Solar power comes from the most abundant energy source available, the sun. It requires no combustion, is non-polluting and emits no greenhouse gasses. In addition, solar is unique in its versatility as a power source. From small solar panels that can power individual devices to rooftop solar systems for houses and businesses to small community solar "gardens" to large commercial scale solar power plants, solar has become a significant component of the US and world's energy mix, and will continue to increase as society transitions away from fossil fuels.
The largest challenges to solar power have been efficiency, capacity factor, cost, and the fact that the electricity generated is not dispatchable, i.e., not necessarily available when needed by the grid. On the hardware side, the photovoltaic components that are used in most solar installations are relatively inefficient in their ability to convert solar energy to electricity, with
typical solar panel efficiencies in the 17-20% range as compared to
wind turbines in the 40-50% range, and
conventional fossil fuel power plants in the 35-45% range. On the operational side, being dependent on the sun, solar power can only be generated during daylight hours and varies with weather and cloud cover. Thus, solar installations only function at peak capacity for a fraction of the year, as compared to fossil fuel plants which can operate at capacity nearly continuously. Per the US EIA (Energy Information Administration) in 2020 typical
system capacity factors (yearly total production divided by yearly production capacity) are 10-30% for solar panel systems, compared to wind turbines at 30-40%, and fossil fuel plants at 80-100%. Given these efficiency and capacity factor limitations, solar facilities require very large areas for solar panels. On the positive side, due to technology and manufacturing advances, solar panels have dropped significantly in price, and solar power installations are competitive with other sources of electricity in many locations.
Other technology developements should also help address issues around dispatchabiliy. New technology in the form of molten salt as a heating medium for Concentrated Solar Power (CSP) plants (See OWOE:
How can a solar power plant generate electricity at night?) has now been deployed in a utility scale plant, the Crescent Dunes Solar Plant near Tonopah, Nevada. Concentrated solar energy in the form of heat raises the temperature of the liquid salt which can be either used immediately to generate steam or stored for later use. This allows the utility to generate on-demand, reliable electricity even after dark. And the next wave of storage technology in the form of low cost battery systems or pumped hydroelectric systems (See OWOE:
What is pumped hydroelectric storage?) that allow electricity that is generated when the sun is shining to be saved and then transmitted or used when needed, is starting to gain traction in the industry.
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