Most people think of solar energy generation in terms of the photovoltaic solar collectors they see on roofs and in back yards around town. Sunlight hits big dark rectangular shiny things and somehow powers the swimming pool heater and appliances inside the house.
All solar power technology works by collecting energy from the Sun. Since heat is energy, it is actually the heat from the sunlight that is being collected. The more heat collected, the more power generated.
Solar utility companies must generate a lot of power, so they concentrate the sunlight to produce greater heat. The heat is then stored so it can be used to generate the electricity at night and during stormy weather.
The latest solar power technology is Concentrating Solar Power (CSP). It was originally developed in the late 1980’s by Luz Industries. CSP systems collect solar energy and concentrate it through transfer to a single collection point. Several different procedures for this have emerged.
The current leading technology employs thousands of giant reflective mirrors with tracking systems to concentrate a large area of sunlight onto a centralized absorber tower. Because hundreds of acres of land are required for the mirrors and tower installation, and need for strong and reliable sunlight, most of these solar power plants are in desert regions.
Currently, concentrated sunlight is absorbed through a heat transfer fluid, typically water or molten salts. The transfer fluid must be capable of retaining high thermal temperatures between 800 F and 1300 F - molten salts are particularly effective in this capacity. The downside is molten salts can be highly explosive – on the scale of a nuclear bomb.
Thermal storage tanks must store thermal energy for several hours until it is transferred from storage tanks and used to create superheated steam to power steam turbines, which produce the electricity that is sent out via power lines to commercial and residential users.
A major advantage of CSP over other renewable technologies is its two-part system: first being the collection of thermal energy, and the second being the ability to store the collected solar heat/energy in a heat transfer fluid, allowing its energy to be used when needed rather than when generated.
New ways of collecting, concentrating and storing the Sun’s energy are being developed every day. Current systems use mirrors to reflect light to a tall collection tower, but breakthrough technologies are being developed to collect and concentrate the sunlight in place and transfer the thermal energy via pipeline to storage tanks. Storage technology is also changing in favour of less volatile storage mediums than molten salts.
Photovoltaic and wind energy generation installations which directly generate electricity rather than store thermal energy for later electricity generation, are affected by weather conditions making them unreliable sources of energy during certain seasons. On the other hand, CSP technology can store and produce electricity in response to demand rather than as a result of the weather conditions. This is why CSP is considered the most promising technology for alternative energy generation.