Energy input to the heating instead of sewage: Technische Hochschule Mittelhessen, a university of applied science, uses HUBER ThermWin for heating and cooling with wastewater

Mittelhessen University of Technology (THM) university of applied science intends to exploit a previously quite unknown potential with a new system: heating and cooling with energy from wastewater.

The new plant, with the HUBER ThermWin system at its core, was commissioned at the end of May by THM's executive committee, Giessen's Mayor Frank Tilo Becher and Ayse Asar, State Secretary at the Hessian Ministry of Science and Art (HMWK).

THM President Prof. Dr Willems: “previously untapped wealth”

The plant is located at THM's Wiesenstraße campus. With canteens, numerous lecture halls, central administrative facilities as well as laboratories and workshops in several specialist areas, the campus is always a bustling hive of activity. The amount of wastewater generated is correspondingly high. In addition, the university primarily uses the wastewater from public sewers. “It may sound strange, but this wastewater represents previously untapped wealth,” THM President Prof. Dr Matthias Willems said during commissioning. Wastewater has average temperatures of 10 to 12 degrees Celsius in winter and just under 20 degrees in summer. Using heat exchangers and heat pumps, this “wealth” can be used for cooling and heating.

Saving 300 tonnes of CO₂ per year with HUBER ThermWin

At THM, the wastewater will in future be collected from the sewers of the Central Hessian water utility company using a HUBER ROTAMAT^® RoK4 pumping stations screen. From there, the liquid medium is pumped into the HUBER RoWin heat exchanger installed in the building, while the solids are directly returned to the sewer. The heat exchanger operates a heat pump in winter and a chiller in summer. The heat pump can provide around 850 kW of heat output, while the chiller generates around 600 kW of cooling energy. The aim is to save around 300 tonnes of CO₂ per year.

Hessen’s State Secretary Asar: “system saves CO₂ and advances research into sustainability”

“Hessen plans to be climate-neutral by 2045, the state government wants to lead by example and be CO₂ neutral by 2030 – universities will make an important contribution to this as a result of their share of energy consumption in the state properties,” Ayse Asar explained. "And, it goes without saying that our universities are also training the bright minds of tomorrow who are developing solutions for a climate-friendly energy supply. The wastewater heat recovery plant not only saves CO₂, it also represents a big step forward in sustainability research."

Around EUR 1 million in funding

HMWK is supporting the construction and operation of the plant with around one million euros from the “REACT-EU” fund, which was set up in response to the Covid pandemic to promote projects in the European Regional Development Fund (ERDF), especially at educational institutions.

However, the idea of using the heat from wastewater was already floating around at THM before the pandemic, as Prof. Dirk Metzger, Vice President of Strategic Construction Planning and Sustainability, explained. The project was implemented in 2022, when THM’s facility management developed an energy concept and, following a tour of the HUBER pilot plant at the Museum of Bavarian History in Regensburg, started with the concrete planning. The structural key elements of the plant for the use of energy in wastewater were delivered last December before commissioning was completed in May of this year.

Federal Minister Geywitz found out more on site

At the end of August, Klara Geywitz, Federal Minister for Housing, Urban Development and Building, gained first-hand information on site about the potential of municipal wastewater for heating and cooling: “it is becoming increasingly more important that we have as many decentralised solutions as possible in terms of energy and heat supply,” Geywitz said. During a guided tour of the technical facilities, she was impressed by the engineering performance and its compact implementation, which also enables its use in existing buildings or new residential housing districts.

“What you are doing here is basically municipal heat planning – just on a campus,” emphasised Federal Minister Geywitz. The fact that the university relies on wastewater as an energy source that is available anywhere is innovative: “you are using something that is actually seen as a problem, without generating additional costs or an environmental impact.” The fact that the technology is also available for teaching and research purposes in the sense of an actual laboratory completes the idea of sustainability.