What is a solar thermal collector and how does it work?
When we talk about solar energy, we always think first of all about photovoltaic energy through which, thanks to sunlight, we can generate electricity. But there is another type of energy that is less known, but no less important, viz thermal solar energy, thanks to which we can heat water.
A solar thermal collector or solar thermal collector or solar thermal panel, is a device that allows us to take advantage of solar thermal energy, that is, it serves to capture solar thermal energy through solar radiation and thus heat the water. Hot water can be used both at home and at industrial level, for example for you heat the water in the poolof the bathroom or shower or as a water heating system led through pipes capable of heating the rooms through which they pass.
By using solar thermal collectors we can have hot water and heating in a clean and ecological way.
It should be noted that Solar thermal energy can also be used to generate electricity. This is done in solar thermal plants that heat water and generate steam capable of moving a turbine that is used to produce electricity. When solar energy is harnessed to generate electricity for household use, a photovoltaic solar installation.
Operation of a solar thermal collector
A thermal solar collector is consisting of several elements:
- Covers or thermal plates. They are usually made of glass or special plastic materials. When the sun shines on them, they capture all the energy possible, minimizing losses due to convection.
- Air channel It may or may not be empty and is responsible for separating the cap from the absorbent. The thickness of this channel varies depending on the losses due to convection and the excessively high temperatures that can occur if it is too narrow.
- The absorbent. As the name indicates, it is responsible for absorbing solar energy and transmitting it to the fluid in which the heat is stored. It is essential that it has a high absorption capacity and reduced thermal emission, for which a mixture of various materials such as copper or aluminum, with titanium oxide treatments, is used.
- The accumulator. Not all solar thermal installations have it, although it is a practical element. It consists of a tank in which hot water is stored, that is, the collected thermal energy, so that it can be used whenever it is needed, even when there is no sun.
- Pipes, circuits, insulating layers and other elements. The tube system can transport the installation fluid and insulating elements to avoid energy losses. Main and secondary circuits allow it to function properly.
Types of thermal solar collectors
When it comes to solar thermal collectors for domestic use, the three most common types are:
- flat solar collectors: Composed of tempered glass and designed to capture solar energy and transmit it through pipes to a heating fluid, which when heated will transport the energy to where it is needed. They are one of the most requested and efficient, being indicated especially for the production of hot water and also for heating swimming pools, low temperature heating and absorption cooling.
there is two fundamental classes of flat solar collectors: normal and selective. The former are not suitable for areas with low temperatures or diffuse irradiation, while the selective ones are suitable for both situations because, as the name suggests, they provide a selective coverage that makes it possible. - Collectors with vacuum tubes: Composed of a set of solar tubes that keep the vacuum and inside which we find the heating fluid. Compared to flat solar collectors, they offer higher performance at high operating temperatures. They are recommended for areas with very low insolation or for installations where it is necessary to work with high temperatures. They are also indicated for heating that requires a lot of solar input and absorption cooling, as well as in industrial processes.
- Polypropylene pickups: They do not have a glass cover and are made of plastic. Its operation is very similar to that of flat solar collectors, although they are cheaper. They are only used for heating the water of swimming pools which are discovered due to their low performance at medium and high working temperatures and in cold climates.
In addition to these types, solar thermal collectors are also classified according to the power of their accumulators:
- Low temperature accumulators. They provide heat at less than 65 degrees. These are usually the ones used at home.
- Medium temperature accumulators. They provide heat between 100 and 300 degrees. They are more used for industrial processes that require temperatures above 100 degrees.
- High temperature accumulators. They provide heat over 500 degrees. They are used to generate electricity through steam.
