Which country built the first large-scale solar thermal power station, Solar One?

The United States built the first large-scale solar thermal power station, Solar One.

Solar One was constructed in California's Mojave Desert near Barstow and began operating in 1982. It used hundreds of heliostats, computer-controlled mirrors that reflected sunlight onto a receiver at the top of a central tower. The receiver heated a fluid, which was used to produce steam and drive a turbine.

The project was a pioneering demonstration of central-receiver solar thermal technology. It was later upgraded as Solar Two, which tested molten salt for thermal storage and heat transfer. That upgrade allowed the plant to demonstrate generation after sunlight hours more effectively.

Solar One was not a photovoltaic plant: photovoltaic panels convert light directly into electricity, while solar thermal plants first collect heat. The facility was eventually dismantled, but its design influenced later concentrating solar power projects.