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British scientists have designed a new heat pump concept that they say could be particularly beneficial for newly developed areas or potential residential complexes. The system uses ice or ice slurry as a heat source and its energy consumption is reportedly lower than that of several types of heat pumps available on the market.
A research group at the University of Nottingham (UK) has developed a heat pump system that uses water or ice as a heat source and takes advantage of existing gas pipelines for energy transfer.
The researchers explained that ice-source heat pump systems generate heat from ice or ice slurry derived from water supplied through underground pipelines or from stored water provided by seasonal rainfall. “This process takes advantage of the high enthalpy of phase change, allowing for significant energy absorption with minimal mass or volume,” they added. “This heat pump concept is effective with water as a heat source due to water’s high latent heat of fusion, which allows for substantial energy absorption with little mass.”
The proposed system, like ground source heat pumps, can be connected to a central heat pump system, where numerous residential units are interconnected. This configuration is said to be especially beneficial for newly developed areas or potential residential complexes, “where the dimensions and piping layout of the new units can be meticulously planned.”
The system uses a compression refrigeration cycle that moves hot compressed gas from the compressor to the condenser, which releases heat to the heat sink, where it undergoes a phase change and turns into a liquid, causing a drop in temperature. The liquid refrigerant then enters the evaporator, where it absorbs heat from the cold source and evaporates. In the next stage, the evaporated refrigerant returns to the compressor, where it is compressed again to restart the cycle.
The academics acknowledged that the proposed heat pump has a lower coefficient of performance (COP) than conventional heat pumps, but also highlighted that these systems have reduced water circulation, which translates into lower additional costs due to higher energy consumption and pipe installation.
They also explained that the proposed solution is ideal for rainy countries like the UK, which is equipped to use wastewater from ice production in city sewer systems without significant impact.
“Importantly, the water used by the ice-source heat pump in this scenario undergoes a closed loop: A portion of the wastewater is treated and injected into the city’s gas pipes, absorbing heat from both the wastewater and the soil within the sewer walls and gas pipes,” they further explained. “In this setup, the heat pump releases chilled water or ice slurry into the city sewer, which, after simple treatment, is partially returned to water storage tanks for reuse in the process and to continue feeding the heat pumps.”
Using a series of simulations, the researchers evaluated the performance of the ice source system and compared it to that of air-source and water-source heat pumps, focusing in particular on a comparison with a commercial 10 kW air-source heat pump from the German manufacturer Vaillant.
Their analysis showed that the ice source system has a higher energy consumption by a factor of 2.7 compared to conventional gas boilers, while electric resistance heating, air source systems and water source systems have values ??of 7.5, 3.2, 2.5 and 2.7, respectively.
“Furthermore, electricity consumption exceeds the current peak during 89%, 47%, 35% and 39% of the hours of the year for each respective system,” they stressed. “These results emphasize the role of the proposed system in managing peak electricity demand and improving generation and transmission capacity following the phase-out of natural gas.”
The system was presented in the article “ Ice source heat pump system for energy supply via gas pipelines – Part1: Performance analysis in residential units”, recently published in Energy . |
