California battery storage is greening the grid

 A fascinating chart from Brian Bartholomew

Explanation of the chart:

The black line ("emissions intensity") shows how many tonnes of CO2 are emitted for each MWh of production during the course of the day.  Notice how it drops during daylight hours because of solar.

The blue bar chart shows battery charging and discharging.  The batteries charge up during the solar surplus, i.e., while emissions intensity is low, and discharge during peak demand, from 4 to 9 p.m.  There is some charging during the night, when emissions intensity is high, but much less than during the day, when it is low.

The implication is that, even if there is still coal/gas in the grid, the mixture of solar and batteries will still reduce emissions.  In fact, it will allow coal power stations to continue to operate while we move to 100% renewables, because they won't have to throttle output down during the solar peak as batteries will be taking any solar surplus up.  At the same time, emissions intensity will be reduced.  The goal must be to progressively reduce emissions intensity to zero.  And expanding solar plus battery storage will do that.