Sustainable wellness with solar energy

The Solar Fitness and Wellness Unit's concept has two purposes: to substantially reduce the energy consumption of wellness facilities, and to produce the remaining energy by itself. It is part of NEST, the modular research and innovation platform on the Empa campus in Dübendorf, and it is enthroned on the building's uppermost platform. Two glass facades, each around eight meters high, are its eye-catching exterior features. But the architectural design by architect Peter Dransfeld is also spectacular on the inside: in the interior space, which is open throughout, three ellipsoids hover below the ceiling. They house two saunas and a steam bath. Under the wellness modules, a range of fitness equipment invites you to work out. Soon, this equipment will be used by the staff of both research institutes, Empa and Eawag.

At NEST, research, industry, and the public sector work together in order to test new technologies, materials, and systems in the fields of construction and energy under real-world conditions. NEST is designed as a "living lab" – which means that its flats and office spaces are actually used, while simultaneously serving as experimental environments for innovation. This means that, even in the case of Solar Fitness and Wellness, the experience of using the wellness facilities is still a means to an end: "Our objective is to be able to meet an energy-intensive need such as wellness entirely through renewable energy," explains Peter Richner, Deputy Director of Empa and Strategic Manager of NEST.

Only the practical test will show whether the energy objectives that have been set can be achieved. And the objectives are ambitious: "We want to operate the facility with one sixth of the energy that it would need with conventional operation," says Mark Zimmermann, Innovation Manager for NEST. More specifically: the aim is to reduce the 120,000 kWh of electricity that the Finnish sauna, the bio sauna, and the steam bath would normally swallow up each year to a figure of 20,000 kWh. This massive reduction is to be achieved by using a high-temperature CO₂ heat pump (see box) from the company Scheco, which can generate temperatures of up to 130°C. For efficient operation, the generated heat must be used over as great a range of temperatures as possible. To this end, the respective heat levels required for the different wellness modules are coordinated as a cascade. The heat is stored in layers in a large tank and made available for each of the various uses: 120°C for the Finnish sauna, 90°C for the steam generator in the steam bath, 70°C for the bio sauna, and finally 50°C and 30°C for the showers and the heating, respectively. The underlying energy concept was developed jointly by Empa researchers, the NTB International University of Applied Sciences and Technology at Buchs, and Lucerne University of Applied Sciences and Arts.