How to make solar energy more efficient

Solar energy has great potential to become one of our most important energy sources. The energy in the sun’s rays corresponds to more than 15 000 times the electricity that the global population needs in everyday life. But the way we capture solar rays, and convert the radiation into energy, needs to become more efficient. Only then can renewable energy sources completely replace fossil fuels – which currently account for around 40 per cent of all the electrical power produced in the EU.

New ways of exploiting solar energy

Heiner Linke, professor of nanophysics at Lund University and director of NanoLund, conducts basic research in nanophysics and solar cells.

The aim of his research is to find a new way of exploiting the sun’s energy to produce electricity. Energy cannot be created, only converted from one form into another, such as from solar energy into electricity. In the process, energy often escapes in the form of heat, which means it is lost. The effectiveness of an energy conversion process can be measured by comparing how much energy goes in and how much comes out. This is known as the degree of efficiency.

“In practical terms, what we are trying to do is to capture more of the heat that is lost from the sun’s rays. If we manage to do that, we will have a higher degree of efficiency in the solar cells, as we can convert more solar energy into electricity.”

Getting inspiration from biological processes

Heiner Linke and his team are looking specifically at how individual electrons behave, an area which could potentially lead to the discovery of new ways of increasing efficiency. He compares the approach to biological processes. In each living being, chemical energy is converted into movement by individual molecules which have a very high degree of efficiency, but function completely differently to the engines we use with current technology. Linke thinks it could therefore be interesting to get inspiration from the way in which molecules function and to see whether biology’s strategies could be applied to electrons and photons.

“The hope is that the research will lead to solar cells with a higher degree of efficiency without an increase in cost, if we can utilise all the energy and not lose any of it as heat. In that case, solar panels could become even more competitive and solar cells would start to be used more commonly. But it is difficult to say exactly what we will find and how it will be used; this uncertainty is inherent in basic research”, says Heiner Linke.

How can we store large amounts of electricity?

Even if Heiner Linke and his research team succeed in converting the sun’s rays into energy with a higher degree of efficiency, there are many challenges to solve in order to be able to exploit the sun as an energy source, such as storage and distribution of electricity. The sun shines during the day but electricity is needed around the clock. There are solar panels in many different places and the electricity needs to be distributed, sometimes over great distances.

“In the long term, we must create systems to store and transport energy from the sun on a much larger scale than what is currently possible. These are questions that must be solved in order to scale up the use of solar energy.”

In addition to theorising, progress within Heiner Linke’s own research also requires new and better measurement methods in experiments.

“Measurement sensitivity is extremely important to enable accurate investigation of the energy conversion between individual electrons and photons.”

Interaction drives development

Heiner Linke’s research is different from what is known as application-based research, which often takes problems posed by industry as a starting-point, and from which companies and organisations expect a usable result within a fairly short time. Currently, it is the type of research getting most attention as it is urgent to achieve a more sustainable society.

However, both basic research and application-based research are needed, and preferably in close interaction with each other, to drive development forwards.

" One cannot come up with anything fundamentally new if one focuses only on optimizing what is already consolidated and developed. One must also try to discover entirely new knowledge that can lead to completely new and unexpected ideas."

Basic research must be allowed to take time

A long-term research horizon is absolutely essential, according to Heiner Linke. About 150 years ago, researchers first understood what heat was and its connection to movement in individual molecules, a discovery that gave rise to the first notions of thermodynamics. In the 1950s, solar cells started to be used, initially in space, to supply electricity to satellites.

Heiner Linke’s own greatest milestone was an article he and his colleagues published in 2018. It was the result of 10-15 years’ work, with the aim of realising a theory on how energy conversion can occur with a high degree of efficiency – a long-drawn out process as it took time to conduct the necessary experiments.

“Basic research takes time. We want to develop new ways of thinking and new concepts, and then realise them. This requires you to work on long projects and to have a lot of patience. But there is no contradiction between basic research and applied research. Both are needed and benefit from each other”, concludes Heiner Linke.