meteorological conditions that could be expected at the BESS site. A wind rose plot showing the speed and direction of winds at Imperial Beach Airport from 2021-2023 is presented in Figure 7. 94 Risk Management Program Guidance for Offsite Consequence Analysis. USEPA. Available at:
https://www.epa.gov/sites/default/files/2013-11/documents/oca-chps.pdf. 95 Ibid.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
34 Off-Site Consequence Analysis Ramboll
Figure 7: Wind Rose for Meteorological Data at the Imperial Beach Airport (2021-2023)
As shown in Figure 7, the prevailing winds are from west and west-northwest. Further discussion of the meteorological conditions at Imperial Beach Airport from 2021-2023 is provided in Section 8.6.4 of this report. Between 5 a.m. and 9 a.m., winds are dominated by easterlies, which means that on average, plumes are blown towards the west during morning rush hour. The closest sensitive receptor west of the facility is Glenner Alzheimer’s Family Centers, located approximately 0.83 mi west of the Project site. Between 3 p.m. and 7 p.m., winds are dominated by westerlies and north-westerlies, which means that on average, winds are blowing towards the residential areas located 0.55 mi east of the facility during afternoon rush hour.
This OCA considers meteorological conditions that are likely to result in worst-case impacts when ground-level concentrations are at their maximum. Maximum concentrations are likely to occur during stable conditions and at moderate wind speeds (detailed further in Section 8.6.4of this report).
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
35 Off-Site Consequence Analysis Ramboll
8.6.3 Selection of Dispersion Models Used for Off-Site Consequence Analysis There are several options for air dispersion models that could be used to estimate off-site consequences. Table 10 presents a list and description of available dispersion models.
Table 10: Dispersion Models
Dispersion Model Description
ALOHA96
Estimates the downwind dispersion of a chemical cloud based on the toxicological and physical characteristics of the released chemical, atmospheric conditions, and specific circumstances of the release; can model hazards associated with fires and explosions
PHAST97
Proprietary model used for modeling discharge, dispersion, fires, explosions, toxic effects, and consequence estimation of a wide range of loss of containment scenarios; does not have a module associated with battery fires
SCREEN398 Used to analyze single source release scenarios over simple or complex terrain; can predict downwind short-term (1-hr average) exposure for a single source for a range of wind speeds and stability classes; does not provide mapping
AERSCREEN99 Produces estimates of “worst-case” 1-hour concentrations for a single source, without the need for hourly meteorological data Second Order Closure
Integrated Puff Model
with Chemistry
(SCICHEM)100 Reactive puff model that can be used to calculate single or multi-source impacts of emissions at downwind locations; can be used for both short-range calculations or long-range calculations for primary and secondary pollutant impacts
RMP*Comp101 Simple online tool that uses release quantity and temperature and surrounding terrain type to estimate the downwind distance to the toxic endpoint specified for regulated substances under the Risk Management Program (RMP) Rule
SCREEN3 and AERSCREEN are simplistic screening models. PHAST is a proprietary model which is not appropriate for use in a public-facing evaluation. RMP*Comp does not assess the off-site impacts for a few chemicals that are required to be evaluated in this analysis.
Thus, ALOHA and SCICHEM were determined to be most appropriate options for this modeling analysis. A comparative assessment was performed to understand which of these two models would provide the most conservative results for this particular modeling application. The results of Ramboll’s evaluation indicated that SCICHEM predicted smaller 96 ALOHA Software Version 5.4.7. USEPA. Available at: https://www.epa.gov/cameo/aloha-software. 97 PHAST Model. DNV. Available at: https://www.dnv.com/software/services/plant/consequence-analysis-phast/. 98 Air Quality Dispersion Modeling - Screening Models. USEPA. Available at: https://www.epa.gov/scram/airquality-dispersion-modeling-screening-models. 99 Ibid. 100 Second Order Closure Integrated Puff Model with Chemistry (SCICHEM), version 3.1. Energy & Environment, 2017. Available at: https://www.epri.com/research/products/1025626. 101 RMP*Comp. USEPA. Available at: https://cdxapps.epa.gov/olem-rmp-maintain/action/rmp-comp/home.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
36 Off-Site Consequence Analysis Ramboll
threat zone distances than ALOHA. On this basis, ALOHA was determined the most appropriate choice.
8.6.4 Assessment Model
ALOHA is used in this OCA as it is referenced by the USEPA Risk Management Program Guidance for Off-Site Consequence Analysis and was found to provide more conservative results.102 The ALOHA model was developed to produce results for the use of first responders during a real emergency. It estimates the potential hazard impacts by generating hazard threat zone estimates based on user-defined scenarios such as toxic and flammable vapor clouds. A hazard impact area or threat zone estimated by the ALOHA model encloses an area where a hazard could exceed a specific LOC surrounding a release point. The LOCs relevant to this Project are as follows:
For Toxic Vapor:
• AEGL-3: The maximum airborne concentration below which nearly all individuals could be exposed without experiencing or developing life-threatening health effects. • AEGL-2: The maximum airborne concentration below which nearly all individuals could be exposed without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action. • AEGL-1: The maximum airborne concentration below which nearly all individuals could be exposed without experiencing more than mild, transient adverse health effects or without perceiving a clearly defined objectionable odor.
For Flammable Vapor:
• 60% of LEL
• 10% of LEL
This analysis followed the Environmental Protection Agency’s (EPA’s) “Risk Management Program (RMP) Guidance for Off-Site Consequence Analysis” (EPA RMP Guideline; 40 CFR
68.22).103 The analysis is based on the following release and meteorological conditions:
Release Conditions:
• Worst-Case Release Condition: Release at ground level.
The EPA RMP Guideline requires assessment of toxic release at ground level; however, the on-site release height is expected to be at 10 ft. As a result, the EPA RMP assessment requirement is more conservative than the release level applicable to the Project due to actual physical dimensions of the Project’s Megapacks. • Alternative Release Condition: Release at 9 ft. 1 in. height. 102 Risk Management Program Guidance for Offsite Consequence Analysis. USEPA. Available at:
https://www.epa.gov/sites/default/files/2013-11/documents/oca-chps.pdf. 103 40 CFR Part 68 §68.22: Offsite Consequence Analysis Parameters. Available at:
https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-68/subpart-B/section-68.22.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
37 Off-Site Consequence Analysis Ramboll
For all the release conditions, a release duration of 60 minutes was assumed. This assumption is likely conservative (i.e., health protective) considering the risk management design features that will be applied to the facility to limit the release duration and risk associated with the release event.
Meteorological Conditions:
The ALOHA model considers the full range of potential meteorological conditions to arrive at worst-case results for a given release scenario in a given location. The range of meteorological conditions is informed by the meteorological data for a specific location. The model allows for the use of site-specific meteorological data to determine atmospheric stability class. This modeling analysis considered meteorological data from the NWS station at the nearby Imperial Beach Airport for the 2021-2023 period. The Imperial Beach Airport is roughly 3.6 miles southwest from the CVEC2 Project site. This NWS station is representative of the range of potential meteorological conditions that could be expected at the CVEC2 Project location. This assessment is further described below. • Worst-case Meteorological Conditions: Wind speed of 1.5 m/s (at 10-meter anemometer height) under very stable atmospheric conditions (Pasquill-Gifford [PG] Class F). The F stability typically represents nighttime conditions. The 1.5 m/s and F stability are the EPA RMP requirements for the worst-case meteorological condition. Based on an analysis of the 2021-2023 meteorological data at the nearby Imperial Beach Airport, the average wind speed is 3.5 m/s, with about 21% of winds below or equal to 1.5 m/s for night hours from 9pm to 5am; nighttime is dominated by a stable atmosphere. • Alternative Meteorological Conditions: Wind speed of 3 m/s under neutral atmospheric conditions (PG Class D). The D stability is used to represent daytime conditions. The 3 m/s and D stability are the EPA RMP requirements for the alternative meteorological condition. The 3 m/s wind speed is close to the average wind speed at the nearby Imperial Beach Airport from 2021 to 2023 (3.5 m/s). About 11% of the winds from 2021-2023 are below or equal to 3 m/s for daytime hours from 9am to 5pm; atmospheric stability during daytime ranges from unstable to neutral. • Other meteorological parameters that were considered for both meteorological scenarios (i.e., worst-case and alternative) are summarized below:
Ambient Temperature: 25°C (77°F), which is the EPA RMP Guideline recommendation. From the 2021-2023 Imperial Beach Airport data, the maximum hourly temperature is 35.0°C (94.9°F) and the average hourly temperature is 16.4°C (61.5°F). From the 1991-2020 Long Term Climate Normals104 for Chula Vista, the maximum daily average temperature is 77.1°F which is similar to the ambient temperature used for modeling. 104 U.S Climate Normals. Available at: https://www.ncei.noaa.gov/access/us-climate-normals/#dataset=normalsmonthly&timeframe=30&station=USC00041758.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
38 Off-Site Consequence Analysis Ramboll
Relative Humidity: 50%, which is the EPA RMP Guideline recommendation. From the Long Term Climate Normals,105 the summer months (June to September) are relatively dry, with monthly precipitation ranging from 0.01 to 0.09 inch; the non-summer monthly precipitation ranges from 0.27 to 2.33 inches.106 Sky Condition for Solar Insolation: Partly cloudy, which is the EPA RMP Guideline recommendation.
Temperature Inversion: No ambient temperature inversion for this analysis, which is the ALOHA model default.
Surface Roughness: Urban, which is based on the local surface cover from Google Earth imagery.
The prevailing winds are from west (see the wind rose in Figure 7).
These release and meteorological conditions were organized into four subcases:
1. Worst-Case: 1.5 m/s wind speed, F stability, release height at ground
2. Alternative Case 1: 3 m/s wind speed, D stability, release height at ground
3. Alternative Case 2: 1.5 m/s wind speed, F stability, release height at 9 ft. 1 in.
4. Alternative Case 3: 3 m/s wind speed, D stability, release height at 9 ft. 1 in. 105 Ibid. 106 Ibid.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
39 Off-Site Consequence Analysis Results Ramboll
9. OFF-SITE CONSEQUENCE ANALYSIS RESULTS
The results of the health risk screening impacts and modeling are presented below for the potential 1-hour battery malfunction/fire scenario.
9.1 Screening of Toxic Impacts
The CAPCOA Guidelines were used to estimate potential off-site impacts of a battery failure scenario. Because chronic (i.e., long term exposure) non-carcinogenic total TS is not expected for the type of release resulting from a thermal runaway scenario, only results for acute screening are presented. CAPCOA TS is calculated using hourly release rates (E) of toxic substances (t), REL of the toxic substance (Pt), a receptor proximity adjustment factor (RP), and a normalization factor for acute exposures (1500) as follows:
Non-Carcinogenic Acute TS: = ( )( )(1500)
Release calculations and information related to the speciation and quantity of air toxics released from battery combustion are based on a Tesla Megapack battery (Appendix A). An Emergency Response Guide for the same Tesla Megapack is provided in Appendix B.
Table 11 presents a summary of the TS values for the four thermal runaway scenarios (detailed calculations presented in Appendix C). Because these scores fall below a TS value of 1.0, the Project would be less than significant for a reasonable worst-case or worst-case module failure scenario.
Table 11: CAPCOA Risk Prioritization Results
Scenario CAPCOA Total Score
1a. Failure of seven cells forced into a vent gassing state (i.e., non-flaming) 0.0184
1b. Failure of seven cells forced to thermal runaway with combustion (i.e., flaming) 0.00253
2. Failure of one module consisting of 336 cells forced into a thermal runaway with combustion (i.e., flaming) 0.061
9.2 Modeling Results
The modeling results for the thermal runaway scenarios are presented in Appendix D. The LOC for each flammable/toxic substance are presented in the tables. It should be noted that ALOHA does not account for reactions of the individual substances/chemicals with water or other chemicals.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
40 Off-Site Consequence Analysis Results Ramboll
The modeling results are summarized below:
Reasonable Worst-Case Scenarios
• Scenario 1a: Represents the reasonable worst-case scenario (non-flaming) under worst-case release and meteorological conditions. The ALOHA model predicted that all threat zone distances would be less than 10 m. Figure E1 (Appendix E) presents the projected threat zone extents for Scenario 1a.
• Scenario 1b: Represents the reasonable worst-case scenario (flaming) under worst-case release and meteorological conditions. The ALOHA model predicted that all threat zones would be less than 10 m.
Alternative Case Scenarios
• Scenario 2: Represents the alternative module failure scenario (flaming) under worst-case release and meteorological conditions. The ALOHA model predicted that all the threat zones would be less than 10 m. Figure E2 (Appendix E) presents the projected threat zone extents for Scenario 2.
As shown in the figures presented in Appendix E, the maximum toxic and flammable vapor extents for the reasonable worst-case and alternative case scenarios could encroach less than 5 meters into properties immediately adjacent to the Project’s fenceline. The areas of encroachment appear to be infrequently occupied. Both of these scenarios are highly conservative given that they as based on testing that assumes that all “active” design measures are not functional. As described in Section 6.2, the Tesla MP2XL product includes a number of active design measures which are intended to mitigate the possibility of a thermal runaway condition.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
41 Summary of Impacts and Conclusions Ramboll
10. SUMMARY OF IMPACTS AND CONCLUSIONS
Multiple modeling analyses were performed to understand potential off-site impacts of unplanned (and unlikely) BESS battery failure scenarios as detailed in Section 8. First, an air toxics screening approach was conducted in accordance with San Diego County Air Pollution Control District and CAPCOA guidance. Results from that prioritization analysis indicated that the Reasonable Worst-Case Scenarios and the Alternative Case Scenarios would result in maximum acute impacts for toxic pollutant exposure below the significance threshold of
1.0 TS.
For the OCA, the projected distances for the reasonable worst-case scenarios and the alternative case scenario, which were derived from a fire protection engineering analysis of the Tesla MegaPack 2 XL based on the UL9540A standard, were limited to areas immediately adjacent to the Project fence line with predicted threat zones at <10 m from the perimeter of the land on which the Tesla MP2XL units would be situated. As discussed in Section 8.2, the scenarios presented are considered highly conservative given the UL 9540A data. The facility’s emergency response plan will include signage and alarm systems to ensure any human present at these near-fenceline locations would be provided notification to evacuate in the event of an emergency.
On this basis, the potential impacts for the Project would not pose a public health threat.
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Ramboll
APPENDIX A
EMISSION CALCULATIONS
Table A.1. Scenario 1a Emission Estimate Chula Vista Energy Center 2 Chula Vista, CA Pollutant Name TAC? Flammable? Vol % Volume (Liter) MW (g/mol) Multicell Rate (g/s) Multicell Rate (lb/hr) H2 Hydrogen No Yes 50.148 46.8 2.0 8.19E-03 6.50E-02 CO Carbon Monoxide Yes Yes 10.881 10.2 28.0 2.47E-02 1.96E-01 CO2 Carbon Dioxide No No 27.107 25.3 44.0 9.66E-02 7.67E-01 CH4 Methane No Yes 6.428 6.0 16.0 8.35E-03 6.63E-02 C2H2 Acetylene No Yes 0.264 0.2 26.0 5.57E-04 4.42E-03 C2H4 Ethylene No Yes 3.283 3.1 28.1 7.46E-03 5.92E-02 C2H6 Ethane No Yes 1.1 1.0 30.1 2.68E-03 2.13E-02 C3H6 Propene No Yes 0.379 0.4 42.1 1.29E-03 1.03E-02 C3H8 Propane No Yes 0.125 0.1 44.1 4.46E-04 3.54E-03 C4 Butanes No Yes 0.19 0.2 58.1 8.94E-04 7.10E-03 C5 Pentanes No Yes 0.027 0.0 72.2 1.58E-04 1.25E-03 C6 Hexanes No Yes 0.005 0.0 86.2 3.49E-05 2.77E-04 C6H6 Benzene Yes Yes 0.002 0.0 78.1 1.27E-05 1.00E-04 C7H8 Toluene Yes Yes 0.002 0.0 92.1 1.49E-05 1.18E-04 C3H6O3 Dimethyl Carbonate No Yes 0.055 0.1 90.1 4.01E-04 3.18E-03 C4H8O3 Ethyl Methyl Carbonate No Yes 0.004 0.0 104.1 3.37E-05 2.68E-04 Total -- -- -- 100 93.3 -- 1.52E-01 1.20 Parameters: 93.3 L, volume of gas emitted per cell 7 Total number of cells for worst-case fire, Tesla documentation 60 minutes, time of event Constants: Abbreviations: 60 min/hr atm - atmosphere mol - mole 60 min/s g - gram MW - molecular weight 453.59 g/lb hr - hour s - second 22.40 L/mol at STP K - Kelvin STP - standard temperature and pressure 0.0821 L-atm/mol-K L - liter TAC - toxic air contaminant 273.15 K lb - pound Vol % - percent volume 1.00 atm min - minute Page 1 of 1 Ramboll Table A.2. Scenario 1b Emission Estimate Chula Vista Energy Center 2 Chula Vista, CA Pollutant Name TAC? Flammable? ppm MW (g/mol) Multicell Rate (g/s) Multicell Rate (lb/hr) CO Carbon Monoxide Yes Yes 205 28.0 4.65E-05 3.69E-04 CO2 Carbon Dioxide No No 6721 44.0 2.39E-03 1.90E-02 CH4 Methane No Yes 68.8 16.0 8.93E-06 7.09E-05 C2H2 Acetylene No Yes 17.1 26.0 3.60E-06 2.86E-05 C6H6 Benzene Yes Yes 9.0 78.1 5.69E-06 4.51E-05 H2 Hydrogen No Yes 446 2.0 7.27E-06 5.77E-05 Parameters: 93.3 L, volume of gas emitted per cell 7 Total number of cells for worst-case fire 60 minutes, time of event Constants: Abbreviations: 60 min/hr atm - atmosphere 60 min/s g - gram 453.59 g/lb hr - hour 22.40 L/mol at STP K - Kelvin 0.0821 L-atm/mol-K L - liter 273.15 K lb - pound 1.00 atm min - minute mol - mole MW - molecular weight ppm - parts per million s - second STP - standard temperature and pressure TAC - toxic air contaminant Page 1 of 1 Ramboll Table A.3. Scenario 2 Emission Estimate Chula Vista Energy Center 2 Chula Vista, CA Pollutant Name TAC? Flammable? ppm MW (g/mol) Multicell Rate (g/s) Multicell Rate (lb/hr) CO Carbon monoxide Yes Yes 205 28.0 1.11E-03 8.85E-03 CO2 Carbon Dioxide No No 6721 44.0 5.74E-02 4.56E-01 CH4 Methane No Yes 68.8 16.0 2.14E-04 1.70E-03 C2H2 Acetylene No Yes 17.1 26.0 8.64E-05 6.86E-04 C6H6 Benzene Yes Yes 9.0 78.1 1.36E-04 1.08E-03 H2 Hydrogen No Yes 446 2.0 1.75E-04 1.39E-03 Parameters: 93.3 L, volume of gas emitted per cell 336 Total number of cells for worst-case fire (one module) 120 minutes, time of event Constants: Abbreviations: 60 min/hr atm - atmosphere 60 min/s g - gram 453.59 g/lb hr - hour 22.40 L/mol at STP K - Kelvin 0.0821 L-atm/mol-K L - liter 273.15 K lb - pound 1.00 atm min - minute mol - mole MW - molecular weight ppm - parts per million s - second STP - standard temperature and pressure TAC - toxic air contaminant Page 1 of 1 Ramboll Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Ramboll
APPENDIX B
BATTERY EMERGENCY RESPONSE GUIDE
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Ramboll
APPENDIX C
PRIORITIZATION SCORE CALCULATIONS
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Ramboll
APPENDIX D
MODELING RESULTS
Table D.1. ALOHA Modeling Results for Scenario 1a. Failure of 7 Cells Forced into a Vent Gassing State (i.e., non-flaming) Chula Vista Energy Center 2 Chula Vista, CA Worst Case (1.5 m/s wind speed F stability Release Height at Ground) Alternative Case 1 (3 m/s wind speed D stability Release Height at Ground) Alternative Case 2 (1.5 m/s wind speed F Stability Release Height at 9 ft 1 in) Alternative Case 3 (3.0 m/s wind speed D Stability Release Height at 9 ft 1 in) 60% of LEL: 24000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 4000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-3 (60 min): 330 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-2 (60 min): 83 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-1 (60 min): n/a n/a n/a n/a n/a 60% of LEL: 75000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 12500 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded Carbon Dioxide 7.67E-01 toxic IDLH: 40000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 30000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 5000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 15000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 2500 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 16200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 2700 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 18000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 3000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 12900 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 2150 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 12600 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 2100 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 9600 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 1600 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 8400 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 1400 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 7200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 1200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-3 (60 min): 4000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-2 (60 min): 800 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-1 (60 min): 52 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 7200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 1200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-3 (60 min): 3700 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-2 (60 min): 560 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-1 (60 min): 67 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 6600 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 1100 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 18600 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 3100 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded Notes: AEGL - Acute Exposure Guideline Levels in - inch min - minute ALOHA - Areal Locations of Hazardous Atmospheres lb/hr - pound per hour n/a - not applicable ft - feet LEL - lower explosive limit ppm - parts per million IDLH - Immediately dangerous to life and health m - meter s - second Threat Zone Distance Predicted by ALOHA (meter) Release Substances Release Rate (lb/hr) Potential Hazard Level of Concern (LOC) Hydrogen 6.50E-02 flammable Carbon Monoxide 1.96E-01 toxic flammable Methane 6.63E-02 flammable Acetylene (C2H2) 4.42E-03 flammable Ethylene (C2H4) 5.92E-02 flammable Ethane (C2H6) 2.13E-02 flammable Propylene (C3H6) 1.03E-02 flammable Propane (C3H8) 3.54E-03 flammable Butane (C4H10) 7.10E-03 flammable Pentane (C5H12) 1.25E-03 flammable Hexane (C6H14) 2.77E-04 flammable Benzene (C6H6) 1.00E-04 toxic flammable flammable Toluene (C7H8) 1.18E-04 Dimethyl Carbonate (C3H6O3) 3.18E-03 flammable toxic Page 1 of 1 Ramboll Table D.2. ALOHA Modeling Results for Scenario 1b. Failure of 7 Cells Forced into a Thermal Runaway with Combustion (i.e., flaming) Chula Vista Energy Center 2 Chula Vista, CA Worst Case (1.5 m/s wind speed F stability Release Height at Ground) Alternative Case 1 (3 m/s wind speed D stability Release Height at Ground) Alternative Case 2 (1.5 m/s wind speed F Stability Release Height at 9 ft 1 in) Alternative Case 3 (3.0 m/s wind speed D Stability Release Height at 9 ft 1 in) 60% of LEL: 24000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 4000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-3 (60 min): 330 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-2 (60 min): 83 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-1 (60 min): n/a n/a n/a n/a n/a 60% of LEL: 75000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 12500 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded Carbon Dioxide 1.90E-02 toxic IDLH: 40000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 30000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 5000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 15000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 2500 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-3 (60 min): 4000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-2 (60 min): 800 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-1 (60 min): 52 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 7200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 1200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded Notes: AEGL - Acute Exposure Guideline Levels ALOHA - Areal Locations of Hazardous Atmospheres ft - feet IDLH - Immediately dangerous to life and health in - inch lb/hr - pound per hour LEL - lower explosive limit m - meter min - minute n/a - not applicable ppm - parts per million s - second Threat Zone Distance Predicted by ALOHA (meter) Release Substances Release Rate (lb/hr) Potential Hazard Level of Concern (LOC) Hydrogen 5.77E-05 flammable Carbon Monoxide 3.69E-04 toxic flammable Methane 7.09E-05 flammable Acetylene (C2H2) 2.86E-05 flammable Benzene (C6H6) 4.51E-05 toxic flammable Page 1 of 1 Ramboll Table D.3. ALOHA Modeling Results for Scenario 2. Failure of 1 Module Consisting of 336 Cells Forced into a Thermal Runaway with Combustion (i.e.,flaming) Chula Vista Energy Center 2 Chula Vista, CA Worst Case (1.5 m/s wind speed F stability Release Height at Ground) Alternative Case 1 (3 m/s wind speed D stability Release Height at Ground) Alternative Case 2 (1.5 m/s wind speed F Stability Release Height at 9 ft 1 in) Alternative Case 3 (3.0 m/s wind speed D Stability Release Height at 9 ft 1 in) 60% of LEL: 24000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 4000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-3 (60 min): 330 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-2 (60 min): 83 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-1 (60 min): n/a n/a n/a n/a n/a 60% of LEL: 75000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 12500 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded Carbon Dioxide 4.56E-01 toxic IDLH: 40000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 30000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 5000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 15000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 2500 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-3 (60 min): 4000 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-2 (60 min): 800 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded AEGL-1 (60 min): 52 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 60% of LEL: 7200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded 10% of LEL: 1200 ppm < 10 m < 10 m LOC is not exceeded LOC is not exceeded Notes: AEGL - Acute Exposure Guideline Levels ALOHA - Areal Locations of Hazardous Atmospheres ft - feet IDLH - Immediately dangerous to life and health in - inch lb/hr - pound per hour LEL - lower explosive limit m - meter min - minute n/a - not applicable ppm - parts per million s - second Threat Zone Distance Predicted by ALOHA (meter) Release substances Release Rate (lb/hr) Potential Hazard Level of Concern (LOC) Hydrogen 1.39E-03 flammable Carbon Monoxide 8.85E-03 toxic flammable Methane 1.70E-03 flammable Acetylene (C2H2) 6.86E-04 flammable Benzene (C6H6) 1.08E-03 toxic flammable Page 1 of 1 Ramboll Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Ramboll
APPENDIX E
TOXIC AND FLAMMABLE VAPOR EXTENTS
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
APPENDIX F
MODEL OUTPUT FILES
Ramboll
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Ramboll
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Ramboll
Hazards Analysis
Chula Vista Energy Center 2
Chula Vista, California
Ramboll