A recent tweet celebrated the supposed fact that at peak, recently, Germany derived 25% of its power from solar. The source given was data published by the Fraunhofer ISE at https://www.energy-charts.de/power_de.htm. But is the claim true?
no. The highest proportion in recent weeks was reached during August
2nd when a combination of low demand, low winds and strong sun produced
about 56% of Germany's electric power from solar pv. A
very good result - though obviously excluding fuels used for space
heating, travel, etc.
But it's a power number - a
measurement over a short time - specifically the middle of the day.
There is no solar power at night and not much in the early morning and
evening. A bit of rough analysis for a more representative day, 27 July
in fact, shows that solar produced 22% of the power at peak but 10% of
the day's energy. Extra investment in solar PV could increase the peak
as much as you like - even to 100% - but that would still need over 50%
of the energy to come from somewhere else (possibly wind or a storage
And this is mid summer.
A similar analysis for
January shows a solar PV power peak of c8% but providing only c2% of the
day's electricity. And the average over that week is much worse.
wind the answer? Sort of. Germany gets more energy from wind than from
solar PV and it's available at night and in winter. But it's even less
predictable than solar. At midnight on January 5th it provided just 3%
of the needed electrical power.
Moreover periods of low wind can last for days - there was almost no wind for the whole seven days starting January 17th.
are partial low-carbon solutions - nuclear, tidal, hydro, import of
power from very large new solar farms in north Africa and various kinds
of storage - but they all have their own problems.
Any responsible plan for our energy future must show how it would cope with periods like 17 to 14 January - and at what cost.