There are several CSP or concentrating solar power technologies. Usually CSP refers to large solar thermal electricity producing plants. Merely because with the thermal nature of this unique type of solar plant, the particular heat energy can be saved a lot more conveniently than electrical energy, increasing the ability to dispatch energy as well as minimizing abrupt fluctuations in output with regards to grid operators.
Central receiver is the CSP concept when a good-sized area of sun-tracking heliostats can be used to redirect and concentrate sunlight onto a tower positioned single receiver. The actual heat transfer liquid in the tower system is either water/steam or even nitrate salt, plus the latter typically features storage containers.
A majority of these nitrate salts normally consist of 60% NaNO3 and 40% KNO3 and also have extremely high freezing temperatures, well over 250 degrees Fahrenheit that could be maintained using natural gas boilers along with strategic heating conduits along with the piping pathways. In case the temperatures fall below the limit, the salts freeze solid within the pipes as well as tanks, which will make restarting the system rather challenging.
One good thing about tower technologies would be that the distances between the heat collection and the extraction, tend to be very short, on the order of hundreds of meters as well as maintaining greater temperatures is more controllable. This storage process can be built to meet the needs of the utility grid and 3-16 hours of full generator load are realistic.
Parabolic trough techniques make use of a field of linear parabolic collectors spread out horizontally, as opposed to vertically, over hundreds of acres in order to focus sunshine onto long tube receivers. The heat transfer solution is normally synthetic oil, which has a freezing point of nearly 55 degrees Fahrenheit. However that is a more reasonable minimum temperature to keep within the system across several kilometers of piping.
Natural gas boilers retain a minimal temperature and keep the particular field circulating throughout the night or over cast days. Across the complete system there exists a substantial amount of heat transfer fluid inside the piping, and this technology provides approximately 30 minutes of inherent storage within a basic design. However, a two-tank molten salt storage process, with a heat exchanger between the liquid and the salts, may be included to achieve several hours of storage.
Trough plants equipped with storage improve the size of the mirror field proportionally to the storage and ensure that one part is dedicated to day-time generation and the other to recharging the storage, which is then discharged as the sun is going down.