Generating heat with horses
The first hippothermia plant is located on the Haghof horse riding stable in the Swabian town of Altdorf where horses and ponies provide manure for heat generation.
The heat pump with a maximum heat output of 22 kW operates not only with a frequency-controlled piston compressor for stepless performance adjustment from 28 to100 % but also with a separate desupertheater for efficient service water heating up to +70 °C and environmentally sound refrigerant R134a. Stainless steel corrugated hoses are set in concrete and in the dung heap together with temperature sensors. The unit determines automatically whether energy may be drawn from the slurry or the dung heap. The storage volume of the dung pit is 30 m³ as a maximum. If used as ice storage the resulting storage volume may be in excess of 1.000 kWh i.e. sufficient for one week of operation without external heat supply. All temperatures in the cesspool and the dung heap are noted and evaluated in order to optimise energetic and biological processes.
While temperatures in the horse manure can go as high as 80°C, they may only be exploited for a short time. On average, heat extraction performance is 20 W/sqm with an average dung heap temperature of 20 °C.