Researchers from Sintef Energy Research in Norway, the Norwegian University of Science & Technology (NTNU), and industrial partner ToCircle, have developed a new high-temperature water-based heat pump suitable for many industrial processes, and capable of producing temperatures of up to 180°C (356°F).
Sintef is calling this the “world’s hottest heat pump” and the first to reach temperatures of up to 180°C.
The new heat pump is “perfect” for the (roughly) 20% of Europe’s industries that require temperatures between 100°C (212°F) and 180°C, according to Sintef. Suitable industries would include “foodstuffs, fisheries and aquaculture, paper, oil and gas and metallurgy sectors,” Sintef said on its website.
The technology is not yet commercially ready, but is available for prototype and proof-of- concept projects, according to Michael Bantle, Senior Research Scientist at Sintef.
The new heat pump is designed to use water as the refrigerant. “However, you can mix in some ammonia as well so you have a refrigerant mixture to match temperature glides in the heat sink and heat source,” Bantle explained. “However, at 180°C the amount of ammonia is marginal.”
The compressor in the heat pump — built by Norwegian manufacturer ToCircle — uses steam technology in a rotary vane machine. “The vane machine is a type of compressor equipped with vanes that rotates such that it changes the compressor volume with each revolution,” Bantle explained. “The secret behind Tocircle’s compressor is that all the moving parts in contact with the work medium are lubricated using water.”
Using injected liquid water together with with steam compression promotes lubrication and also reduces the thermal stress on the system. The liquid water is used to de-superheat the steam during compression. Without the injected water there is a danger of overheating the compressor.
“All these factors combined in a single machine offer a very promising platform for the development of a high-temperature heat pump with pure water as its work medium, and not least because many industrial processes already use steam as an energy carrier in the first place,” Bantle said.
Cutting energy consumption
In addition to being able to produce very high temperatures, the researchers expect the new technology to reduce energy consumption by 40 to 70% by using the low-temperature waste heat that is readily available in many industrial manufacturing processes.
“This means that we no longer have to waste any heat, but can keep the heat we generate all to ourselves,” Bantle said. “This in turn will drastically reduce our greenhouse gas emissions because it will be possible to retain the surplus heat generated by the industrial process, feed it into the heat pump, and so increase the process temperature.”
“Investment in a heat pump costs money, but this technology will guarantee big savings that will enable us to recover our investment costs relatively quickly,” Bantle added.
The heat pump is a further development of a technology originally developed for TINE, a Norwegian dairy located in the western city of Bergen. The original technology produces temperatures around 100°C and enabled TINE to become the world’s first zero-emission dairy, according to Sintef. The series of heat pumps used by TINE include both ammonia-water and propane-butane units.
“In order to achieve temperatures of up to 180 degrees, we had to identify a refrigeration agent with somewhat different thermal properties, and we finally ended up with the most natural of them all – water,” said Bantle.
“All these factors combined in a single machine offer a very promising platform for the development of a high-temperature heat pump with pure water as its work medium, and not least because many industrial processes already use steam as an energy carrier in the first place,”Michael Bantle, Sintef.
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