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 Maison de Retraite du Petit-Saconnex buildings, providing living and care facilities for the elderly. This site will be upgraded over the next few years by expanding an existing building and adding three new buildings. The aim of the Côté Parc project is to create a sustainable neighbourhood for different uses and user groups. Completion is planned for 2023.

We are responsible for the entire energy supply of the new site. Using a contracting model, we will plan, finance, implement and operate the energy infrastructure and energy services for Côté Parc. This includes the supply of heating, cooling and electricity, as well as electromobility, photovoltaic systems and the self-consumption association (ZEV), including individual electricity billing for tenants.

District heating and anergy

We operate various networks to supply the site with energy: a heating network, an anergy network and a power grid. The core of the system is the energy centre with a total output of around 600 kilowatts. It supplies the district heating network with the thermal energy required to heat the buildings on the site via geothermal heat pumps. Gas heating will also be installed to cover peak loads. The aim is for at least 90 per cent of the energy supply to come from renewable sources.
In addition to the district heating network, a separate anergy network will also be implemented. This will connect the substations in the individual buildings, which use high-temperature heat pumps to heat around 35 cubic metres of hot water per day.

In summer, the heat pumps in the energy centre are not operational. The high-temperature heat pumps in the substations are in use all year round. They use the anergy network, waste heat from the ventilation systems and outdoor air as their source.

The anergy network has another function: it provides cooling energy for free cooling in the summer months. On hot days, water is pumped into the building through the underfloor heating at a maximum temperature of 14 °C to regulate the interior temperature. This version of building cooling is much more energy-saving and climate-friendly than the use of energy-intensive air conditioning units.

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 a bit cooler than the external one and is used for cooling, especially in summer. The external field, on the other hand, is operated at a higher temperature by actively regenerating it. 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.