Solar thermal energy consists of the transformation of solar energy into thermal energy. It is a form of renewable, sustainable, and environmentally friendly energy.
This way of generating energy can be applied in homes and small installations, and large power plants.
There are three main uses of solar thermal systems:
-
Electricity generation
-
Thermal energy by heating fluid
-
Mechanical energy using a Stirling engine.
There are three types of solar thermal technologies:
-
High-temperature plants are used to produce electricity working with temperatures above 500 ºC (773 kelvin).
-
Medium-temperature plants work with temperatures between 100 and 300 degrees Celsius.
-
Low-temperature installations are commonly used in homes. They work with temperatures below 65 degrees Celsius.
What is a solar thermal installation for a home?
The basic scheme of a solar thermal energy installation is as follows:
These are two closed circuits with a heat exchanger. In the primary circuit, the cold heat transfer fluid passes through the solar panels. Radiation from the Sun heats it and goes to a heat exchanger to transfer thermal energy to the secondary circuit and then, repeat the cycle.
In the secondary circuit, the heat transfer fluid goes to the storage system. Inside the storage system, it gives up its thermal energy to the water stored inside.
What is a thermal storage system?
This system consists of storing heat energy in a water tank. It acts like a battery, but instead of storing chemical energy, it holds heated water.
Conventional energy support systems
Solar thermal facilities need energy support systems. These systems prevent a lack of solar radiation or a consumption higher than the dimensioned.
These energy support systems can be from various sources:
-
Directly from the electricity company's network.
-
Other sources of renewable energy - for example, wind energy.
-
By using non-renewable energy sources (fossil fuels). Some installations use pellets or biomass boilers.
What is a solar thermal power plant?
A solar thermal power plant is a thermal power plant whose objective is the production of electrical energy. This type of solar plant is classified as a type of high temperature solar thermal energy.
In solar thermal power plants, solar radiation is concentrated at one point to produce steam. The steam drives a steam turbine that converts the energy to mechanical energy to drive an electric generator.
The thermodynamic performance is low, but the price of fuel is zero.
How is solar thermal energy obtained? Types of solar collectors
A solar collector is a type of solar panel for solar thermal energy.
The collectors obtain thermal energy by taking advantage of solar energy. There are three types of collectors, depending on the use they are going to have:
-
The flat solar collector is the most widespread. It allows raising the temperature of 60 degrees Celsius.
-
Unglazed solar thermal collectors are commonly used for the production of hot water in swimming pools. The temperature rise is low, around 30 ºC.
-
Solar vacuum collectors consist of metal tubes. Inside the line, there is another tube that contains the heat transfer fluid. Between them, there is a chamber that acts as an insulator.
-
Solar collectors with radiation concentration systems obtain higher temperatures.
-
The collectors tracking the sun vary their position following the sun from east to west - for example, solar dishes.