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Emission free energy: Development of effective two-phase heat pump for industrial steam applications.

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Principle sketch for a vane compressor © ToCircle Industries AS
Principle sketch for a vane compressor © ToCircle Industries AS

Free2Heat will develop a validated concept for high temperature heat pumps. The main objective is the development of a robust and sustainable two-phase heat pump which can be implemented in an open heat pump cycle in order to recover excess heat from thermal processes and upgrade it to useable, high temperature process heat.

Excess heat streams contain often several phases (like water and steam) as well as air and other contaminations. The requirement for a robust, effective, temperature stable and flexible heat pump demand therefore the development of compressor technology which can operate with several phases.

Today, the energy of the process industry is mainly delivered from fossil-fuelled sources of energy (e.g. fire or gas boiler) that contribute significantly to greenhouse gas emissions. At the same time, the temperature of excess energy from different process steps is too low for direct recycling and reuse. SINTEF and ToCircle have identified the industry's need for high temperature heat pumps that can replace steam production from fossil-fuelled energy sources and reduce specific energy consumption.

The technical potential of an industrial heat pump in the range of 100 to 150 ° C is estimated at 172 TWh / year in the EU, with a market potential of 4400 plants and a value creation potential between 13 200 and 35 200 MNOK. The capacity requirement for thermal systems lies in the power range 0.5-4 MW. High-temperature heat pumps can be integrated into thermal processes where steam is often used as heat carrier. Today's available technology is limited to small temperature elevation or very large thermal capacities, and does not cover industry needs.

The investigated compressor is based on expander technology from Kjell Vadings patented principle (Vading, K. ,2011,  Unite States of America Patent No. US9376914B2). The patented ToCircle compressor technology enables lubrication and cooling of the compressor unit by targeted injection of water. This process which encounter two-phase compression avoids superheating of the working media (R718). Since the main function of the compressor is to increase the pressure of the working media steam (R718) the injected water will be used further in the heat pump cycle as working media. The heat pump system is therefore free of lubrication oils, does not need external de-superheating and has optimum temperature conditions for steam applications while maintaining a high efficiency.

Free2Heat is an Innovation Project for the Industry, funded by the Research Council of Norway and the project owner is ToCircle.

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