By Dr. Phillip Dale, University of Luxembourg
We love energy. It’s really addictive. Whether it is food or fossil fuels, they are really hard to cut down on. What does that have to do with solar cell research anyway? The answer lies in the fact that solar cells are one of the few answers we have in overcoming our growing energy and climate problem.
Solar cells, in the form of photovoltaic modules, convert freely available sunlight into electrical energy at a price competitive with fossil fuels[1], whilst producing around 15 to 50 times less greenhouse gasses[2]. They are considered a renewable energy source, unlike oil, gas or coal. The nice thing about electrical energy is its versatility, we can directly convert it to any other form of energy or fuel that we need, such as chemical energy for batteries, or generating hydrogen to be used as a fuel, or heating / cooling to make our lives comfortable.
It is important to stop burning fossil fuels because they create greenhouse gasses that increase climate heating and, in any case, we are going to run out of fossil fuels in the lifetime of our children. Furthermore, we still use gas and oil as feedstocks for plastics, and fine chemicals. Therefore, replacing fossil fuel burning with renewable sources of energy is of paramount importance. Photovoltaics will provide a good part of the answer to this problem.
But, if photovoltaics provide energy at an already competitive price with fossil fuels, why do we need to improve them? Simply put, we need to make as much electricity by photovoltaics as possible, since we have to replace the tens of thousands of fossil fuel burning power stations. We can do this quicker, if we can improve the amount of energy generated per unit cost (it seems perverse that humanity is facing a catastrophe, but we still have to worry about financial cost).
The total energy generated in a solar cell is proportional to its efficiency in converting light energy to electrical energy, whilst surprisingly, the majority of the cost is related to the other parts around the cell, such as the protective glass sheets top and bottom, the electronics to control the module, as well as the transport and installation. These costs are unlikely to change too much, so the only way to improve energy output per unit cost is to improve the energy conversion efficiency. Luckily, solar cell scientists do see a way to improve the energy output. Currently, the best commercial modules use solar cells that convert 22% of the light energy into electrical energy. Meanwhile, in the laboratories, the best research devices can convert 46% of the incoming light, which means they produce more than double the energy of solar cells used in commercial modules. Theoretical calculations show this could even reach near 70%. However, lots of research and development effort are required to bring these results from the laboratory into the real world.
Given that we must stop using fossil fuels for energy, and that photovoltaics are a guaranteed way of producing renewable energy, as well as the fact that scientists have a clear way forward to improving them still further, it would seem eminently sensible to push forward with research and development as fast as possible.
About the author
Phillip Dale is an Associate Professor at the young University of Luxembourg, part of the photovoltaics cluster. He currently researches new materials for solar cells, as well as micro-solar cells for high efficiency, semi-transparent and sensor applications. When he is not directly researching or teaching or doing admin, he participates in scientific outreach. In particular, whilst thinking about ways to engage the public more in renewable energy he decided to start a Youtube channel named “Energy Balance”, hopefully launching in September 2019….
This blog was produced as part of the Solar Commission, a UKERC funded project, which aims to stimulate new thinking and encourage collaboration between academics, industry and system operators on the role of solar in the UK energy system and Industrial Strategy.
[1] https://www.lazard.com/media/450784/lazards-levelized-cost-of-energy-version-120-vfinal.pdf
[2] Thin film photovoltaic technologies require less energy to make than silicon based photovoltaic technologies – see figure 11 of UNEP (2016) Green Energy Choices: The benefits, risks and trade-offs of low-carbon technologies for electricity production. Report of the International Resource Panel. E. G. Hertwich, J. Aloisi de Larderel, A. Arvesen, P. Bayer, J. Bergesen, E. Bouman, T. Gibon, G. Heath, C. Peña, P. Purohit, A. Ramirez, S. Suh, (eds.).