Evaluation of Integrated Concepts with CO 2 for Heating, Cooling and Hot Water Production

Silje Smitt, Ángel Pardiñas and Armin Hafner
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Silje Smitt: Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1D, 7491 Trondheim, Norway
Ángel Pardiñas: SINTEF Energy Research, Kolbjørn Hejes vei 1D, 7465 Trondheim, Norway
Armin Hafner: Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1D, 7491 Trondheim, Norway

Energies, 2021, vol. 14, issue 14, 1-28

Abstract: The hotel sector is characterized by high thermal demands and a large carbon footprint, which greatly contributes to the global warming effect. Consequently, there is a need to investigate solutions that can reduce energy usage within this sector by means of environmentally friendly and sustainable technologies. Integrated CO 2 heat pump systems for heating, cooling, and hot water production in hotels have demonstrated promising results. This paper theoretically compares the energy consumption, environmental impact, and cost of three different design concepts for integrated CO 2 units equipped with thermal storage. The main characteristics of the evaluated designs are single-stage compression, parallel compression, and ejector-supported parallel compression. Furthermore, two separate hot water charging strategies were implemented and investigated over a large span of ambient temperatures and loads. The evaluations were carried out by considering eight different European locations, ranging from Scandinavia to the Mediterranean. The results revealed that the ejector-supported parallel compression design was superior in terms of annual COP, which was found to be in the range of 4.27 to 5.01 for the Scandinavian locations and 5.03 to 5.71 for the other European locations. When accounting for investment cost and electricity prices, the payback period at the Scandinavian locations was 6.3 to 7.7 years. Payback periods of 3 and 4.5 to 7.5 were obtained for hotels located in the temperate and Mediterranean climates, respectively. The investigation also revealed that the hot water charging strategy, rather than the specific CO 2 heat pump design, is the least expensive measure to enhance performance.

Keywords: heat pump; system design; heating and cooling; hotels; CO 2; thermal storage; numerical modeling; concept evaluation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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