Solar thermal energy is the process of concentrating the sun's light to create heat, which is then used to generate electricity. It is also known as concentrating solar power (CSP) as to not confuse it with solar energy (PV)
How does it work?
Solar thermal energy captures the sun's light in a similar way as solar photovoltaic cells (solar energy) does. However, it concentrates the energy and is used to generate heat. There are two parts of the solar thermal power systems that are used to do this. The first one, the reflector, a mirror, that captures and focuses sunlight onto the next part, which is the receiver. The receiver had a fluid going through it that the sunlight heats up, turning it to steam. The rest is almost exactly the same as geothermal energy: the steam turns a turbine and the turbine spins a generator, which converts mechanical energy into electric energy.
While this is how we generate solar thermal energy, there are different methods as to how the reflector part focuses energy onto the receiver. The parabolic trough system has a long u-shaped parabolical reflector that focuses the sun's rays on a receiver pipe located at the center of the curve. The collector tilts with the sun to keep sunlight focused on the receiver as the sun moves from east to west during the day. This means that a parabolical system can concentrate the sun's energy to 100 times its normal intensity because of its shape.
Linear Fresnel reflectors are a type of system where the receivers are located just above the reflectors. They use the focal lens effect, which allows the systems to have concentrate the sun's energy 30 times its normal intensity. Multiple receivers in the single panel make it less able to block the sunlight from adjacent panels. This also reduced material cost.
Central receivers are where there is a large field of flat reflectors called heliostats. All of them concentrate sunlight onto a single receiver at the top of a tower. This allows the system to concentrate the sun's energy to as much as 1,500 times its normal intensity.
Finally, the dish/engine systems use a mirrored dish very similar to a large satellite dish. The dish is covered in reflectors that concentrate the sun's power onto a receiver that is pushed out in front of the reflectors. These systems always point directly at the sun, heating the working fluid to as much as 1,380ºF.
How is this renewable energy?
This is renewable energy for a different reason than geothermal energy. Geothermal power plants put the water back into the Earth, making it renewable. However, the sun is a giant generator: it has nuclear fusion in its core so that it will always produce more energy. This is why solar thermal energy is renewable; the sun will always be producing more sunlight. Therefore, we are fine by using what is thrust upon the Earth. This is the exact same reason with solar PV cells.
The Presence of Solar Thermal Energy In America and the Rest of the World
Solar thermal energy is still in its infancy in the world. There are only 18,550,800 mWh in production in the entire world. To put that in perspective, the world consumes 168,516 tWh (2017 data: 2018 data is not currently out), or terawatt hours (1 terawatt-hour is equal to 1 million megawatt hours). This is only 0.03% of all global energy production.
The Negative Impacts of Solar Thermal Power Plants on the Environment
While they combat climate change, solar thermal power plants have a few environmental drawbacks that we will discuss here. One is land use. Solar thermal technologies use land, which can lead to habitat loss. However, other than that, there are no other significant negative environmental impacts.
How is this renewable energy?
This is renewable energy because the sun will never stop supplying energy. This is the exact same reason that solar PV is renewable.
Solar photovoltaic energy (PV) is actually quite different from this type of solar energy.