Fraunhofer ISE: heat pumps deliver 160 C process steam, if the system fits
Victoria Shinder2 min readThe Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) has reported results from two research projects on large heat pumps, pv magazine reported on 9 October: one on industrial process steam up to 160 C, one on five large heat pumps running in German district heating networks.
Industrial steam (FernWP). Fraunhofer built a test rig to characterise high-temperature systems up to 160 C, delivering process steam and pressurised hot water. Testing focused on heat pumps using butane as the refrigerant; because butane is flammable, the work also covers safety requirements and installation conditions. The institute's main finding is about design, not peak temperature: simply scaling up components designed for refrigeration or building HVAC is insufficient. Technical lead Ursula Wittstadt said the maximum temperature is not the only criterion — the equipment must supply steam efficiently and reliably while heat sources, loads and operating modes change. FernWP runs until September 2027, funded by Germany's economy ministry, with Fraunhofer ISE, IEG and ISI and industry partners.
District heating in practice (Reallabor GroßWP). Since 2023 the project has collected operating data from five large heat pumps in German district heating networks. They do reach their target operating points, but efficiency and availability depend on the heat source, hydraulic configuration and the other generators in the network. Two observations stand out:
- River-source heat pumps lost output as water cooled, especially when source temperatures dropped below about 6 C and units ran at part load — a winter limitation exactly when heat demand peaks.
- Operating strategy shifted from the planned seasonal operation to running on daily demand profiles and energy-market prices, which means more start-stop cycles and greater demands on maintenance and availability.
Why it matters. Process heat is one of the hardest parts of industrial decarbonisation, and 160 C covers a large share of food, paper and chemical steam needs. Fraunhofer's results say the technology works but is a system-integration problem: utilities and plant owners should size around source-temperature drops and market-driven cycling, not nameplate ratings. Next, Fraunhofer plans models from the measured data and expanded safety rigs for high-temperature refrigerants.
Source: pv magazine, "Fraunhofer ISE demonstrates industrial heat pumps capable of producing steam at 160 C", 9 October 2026 — https://www.pv-magazine.com/2026/10/09/fraunhofer-ise-demonstrates-industrial-heat-pumps-capable-of-producing-steam-at-160-c