Conference Paper

Energy and Efficiency Analysis of Heat Pump Systems in Nonresidential Buildings by Means of Long-Term Measurements

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... Winiger et al. [42] report on analysis of ten ground-source heat pump systems serving non-residential buildings in Germany. These systems were monitored as part of the broader Energy-Optimized Building (EnOB) project [47]. ...
... The fraction of the electrical energy consumed by the circulating pump allocated to cooling is then: The scheme used to allocate the electrical energy consumed by the circulating pump is admittedly arbitrary, but a better scheme has not, to the authors' knowledge, been suggested in the literature. A similar approach was used by Winiger et al. [42]. ...
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When the new student center at Stockholm University in Sweden was completed in the fall of 2013 it was thoroughly instrumented. The 6300 m2 four-story building with offices, a restaurant, study lounges, and meeting rooms was designed to be energy efficient with a planned total energy use of 25 kWh/m2/year. Space heating and hot water are provided by a ground source heat pump (GSHP) system consisting of five 40 kW off-the-shelf water-to-water heat pumps connected to 20 boreholes in hard rock, drilled to a depth of 200 m. Space cooling is provided by direct cooling from the boreholes. This paper uses measured performance data from Studenthuset to calculate the actual thermal performance of the GSHP system during one of its early years of operation. Monthly system coefficients-of-performance and coefficients-of-performance for both heating and cooling operation are presented. In the first months of operation, several problems were corrected, leading to improved performance. This paper provides long-term measured system performance data from a recently installed GSHP system, shows how the various system components affect the performance, presents an uncertainty analysis, and describes how some unanticipated consequences of the design may be ameliorated. Seasonal performance factors (SPF) are evaluated based on the SEPEMO (“SEasonal PErformance factor and MOnitoring for heat pump systems”) boundary schema. For heating (“H”), SPFs of 3.7 ± 0.2 and 2.7 ± 0.13 were obtained for boundaries H2 and H3, respectively. For cooling (“C”), a C2 SPF of 27 ± 5 was obtained. Results are compared to measured performance data from 55 GSHP systems serving commercial buildings that are reported in the literature.
The medium-depth geothermal heat pump systems (MD-GHPs) use vertical concentric deep borehole heat exchangers (DBHEs) with depth more than 2 km to extract heat from medium-depth geothermal energy, which provides a higher-temperature heat source and improve the energy performance of heat pump obviously. This paper introduces the field test on energy performance of heat pumps in MD-GHPs. Results show that the outlet and inlet water temperature of DBHEs reach 33.0℃ and 23.7℃ respectively, thus the COP of heat pumps reaches 5.70. However, the heat pump with constant speed compressor is identified unsuitable for operation with high-temperature heat source. Besides, the high water resistance, low water temperature difference and energy efficiency lead to the poor energy performance of water pumps. Thus the high-temperature heat source hasn't been fully utilized. Then based on analysis of field test results, the design parameters of heat pump are optimized and the variable speed centrifugal compressor is applied. While the design parameters and control strategy of water pumps are optimized. Finally, the optimization effect is examined through practical application and the SPFH1, WTFu, WTFg, SPFH3, and SPFH4 of MD-GHPs reach 7.71, 57.2, 97.6, 7.15 and 6.35 separately, which are obviously improved.
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The world is facing a crisis due to energy depletion and environmental pollution. The ground source heat pump (GSHP) system, the most efficient new/renewable energy (NRE) system that can reduce the load of heating/cooling equipment in a building, can be used to address this crisis. Designers and contractors have implemented such systems depending on their experience, although there are many factors that affect the performance of the GSHP system. Therefore, this study aimed to conduct a sensitivity analysis on the impact factors in terms of energy generation and environmental impact. This study was conducted as follows: (i) collecting the impact factors that affect the GSHP system's performance; (ii) establishing the GSHP system's scenarios with the impact factors; (iii) determining the methodology and calculation tool to be used for conducting sensitivity analysis; and (iv) conducting sensitivity analysis on the impact factors of the GSHP system in terms of energy generation and environmental impact using life cycle assessment. The results of this study can be used: (i) to establish the optimal design strategy for different application fields and different seasons; and (ii) to conduct a feasibility study on energy generation and environmental impact at the level of the life cycle.
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