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Efficient CO2 heat pumps for non-residential use |
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In large buildings CO2 heat pumps can cover the entire cooling and heating demand with high energy efficiency, according to the latest study by SINTEF. The research institute will now develop a prototype heat pump to prove its efficiency in practice.
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2007-08-20
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This is the 3rd in a series of articles about the International Congress of Refrigeration in Beijing. Starting from Wednesday, 22 August, R744.com will report live from this key event.
CO2 heat pump systems in non-residential buildings can achieve the same or higher Seasonal Performance Factor than systems using conventional working fluids. Provided that the heat distribution system is designed for a low return temperature, a CO2 heat pump may therefore outperform the energy efficiency of current installations, and cover the entire cooling and heating demand in office buildings, schools, hospitals, or hotels.
This has been demonstrated in computer simulations by Norway's leading research institute SINTEF which have also proved that by making a serial connection of the radiator system and the ventilation heater batteries it is possible to obtain a low return temperature and therefore favourable conditions for CO2 heat pumps. Preheating and reheating of hot water will lead to a further increase in the Coefficient of Performance (COP) for CO2 heat pump systems
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Test conditions & results
Researchers from SINTEF calculated the Seasonal Performance Factor (SPF) for single-stage CO2 and R134a heat pumps for heating and cooling a 7,000 m2 office building in Oslo. Operating the heat pumps in either cooling or heating mode, the researchers could prove the following:
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- In heating mode, the CO2 heat pump achieved the highest SPF at most operating conditions.
- The CO2 heat pump will achieve a higher SPF if the heating of ventilation air is dominating the total heating demand of the building, and if there is a considerable hot water demand.
- CO2 heat pumps will make auxiliary heating only necessary at very high supply water temperatures due to the high outlet temperature from the gas cooler.
A detailed paper with all test results will be available on R744.com soon.
SINTEF's heat pump prototype
Encouraged by these promising results, SINTEF is planning the construction of a brine-to-water CO2 heat pump system for heating and cooling a 3,000-5,000 m2 Norwegian non-residential building. The heating capacity of the CO2 heat pump will be in the range of 50 to 150 kW, and it will be designed as a single stage unit using an inverter controlled reciprocating compressor.
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More information:
› Find out more about SINTEF in our Engineering Services Section
 SINTEF study - Abstract ICR 2007, page 176 (1.3 MB)
SINTEF study - Topical Article, Heat Pump Newsletter 2006, (1.6 MB)
1st ICR article: "SINTEF: Ejectors will make R744 systems even more efficient"
3rd ICR article: "UNEP calls for sustainable refrigeration"
ICR feature article: "ICR 2007 - CO2 in the global spotlight"
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