An international research group has investigated how PV-driven heat pumps and district heating can be combined to heat a building with several apartments in Sweden and has discovered that of the three combinations they evaluated, dependent on heat pumps, since the primary heat source was the “most advantageous solution” in terms of operational costs and environment.
A European research group has conducted a study into the performance of a hybrid PV -driven heat pump (HP) and district heating (DH) system in a building with several apartments. It was simulated via Trnsys software, based on the real parameters of an apartment building in Gothenburg, Sweden.
“The building is a 5 -storey test bed, called ‘HSB Living Lab’, with 29 apartments. It can be assumed that the building is always occupied, even during the summer holidays,” the team said. “The weather in Gothenburg is characterized by maritime moderate with cool summers and mild winters. The annual rainfall is around 850 mm, evenly spread throughout the year. The daylight takes between 6 – 18 hours a day, depending on the season.”
The heating system consists of two air-water heat pumps, district heating and an extra electric heater. Each heat pump has a total airflow speed of 1500 l/s and a nominal heating capacity of 9.8 kW. The electrical consumption of the compressor is 2.31 kW and the fan is 0.18 kW. The heating system delivers three 0.5 m³ of water tanks: one for household water, a second for the radiators and a third for the radiant floor. On the roof and a facade of the building there are PV panels with a total surface of 186 m² and a peak power of 17.1 kW. They are connected to a 7.2 kWh electric battery.
Control strategies
The scientists considered three control strategies to meet the thermal demand of the building: operation with priority in district heating; operation with priority in heat pumps; And only operate with district heating. The comparison was aimed at the thermal quantities, electrical energy consumption and production, the costs of energy and the environmental impact.
The simulation has taken into account that the annual thermal demand of buildings is 26,240 kWh for domestic hot water and 42,067 kWh for space heating. In the case of the DH priority, the district heating supplied 39.189 kWh, the HPS 27,099 kWh, with a monthly performance companies (COP) from 2.2 to 3.4, and the electric heating supplied 4,361 kWh.
On the other hand, when the strategy for the priority control of the heat pump was used, DH 16,406 kWh, the electric heating, had a negligible contribution and the heat pumps made 54,346 kWh with a cop with a cop ranging from 2.2 to 4. Finally, he delivered 70.9, while only district heating was used,, while only district heating was used,, while only district heating was used,, while only district heating was used,,, while only heating heating was used.
Result
“The annual photovoltaic Array -OverToplige energy is equal to 10,934 kWh. It is high during hot months and low during cold months. In the control strategy with district heating priority, 1,603 kWh of this excess energy has the potentially to provide the heat pumps in a 14.8% reduction in electricity, which results in a 14.8% reduction in the electricity consumption in a 14.8″%. ” the team added. “In the control strategy with heat pumps priority, 2,805 KHE of this excess energy have the potential to provide power to the heat pumps, resulting in a 13.5% reduction in the electricity consumption of heat pumps.”
According to the results, the annual costs for district heating and electricity were € 2,627 ($ 3,081), € 4,348 and € 6,312 for the priority of the heat pump, district heating priority and district heating only control strategies, respectively. They had 7,865 kg respectively, 13,716 kg and 21,854 kg CO2 equivalent emissions.
The researchers concluded that the use of HPS as the primary heat source in buildings with multiple apartment was the “most useful solution” in terms of operating costs and environmental impact.
Their findings were presented in “Analysis of a hybrid heating system with TRNSYS: district heating, heat pumps and photovoltaic in a building with several apartments“Published in Energy and buildings. Researchers from Greece for Research & Technology Hellas/Chemical Process and Energy Resources Institute (Certh/CPERI), Spain’s Fundacion Cartif and Sweden’s Rise Research Institutes of Sweden participated in the study.
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