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Analysis of CO2 heat pump for low energy residential building
Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, Department of Electrical Power Engineering.
2013 (English)MasteroppgaveStudent thesis
Abstract [en]

In low energy buildings heat loss is reduced through energy-saving measures like heat recovery of ventilation air and a well-insulated building envelope. Consequently the demand for domestic hot water often makes up a larger share of the annual heating demand than in traditional buildings. For this application heat pumps using CO2 as a working fluid are seen as a promising alternative to conventional heat pumps. In the current study a transcritical CO2 heat pump model for use in building simulations was developed. Some challenges related to the development and implementation of the model were pointed out. A preliminary study of the model was performed in order to determine the optimal input parameters for the heat pump in the building of interest. The performance of the heat pump was analyzed over a range of operating conditions. Sizing recommendations for the main heat pump components were made, and a strategy for optimal control of the gas cooler pressure was presented. The model was implemented into EnergyPlus and used for energy simulations of a low energy residential building consisting of three apartments. The heat pump performance was analyzed for different building usage patterns including ?normal? use, increased demand for domestic hot water and night-time reduction of the indoor temperature. Simulation results showed and increase in overall system SPF from 2.51 to 2.64 in the case of increased domestic hot water demand because of more favorable operating conditions for the heat pump. Results further suggested that energy savings in the case of night-time temperature reduction would be minimal due to an increased demand for supplementary heating when reheating the building. In the latter case the overall system SPF was reduced to 2.43. Recommendations for achieving a better performance were made based on the simulations results.

Place, publisher, year, edition, pages
Institutt for energi- og prosessteknikk , 2013. , 98 p.
URN: urn:nbn:no:ntnu:diva-21999Local ID: ntnudaim:9504OAI: diva2:646737
Available from: 2013-09-09 Created: 2013-09-09 Last updated: 2013-09-09Bibliographically approved

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