With over 12,000 students and staff, the ETH Zurich Hönggerberg campus is an urban district in its own right. It comprises more than 30 buildings, including several teaching and research buildings equipped with the latest technologies. Each year, they consume nearly 77 gigawatt hours of energy (electricity and heat) – 22 gigawatt hours of which is for heating alone.
Until 10 years ago, heat was generated almost entirely from natural gas. In 2013, ETH Zurich began operating its Anergy Grid with an underground storage system to heat and cool the buildings at the Hönggerberg campus energy-efficiently and sustainably, as well as to reduce CO2 emissions. Both these aspects are an important part of the puzzle for meeting ETH Zurich’s goal of reducing CO2 emissions at Hönggerberg by at least 80% by 2040 compared to 2006 levels. This would be equivalent to cutting around 8,000 tons of CO2 annually. For 2020, the reduction target is 50% or 5,000 tons of CO2 annually.
The idea behind the dynamic underground storage is as simple as it is clever: it works like a battery that charges or supplies energy depending on the season. While some buildings might need to be heated in winter, others – in particular those with servers or lab equipment for research – give off heat year-round and have to be cooled. Instead of being released into the atmosphere, the excess heat is stored 150-200 meters below ground using water-filled probes that make it possible to use it for heating in the winter. Once the heat has been used, the temperature of the circulating water in the probes drops again. The process can be reversed in the summertime: ETH can use the cooler water to cool the buildings on the Hönggerberg campus.
The Anergy Grid or “cooling distribution grid” enables energy to be transported between buildings. Depending on the heating requirements in each building, the five connected energy centres suction or pump the water out of or into the Anergy ring. The connections created by the ring also allow unused energy from particular buildings to either flow to a different building or to be stored underground. Essentially, the dynamic underground storage system uses conventional technologies, such as heat pumps.
What makes the Anergy Grid a flagship project for sustainable energy supply are its intelligently connected heat sources and its size: the system currently consists of three underground storages and five centres that provide for heating and cooling in 14 buildings. Three other underground storages and one additional centre are being planned so that nearly all new and renovated buildings can eventually be connected to the Anergy Grid. Monitoring operations on an ongoing basis allows experience gained in the process to be applied directly to optimizing and further developing the Hönggerberg campus.
“The Hönggerberg campus and its ongoing development are very important for ETH Zurich’s future,” says Ulrich Weidmann, ETH Vice President Human Resources and Infrastructure. “The Anergy Grid is helping us to realise our concept of sustainable campus and university development, because it allows us to operate this location in an energy-efficient manner.”
Watt d’Or provides a motivational boost
Today, the Federal Office of Energy recognised the Anergy Grid at the Hönggerberg campus with the Watt d’Or 2020 award in the category of “Buildings and space”. The Watt d’Or honours outstanding achievements in the area of energy, with the aim of motivating businesses, policy makers and the public at large to discover the advantages of innovative projects and energy technologies for themselves.
Tours and exhibitions
Would you like to experience ETH Zurich’s Anergy Grid up close and personal? Take a tour!
- Public tour: Tuesday, 25 February 2020 from 6.15 p.m. to 7.15 p.m. Sign up here from 2020.
- Tour for ETH members: Friday, 4 March 2020. English from 12.00 p.m. to 1.00 p.m.; German from 1.00 p.m. to 2.00 p.m. Sign up here from 2020.
- Additional tours will be offered as part of the Treffpunkt Science City event series in autumn 2020.
Or visit the exhibit on the Anergy Grid
from 12 February through 26 March
at Campus Info (HIL building)
on the Hönggerberg campus.
Opening hours Monday to Friday, 7.30 a.m. to 5.00 p.m.