Abstract
Silicon based photovoltaic modules (PV) are a wide spread technology and are used for small and large PV power stations. At the moment, the most efficient method which can be used to improve the annual electrical energy production of PVs is solar tracking systems. However, solar tracking systems increase substantially the initial cost of the investment and insert maintenance costs. During the last few decades, alternative improving methods have been investigated. These methods are based on the reduction of the PV cell temperature, which adversely affects the power production. In the present study, a system with water based photovoltaic-thermal (PVT) collector paired with geothermal heat exchanger (GHE) is compared on the electrical energy basis with a conventional PV system. As the first approach on the topic, the aim is to find out in which extent the PVT-GHE system improves the electrical energy generation by cooling down the PV cells and which parameters influence the most its energy performance. With this aim in mind, the model of the system with the PV, PVT, and GHE was formulated in TRNSYS and validated via experimental data. Meteorological data for Athens (Greece) were used and parametric analyses were conducted. The results showed that the PVT based system can increase the generated electricity from 0.61 to 5.5%. The flowrate, the size of the GHE and the number in-series connected PVTs are the parameters which influence the most the energy performance of the system.
Highlights
The idea of coproducing heat and power from the same surface by means of photovoltaicthermal (PVT) collectors was established during the energy crisis at 1970s [1,2]
The results shown that PVTs did not manage to generate more electrical energy than the PVs, even though the overall daily efficiency of PVTs was measured up to 80%
The results showed that the electrical efficiency of the PVT improved and that the synergy of the geothermal heat exchanger (GHE) with PVT is a promising active cooling system, which can be used to regulate the temperature of the PV cells
Summary
The idea of coproducing heat and power from the same surface by means of photovoltaicthermal (PVT) collectors was established during the energy crisis at 1970s [1,2]. Systems which are based on PVTs can cooperate successfully with heat pumps by providing heat and electricity for energy efficient buildings [7,8,9]. From the absorbed solar energy by a conventional photovoltaic (PV) panel, the minor portion of this converts to DC electricity (10–20%), most converts to heat. A larger portion dissipates to the environment and a remaining part heats up the PV cells and increases their temperature. As it is well known, the efficiency of PV cells is related to temperature. The passive type of systems is based on standalone procedures without electromechanical equipment, while for active systems, circulation pumps and automation control are necessary
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