Scientists develop system to recover waste heat from PV Units
A thermally-coupled electrically-separated hybrid thermoelectric, photovoltaic system (HTEPV)-based device based on a thermoelectric generator and a wide-gap perovskite solar cell has been fabricated by scientists from the University of Milano-Bicocca, University of Rome Tor Vergata, and Massachusetts Institute of Technology. The device allegedly recovers waste heat from the PV unit and generates additional power.
Due to their high efficiency and low cost, silicon solar cells dominate the PV market. However, they are sensitive to temperature, which can result in significant energy losses throughout a solar panel's lifetime. Temperature changes can cause them to lose up to 20% of their room temperature efficiency. Hybridization with thermoelectric generators (TEGs) has recently gotten a lot of attention.
TEG can recover heat lost from solar cells in HTEPV systems to generate additional power and improve the overall device output power and efficiency.
Many studies and reviews have been conducted on HTEPV systems. However, opinions on how effective they are have been mixed. HTEPV systems have been described as both convenient and ineffective in terms of increasing PV efficiency.
For the experiment, the researchers used three different types of solar cells: perovskite, gallium indium phosphide (GaInP), and amorphous silicon (a-Si).
A customised bismuth telluride TEG hot plate with a surface area of 1 cm² is placed in thermal contact with a perovskite solar cell's back using a layer of Silicone-free thermal grease. Thermally, the two units are connected, but electrically, they are not. The vacuum chamber bottom was attached to the TEG cold side with thermal grease. For the final hybrid device, a K-type thermocouple was used to regulate the temperature. The temperature of the chamber bottom was controlled by a dissipation liquid circuit that was fed by a temperature-adjustable chiller.
A layer of thermal grease was used to connect the solar cells to the TEG top electrode, and a K thermocouple was placed between the hot electrode and the solar cell bottom. A Keithley 2440 source metre was used to record the J-V curves, which was controlled by a LabView programme.
To determine the effect of optical concentration on temperature sensitivity, the researchers characterised all three cells between 1 and 5 Suns. The incoming power of the solar simulator was continuously measured and adjusted using a certified reference silicon solar cell. To accurately evaluate incoming power density, a stainless-steel mask with known areas was used.
In comparison to a-Si and GaInP, perovskites showed efficiency gains of more than 2% at all-optical concentrations, namely 2.64% at 337.43 K, 2.90% at 340.59 K, and 3.05% at 343.13 K. At moderate temperatures of around 340 K, maximum efficiency gains were achieved.
This temperature is well within the range of temperatures commonly experienced by solar panels, implying that complex thermal management strategies are not required. As a result, the HTEPV device is directly comparable to and compatible with real solar cells in this case.
These improvements were then experimentally confirmed in the case of perovskites solar cells, with the highest gains occurring at conventional PVs normal operating temperatures. This experiment accurately demonstrated the thermoelectric hybridisation of solar cells' true potential.
Also read: BHEL floats tender for supplying multicrystalline solar modules
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