Green heat from wastewater for Jena's north

The industrial estates along Wiesenstrasse in Jena-Nord are expected to be supplied with green and CO2-neutral heat from 2028. Wastewater heat pumps at the central sewage treatment plant will be used to recover the heat from the treated wastewater and thus contribute to climate protection. Christoph Kindt, Head of Generation and Renewable Energies, and Jonas Waldhäusl, Project Developer Renewable Energies, presented the corresponding plans of Stadtwerke Energie Jena-Pößneck to the members of the Jena-Nord interest group (IG) at a general meeting this week.

The approach of Stadtwerke Energie envisages using the principle of heat recovery via wastewater heat pumps with a thermal output of around 20 megawatts: Warm wastewater flows reliably all year round in the downstream treatment of the central wastewater treatment plant. In future, this will flow through a heat exchanger containing cold water. The cold water is then heated and feeds a heat pump. The resulting heat can then be distributed via an appropriate local heating network and used for heating in a completely CO2-neutral way.  

Georg Hädicke, Chairman of the Jena-Nord interest group: "The tradespeople from 25 companies in Jena-Nord have welcomed the plans for the future heat supply with great interest. It was particularly well received that we do not expect high investments or conversions in the buildings, and that Stadtwerke Energie will organize the operational management. In addition, the use of innovative technology and green heat and cold is a positive location factor for our business park. We would be delighted if other companies from Jena-North were to join our initiative.

Christoph Kindt: "The use of wastewater heat is both ecologically and economically highly efficient. This is because it is permanently available at the central sewage treatment plant and can be used all year round via heat pumps. By tapping into this considerable heat potential, we are taking a further step towards the heat transition and climate neutrality for Jena.The local heating network still to be built in Jena-North is to be set up in such a way that businesses can also be supplied with cold in summer and can feed unavoidable waste heat into the grid themselves. In the future, around 3,000 residents and commercial units in the Wenigenjena residential district around the Schiller Church could also be connected to the green heat network.

However, there are still some preparatory steps to be taken before this can happen. First of all, the current plans are to be fleshed out by the end of 2024 as part of a feasibility study. Implementation could then begin with the construction of the new local heating network in 2025. From today's perspective, the aim is to commission the new wastewater heat pump by the end of 2028.

Background: 2040 heat network strategy for Jena 

The city of Jena has set itself the goal of becoming climate-neutral by 2035 and has described specific steps to achieve this in its climate action plan. In addition, the Thuringia Climate Act defines the goal of ensuring an emission-free heat supply in the state by 2040. The federal government wants to achieve the goal of climate neutrality by 2045.  

Stadtwerke Energie supports these climate policy goals. In the 2040 heat network strategy, they have described a concrete transformation path for decarbonizing their district heating supply. While the share of renewable energies in Jena's district heating generation is currently around two percent, this share is to increase to more than 90 percent by 2035 and the goal of climate-neutral district heating generation is to be achieved by 2040 at the latest. A mix of different renewable energy sources is to be used; river thermal energy, solar thermal energy and near-surface geothermal energy are planned, as well as biogas, large heat pumps and power-to-heat. In addition, green hydrogen plays an important role in the targeted green energy mix. Info at: www.stadtwerke-jena.de/waermenetzstrategie