Solar collectors are devices designed to take advantage of sunlight to generate hot water and heating to homes
WHAT IS A SOLAR COLLECTOR AND HOW DOES IT WORK
Below we will see what solar collectors are and how they work
What are solar collectors?
The main applications of solar collectors are usually for the preparation of hot water for sanitary purposes, the heating of swimming pools or for heating
The solar collectors are devices that are designed to capture the energy generated by the sun and convert it to thermal energy. They are divided into two large groups, the low temperature collectors (used mainly in domestic heating systems) and the high temperature collectors (which are made up of mirrors and used to produce electrical energy).
There are several types of solar collectors:
- Protected flat collectors : they are the most used since the cost-production ratio is the most profitable and favorable. In this type of collector, the collector is in a rectangular box that is about one meter wide and two meters high. The face that is exposed to the sun is covered with a very thin glass, while the rest of the faces are opaque and thermally insulated.
- Flat unprotected collectors : they are a more economic variant of the previous type, in which the protective glass is omitted and the plate is directly exposed to the external environment. They also do not have perimeter isolation. Their efficiency is more limited, so they need a larger surface area in order to achieve the desired performance.
- Vacuum tubes : they reduce the surface capture in exchange for small losses of heat. The collecting foil is placed inside the tubes, which look like a traditional fluorescent tube but with a dark color. The panels with these tubes are formed with several mounted on a comb structure. This system has advantages such as its isolation is greater, which makes it the best choice for very cold climates. Its flexibility makes its placement better and easier without noticeable performance.
The main applications of solar collectors are usually for the preparation of hot water for sanitary purposes, the heating of swimming pools or for heating.
How do solar collectors work?
The sun is a source of unlimited renewable energy. There are several techniques that can transform the sun’s rays into energy: solar thermal energy and photovoltaic solar energy.
- Photovoltaic modules: transform sunlight directly into electricity.
- The solar thermal sensors: they allow to use the solar energy to produce hot water.
How does a solar thermal collector work?
The solar thermal collectors capture solar thermal energy through the sun’s radiation and heat the water. For that, the sun’s rays first pass through a glass transparent to the light. Under this glass, an absorber (a plate formed by sheets of copper or aluminum with a treatment of chromium or titanium oxide) absorbs 80 to 90% of the sun’s rays.
This absorber is welded with ultrasound or laser welding, to a copper pipe and thanks to the contact temperature transfer, that copper pipe is heated.
The thermal energy or heat transferred to that copper pipe heats a solution of water and heat transfer fluid that prevents freezing of the same in case of low temperatures.
This solution of water and glycol at the acquired temperature is the vehicle to transfer the temperature to the different systems.
In addition, the solar thermal collectors, on the back, have an insulating coating that prevents the loss of the temperature accumulated in it.
Once we have this fluid at the temperature provided by the solar radiation, we circulate it to an accumulator, either by natural circulation giving rise to thermosiphon equipment or forced by a pump and resulting in forced equipment.
How does a thermosyphon or natural circulation equipment work?
The fluid with the temperature that we have obtained in the collectors, is circulated to an accumulator, where it transfers the temperature of this fluid, to the domestic water of consumption, without ever mixing with it. This transfer is achieved in two different ways that determine the operation of the system:
- Accumulation system, the accumulator has a double jacket or envelope, where the heat transfer fluid circulates through the outside and in the interior we have accumulated drinking water. Being both metallic deposits, the temperature is transferred by contact.
- Step heating system, the accumulator is completely filled with that water glycol solution fluid and the drinking water would enter through a stainless coil, which goes through the tank. Transferring the temperature of the fluid to drinking water by contact with that coil.
- In both systems the circulation and accumulation within the elements, is done by natural circulation, where hot water goes up and cold water down. For this the accumulator and the collectors must be very close, or else this physical effect would not occur.
How does forced or forced circulation equipment work?
When the accumulator and the collectors are not close together, it is necessary for a pump to force the circulation of the heat transfer fluid between them. This pump will be managed by an electronic control unit, in case of temperature difference between the solar collectors and the consumption accumulator.
In both systems, when the sun is not enough to heat the water to consumption temperature, an auxiliary system is needed to reach that temperature. This system can be a gas heater, an electric water heater connected in series with the equipment, or an electrical resistance included within the equipment itself. These auxiliary elements, would be used only in case of lack of temperature in the drinking water.
Elements of a thermal installation
A solar thermal installation consists of the following elements:
Solar collectors or solar panels.
The solar thermal panels are those that capture the solar radiation to convert them into heat and then into hot water. Unlike photovoltaic solar panels, they lack photovoltaic cells that transform photons of light into energy, but use solar radiation to heat the fluid that circulates inside them.
They are tanks of different sizes connected to the collectors and that is where the ACS is stored.
They are the ones that carry heat through the circuit thanks to its hot fluid. These can be internal, inside the warehouse, or external.
Auxiliary energy systems
These systems are designed to supplement the demand for hot water in case of lack of solar radiation. To minimize its use and consumption, the water is heated first in the accumulator and then passes through the auxiliary equipment until it reaches the necessary temperature. There are several types: gas boilers, electric thermos, electric resistance, …
In SOLBIOMAS we have all types of solar thermal systems: thermosiphon equipment and forced equipment. If you are thinking of switching to renewable energies in SOLBIOMAS we can advise you on those systems that best suit your needs.