The Truth about Battery storage (BESS) by Bill Fraser

Battery Energy Storage Systems (BESS) applications often suggest that the applicant is either technically incompetent, or doesn’t want you to know how big the proposed BESS will be. Giving the size of a BESS in megawatts (MW) is nonsensical. MW is a measurement of the rate at which electricity can flow into or out of the BESS. (Like the size of the pipe connected to a water tank). It tells you nothing about the SIZE of the BESS. (The size of the water tank). For the size of a BESS, you need to know the number of hours for which the BESS will be able to produce electricity at the quoted rate. This is measured in megawatt-hours (MWh). A few other facts may be useful. One hazard associated with BESS is the potential for “Thermal Runaway” (TR). This occurs when an internal failure results in a chemical interaction commencing inside the battery. Unlike a fire, it does not require a supply of oxygen to continue. It therefore cannot be extinguished using existing firefighting techniques, which all work by seeking to deprive a fire of oxygen. The only emergency response currently available in the event of TR is to try to cool it using copious amounts of water to stop it spreading. The smoke and fumes given off during TR, and the run-off from the cooling water are both extremely toxic. The TR will continue until the chemical interaction between the materials inside the battery is complete, which may take several days. Spontaneous re-combustion can occur for a significant time after it seems to have gone out, It’s useful to have an idea of how big the conflagration resulting from a BESS TR could be. In energy terms, 40KWh of electricity is equivalent to around 2-1/2 gallons of petrol. So TR in a BESS would be the equivalent of setting fire to around10 tons (!) of petrol for every 100MWh of the BESS’s size! (Except, of course, you can extinguish 10 tons of petrol, but you can’t extinguish a TR). So you want to be pretty careful where you go putting BESS’s!!!