| Work Detail |
Indian scientists have built a photovoltaic system coupled to a thermoelectric generator that uses graphite as a heat sink. The graphite-based system achieved higher throughput and temperature gradient than a reference system without heat dissipation.
Researchers at the Vellore Institute of Technology in India have developed an experimental system that combines photovoltaics with a thermoelectric generator (TEG) and a graphite sheet as a heat dissipation element.
TEGs can convert heat into electricity through the “Seebeck effect,” which occurs when a temperature difference between two different semiconductors produces a voltage difference between two substances. These devices are commonly used in industrial applications to convert excess heat into electricity. However, its high cost and poor performance have so far limited its adoption on a larger scale.
“The fundamental purpose of this research is to integrate FV-TEG with graphite as a heat sink,” the academics explained. “The TEG converts excess heat into electricity, while graphite increases heat dissipation and temperature difference. Therefore, the back of a low-power photovoltaic panel glued with a TEG-graphite sheet has been tested and controlled to study this approach.”
The TEG part of the experimental setup consists of n-type and p-type pairs, which generate electrical voltage with temperature differences. The setup included a 150 W, 1135 mm × 665 mm, monocrystalline silicon photovoltaic panel with an efficiency of 18%. Using a thermally conductive adhesive, the researchers glued 186 commercially available TEG cells to the back of the photovoltaic module. Each TEG consists of two ceramic layers of 0.5 mm and 2 mm, respectively.
The academics tested the configuration by comparing it with a reference system consisting of a graphite sheet as a heat-dissipating element. The graphite sheet, 0.05 mm thick, was glued with the same adhesive to the heat dissipation face of the TEG.
“The remarkable heat resistance of the graphite sheet and its reliability contribute to a possible longer life and higher performance,” explains the research group. “It is cost-effective because it can help streamline some existing procedures. Although graphite is a much lighter material, its conductivity is comparable to that of copper.”
The academics carried out measurements of the systems on a roof at an average interval of 48 minutes under a solar irradiance of 425.1 W/m2. “The energy production of the TEG depends on the temperature gradient between the rear part of the photovoltaic panel and the cold part of the TEG,” they explain. “The graphite sheet aims to increase the heat rejection rate of the cold side of the TEG. Therefore, the cumulative result for this case is that the TEG-graphite increases.”
Through testing, they found that the maximum output of the system without the graphite sheet was 10.871 V, with a temperature gradient of 4.567 °C. This must be compared with a maximum output of 13.515 V, with a temperature gradient of 6.682 ºC, when using a graphite sheet. They also verified that the temperature on the graphite side was 31.255 ºC, while on the opposite side of the TEG it was 37.937 ºC.
“It is a general estimate that the peak radiation in summer exceeds 900 W/m2, which causes an increase in the temperature gradient,” they add. “Therefore, it is more likely that the same PV-TEG system can give a relatively higher output voltage. In this case, the theoretical estimate of the increase in voltage of the TEG module is 24 V, which is equivalent to the voltage of the PV panel.”
Their results were presented in “ Experimental study of photovoltaic-thermoelectric generator with graphite sheet ,” published in Case Studies in Thermal Engineering . |
