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The share of solar thermal energy in the residential sector is increasingly stagnant compared to other forms of solar energy (e.g., photovoltaics). Further share increase might be achieved through improvement of thermal efficiency and/or a reduction in production costs. Nowadays, thermal performances of the mostly used state-of- the-art classic flat plate solar collectors have already reached high values and it is not expected that significant improvements of thermal performances can be achieved. For this reason, the development of solar technology is increasingly directed towards the use of polymeric materials in solar collectors to further decrease production costs. This paper presents evaluation of thermal characteristics of a novel prototype polymer solar collector design. The assessment of thermal characteristics on a segment of a polymer solar collector comprises experimental and numerical approach. Experimental part of research is performed using open test rig. Useful heat gain and efficiency factor is calculated for different inlet water temperatures. Functional dependence of efficiency factor on insolation, water and air temperature is computed. In order to validate numerical model developed in ANSYS FLUENT software package, simulations are firstly performed on a segment of a polymer solar collector and results are correlated against experimental ones. Afterwards, simulations are conducted for a whole collector that comprises 8 proposed segments and for such efficiency curve coefficients (η0, a1 and a2) are given. The estimated efficiency of proposed polymer collector design is 30-37% lower for typical summer operating regime compared to the state-of-the-art FPC. In addition, stagnation temperature measurements are performed according to EN ISO 9806:2017, when stagnation temperature of 125.1°C is determined after applying protective measures from overheating. |
