Thermal regulation of building-integrated photovoltaics using phase change materials

Benlakam

Period. Polytech. Mech. Eng.

2016

A two-dimensional (2D) Keywords PCM, Natural convection, Cooling PV panel IntroductionThe photovoltaic (PV) panel absorbs only about 16 % of the incident solar energy that is converted into electricity; the remaining insolation absorbed is transformed into heat [1]. The photovoltaic cell efficiency decreases with increasing temperature [2]. This can typically result in an efficiency drop off of 0.5 % per °C increase in the cell operating temperature. Since, for example, silicon solar cells are characterized at 1000W/m 2 and 25 °C as ideal temperature for the cell, maintaining the cell temperature at 25 °C can retain the rated efficiency of the cell. Cells will also exhibit long-term degradation if the temperature exceeds a certain limit [3].This problem can be avoided by keeping a uniform temperature across the panel. The use of the extracted thermal energy from cooling can lead to a significant increase in the total conversion efficiency of the receiver. Natural or forced air circulation is a simple and low cost method to remove heat from PV modules, but it is less effective if ambient air temperature is over 20 °C, as it is usual for many months in low latitude countries.Another, more efficient way is to use a liquid as the coolant of the panel, in order to absorb more heat and to cool the panel more effectively [4]. This is the general philosophy of hybrid photovoltaic-thermal collectors. In such kind of cooling, various investigations have been made producing interesting results.In the desert, the PV temperature can exceed 40 °C inducing a power drop in crystalline silicon PV. Increased operating temperature also results in accelerated PV degradation due to cell delamination allowing moisture ingress. The air or water cooling systems are limited by very low heat transfer and large capital as well as maintenance costs [5].However, a novel method to regulate the rise in PV temperature, phase change materials (PCM), which absorb energy as latent heat at a constant phase transition temperature has been developed and employed recently. The phase change materials undergoing solid-liquid phase transition at or close to 25 °C can absorb the excess thermal energy during phase change, which otherwise would raise PV operating temperature, and can maintain the PV operating temperature at or close to 25 °C.

Section: Validationsupporting

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Section: Numerical Modellingmentioning

confidence: 99%

“…The numerical model was validate against the experimental and numerical data of Huang et al (2004) for the temperature (Fig. 2 and Fig.…”

Section: Validationmentioning

confidence: 99%

mentioning

confidence: 99%

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Effect of the Fins Length for the Passive Cooling of the Photovoltaic Panels

Benlakam

Period. Polytech. Mech. Eng.

2016

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Norton¹

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Entwicklung eines temperaturregulierenden Fotovoltaik‐Fassadenpaneels mit PCM

2017

Development of a temperature-regulating photovoltaic façade panel with phase change material − a contribution to buildingintegrated PV in mullion and transom façades Opaque façade areas show great potential for generating energy by using photovoltaic (PV) modules. Their use in the façade sector has so far been limited mainly to cold fronts because the performance of these modules drops with increasing temperature of the PV cells. In contrast to cold fronts, rear ventilation in order to cool the modules is not possible in standard mullion and transom façades. To ensure low module temperatures and thus a high performance, the PV modules are combined with rear-mounted phase change materials (PCM). When the temperature in the façade reaches the defined melting point of the selected PCM, it results in a phase transition from solid to liquid. The material absorbs thermal energy from the PV module and the temperature increase of the module can be buffered. At night, the thermal energy which is latently stored in the PCM is released back into the ambient air.