The Erlenmatt Ost site in Basel is home to one of the largest self-consumption communities in Switzerland, where over 500 people consume mainly locally produced, renewable electricity. The project, which won the Watt d’Or award, signifies the trend throughout Switzerland towards a more decentralised electricity system.
Urs Buomberger: Erlenmatt Ost is the first large-scale site that we have developed from scratch as a housing foundation and built in association with various property developers. It enabled us to give shape to our ideas, including making affordable housing available to people from all walks of life and promoting the concept that it is possible to live and work in the same neighbourhood. We also broke new ground in terms of the energy supply by making the site a self-consumption community. This model is expected to become more widespread. Consumers have become more aware of energy production issues in recent years, particularly as a result of climate change and the war in Ukraine. More and more tenants want to know where their energy comes from.
The inspiration for creating a self-consumption community with its own energy centre on the Erlenmatt Ost site came from the internal workshops we held with external experts. During these workshops, we discussed at length different approaches to energy issues, construction logistics, schedules, etc. We grappled with a simple but fundamental questions: what goals do we want to achieve with the site, and what signals do we want to send out? This led to an unconventional approach. We decided to organise a private urban development competition based on the development plan that emerged from the public competition. Our intention was to enable a small-scale development. In terms of the energy supply, we deliberately opted for an ecological solution rather than the obvious, standard solution with a local electricity supplier.
Energy was one of the key considerations during the development of the site. The focus was on the site’s small footprint and other ecological considerations. With this in mind, we tried to find the best solution, and finally decided on pooling energy for self-consumption. As a foundation that is primarily committed to maintaining affordable rents and creating an urban neighbourhood worth living in, it was not within our remit to operate our own energy centre. We therefore set about looking for a suitable partner, which we found in the ADEV energy cooperative. We also established an ecological groundwater cycle with the nearby company Roche: the heating on the Erlenmatt Ost site is powered by heat extracted from the groundwater. The cooled water is then passed on to Roche, which uses it to cool its systems.
All the roofs are equipped with photovoltaic systems. This is mandatory to ensure that the energy centre can be operated in the most efficient way. In the summer, the site often covers its own electricity requirements during the day. There are also three heat pumps and a heat storage tank with a capacity of 70 m3. This configuration makes it possible to generate heat when enough solar power is available. Any surplus is used to fill the hot water buffer tanks. Anything in excess of this is fed into the grid. Overall, we achieve a self-consumption rate of over 80%.
During the winter months in particular, the energy required is obtained from the Moosbrunnen small hydropower plant via the AEDV energy cooperative. This ensures that all energy is produced 100% ecologically in Switzerland.
Right from the start of the project, our aim was to achieve a completely self-sufficient energy supply.
Urs Buomberger
Right from the start of the project, our aim was to achieve a completely self-sufficient energy supply, as shown by the inclusion of a special battery room for storing electricity in the initial plans. However, working together with external specialists, we realised that a project of this kind did not make ecological or economic sense for an area of this size. Erlenmatt Ost is not meant to be a neighbourhood within a neighbourhood, but part of the city and part of the overall energy supply, albeit with its own energy centre.
In our compulsory sustainability concept for all buildings, we stipulate that households must use efficient appliances and light sources. The actual energy consumption is measured and billed by the ADEV energy cooperative. Basically, a specially developed set of regulations governs the supply of electricity to the site. This not only applies to our tenants, but is also an integral part of the building lease agreements and sets outs the conditions under which ADEV supplies electricity to consumers. If the electricity costs are 5% below the small consumer tariff, the difference is used to build up a fund for sustainable investments.
ADEV approached us with the idea of using vehicles for bidirectional charging, and we found it a fascinating concept that would be suitable for Erlenmatt Ost. We actively supported the idea. Again, as a housing foundation, it was clear that we could not be the operators of the vehicles because that requires specific infrastructure and technology, as well as special types of cars. Scientific researchers monitored the pilot project and were able to draw important conclusions about scaling. We are very pleased that Erlenmatt Ost was the first site in Switzerland to introduce bidirectional charging. It is an example of the many innovative projects on site.
We were delighted to win the award in the «Buildings and space» category.
Urs Buomberger
The Watt d’Or is probably the most important national sustainability award in Switzerland. We were delighted to win this award in the «Buildings and space» category. The jury was impressed not only by the technical solution, but also by how sustainability is lived actively at Erlenmatt Ost, for example, by having hens hatching their chicks in the local kindergarten. As already mentioned, Erlenmatt Ost presents a multifaceted selection of different sustainable projects.
The Habitat foundation does not currently have any overarching sustainability guidelines. Nevertheless, we carefully examine which measures are possible and make sense in terms of sustainability for each project. One of our current construction projects, Lysbüchel South, is focusing on the topic of re-use, for instance, so that existing kitchens and other building materials can be re-used. In another project, we have created affordable living space for large families. Naturally, the focus is always on issues that will help ensure an ecological energy supply.
It goes without saying that we always learn new lessons from completed projects and can incorporate this knowledge into future projects. We carefully examine which measures are possible and make sense in terms of sustainability for each project. The Lysbüchel Süd site, which was created after the development of Erlenmatt Ost, also pools energy for self-consumption. Compared to Erlenmatt Ost, we have simplified the contractual arrangements by making the individual leaseholders direct contractual partners of ADEV.
