Medium temperature solar thermal energy is a renewable energy source that converts solar energy into thermal energy, used in applications requiring temperatures between 100 and 400 degrees Celsius. In general, medium temperature solar thermal energy systems use collectors different from those used in low temperature systems, typically being more complex and efficient.
Medium temperature solar thermal energy harvesting systems are used for industrial applications. They are different from low temperature systems, which provide domestic hot water, and high temperature systems, which produce steam and generate electrical energy. Medium temperature systems are the focus of this passage, with two types being described:
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.
First, solar radiation strikes an absorbing surface which converts radiant energy into thermal energy. This thermal energy is transferred to a transfer fluid (usually water or a mixture of water and antifreeze) which circulates through the collector.
Solar thermal collectors work based on the principle of absorbing solar energy. Although there are different types of solar collectors, as we will see later, the operating principle is similar in all of them. First, solar radiation strikes an absorbing surface which converts radiant energy into thermal energy.
The common methods used for solar thermal energy storage include sensible heat energy storage, latent heat energy storage using phase-change materials (PCMs), and thermochemical energy storage.