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Liquid solar energy

The discovery of solar thermal fuel could solve the renewable energy storage problem.

by Amanda Saint
11 March 2020
4 min read
by Amanda Saint
11 March 2020
4 min read

Scientists working at the Kasper Moth-Poulsen Research Group based on the campus of Chalmers University of Technology in Gothenburg, Sweden, have made a discovery that turns energy captured from the sun into a fluid fuel. Named MOST (Molecular Solar Thermal Energy Storage), this could be a major step forward in moving the world away from fossil fuel-powered energy systems. The researchers' hope: That MOST could solve the storage problem for solar power once and for all.
Solar has long been lauded as a major tool in the sustainable, low carbon energy solution, but having consistent access to energy generated by the sun has proven difficult to store for long periods of time. The new solar thermal fuel invented by Dr. Kasper Moth-Poulsen and his team, however, can purportedly stored this energy for up to 18 years.
The team first released information on their invention in 2018; in early 2020, Dr. Moth-Poulsen revealed that many advances have been made in developing MOST for commercialisation.
The team initially thought it would not be ready for market in 2028, but Dr. Moth-Poulsen explains that much progress has been made. "We hope to implement some of the systems before then, and are in the process of setting up a startup company to accelerate the development".

Solar thermal fuel

So, how has this ingenious team of researchers created fuel from sunlight?
It's done using a molecule the team creates from carbon, nitrogen and hydrogen that controls when the stored energy is released. Dr. Moth-Poulsen refers to it as a molecular photoswitch that transforms when sunlight shines on it.
It becomes an energy-rich isomer – a molecule comprised of the same atoms that have combined together in a different way — taking on the form of a liquid that can be stored for later use. It's then filtered through a catalyst, which warms the liquid by 63 degrees Celsius before returning the molecule to its original form, so that it can be reused in the heating system over and over again.


Solar thermal collectors, devices that convert solar radiation into thermal energy

The catalyst is made using a small amount of cobalt phthalocyanine, an element used in organic electronic devices, such as light-emitting diodes (LEDs) and organic photovoltaics (OPVs), as a semiconductor.
The mining of cobalt comes with its own environmental sustainability issues, however, which presents some long-term viability concerns for this system. But as Dr. Moth-Poulsen explains, those issues are being addressed. "We are currently looking into way to replace the cobalt for more sustainable choices".
This drive for safety and long-term sustainability means the researchers are constantly refining every part of their invention.

Future development

In addition to considering the safety and environmental sustainability of the elements that make up the system, the team has been developing the system further in order to make it more efficient and commercially viable.
"We are continuously learning about our molecules, and once we have learned about how they work and what their limits are, we can use that information to design better molecules, so our research is a constant learning curve", says Dr. Moth-Poulsen. "The same goes for our devices — we start by making the simplest possible demonstrations, and then we can learn something from the demonstrations and move onward toward more advanced demonstrators".
Maintaining commercial viability is also about the cost and ease of manufacturing, another area of MOST's performance that the team has been enhancing. To help with the ongoing development of the system, Dr. Moth-Poulsen has applied for funding to support the startup company's development of this breakthrough invention.
With the right funding and support to advance the way the system works and how it is manufactured, the team is confident their invention can be an important element in the energy mix of the future.
"The major advantage is in the local delivery of heat on demand. The systems could be integrated in unconventional materials solutions where local delivery of heat is needed" says Dr. Moth-Poulsen.
The refinements continue, and there will be some real-life demonstrations coming up in the next three to six months to reveal how the system can help take solar energy to the next level of sustainability.


The author: Amanda Saint

Journalist specialising in stories about renewable energy, climate change, smart cities, sustainability, and urbanization.