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Spanish scientists have proposed a new approach to combine photovoltaic-thermal panels with a reversible air-to-water heat pump in industrial buildings.
Researchers from the Spanish University of Zaragoza have proposed a new design for energy systems based on photovoltaic-thermal panels (PVT) integrated with an air-water heat pump using thermal storage tanks.
The system is designed to provide heating, cooling, domestic hot water (ACS) and electricity to industrial buildings.
"The space heating/cooling distribution circuit uses fan coils as terminal units, which allows a minimum supply temperature of 35ºC in winter and 7ºC in summer", they explain when describing the systems operating mode. "To increase the use of low-temperature heat, the DHW is supplied at 50 ºC instead of 60 ºC, performing periodic heat treatments at 60 ºC to prevent legionellosis according to health regulations."
The scientists tested the proposed system design over a 5-month period on a real system deployed at an industrial facility owned by Spanish PV specialist Endef in Zaragoza. The hybrid pilot plant consists of eight photovoltaic modules with a combined capacity of 2.6 kW covering an area of ??13.6 m2, two water storage tanks with a capacity of 350 l for DHW and 263 l for heating and cooling, as well as a Yutaki S6 reversible air-water heat pump supplied by the Japanese manufacturer Hitachi.
The heat pump has a nominal capacity of 16 kW in heating mode and 10.5 kW in cooling mode. Its nominal coefficient of performance (COP) in heating mode is 4.57 and in cooling mode it is 3.31. The domestic hot water tank uses two internal heat exchangers, one for the solar circuit and the other for the heat pump. The system can provide from 20 ºC to 60 ºC in heating mode, from 30 ºC to 60 ºC for DHW production, and from 5 ºC to 22 ºC in cooling mode.
The research team used temperature sensors and flow meters to monitor the thermal performance of the system and a DC/AC inverter to analyze that of the photovoltaic power generation unit. “The real meteorological data monitored in the pilot plant is integrated into the model. The transient model is executed with a time step of 5 minutes, and the results shown in this work are averaged every hour to smooth the results, since otherwise the fluctuations obscure the graphical interpretation and the comparison of the results”, he further explains. . "The weekly energy results are also calculated, by integration, to compare the weekly performance indicators."
Through this analysis, the academics discovered that the system is potentially “generally self-sufficient” in meeting the energy demand of the building. They also found that the pilot plant shows a negligible deviation from the simulated configuration. "The results show that the COP of the heat pump estimated in the transient model is similar to that obtained in the pilot plant, with a mean error of -10%," they further explained.
The proposed system is presented in the article “ Experimental validation of a solar system based on hybrid photovoltaic-thermal collectors and a reversible heat pump for the energy provision in non-residential buildings ”. systems and a reversible heat pump for energy supply in non-residential buildings), published in Renewable and Sustainable Energy Reviews . |
