What types of solar power systems are being used today?

Solar power is the most flexible energy source available, with applications from small solar panels that can power individual devices, to rooftop solar systems for houses and businesses, to small community solar "gardens", and to large commercial scale solar power plants that can generate hundreds of megawatts of electricity. Photovoltaic (PV) systems are the most versatile (see OWOE: How do photovoltaic cells work to generate electricity?), and are the preferred options for all small to medium systems and, in fact, are used in the largest utility scale plants currently in service. PV panels can be fixed (Figure 1), typically facing south for maximum solar exposure, or mounted on mechanisms that allow them to track the sun (Figure 2). Such systems are more efficient, and can increase energy output by 25-30%, although more costly. A concentrator PV system is even more complicated, with a lense mechanism that focuses the energy onto the PV cells, but more efficient. Regardless of type of PV panel, a large solar farm requires many panels and a significant amount of land. See OWOE: How much land does a solar power plant require?.Figure 3 shows a view from space of a farm consisting of 4 million panels.

Global solar capacity was at one terawatt (TW) at the end of 2022, a tenfold increase from the 100 gigawatts (GW) of solar capacity in 2012. The Golmud Solar Park in China is the world's largest solar farm with an installed solar capacity of 2.8 GW generated from nearly seven million solar panels and plans for expansion to reach 16 GW within the next five to six years. The largest solar power plant in the the United States, Solar Star, located near Rosamond, California, has a capacity of 579 MW. It utilizes approximately 1.7 million high efficiency arrays that are mounted on single axis trackers. Although it is currently only the 15th largest utility solar farm in the world, it is one of the most efficient in terms of capacity per area.

Alternatively, solar thermal power systems, also called concentrating solar power (CSP) systems, utilize mirrors to focus the sun's energy onto a receiver where a fluid is heated and used to drive a generator. Originally water was used to produce steam, but modern CSP systems now utilize molton salt as the fluid. It can be used to boil water and generate electricity immediately, or it can be stored for later use, which allows the system to continue to generate electricity during cloudy weather or at night. The Noor Quarzazate power station in Morocco is the largest CSP plant in the world with a total of 510 MW capacity. It has the ability to store up to 8 hours of electricity. The largest CSP plant in the US, and second largest in the world, is the Ivanpah Solar Electric Generating System with 392 MW capacity, bu which uses water as the fluid and, therefore, has no storage capability . (See Figure 4.) See also OWOE: How do solar thermal power plants generate electricity?

At the other end of the spectrum of solar power systems, hundreds of thousands of people power their homes and businesses with individual solar PV systems. In the US, at the end of 2022, the combination of residential and commercial rooftop solar installations had a capacity of approximately 48 GW, and the EIA estimated that approximately 3.7% of all single-family homes in the US had a rooftop solar system. See OWOE: What are home solar systems?.

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