Tuesday, September 19, 2017

48% of electricity from rooftop solar

In the chart below, the blue area shows net demand from the South Australian grid on the 17th of September 2017 after output from rooftop solar.  The yellow shows output from rooftop solar.  The black line shows the wholesale price of electricity.  The downward spike between 5 a.m. and 6 a.m. is because there was trouble with SA's interconnector with Victoria.  In fact the wholesale price went negative (-$44/MWh) because there were strong winds and nowhere to ship the power.  (A perfect opportunity for batteries, you'd think.)  The peak in demand at 1 a.m. is because everybody's geysers (hot water cylinders) are timed to go on, a relic of the days when electricity was produced by coal power stations and all that excess supply from invariable baseload had to be soaked up when demand was low between midnight and 5 a.m.

This is a record for SA, and it happened in spring.  It's a couple of months from midsummer. Rooftop supply will be much larger in December, but so will demand because of aircon.   Ultimately, a big percentage of daylight demand for places between latitudes 35 or 40 north and south of the equator will be satisfied by rooftop solar.  And we will rely on wind, CSP and batteries to provide power at night.

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