- 600 kW heat output
- 220 kW cooling capacity
- 290 kWp PV output for ZEV self-consumption
- 20 e-mobility charging stations
- 270 tons of CO₂ saved per year
Petit-Saconnex has been part of the city of Geneva for more than 90 years. The district is dominated by a five-hectare park that serves as a recreation area and meeting place. Right next to the park are the buildings of the ‘Maison de Retraite du Petit-Saconnex’ with accommodation and care facilities for the elderly. This area has been upgraded in recent years by upgrading an existing building and building three new buildings. The aim of the Côté Parc project was to create a sustainable neighbourhood for different uses and user groups.
Different temperatures
Coté Parc is supplied with thermal energy by two on-site networks – one operating at medium and the other at low temperatures. The choice of two separate networks was made because it allows cooling energy to be extracted from the geothermal probe field and transmitted to the buildings without the use of a cooling machine. To heat the four buildings, an energy centre with a total output of about 600 kW supplies the network with the average temperature level (about 35 °C) via a heat pump with the required thermal energy. The peak load is covered by a gas-fired boiler, but at least 90 per cent of the total heat supply should come from renewable sources. The heat pump in the energy centre and the network with the average temperature level are only used during the heating period.
On the other hand, the network operates all year round with the lower temperature, which is between 1 and 13 °C. It connects the substations of the individual buildings. Heat pumps provide around 35 m³ of domestic hot water every day, for which they also use waste heat from the ventilation systems and the outside air. In summer, the low-temperature network also provides cooling for the free cooling of the buildings via a heat exchanger. On hot days, cool water can be pumped through the underfloor heating pipes and thus the indoor temperature can be regulated. This passive cooling method saves a lot of energy compared to electricity-intensive air conditioners.
Two geothermal probes
The energy for heating and cooling the site comes from a total of 41 geothermal probes, each at depths of 250 or 300 metres. Due to their proximity to a groundwater zone, the probes are operated using water instead of glycol. The probes can be divided into an internal and an external field. The two fields differ in their temperature level: the internal field is cooler than the external one and is used for cooling, especially in summer. The outer field, on the other hand, is operated at a higher temperature by absorbing the waste heat from the free cooling in summer and thus being actively regenerated. In winter, both fields provide the thermal energy for heating the four buildings.
Plenty of photovoltaics
It’s not just the heating and cooling supply at the ‘Côté Parc’ that is largely renewable, but also the electricity supply. This is provided by 776 photovoltaic panels with a total surface area of 1,300 m2 on the roofs. With output power of around 290 kWp, they will generate around 275,000 kWh of electricity annually, which is equivalent to about a quarter of the site’s electricity requirements. In order to operate the system as economically as possible and to be able to offer users the solar power at low cost, the owners have joined us to form a ‘self-consumption association’ (ZEV). This includes all consumers on the site. Two of our transformers and the site grid will provide access to the public electricity grid and serve as a hub for the self-produced solar power.
We will equip all residential, office and commercial units with an electricity meter. We will also handle the billing of the electricity consumed. This will detail how much solar power was consumed and how much electricity was drawn from the public grid. We will offer the locally produced solar power at a price that is around a third cheaper than the normal grid tariff. These prices also include the costs for the site’s electricity infrastructure (photovoltaics, transformers, transmission lines). Users will therefore gain significant financial benefit from the self-generated solar energy and the complete solution from ewz.
Future-proof charging infrastructure
Electromobility is also an important component of the comprehensive energy solution. The first step will be to equip 20 parking spaces with a dynamic charging station so that owners of electric vehicles can charge them at home. If necessary, the number of charging stations can be increased without affecting the area’s power supply. The charging infrastructure has a load management system that coordinates the consumption of the charging stations with that of the buildings. In this way, we can ensure that there are no overloads or even power outages. Charging electric vehicles is billed to a credit card via the ewz app, allowing users to see at any time how much electricity they have already used for charging and how much it costs. This convenient charging solution will help to spread electromobility and make the ‘Côté Parc’ project more sustainable in terms of mobility.
Sustainable and practical
The collaboration with ewz offers the owners of ‘Côté Parc’ various benefits. The planning, financing, implementation and operation of the energy infrastructure from a single source will ensure that users are supplied with an efficient and practical energy solution in the long term by the same reliable provider. After all, as a long-standing provider, we have a wealth of expertise and experience. Simple, sustainable and cost-effective – our comprehensive energy solutions impress customers throughout Switzerland.
