Production hall in Düsseldorf

Within the framework of a heat supply contract the local energy supplier Stadtwerke Düsseldorf realised the installation and operation of two electric ground source heat pumps to heat a new production hall in Düsseldorf. The neighbouring office building needs heating and cooling. The heat source consists of 50 borehole heat exchangers of 30 meters depth each, which are installed under the baseplate of the production hall. The Seasonal Performance Factor (SPF) for the heating season 2006/2007 was 4,6.

Project description

Building, overall energy concept

Photo: Aerial photo of the premises of Walther Flender GmbH in Düsseldorf

Walther Flender GmbH is a manufacturer of drive systems and components located in Düsseldorf, Germany. An innovative geothermal heat pump system was installed to supply heat for a newly errected production hall of 2000 m². In summertime the system can be switched to free cooling mode. Thus the system can provide heating and cooling for a neighbouring office building too.

According to DIN EN 12831 the design heat load of the building is around 102 kW and the cooling load about 25 kW.

Heat pump system

The geothermal system started its operation in the year 2006. It consists of two electrically driven brine-to-water heat pumps (Alpha Innotec SWP 670) with a heating capacity of 67,6 kW each (at S0/W35) as well as 50 borehole heat exchangers with a depth of 30 meters each. The borehole heat exchangers were installed under the baseplate of the production hall. The brine used consists of a etylenglycol(25%)/water mixture.

The dimensioning of the borehole heat exchangers was based on Thermal Response Tests carried out by the University of Karlsruhe and computer simulation using Earth-Energy-Designer (EED). The tests showed a heat conductivity in the range of 3,1-3,4 W/mK and the map below displays the high geothermal productivity of the area investigated.

Operation experiences

Aimed at recording the system efficiency and to be able to adjust the operation of the plant to the actual needs a comprehensive monitoring system was installed.

The geothermal system for heating and free cooling proved to be highly efficient and an economic success. The SPF reached (SPF=4,6) exceeded all expectations. Also free cooling mode proved to be very energy saving. Display of measuring results shows a minimum brine temperature in winter of 2,5°C and in summer a maximum brine temperature of 17°C. At the beginning of the new heating season the brine temperature is 13°C again, like at the beginning of the last heating season and equal to the ground water temperature.Due to these results a long-term stable operation of the heat source system can be expected.

 Enlarge image 

Diagram: Profile of brine supply and return temperature during the period October 2006 to September 2007

Costs, economic efficiency, incentives

- Heating cost: 0,024 €/kWh

- Cooling cost: 0,0036 €/kWh

Regulations, guidelines, benchmarking

Not available

References

Not available

¹ Monitoring results covering the period 1 October 2006 - 8 September 2007
² at S0/W35, two heat pumps á 67,6 kW
³ Period covered: 1 October 2006 - 31 March 2007
⁴ Period covered: 1 April 2007 - 8 September 2007