The capturing of solar energy, holding it in a liquid state, and then releasing it as needed as heat, has been demonstrated at the laboratory scale by technologists working at the Chalmers University of Technology in Sweden.
Solar energy remains regarded by many as the main energy capture form of the future. However, the process is hampered by relative inefficiencies in terms of power conversion and with energy storage. There are also problems with the release of energy, making current technologies less adaptable to ‘energy on demand’ scenarios.
To allow captured solar energy to be stored and released as required the Swedish researchers have shown how solar energy can be transformed into energy stored in the bonds of a chemical fluid. This becomes what is termed a “molecular solar thermal system.” Key to this is the liquid used and a number of organic compounds have been scrutinized for this purpose, such as the norbornadiene-quadricyclane system. Here organometallic-diruthenium compounds have shown promising solar energy conversion and storage properties, which is a product of their inherent stability and large energy storage enthalpies (a measurement of energy in a thermodynamic system).
The Swedish development has made it possible to store and transport the stored solar energy and release it on demand, with near to full recovery of the storage medium, using the organic compound norbornadiene. On exposure to light the chemical converts into quadricyclane.
The following video provides more details about the process:
Outlining that this represents a breakthrough in energy storage, lead researcher Professor Kasper Moth-Poulsen explains: ‘The technique means that that we can store the solar energy in chemical bonds and release the energy as heat whenever we need it.”
The academic adds: “Combining the chemical energy storage with water heating solar panels enables a conversion of more than 80 percent of the incoming sunlight.”
To get to this stage has taken six years of intensive effort with the conversion of sunlight to power increasing from 0.01 percent to 1.1 percent. The chemical system is capable of storing some 140 energy storage and release cycles without degrading.
The research is published in the journal Energy & Environmental Science, in the science paper “Exploring the potential of a hybrid device combining solar water heating and molecular solar thermal energy storage.”
