Safety of Grid Scale Lithium-ion Battery Energy Storage Systems

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– 17 – June 5, 2021
6. Applicability of the COMAH (Control of Major Accident Hazard) Regulations 2015 The governing criteria for application of the COMAH Regulations [17] are:
1. The presence of hazardous materials, or their generation, “if control of the process is lost.” 2. The quantity of such hazardous materials present or that could be potentially generated.
There is no doubt that hazardous substances such Hydrogen Fluoride (an Acute Toxic controlled
by COMAH) would be generated in a BESS accident (i.e., in “battery fires”). Similarly highly
Inflammable Gases (also controlled by COMAH) would be evolved even if the atmosphere remained
oxygen-free. Depending on the size of the “establishment” these could be produced in sufficient
quantities to be in the scope of COMAH. In Appendix 2 we estimate quantities guided by the
literature, where fire tests have directly measured evolution of the hazardous gases.
For small capacity BESS installations, under 25 MWh capacity, the quantities (“inventory”) of the evolved hazardous substances might be outside COMAH. This paper however addresses the recent trend towards “mega-scale” Li-ion BESS (Table 2) with very large quantities of stored energy, where the inventory should be large enough to bring the installation within scope.
Broadly speaking, the threshold for applicability of COMAH will be dependent on the precise BESS technology chosen, but likely to be for BESS in the region of 20 – 50 MWh. See Appendix 2.
A letter to the HSE regarding applicability of COMAH to large-scale BESS (dated 25 Nov 2020 [18]) received no reply until follow-up letters were sent addressed personally to the Chief Executive on 7 February 2021, with the intervention of Mrs Lucy Frazer MP. The reply from the Chief Executive [19] dated 22 February 2021 stated that “Li-ion batteries are considered articles and are not in scope of COMAH”.
We believe the current attitude of the HSE – that even large-scale Li-ion BESS are “articles” best regulated by operators – is not consistent with the law.
Unless tested in the Courts however, this throws the entire responsibility for ensuring the safety of major BESS “battery fires” onto the Fire and Rescue Services. Currently the HSE makes no representation to the Planning Inspectorate in respect of BESS hazards.