Since 24 August, the Solar Fitness and Wellness Unit has been operating at the Swiss Federal Laboratories for Materials Science and Technology’s (EMPA) campus in Dübendorf, near Zurich.

All the gym’s electricity demand – for the bikes and treadmills – is satisfied by energy from the sun, with its three saunas and showers for the saunas and gym heated by a CO2 heat pump.

The building contains two saunas, a steam bath, workout equipment and locker rooms that can be used by staff from EMPA and Eawag (the Swiss Federal Institute of Aquatic Science and Technology) and is part of a wider building project run by EMPA initiative NEST (Next Evolution in Sustainable Building Technologies).

“We want to operate the facility with one sixth of the energy that it would need with conventional operation.

Mark Zimmermann, NEST

NEST is not just aiming to use renewables but also to reduce energy demand. “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.

The aim is to reduce 120,000 kWh of electricity that the three saunas – the Finnish sauna, the bio sauna, and the steam bath – would normally swallow up a figure of 20,000 kWh each year.

NEST was able to meet this reduction by using a high-temperature CO2 heat pump, from the Swiss refrigeration, heat pump and air-conditioning company Scheco, which is delivering temperatures of up to 120°C (Finnish sauna) and down to 30°C (for shower water). 

The heat pump achieved a coefficient of performance (COP) of approximately three and reduced energy consumption by around two-thirds for the Solar Fitness and Wellness Unit.

“The capacity of our heat pump is 19 kW thermal, 5.7 kW electric,” Zimmermann told

The heat and moisture recovery from the sauna and steam bath also reduced ventilation loss by 50%.

“There is also a control system that responds to actual bookings of the wellness modules and only heats them up when necessary,” explains Zimmermann. In addition, improved heat insulation ensures minimal heat losses

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.

Leave a Reply

Your email address will not be published. Required fields are marked *