By Isabelle Robinson, M.Sc.Nov 19 2018.jpg)
Image Credit: ThingsukAtiwannakul/Shutterstock.com
Recently, there has been a large shift in the STEM community to increase efforts to develop sustainable technology. One area of interest has been improving photovoltaic materials in order to make them more efficient for use in solar panels. Due to the sustainable global energy policy, there has been an aggressive increase in the production of solar cells.
Differential Scanning Calorimetry
To address these issues, material scientists have turned to thermal analysis. These analysis techniques allow researchers to measure a specific thermophysical property of photovoltaic materials over time or temperature. According to sources, the most popular common thermal analysis technique is differential scanning calorimetry (DSC), which measures the flow of heat through a material. It is particularly useful for the PV industry due to its sensitivity to many important processes in the materials.
One of the ways that DSC can be used to increase the efficiency of solar cells is as a replacement for the solvent extraction method as a quality assurance test of the crosslinking resins found in solar panels. The encapsulation material, which is usually made from ethylene vinyl acetate, is used to laminate the panels and therefore must have very specific properties in order to keep the solar cell efficiency. These properties include high optical transmittance, adhesion, and be stress resistance in order to accommodate the internal stresses caused by variable thermal expansion coefficients caused by multiple materials in the module.
Advantages of DSC Method
Currently, the quality assurance test relies on chemically determining the degree of crosslinking materials by measuring the difference in mass before and after the additives and other resin has been dissolved away from the material. This is not ideal because the material must be cured for over 24 hours before the test can take place. The data is often unreliable and therefore the efficiency of the solar panels suffers as a result. The DSC method shortens the time required from 24 hours to a mere 30 minutes and increases the accuracy. In addition to this, the DSC method decreases the risk to material researchers by not releasing toxic gasses like its predecessor.
The DSC method measures the heat produced by the crosslinking resin during the curing process. The heat emitted due to the crosslinking reactions is known to be proportional to the degree of cure which means that the quality of the product can be accurately determined using thermal analysis.
Thermal analysis of photovoltaic cells in panels has long been used by material researchers and DSC is just one of many techniques that are of use in the industry. It is known that the efficiency of solar cells is inversely proportional to their operating temperature. Variables such as convection, radiation, reflectivity, and absorptivity all affect the temperature distribution and, therefore, the efficiency of solar. In a 2011 study by the University of Singapore, it was found that cells near the outside of the frame had a 5° difference in temperature across a single cell in comparison to those in the middle which were found to be uniform.
The PV industry has become interested in optimizing the performance of solar panels by improving the efficiency of solar cells and thermal analysis continues to be an important tool for material scientists. It is hoped that in the future, solar cells will be used in every day energy generation.
Sources and Further Reading
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