The cell is combined with a molecular solar thermal energy storage system that cools the unit by 8°C and increases the photovoltaic efficiency by 0.2%
The new photovoltaic system with integrated thermal storage, Swedish innovation
From Sweden comes the new photovoltaic with cooling system included in the facility. A team of scientists at Chalmers University of Technology in Gothenburg has developed a thermal-accumulated solar cell that could improve the overall efficiency of the technology, exceeding some conventional limits.
Loss of thermalization: How can the problem be solved?
The team’s innovation addresses a precise problem of photovoltaics: the loss of thermality or heat. What is this about? It is a phenomenon that occurs when a cell absorbs photons with more energy than the band gap of its semiconductor. In this case, the excess energy is converted into heat and lost, representing a double disadvantage: on the one hand, lower conversion efficiency, and on the other hand, the negative effects that high temperatures can play on the lifetime of the panels.
This is a substantial problem that can be minimized with a multi-joint tandem architecture. What if the joint remains single? This is where Chalmers’ work comes into play.
MOST: optical filter and cooling system for photovoltaic cells
The hybrid device by engineers and chemists consists of a silicon photovoltaic cell placed under a molecular thermal solar energy storage system (MOST– molecular solar thermal). The MOST contains a solution of photomutable organic molecules, i.e. capable of modulating the chemical-physical properties by lighting with light of a specific wavelength. These molecules flow through a microfluidic chip, specifically absorbing blue and ultraviolet photons (typically less than 450 nm), turning into high-energy metastable photoisomers. The energy thus stored can be used as a reserve source or for producing thermoelectric energy.
Obviously, the MOST is transparent at wavelengths greater than 450 nm, thus allowing most of the relevant photons to reach the silicon solar cell below. At the same time, this storage system “reduces the thermal heating of the cell by filtering high-energy photons and actively cooling the microfluidic chip; which improves the conversion of solar energy into power,” the scientists explain.
Operating cells at lower temperatures extends their lifetime, which determines the overall greater sustainability of the same photovoltaic technology. Therefore, this improvement can positively influence the energy return on investment (EROI).
Efficiency of 14.9% for the solar cell with integrated thermal storage
The tests carried out by the team of scientists and researchers have demonstrated that the particular solar cell using integrated heat storage can store up to 2.3% of solar energy as chemical energy. They are decreasing the surface temperature of the cell by about 8 °C under standard solar radiation conditions. Not only. The hybrid system has demonstrated a solar efficiency of 14.9%: 0.2 percentage points more than a system without MOST. For engineers, this is the first step towards achieving even higher conversion rates in future advanced hybrid FV devices.
The cherry on the cake? The MOST system consists of carbon, hydrogen, oxygen, fluoride and nitrogen, thus avoiding using rare and expensive materials.
The results of the study, entitled “Hybrid solar energy device for simultaneous electric power generation and molecular solar thermal energy storage” have been published in Joule.
