This way of generating energy can be applied in homes and small installations and in large power plants.
There are three types of solar thermal energy:
Low temperature. It would be the case of installations in houses. In this case, thermal energy is used directly. They work with temperatures below 65 degrees Celsius.
Solar collectors. What are they and what are they for?
The collectors transform solar energy into thermal energy. There are three types of collectors depending on the use they will have:
The flat solar collector. It is the most widespread solar collector. Temperature increases of 60 degrees Celsius can be obtained at a reduced cost. It is used in low temperature solar thermal plants.
Vacuum solar collectors. They consist of metal tubes that cover the metal tube that contains the working fluid, leaving between them a chamber that acts as an insulator. They have a very high performance, but their cost is also high.
Solar collectors with radiation concentration systems. They are used for installations that require higher temperatures. Solar panels in parabolic or semi-cylindrical forms are used.
Solar thermal power plant. How does it work?
In solar thermal power plants, solar radiation is concentrated at one point to generate steam. With steam a steam turbine is powered. With it you get a mechanical job. Finally, the turbine is connected to an electric generator.
Thermodynamic performance is low, but the fuel price is nil.
Thermal solar energy scheme for a home
These types of installations are low-temperature thermal solar systems.
The basic scheme of a solar thermal energy installation is as follows:
They are two closed circuits with a heat exchanger. In the primary, the cold fluid passes through the solar panel. The radiation from the Sun heats it up. With the high temperature it goes to an exchanger where it transfers the heat to the secondary circuit. Repeat the cycle again.
In the secondary circuit, the fluid, after receiving the heat in the exchanger, goes to the accumulator. The heat is transferred to the accumulator by thermal contact but without mixing. Once cold, it goes back to the heat exchanger.
The water that is going to be used in the installation circulates and is stored in the accumulator. It can be sanitary water or water for heating.
This system consists of storing the heat energy in an accumulation tank for later use. The hot water obtained through the collection system is led to the place where it is going to be used.
Stored hot water can be used directly, as is the case with pool water heating, in domestic hot water or demand heating applications.
Since the time of need for hot water does not always coincide with the time when there is enough radiation, it will be necessary to make the most of the hours of Sun to accumulate thermal energy in the form of hot water.
The thermal energy storage system is made up of one or more hot water tanks. The size of the storage tanks should be proportional to the estimated consumption and should cover the demand for hot water for one or two days.
Once the solar collectors have heated the heat-carrying medium (water or air) by increasing its thermal energy, we can transfer this thermal energy to other cooler sources.
This system includes all the elements intended for the distribution of the heat-carrying medium and conditioning for consumption:
Pipes and pipes.
The support system is also part of this system. The support system is based on conventional energies to supply energy when there is no sun or in high demand peaks.
Conventional energy support systems
Thermal solar energy installations need conventional support systems in anticipation of the lack of solar radiation or a consumption greater than that dimensioned.
In most cases the facilities are designed to provide between 60-80% of the hot water demanded. However, in areas with high insolation throughout the year, the contribution percentage is usually higher.
These energy support systems can be from various sources:
Directly from the network of the electric company itself.
In the months with the lowest solar radiation, 60% of the needs are not covered. On the contrary, in summer it reaches practically 100%.
The objective with which the solar thermal installations are designed is to cover a minimum of 60% of the annual energy needs depending on the geographical area.
Aiming to cover above 60% or 70% annually would require placing a very large solar field. This would be so expensive that it would never be amortized.
On the other hand, in the months of greatest solar radiation, a surplus of production would be generated that could not be used. Also, it would cause overheating problems.
Thermal solar energy is the technique by which solar radiation is converted into thermal energy. For them solar collectors are used.
Solar collectors are a type of solar panel whose function is to convert radiation from the Sun into heat. There are different types of collectors depending on the working temperature.
The smallest low temperature installations can be installed in homes. This type of installation requires:
A thermal accumulation system.
A heat distribution system.
Alternative energy systems. They are used when the demand is higher than the production capacity.