In order to increase the efficiency of concentrating solar thermal power plants, the researchers have found a solution to avoid heat losses. They also use a more compact design and a new heat transfer medium.
New heat carrier for higher temperatures
However, the higher the temperature, the higher the efficiency of the entire power plant. That is why the researchers at Fraunhofer ISE in Freiburg have used a heat transfer medium that consists of solid bodies. This means that operating temperatures of more than 1,000 degrees Celsius are possible.
All combined in one component
In addition, in the new receiver they have combined the solid-state heat carrier with the receiver of the sun's rays and the storage material in one component. This enables the Freiburg researchers to reduce the costs of building such power plants. In addition, they avoid the heat transfer losses and the limitation of the flow rate of the heat-carrying medium, which are typical of traditional tube receivers. As a result, the higher temperatures, which are better maintained even with fluctuating solar radiation, lower the costs of solar thermal power generation.
Measure air wall extensively
The Freiburg researchers have now changed that. They set up a real-scale test station and equipped it with about 50 temperature sensors. They simulated the 600 degree hot receiver with heating elements. For the project, the industrial partner Luftwandtechnik designed an air wall system for high-temperature applications and installed it in the test stand.
Measure new mirrors
The Freiburg researchers also support the further development of the tower power plants themselves. The trend here is towards smaller units that are no longer equipped with the previous parabolic mirrors, but with so-called Stellio heliostats. These are pentagonal segmented mirrors that stand on a pole and reflect the sunlight onto the solar tower. The Freiburg researchers also support the further development of the tower power plants themselves. The trend here is towards smaller units that are no longer equipped with the previous parabolic mirrors, but with so-called Stellio heliostats. These are pentagonal segmented mirrors that stand on a pole and reflect the sunlight onto the solar tower.
Overall system simulated
In the end, the researchers developed an overall concept from all these individual components. This consists of the receiver with solid-state heat carrier and air wall and the optimized Stellio heliostats, which were integrated into a solar thermal power plant. To do this, they also investigated which power plant process is best suited for coupling the individual newly developed components and how the heat can be transferred from the solid bodies to the underlying process of a steam turbine power plant.