Conference centre in Stockholm

Vår Gård is a conference centre with several buildings comprising a total of 9.000 m². It is heated by five electrically driven ground source heat pumps providing a total heating capacity of 225 kW. Also hot water is heated by the pumps.

Project description

Building, overall energy concept

Vår Gård has a total area of 9.000 m² spread into different buildings and including 138 rooms, 16 meeting rooms (the largest seats 240 people), three restaurants (the largest seats 150 guests), and two bars. The peak heating demand of the buildings is approximately 700 kW.

Heat Pump System

Figure 1 illustrates the rock heat pump system from Vår Gård. The first three heat pumps counting from right to left are used for tap water production. This is illustrated with the red lines. Moreover, all five heat pumps are used for comfort heating purposes. These are indicated with pink lines.

Each of the five heat pumps has a heating capacity of 45 kW, resulting in a total capacity of 225 kW. They are used both for comfort heating and tap water production together with a 500 kW oil boiler. The total effect for hot water amounts to approximately 15 KW.

The refrigerant used is R134a.

The total active length of the boreholes is 4.500 m. A total of 23 boreholes are spread over the surrounding area. These are vertical and have an approximate depth of 210 meters, with a diameter of 115 mm. An inclination of 10° is expected in some cases.

Costs, economic efficiency, incentives

The investment cost was 333 SEK/m². The yearly savings are 128 SEK/m². Which leads to a pay-off time of 3 years.

References

• Acuna, Jose et.al.: Trimming of a large heat pump installation. Final report, 2007, Department of Energy Technology, Royal Institute of Technology, Stockholm, Sweden
• Acuna, Jose et.al.: Trimming of a large heat pump installation. Final student presentation, Department of Energy Technology, Royal Institute of Technology, Stockholm, Sweden