Solar Heat

Solar Cooling of Festo AG & Co. KG, Esslingen

In November 2007, a novel solar thermal system commenced operation at Festo AG in Esslingen. It supports the cooling and heating of the buildings. The solar thermal system is the third heat source feeding into the company’s heating network. The existing adsorption chillers used to be operated with gas boilers and the waste heat of the compressors. The collector field covering 1330m² was installed on the sawtooth roof of a production and office building. The storage tanks were installed in the basement. The solar thermal system saves a considerate amount of fuel used for air conditioning and space heating thus reducing greenhouse gas emissions as well as costs. 

With three chillers and a total of 1 MW, Festo AG & Co. KG at Esslingen is currently the largest solar thermal cooling system with the largest adsorptions chiller on silica gel/water basis worldwide. The cold that is generated cools down 26760 m² worth of office space as well as three atria of the technology center with a surface of 2790 m².

In this system, the heat exchanger between the collectors and the storage circuit is not applicable as it operates with a water only circuit. It also avoids using antifreeze agent. The water is pumped from the storage into the collectors upon requirement, so that the water in the collector circuit does not freeze under sub-zero conditions. The solar heat is delivered to the various consumers (not only the chillers) via a heat distributor. Thus, the heat can be used for heating or cooling. To improve the efficiency of the collectors, solar heat can be fed directly into the space heating of a connected building at a low temperature. In this way, the system’s yield is higher when comparing it to a system where the heat is consumed by the adsorption chillers exclusively.

Because of the low temperature levels, adsorption chillers are well suited to be run by heat from solar thermal system. The efficiency depends on the temperature level of the system. It increases with low temperatures.

Festo AG at Esslingen was chosen for Solarthermie2000plus for several reasons:

• the  suitability of the existing roof surface of the sawtooth roof for the installation of the collectors regarding azimuth and inclination,
• the years of experience with adsorption chillers,
• the suitability of the adsorption chillers for solar thermal systems, which is mainly due to the low driving temperatures,
• the option of using the low temperature levels in winter,
• the good demonstration effect,
• the insulation of the buildings, which corresponds to the level of low-energy houses
• the use of passive space cooling and air conditioning
• the high potential of reducing CO₂ emissions.

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