Solar power tower

A solar power tower, also known as 'central tower' power plant or 'heliostat' power plant, is a type of solar furnace using a tower to receive focused sunlight. It uses an array of flat, movable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the target). Concentrating Solar Power (CSP) systems are seen as one viable solution for renewable, pollution-free energy. Early designs used these focused rays to heat water and used the resulting steam to power a turbine. Newer designs using liquid sodium have been demonstrated, and systems using molten salts (40% potassium nitrate, 60% sodium nitrate) as the working fluids are now in operation. These working fluids have high heat capacity, which can be used to store the energy before using it to boil water to drive turbines. These designs also allow power to be generated when the sun is not shining. In 2021, the US National Renewable Energy Laboratory (NREL) estimated the cost of electricity from concentrated solar with 10 hours of storage at $0.076 per kWh in 2021,$0.056 per kWh in 2030, and $0.052 per kWh in 2050. In 2007, companies such as ESolar (then backed by Google.org) were developing cheap, low maintenance, mass producible heliostat components that were to reduce costs in the near future. ESolar's design used large numbers of small mirrors (1.14 m2), to reduce costs for installing mounting systems such as concrete, steel, drilling, and cranes. In October 2017, an article in GreenTech Media suggested that eSolar ceased business in late 2016. Improvements in working fluid systems, such as moving from current two tank (hot/cold) designs to single tank thermocline systems with quartzite thermal fillers and oxygen blankets will improve material efficiency and reduce costs further.