This multifamily residence has 28 dwellings where 67 persons are living. It is heated by two brine-to-water heat pumps fed by a field of 10 borehole heat exchangers. The heated area is of 1.771 m². The two heat pumps, each with a heating capacity of 32.6 kW, are fulfilling the needs for heating and cooling. The hot tap water is provided through solar collectors in addition with electric water heaters.

Project description

This residence was built in 2003. It has 28 dwellings distributed over 4 buildings, two with two storeys and two with three storeys. The heated area is of 1. 771 m². It is located in Besançon in the east centre of France, in a relatively cold climate.

The insulation is good and the buildings have been awarded with a high energy performance labelling. The heating need is of 74,0 kWh/m²/year.

The heating and cooling system uses two identical non reversible heat pumps with a heating capacity of 32,6 kW each. Each heat pump is connected to 5 borehole heat exchangers with a depth of 100 m and a diameter of 32 mm.

The cooling needs are fulfilled in free cooling mode.

The hot tap water is provided by a collective system using thermal solar panels in addition with electric water heaters.

The distribution for heating and cooling is made through thermal floor for each storey. The supply water temperature in the thermal floors is 30°C for heating and 18°C for cooling.

Heat pump system

The heat pumps are brine-to-water machines with compressor driven by electricity. Each one is using five 100m-deep borehole heat exchangers as heat source.

An additional heating resistor of 15,0 kW is also available in case of very cold outdoor temperature. Since 2003, it has been used only during 8 hours in 2005.

The heating capacity of each heat pump is 32.6 kW. The nominal electric power is 7,2 kW, fed in three-phases.

The nominal operating mode is 35°C (condenser output) and 0°C (evaporator input). The maximum temperature output at the condenser is 55°C.

Each heat pump is loaded with 6,8 kg of R407C refrigerant.

The cooling is made in free cooling mode, without the heat pumps. The cold water from the borehole heat exchangers is used in the heating/cooling floors through an intermediate heat exchanger.

The hot tap water is produced through 52 m² of solar collectors in addition with 24,0 kW of electric water heaters.
Operation experiences 

The measurement campaign was made during the complete year 2006. It was funded both by eDF and ADEME during a campaign intended to monitor the performance of ground coupled heat pumps in real conditions.

The heating system was stopped from June 8th, 2006 to October 4th, 2006. During this period, the cooling system was turned on but operated really only between July 20th and July 31st, 2006, during the hottest days of the summer.

One heat pump operated during 1.577 hours (compressor and circulator running time) and the other during 2.286 hours.

No operational problems were experienced.

Costs, economic efficiency, incentives

The operating cost can be estimated at 3,3 €/heated m² during year 2006 (based on an average electricity cost of 13 c€/kWh, excluding yearly subscription costs).

Regulations, guidelines, benchmarking

No information available

References
No information available

¹ Measured during January 2006 to December 2006
² 2 x 32,6 kWth
³ Appliance alone
⁴ Heat pump only, including all pumps and auxiliary systems SPF=2,72
⁵ Only indirect emissions (thus excluding possible refrigerant leaks) due to electricity consumption both for the heat pumps and the auxiliary systems. Measured during year 2006.