Safety of Grid Scale Lithium-ion Battery Energy Storage Systems

Page | 032

– 31 – June 5, 2021
• Environmental impact should include the prevention of ground contamination, water course pollution, and the release of toxic gases.
Preventing the release of toxic gases is all but impossible. A thermal runaway event WILL release toxic gases. If inflammables are vented to avoid /mitigate explosion risk, toxic gases WILL be vented. Ground contamination and water course pollution is almost certain to occur if sufficient water to control a major thermal runaway event is deployed. It will pose a significant challenge to contain, and safely dispose of, such large volumes of contaminated fire water.
The BESS facilities should be designed to provide:
• Automatic fire detection and suppression systems. Various types of suppression systems are available, but the Service’s preferred system would be a water drenching system as fires involving Lithium-ion batteries have the potential for thermal runaway.
This is a correct precaution, but no specification is made of likely water volume requirements, nor for a “dry pipe” system allowing water to be deployed without cabin entry. We provide some water estimates elsewhere in this paper.
Other systems, such as inert gas, would be less effective in preventing reignition.
This is also a correct insight. The so-called “clean-agent” fire suppression system at McMicken was triggered correctly, but was useless to control thermal runaway. Moreover the stratified atmosphere created allowed the build-up of inflammables to a dangerous level, before the explosion occurred.
• Redundancy in the design to provide multiple layers of protection.
• Design measures to contain and restrict the spread of fire through the use of fire-resistant materials,
and adequate separation between elements of the BESS.
This comment only vaguely considers the true essentials. The “elements of the BESS” could be: cells, modules, racks, strings, and the entire system. As discussed in the Hill/DNV report what is required is for the industry as a whole to accept that thermal runaway in an unacceptable hazard, and demand engineering standards that Prevent thermal runaway by design, or if it occurs, Prevent its cascade or escalation to larger system elements. This requires
a. Thermal barriers (i.e. Low thermal conductivity barriers, not merely refractory barriers, ideally with water cooling, between all cells, so that propagation from cell to cell cannot occur. This is precisely the requirement the industry has so far NOT made in the development of its engineering standards.
b. Separation of modules by similar barriers to Prevent module-to-module cascade.
c. Separation of Racks to prevent rack-to-rack cascade, even with ejection of molten metals.
d. Spacing of BESS cabins such that even with “75 foot flame lengths” cabin to cabin escalation
is impossible. This is probably the most critical of all, since cabin-to-cabin escalation could turn a major fire incident into an unprecedented catastrophe, on the scale of the Beirut explosion or a small nuclear weapon.
• Provide adequate thermal barriers between switch gear and batteries,
• Install adequate ventilation or an air conditioning system to control the temperature. Ventilation is
important since batteries will continue to generate flammable gas as long as they are hot. Also, carbon monoxide will be generated until the batteries are completely cooled through to their core.
This comment is very strange. There is no possibility whatsoever that air conditioning could be adequate “to control the temperature”. The importance of ventilation is however recognised, as is