The world’s biggest battery energy storage system (BESS) under development is now a 12.5 GWh portfolio to be built in Saudi Arabia, using BYD products. If the batteries are supplied at (say) a little under $100 per kWh, then that is a $1 billion dollar deal, with the total project (using cheap labour from the subcontinent, on cheaply available land) will likely come to a capex of at most $3 billion, and will help firm the output of, say, 6 GW of solar capacity, representing another $4 billion investment or so (in September, a 5.5 GW solar portfolio in the country obtained funding to cover $3.2 billion capex). Saudi Arabia has had issues meeting its targets or delivering on promised…