A solar thermal collector is a component of a solar thermal installation responsible for capturing solar radiation and transforming it into thermal energy. This type of solar panel is also known as a thermal solar collector or thermal solar panel.
There are many types of solar thermal energy installations depending on the objective for which they are designed. Some common uses of solar collectors are:
Heating the pool water.
Domestic hot water (DHW)
Electricity production in large solar thermal power plants.
Types of solar thermal collectors
There are many types of solar collectors. The solar collector used will depend on the use that will be given to it. Currently, in the solar energy market we can differentiate the following types of solar collectors:
1. Flat plate solar collectors
Flat solar collectors capture solar radiation received on a surface to heat a fluid. The greenhouse effect is often used to reduce heat losses.
The soul of this type of flat plate solar collector is a set of vertically oriented metal tubes that conduct cold water in parallel. These tubes are connected at the bottom by a horizontal tube to the cold water intake and another similar tube to the outlet at the top.
The set of tubes is enclosed by a cover on the upper part that is normally double glass, and on the lower part by an insulating material.
2. Vacuum tube solar collectors
An evacuated tube solar collector is similar to a flat plate solar collector but the metal tubes are replaced with glass tubes. These glass tubes are encapsulated, one by one, in another glass tube between which a vacuum is created as insulation.
These types of thermal solar panels have higher performance but their cost is higher.
3. Concentrating solar collectors
This type of collector captures the radiation received on a relatively large surface and concentrates it using flat mirrors on a smaller surface.
The objective of a concentrating solar collector is to focus all the solar energy received on a surface at one point to obtain high temperatures. This technique is used in high and very high temperature solar installations.
Usually this type of solar collectors are used to generate water vapor at very high pressure and generate electrical energy as in a conventional thermal power plant.
Components of a flat plate solar collector
Standard solar collectors are made up of the following elements:
The cover: The cover of a solar collector is transparent, it may or may not be present. It is generally made of glass, although plastic is also used. Its function is to minimize heat losses through convection and thermal radiation.
Air channel: It is a space that can be vacuum that separates the cover from the absorbent plate. Its thickness is calculated taking into account in order to balance convection losses and the high temperatures that can occur if it is too narrow.
Absorbent plate: it is the element that absorbs solar energy and transmits it to the liquid that circulates through the pipes. The main characteristic of the plate is that it must have high solar absorption and reduced thermal emission.
Tubes or conduits: these elements are touching (sometimes welded) to the absorbing plate so that the energy exchange is as great as possible. The liquid circulates through the tubes and will heat up and go to the accumulation tank.
Insulating layer: The purpose of the insulating layer is to cover the system to avoid and minimize losses.
Accumulator: The accumulator is an optional element, sometimes it is an integral part of the solar panel and in these cases it is often visible immediately above or in the immediate vicinity.