A solar thermal collector collects heat by absorbing sunlight. There are various types of solar thermal collectors, ranging from low-temperature unglazed collectors, which are typically used to heat swimming pools, to evacuated tube collectors, which consist of an array of single or twin-wall glass tubes, with a vacuum providing insulation against heat loss.
The most widely used thermal collectors are flat plate collectors, which are used for domestic hot water applications. Concentrating collectors use reflective surfaces to concentrate sunlight onto a small area, where it is absorbed and converted to heat. Concentrators can increase the power flux of sunlight hundreds of times.
The principal types of concentrating collectors include: compound parabolic, parabolic trough, fixed reflector moving receiver, fixed receiver moving reflector, Fresnel lens, and central receiver. Concentrating solar collectors in concentrated solar power (CSP) facilities concentrate sunlight onto a receiver where it heats a heat transfer fluid that subsequently transfers its absorbed heat to water to produce steam, which in turn powers a steam turbine-generator (STG) to produce electricity.
Thermal collectors are combined with storage systems to provide water for hot water (DHW) and heating purposes. They can also serve as the energy supply unit for heat pumps and sorption cooling technologies. Similar to photovoltaic module, solar thermal collectors can be installed during refurbishing activities in very different kinds of layouts and scales.
