Solar Energy as Liquid Fuel, targeting the Storage Conundrum

Sunlight in a bottle!

A team of researchers from the Chalmers University of Technology in Sweden, claim to have devised a way to store solar energy in a bottle. The team has developed a liquid fuel containing the compound norbornadiene, which when struck by sunlight, rearranges its carbon, hydrogen, and nitrogen atoms into an energy-storing isomer, quadricyclane, which consists of the same atoms but bound together in a different way.

[Chalmers]

[related_post]

Quadricyclane holds onto the energy, estimated to be up to 250 watt-hours of energy per kilogram, even after it cools and for an extended period of time. For use, it’s passed through a cobalt-based catalyst, at which point the energy is released as heat. The catalyst acts as a filter, through which the liquid flows, creating a reaction which warms the liquid by 63 centigrades. If the liquid has a temperature of 20°Celsius when it pumps through the filter, it comes out the other side at 83°Celsius. At the same time, it returns the molecule to its original form, so that it can be then reused in the warming system. The team has named the system MOST (Molecular Solar Thermal Energy Storage).

The energy system MOST works in a circular manner – completely free of emissions, and without damaging the molecules carrying the energy. [Chalmer]

With all the recent advancements the team has made, the system now works in a circular manner. First, the liquid captures energy from sunlight, in a solar thermal collector on the roof of a building. Then it is stored at room temperature, leading to minimizing energy losses. When the energy is needed, it can be drawn through the catalyst so that the liquid heats up. It is envisioned that this warmth can then be utilized in, for example, domestic heating systems, after which the liquid can be sent back up to the roof to collect more energy – all completely free of emissions, and without damaging the molecule.

Kasper Moth-Poulsen [Chalmer]

“The energy in this isomer can now be stored for up to 18 years. And when we come to extract the energy and use it, we get a warmth increase which is greater than we dared hope for. We’ve run it through 125 cycles without any significant degradation. We have made many crucial advances recently, and today we have an emissions-free energy system which works all year round,” said Kasper Moth-Poulsen, Team Leader, Nano Materials Chemistry at Chalmers.

The next steps for the researchers are to combine everything together into a coherent system. “There is a lot left to do. We have just got the system to work. Now we need to ensure everything is optimally designed,” said Poulsen. The group is satisfied with the storage capabilities, but they believe that more energy could be extracted from the system. The research group is working on shortly achieving a temperature increase of at least 110°Celsius.

Ayush Verma

Ayush is a correspondent at iamrenew.com and writes on renewable energy and sustainability. As an engineering graduate trying to find his niche in the energy journalism segment, he also works as a staff writer for saurenergy.com.