Thermal Modeling of Active Solar-Distillation Systems
The coupling of a semi-transparent photovoltaic (PV) module with a conventional solar water collector in a single unit generates a new concept of PVT technology, and it can be considered a hybrid PVT concept. In this case, approximately 15–20% of the inci
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Thermal Modeling of Active Solar-Distillation Systems
5.1
Introduction
The efficiency of a solar still can be enhanced with a forced-circulation mode of operation. In this mode, the temperature of water in the still can be increased. Consequently, the temperature difference between the water and the inner surface of the transparent glass cover can be increased, which increases the heat-transfer rate from the water surface. Soliman [1] suggested the concept of feeding hot water into the basin from a solar-collector panel (high-temperature solar distillation) in 1976. Worldwide, many researchers [2–12] have theoretically and experimentally studied different active solar-distillation systems. Either a conventional or a non-conventional external source of energy is required to increase the water temperature. The forced mode of operation is achieved by using a pump, which can further run either by a conventional source of energy (electricity) or a non-conventional source of energy (photovoltaic [PV]). Therefore, grid electricity as a power source was supplied for the forced mode in a conventional solar thermal collector. Both electrical and thermal energy, in the case of a hybrid photovoltaic thermal (PVT) system, is generated by the PVT collector itself. However, the photovoltaic (PV) systems convert incident solar radiation into electrical energy, but the thermal energy absorbed has been unexploited [13]. Conventional solar thermal systems can be integrated with the photovoltaic cells/module and PVT systems to maximize the energy gain. Therefore, a solar still integrated with solar thermal technology—e.g., a flat-plate collator (FPC), an evacuated tubular collector (ETC), and a compound parabolic concentrator (CPC) —and photovoltaic technology makes the solar still fully dependent on a renewable source of energy. Integration of a solar still with solar thermal technology and photovoltaic technology to fulfill the external energy requirement makes it a “PVT active solar still.”
© Springer Nature Singapore Pte Ltd. 2017 G.N. Tiwari and L. Sahota, Advanced Solar-Distillation Systems, Green Energy and Technology, DOI 10.1007/978-981-10-4672-8_5
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5 Thermal Modeling of Active Solar-Distillation Systems
The external thermal energy can be feed into the basin of the solar still by integrating different PVT systems. For this chapter, a conventional solar still coupled with (a) PVT flat-plate collectors (FPC), (b) PVT compound parabolic concentrators (CPC), and (c) evacuated tubular collectors (ETC) were studied analytically. Moreover, the expression of basin-water temperature is derived for all of these active solar-distillation systems.
5.2
Solar Still Integrated with N-Photovoltaic Thermal Partially Covered Flat-Plate Collectors (N-PVT-FPC)
To determine the performance of a flat-plate collector (FPC), the essential factor is heat loss by convection. As discussed in Chap. 4, the flat-plate collector (FPC) is at the heart of any solar energy-collection system designed for operation in a low or medium temperatur
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