Production of electrical energy from solar energy

Researchers behind an energy system that captures solar energy, stores it for up to 18 years, and releases it when and where it’s needed have now taken the system one step further. Having previously demonstrated how energy can be extracted in the form of heat, they have now succeeded in making the system produce electricity, by connecting it to a thermoelectric generator. Eventually, the research – developed at Chalmers University of Technology, Sweden – could lead to self-charging electronics using stored solar power on demand.

“It’s a radically new way of producing electricity from solar energy. This means that we can use solar energy to generate electricity regardless of weather, time of day, season or geographical location. It is a closed system that can operate without causing carbon dioxide emissions,” says research director Kasper Moth-Poulsen, a professor in the Department of Chemistry and Chemical Engineering at Chalmers.

The new technology is based on the MOST (Molecular Solar Thermal Energy Storage Systems) solar energy system developed at Chalmers University of Technology. Very simply, the technology relies on a specially designed molecule that changes shape when it comes in contact with sunlight. The research has already generated great interest around the world when presented at earlier stages.

The new study, conducted in collaboration with researchers in Shanghai, takes the solar power system even further, detailing how it can be combined with a compact thermoelectric generator to convert solar energy into electricity.

Ultra-thin chip converts heat into electricity

The Swedish researchers sent their specially designed molecule, charged with solar energy, to their colleagues Tao Li and Zhiyu Hu at Shanghai Jiao Tong University, where the energy was released and converted into electricity using the generator that they developed there. Essentially, the Swedish sun was sent halfway around the world and converted into electricity in China.

“The generator is an ultra-thin chip that could be embedded in electronic devices such as headphones, smartwatches and phones. So far, we have only produced small amounts of electricity, but the new results show that the concept really works. It looks very promising,” says researcher Zhihang Wang from Chalmers University of Technology.

Fossil-free, emission-free

The research has great potential for the production of renewable and emission-free energy. But there is still a long way to go in research and development before we can charge our technical gadgets or heat our homes with the solar energy stored in the system.

“In collaboration with the various research groups included in the project, we are now working to streamline the system. The amount of electricity or heat it can extract must be increased. Even if the energy system is based on simple basic materials, it must be adapted to be sufficiently profitable to produce, and therefore possible to launch more widely”, explains Kasper Moth-Poulsen.

A Molecular Solar Thermal Energy Storage System, MOST, is a closed energy system based on a specially designed molecule of carbon, hydrogen and nitrogen, which when struck by sunlight, turns into an energy-rich isomer – a molecule made up of the same atoms but arranged together in a different way. The isomer can then be stored in liquid form for later use when needed, such as overnight or in the winter. Researchers have refined the system to the point that it is now possible to store energy for up to 18 years. A specially designed catalyst releases the saved energy as heat while returning the molecule to its original shape, so that it can then be reused in the heating system. Now, in combination with a micrometer-thick thermoelectric generator, the energy system can also generate electricity order.