Air CSP Tower in Germany

Concentrating solar power (CSP) is considered to have the best potential to supply solar power on utility scale basis. CSP plants had been build as early as the 1970s, but new technological developments are causing CSP to be considered as an effective solution to generate renewable power.

Kraftanlagen Munchen, a construction company, finished constructing a new 1.5 MW (Mega Watt) experimental solar thermal plant in December 2008. This new plant is unique because it's the world's first solar thermal plant that uses air, instead of oil or molten salf, as the medium for heat transport.


Previously, molten salt and oil were used because of their high specific heat capacity. This helps in having low volume flow rates and low pumping losses while the liquid is being circulated to heat up.

The downfall of using liquid medium is that the concetrated solar radiation (500 to 1000 suns) is in the air and that to heat the liquid the heat must pass through a wall. This causes loses in the heat exchange process thus lowering the efficieny of this method.

The new method used by the Jülich power tower takes advantage of the volumetric effect. Ambient air is sucked through a blackened porous structure on which the solar radiation is focused. This causes the air's temperature to rise, the hot air is fed to a heat recovery steam cycle (used for the exhaust heat of gas turbines in combined cycle plants). The heat recovery steam cycle generate steam which drives the steam turbine and generate electricity.

At night exhaust gases from gas turbines can be used to feed hot air to the heat recovery steam cycle and keep the system operation 24 hours per day. Also, heat storage could be used to drive the plant at night.

"The Jülich plant features a storage system consisting of honeycomb-type ceramic blocks, through which air passes in one direction for charging, and in the other for discharging. As the discharged air has the same temperature as when charging, no energy is lost, making the system highly efficient."

Source: Renewable Energy World