Renewables 73% in California

From PV magazine:

California blew through a series of peak solar and renewable energy generation records last week, showing not only the increasing potential of the state to run on renewable energy, but also the work remaining to be done.

According to the California Independent System Operator (ISO), utility-scale solar generation reached 10,521 MW on Thursday April 26, as the first time it had surpassed 10.5 GW. On Saturday it peaked again 10,539 MW at 1:40 PM local time, a new record for the state.

California also hit a new record for the instantaneous portion of demand met by renewable energy on Saturday at 73%, just 15 minutes before the solar record, with solar and wind alone meeting 64% of demand.

What is even more remarkable is that this does not even count all of the solar. California had an estimated 6.6 GW of behind-the-meter solar as of the end of January 2018, which is not reflected in California ISO output data.

Over the full year 2017 renewable energy sources excluding large hydro plants represented 31% of California’s in-state electricity generation. With hydroelectric generation included, the total was more than half of all generation. However, the state also imports large volumes of electricity.

[Read more here]

Of course, this is just for one day.  How can we scale up renewables to reach 100% all the time? 

In that regard, I found this chart most interesting.  The green area shows total renewables electricity production (excluding hydro), the brown nuclear, the light blue gas, the dark blue imports from out of state and purple hydro.  Now note how there is a bulge in renewables production starting at 7 am and ending at 8 pm though maximum output is between 9 and 6.  Of course, this is because of solar.  But, since this excludes rooftop solar which only shows up in the reduction of net demand over the middle of the day, you get no disclosed midday peak in demand  (as you used to have before widespread rooftop solar) but instead a peak between 9 and 10 pm.  The famous peaking duck curve.  Note also that even in the hours of darkness there is still electricity from renewables, from wind and biomass.


So  to stop imports and to stop the need for gas peaking it will be necessary to at least double the output of renewables.  This would mean that much more renewable electricity is produced than net demand  between 10 a.m. and 4 p.m., and this surplus be stored to meet demand over the rest of the day when renewables output is less than demand.  On my reading of the chart that would equal 10 hours of storage of about 1/3rd of demand, or storage equal to 3 or 4 hours of average hourly demand.  Or you could have a mixture of more storage plus overcapacity in renewables, and curtail renewables output when too much is being produced for the sum of current demand and battery charging. 

So yeah, it's good to reach 73% renewables.  But you'll know that California is on the way to 100% continuous renewables penetration when that number reaches 140%.  You do have to give California credit for showing the way.  Remember that if California were a separate country, it would have the world's 6th or 7th largest economy.  And it's moving fast not only to 100% green electricity generation but also to 100% green transport.  Time for the rest of the world to follow suit.