Scientists claim that photovoltaic systems in combination with thermoelectric cooling can achieve a payback period of 6 years

A team of researchers at the Central University of Technology in South Africa has developed a solar module that incorporates a thermoelectric chiller (TEC)-based cooling system.

TECs can convert heat into electricity through the “Seebeck effect,” which occurs when a temperature difference between two different semiconductors creates a voltage between the two substances. These devices are typically used in industrial applications to convert excess heat into electricity. However, due to their high cost and limited power, they have not yet been able to be used on a large scale.

“The PV-TEC system proposed in this study consists of a photovoltaic panel with a TEC device attached to the back, a heat sink attached to the opposite side of the thermoelectric device, and a switching mechanism,” the scientists explain. “The TEC is powered by the photovoltaic panel that it is supposed to cool.”

The group performed a numerical simulation to evaluate the performance of the system. An optimization function was also set to maximize performance, trying to maintain a target temperature between 23 C and 27 C when the cell temperature exceeds 25 C. The PV panel used in the simulation had a power output of 100 W, an efficiency of 17.8 percent and a size of 20,200 cm3. The TEC had a maximum current of 6.1 A, a maximum voltage of 17.2 V and a size of 6.08 cm3. The heat sink had a thermal resistance of 2.6 C/W and a size of 39.2 cm3.

“Meteorological data from Bloemfontein, Free State, South Africa were used for the scenario studied,” the researchers said. “The specific dataset includes horizontal diffuse, normal diffuse and horizontal global irradiance, as well as ambient temperature values describing a typical winter day on July 17, 2021 and a summer day on January 17, 2021.”

The operation of the system was analyzed for both a summer and a winter day, and its performance was compared with that of a reference PV panel without TEC and heat sink. In the simulated winter conditions, the cell temperature never exceeded 25 °C, so the TEC was not active.   Therefore, a peak temperature of 22.9 °C, a constant power output of 86.9 W and a total energy output of 363.47 Wh were measured in both the PV-TEC and the reference case.

In summer, however, TEC was used and allowed the panel to reach a peak power output of 104.1 W, compared with 94.4 W in the reference case. The peak temperature in the reference case was 36.1 C, while the PV-TEC did not exceed 25 C. An energy efficiency of 603.60 Wh was achieved in the TEC case, compared with 547.65 Wh in the reference case. “The results of our proposed model show a significant improvement in power output, especially 9.27 percent in summer,” the scientists point out.

Based on these results, the researchers carried out an economic analysis with an assumed life of 20 years for PV and PV-TEC and an annual electricity price increase of 10 percent and an interest rate of 6 percent. While the initial price of the 100 W solar module alone was assumed to be ZAR 1,235 ($66.9), the total cost for the PV-TEC case was ZAR 1,562.77.

“The break-even point is reached relatively early during the operational life of the project. To be precise, it occurs at 6.5 years,” the scientists concluded. “The economic analysis also showed cost savings of ZAR 2,905.61, which corresponds to a savings of 10.56 percent over the entire project lifetime of 20 years.”