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Could solar energy power the entire electric grid even though the sun is only up, in any given place, an average of 12 hours a day?

Yes. It would be expensive to build solar power plants across every time zone, and interconnect them so that the sun would always be up somewhere over the electric grid, but it could, theoretically, be done.

Projects that seem like that type of science fiction are being developed. Companies in the United Kingdom and Morocco are working on a system that will export electricity generated by a combination of solar and wind power from the Moroccan desert to Great Britain via a 2,400 mile undersea cable. When complete, it is expected to provide more than 7% of the UK’s electricity. Similar projects are being developed to deliver Egyptian renewable power to the European grid through Greece, and from Tunisia to Italy.

Solar mega-projects are not the only electric technology that is being used in the transition from fossil to renewable energy. Other renewable-fuel generators are also very important.

The improved costs of wind power are comparable to the improved costs of solar power over the last 30 years; both have fallen by more than 90% and are still falling. Wind is viable in many locations on its own. As in the Moroccan project, wind turbines can improve the overall results from solar power projects when they can be built in the same location and connected to the same transmission infrastructure. Wind tends to generate more power at night than it does during the day, and tall wind turbines can easily coexist with lower solar panels.

Geothermal electric generation uses heat from very deep underground – the same heat that powers volcanoes – to boil water and provide steam to turn generation turbines. This was first done commercially in California in the 1950s. The equipment downstream of the boiling water is essentially identical to the equipment used in plants that burn coal or gas to boil water. The infrastructure required is some of the smallest in the industry, producing up to 30 times as much energy per acre of disturbed land as solar power.

Geothermal generation requires very hot rocks that large volumes of water can move through, so it can only be developed in locations with the right geology. However, in those places, it’s very inexpensive and reliable, and can produce power 24 hours a day. Geothermal energy can be developed near Mt. Baker and Mt. St. Helens, but Washington has so much well-established hydroelectric power that geothermal development has not been a priority. Work is being done to improve geothermal systems. A relatively recent innovation is using a fluid that boils at a lower temperature than water, so that less heat is required to boil the working fluid and turn the turbine.

Hydroelectric power is even more well-established. Washington’s hydroelectric systems provide our state with a significant advantage in grid management: the ability to pump water back above the dam when inexpensive power is available for later dispatch when maximum generation is required. Add efficient, dispatchable energy storage, efficient end-use technologies like LED lighting and modern grid management systems and solar energy does not have to be available 24 hours a day for a fully renewable grid.