Les Vergers, Geneva

An eco-district including 33 high performance buildings heated by a 5 MWth heat pump on shallow groundwater.

Lessons learned 

  • High DH return temperature (mainly in mid-season in SH mdoe, all year round in DHW mode) causes a degradation of the heat pump Seasonal Performance Factor (SPF), or causes HP shutdowns.

Key facts

BuildingHeat Pump and Source
LocationGeneva, SwitzerlandNumber of HP1
Construction2015-2020Installed power5,000 kWth
Heat distributionunderfloor heatingOperation modebivalent
Heated area170,000 m²Heat sourcegroundwater,
heat recovery
No. of apartments1,350 in 33 buildings
41 per building
Level of insulationhigh performance
Heating sytemDomestic Hot Water
Heat demand46 kWh / (m²a)DHW demand26 kWh / (m²a)
Heating
temperature
35 °CMax. temperature60 °C
SH share64 %DHW share36%
Add. heat
production
Geneva’s main DH
(gas boilers &
waste incineration)
Type of systemcentral per building
Circulation systemYes
Other information
HP share85%COP
Backup heat source share15%SPF3.7
PV installation12,000 m²
Heat Cost (LCOE)CHF 13.-/ (m²a)

“Les Vergers” is an eco-district composed of 33 high performance buildings, whose main heat source is a low temperature district heating network. This network is mainly supplied by a water-to-water HP using two resources: groundwater from the Rhone River and waste heat from the neighboring industries.

The results show that this eco-district is in line with the cantonal energy master plan, both in terms of building energy efficiency and massive integration of renewable energies.

Description of the technical concept

“Les Vergers” is an eco-district including 33 high performance buildings, with around 1’350 dwellings and various activities, totalizing 170’000 m² of heated area. A local low-temperature district heating network (LTDH) distributes heat to the buildings for SH and DHW. Since all connected buildings meet high energy performance standards, the LTDH supplies heat at a low temperature level (50°C). At fixed time, twice a day, the supply temperature of the network is raised from 50°C to 65°C to heat up DHW tanks located within the buildings over a 2-hour period. Compared to a network with a constant supply temperature of 65°C, this lowers DH heat losses and increases the energy performance of the heat production. The LTDH is supplied by a 5 MWth HP, whose heat source is shallow groundwater. Before reaching the HP, this cold water at approximately 12°C supplies a district cooling network, recovering waste heat from the nearby industries, thereby increasing the resource temperature for the HP and improving its efficiency. As complementary or back-up heat source, the LTDH is connected to Geneva’s high-temperature main district heating network, which is supplied by gas boilers and heat recovery from the city’s waste incineration plant.

The DH substations consist here of two parallel primary heat exchangers, one for SH distribution and the other for DHW production. Buildings are equipped with ventilation heat recovery, mostly by way of exhaust air HP, producing heat for DHW preheating and/or SH.

The LTDH heat production (July 2019 – June 2020) is covered at 85% by the HP and at 15% by CAD-SIG (due to HP maintenance). The monitored HP SPF is 3.7, the COP reaches 4.3 in SH mode (condenser outlet at 50°C) and 3.3 in DHW mode (condenser outlet at 65°C). The heat source/evaporator inlet varies between 13-16°C.

Final report: SCHNEIDER, Stefan, BRISCHOUX, Pauline, HOLLMULLER, Pierre (2022). Retour d’expérience énergétique sur le quartier des Vergers à Meyrin (Genève).
Url: https://archive-ouverte.unige.ch/unige:164877

CH012 Les Vergers