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HPT TCP ANNEXES ANNEX 49 DESIGN AND INTEGRATION OF HEAT PUMPS FOR nZEB Nearly zero energy buildings have been introduced for new public buildings in the EU-member states about a year ago, on January 1, 2019. Even though requirement differ among countries, efficient heating systems and other building system technology is advantageous to fulfil the requirements. In less than one year, by the deadline of January 1, 2021, the requirements will be ex- tended to all new buildings. In Task 1 of IEA HPT Annex 49, the requirements in the dif- ferent participating countries are compared and conclu- sions for the heat pump applications are drawn. On this basis, in Task 2, heat pump integration options are as- sessed, and in Task 4 implications for design and control of the heat pump application in nZEB are investigated. In Task 3 the monitoring of heat pumps in real built nZEB is evaluated in parallel to each other. Norway, for instance, has several monitoring projects in larger nZEB buildings, among them a hotel, a supermarket, a school building and a cluster of five office buildings. Even though the measured performance is good in most of the monitored buildings, there are also optimisation po- tentials found for improved heat pump operation. The school building Justvik Skole in Kristiansand, southern Norway, is built with an energy reference area of 3,480 m2 according to the Norwegian passive house standard (NS 3701), see Figure 1. In the design phase, the DHW share was evaluated to 55% of the total heat energy. Therefore, a ground source CO2 heat pump is applied, with high performance values for DHW operation. At the test point of 3 °C/ -2 °C and 30 °C/70 °C, a COP of 2.9 is reached. In order to also achieve good performance in space heating operation, the heat emission system is specifically adapted to create low return temperatures for the heat pump. Since the performance of CO2 heat pumps is strongly affected by the return temperature of the systems connected to the gas cooler, the COP and the heating capacity are impro- ved at low return temperatures. The heating system is thus composed of low temperature radiators with opera- ting temperatures of 45 to 40 °C, a floor heating system working between 35 and 30 °C and ventilation air heat- ing from 30 to 18 °C, in series. The DHW heating, 14 °C inlet and 55 °C outlet on the water side, is connected in parallel and can always be operated. During the monito- ring period Feb. – Sept. 2018, a moderate average COP of 3.0 and a degree of coverage of 78% were measured. This is below the design values of a COP of 3.4 and 94% coverage, and indicates optimisation potential. One reason is a low DHW use, which limits the decrease of the return temperatures and thus the performance of the heat pump. The CO heat pump had a malfunction in the tempera- 2 ture sensor for the gas cooler, which led to sub-optimal pressure and temperatures in the gas cooler. Thus, the performance was reduced, and the heating capacity was affected. Possible optimisation is improved measurement of gas cooler temperatures, with accurate control of gas cooler temperature and pressure. Also, the radiator set point should be lower and ventilation air temperatures increased, lowering the return temperature in the heat- ing system. Further, the source system is undersized and should be extended with an additional borehole, and a higher DHW use would increase the system performance by lower return temperatures for the CO2 heat pump. Annex website http://heatpumpingtechnologies.org/annex49/ Contact Operating Agent is Carsten Wemhoener, for SFOE, Switzerland. carsten.wemhoener@hsr.ch Fig. 1: Schematic of the heating system of Justvik Skole in Kristiansand, southern Norway in Fig 1, with CO2 heat pump and adapted heat emission system 12 HPT MAGAZINE VOL.38 NO 1/2020PDF Image | Integration of Heat Pumps into the Future Energy
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