Forging ahead: SPH and Push2Heat pave the way for high-temperature industrial heat pumps
The EU-funded Push2Heat project aims to identify and eliminate technical, economic, and regulatory barriers to deploying high-temperature heat pumps in industrial applications. SPH is also a member of the Push2Heat consortium. This article provides an overview of the project, its members, and our demonstration plant, which will soon begin operations at a German specialty paper manufacturer.
Advancing heat recovery technologies
Opening and using market potential: Push2Heat for the decarbonization of industry
Push2Heat is funded by the EU as part of Horizon Europe, the EU’s flagship research and innovation program. The objective of this research and innovation project is to break down the technical, economic, and regulatory barriers that currently prevent the widespread adoption of technologies for upgrading low-temperature waste heat. Specifically, this refers to deploying high-temperature industrial heat pumps, which are key to the decarbonization of European industry.
Push2Heat aims to increase energy efficiency in industrial processes, thereby reducing overall industrial energy consumption. It does so by utilizing high-temperature industrial heat pumps to boost industrial waste heat to a higher temperature level, making it reusable as process heat. The project thus makes an invaluable contribution toward meeting climate targets: among all sectors, industry accounts for the largest share of Germany’s total energy demand—it consumes just under 30 percent of all energy used domestically. Of these 30 percent, roughly two-thirds are attributable to process heat generation. To date, however, this process heat is rarely reused after its initial application, resulting in immense energy losses.
Push2Heat: Technological approaches and project objectives
Push2Heat focuses on industry segments where supply temperature ranges between 90 °C and 160 °C are relevant, such as the food, paper, chemical, and pharmaceutical industries.
The decarbonization potential of these sectors is enormous, explains Maider Epelde, coordinator of the Push2Heat project:
“Considering applications up to 200 °C, heat pumps could potentially deliver 730 terawatt-hours per year (TWh/a); this represents 37 percent of industrial process heat, with a corresponding CO₂ emissions reduction potential of 146 megatons per year.”
Maider Epelde, Coordinator of the Push2Heat project
The project partners concentrate on four distinct approaches to upgrading industrial waste heat:
- Industrial heat pumps with piston compressors, including SPH’s Thermbooster™
- Industrial heat pumps with turbo compressors
- Absorption heat transformers
- Thermochemical heat transformers
A consortium backs the project, comprising technology manufacturers such as SPH, industrial end-users, industry associations, and academic research institutions and organizations like the Fraunhofer Society and TU Berlin.
Push2Heat has outlined five objectives:
- Development and integration of heat-upgrading technologies at full scale.
- Demonstration of technologies in real industrial processes.
- Development of funding roadmaps, business models, and contractual framework conditions.
- Assessment of economic and environmental impacts.
- Dissemination of the results achieved.
Push2Heat has been running since October 2022 and will continue until September 2026. The technologies are already being integrated into relevant industries—SPH serves as the technology developer and supplier of the high-performance, two-stage industrial heat pump system Thermbooster™.
Thermbooster™ as part of the Push2Heat project: Steam generation for the paper industry
As a high-temperature heat pump capable of reaching temperatures of 180 °C and above thanks to a specially developed high-performance piston compressor combined with innovative process technology, the Thermbooster™ is the ideal demonstration system for providing process steam.
To demonstrate and evaluate this technology within the Push2Heat project, SPH, together with specialty paper manufacturer Felix Schoeller and Fraunhofer IEG, has planned and installed a Thermbooster™ system at the Weißenborn site, which will soon begin operations—marking the first such project in Germany. The aim is to generate new process steam for the drying process from low-grade waste heat at temperatures of 45 °C.
Felix Schoeller is one of Europe’s largest specialty paper manufacturers. At its Weißenborn site, the company operates a plant that is so far powered exclusively by fossil fuels. Steam production for drying processes in paper manufacturing leads to high CO₂ emissions. Although the production process offers immense potential for recovering and upgrading waste heat, this potential has not yet been fully exploited. SPH’s goal is to tap into a portion of this potential and make it usable as process heat.
Thermbooster™ at Felix Schoeller Weißenborn: Project overview
Heat Source:
Waste heat from the paper machine dryer; water-glycol circuit from the exhaust air moisture heat recovery system
Heat Source Temperature:
46 °C supply; 41 °C return
Heat Sink:
Steam at 2.2 bar (a)
Heat Sink Temperature:
123 °C
Refrigerants:
R515B (first stage) and R1233zd (second stage)
Electrical Power Input:
520 kW
Heating Capacity:
1,180 kW
COP:
2,3
Projected CO₂ Savings:
Approximately 1,200 tons of CO₂ per year
The Thermbooster™ operates with two refrigerant circuits to achieve the required high-temperature lift: our high-temperature industrial heat pump produces steam at 123 °C—ready for immediate production use—achieving a COP of 2.3.
ThermBooster™ in Use at Felix Schoeller: Overview of the System's Schematic Structure
The waste heat originates from the exhaust air of various production areas. Three air-to-water heat recovery systems are employed, enabling a water-glycol circuit to serve as the heat source for the Thermbooster™. In the low-temperature range, the system uses conventional screw compressors to accomplish the desired temperature lift. For the high-temperature range, SPH’s specially developed, high-efficiency piston compressors come into play. All compressors are driven by variable-speed, high-efficiency electric motors, ensuring a high efficiency factor even under stepless partial-load operation. The synthetic refrigerants used have a low global warming potential (GWP) and are non-flammable.
Container integration enables high prefabrication levels
The Thermbooster™ system is integrated into a sound-insulated container positioned outside the production building to ensure rapid, straightforward installation and maintenance. Because the entire heat pump system— including control cabinets and electronic controls—resides within the container, we can achieve a high degree of prefabrication and fully test the completed system on our test bench beforehand. The main heat pump installation takes place outside the production building, requiring only a brief interruption of the paper machine’s operation to connect to the integration points—namely, the water-glycol piping and the paper machine’s steam supply lines.
“The Push2Heat project is part of our ‘Green Lighthouse’ initiative, through which we develop and deploy sustainable technologies at an industrial scale at the Weißenborn site. Sustainable process steam generation plays a key role in the successful transformation of our industry.”
Hans-Christoph Gallenkamp, CEO, Felix Schoeller
Sophisticated measurement and control concept
Ensuring optimum efficiency and performance, the system uses a sophisticated measurement and control concept. On the heat sink side, the process steam generated by the heat pump feeds the dryers. This is mainly a steam pressure control loop. When the Thermbooster™ reaches the required steam pressure for the paper machine, steam from the heat pump can be used for this dryer group and thus for the drying process.
The heat pump system has two main actuators in each of the two stages: The first actuator is an expansion valve that regulates the superheating in the evaporator so that the evaporator runs at the best possible efficiency and protects the compressor from liquid in the suction gas.
The second actuator is the continuously variable speed control of the compressors, which has a direct influence on the heat output generated by the Thermbooster™. The heat pump system has two speed controllers for the compressor: The first controls the steam pressure at the heat sink. As steam consumption in the paper machine decreases, the steam pressure increases. If the steam pressure is going to exceed the setpoint, the system reduces the speed of the compressors to keep the steam pressure constant by reducing steam production. As demand increases and steam pressure decreases, the speed of the compressors is increased accordingly to maintain the steam pressure. The second controller controls the outlet temperature of the heat source to prevent the temperature from falling below the setpoint and thus more heat being extracted from the heat source than is available. In these cases, the controller reduces the compressor speed. As the speed of the compressor decreases, both the steam mass flow generated and the heat energy consumed from the source decrease.
Sensors enable remote maintenance and comprehensive data collection
In addition to heat meters for measuring the heat generated by the source and consumed by the heat sink, the system incorporates electrical consumption meters that record all electrical consumers: electric motors, circulation pumps, auxiliary heaters, and the control electronics. Based on these measurements, key performance indicators such as COP, SPF, and PER (performance efficiency ratio), as well as other metrics crucial for evaluating the system’s efficiency and effectiveness, can be calculated. From this data, optimization measures can also be derived and implemented in a timely manner.
Furthermore, temperature and pressure sensors are installed to monitor the heat pump’s condition remotely. Remote maintenance enables the timely analysis of operating conditions, direct implementation of straightforward fault remediation, and ongoing performance optimization.
The system is designed in accordance with the European standard EN 378 for heat pumps, which details requirements for installation depending on the chosen refrigerant, including specifications for ventilation systems and required safety devices. EN 378 also prescribes the necessary safety components on the heat pump itself, such as overpressure safety valves on both high- and low-pressure sections of the refrigerant circuits. These safety valves are installed so that any released refrigerant released in an emergency can safely vent to the environment.
Kick-off at Felix Schoeller: Commissioning in June
The Thermbooster™ heat pump system at Felix Schoeller is scheduled to begin operations in June 2025. The KPIs collected from real-world operation will be used to evaluate and analyze the system’s efficiency and performance under real working conditions. The teams at Felix Schoeller and SPH look forward to demonstrating the capability and practical viability of high-temperature heat pump technology through this implementation.
The system at Felix Schoeller in Weißenborn is one of more than ten commercially operated high-temperature heat pump systems that SPH will commission or has already commissioned in 2025.
Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Climate, Infrastructure and Environment Executive Agency (CINEA). Neither the European Union nor the granting authority can be held responsible for them.
