Abstract
The paper deals with the three-dimensional theoretical and numerical investigation of the electrical performance of a Photovoltaic System (PV) with active fluid cooling (PVFC) in order to increase its efficiency in converting solar radiation into electricity. The paper represents a refinement of a previous study by the authors in which a one-dimensional theoretical model was presented to evaluate the best compromise, in terms of fluid flow rate, of net power gain in a cooled PV system. The PV system includes 20 modules cooled by a fluid circulating on the bottom, the piping network, and the circulating pump. The fully coupled thermal and electrical model was developed in a three-dimensional geometry and the results were discussed with respect to the one-dimensional approximation and to experimental tests. Numerical simulations show that a competitive mechanism between the power gain due to the cell temperature reduction and the power consumption of the pump exists, and that a best compromise, in terms of fluid flow rate, can be found. The optimum flow rate can be automatically calculated by using a semi-analytical approach in which irradiance and ambient temperature of the site are known and the piping network losses are fully characterized.
Highlights
The algorithm is implemented in the commercial software tool ANSYS/FLUENT, which offers the advantage of studying complicated geometries, generating both structured and unstructured meshes, and of solving thermo-fluid dynamic equations with customized source terms by means of a User-Defined Function (UDF), in which thermal and electrical models have been fully coupled with the solver
The competitive mechanism related to these opposite effects is characterized by a maximum value of the net power gain, i.e., the power gain due to the cell temperature reduction less the power absorbed by the circulating pump, and can be reached at the best compromise of the fluid flow rate
The Photovoltaic System (PV) modules were modeled by using ANSYS/FLUENT according to Sections 2 and 3 and to the geometry, the electrical characteristics, and the thermal properties given in [24,25]
Summary
In order to improve the efficiency of photovoltaic (PV) cells, several research studies have recently been carried out to investigate, both theoretically and experimentally, the possibility of increasing the maximum power by reducing the cell temperature, thanks to the adoption of cooling systems [1,2,3]. The main advantage of active cooling systems is a more efficient heat removal rate; for this reason, they are generally preferred to passive systems, in which a cooling fluid circulates without needing additional power. In this case, active cooling systems present an additional advantage related to the possibility of supplying an Energies 2020, 13, 852; doi:10.3390/en13040852 www.mdpi.com/journal/energies. The algorithm is implemented in the commercial software tool ANSYS/FLUENT, which offers the advantage of studying complicated geometries, generating both structured and unstructured meshes, and of solving thermo-fluid dynamic equations with customized source terms by means of a User-Defined Function (UDF), in which thermal and electrical models have been fully coupled with the solver.
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