Most of the world’s electricity comes from turbines driven by steam. The heat for that steam comes from coal, gas or nuclear power and in some places solar thermal. Solar thermal power stations can replace coal and nuclear simply by using the sun’s heat, and can continue to use the turbines and infrastructure which exist already.
As the sun shines most days in the hot areas chosen to build the power stations the ‘fuel’ needed to run the stations is delivered free of charge by the sun, and without the digging, extraction, refining, transport, health or safety risks of coal, gas or nuclear.