The earth intercepts up to 173 trillion terawatts of solar power, which is ten thousand times more than what the entire population on the planet utilizes. Safe to say, the sun is the amplest source of energy we could ever have.
Although a far better alternative to fossil fuels, solar energy still has its limitations. Biggest of them all is its high dependency on clear weather conditions. Solar energy cannot be collected at night and evident effects can be seen in the efficiency of the system in case of a few cloudy days. Also, seasonal changes affect system design.
This issue of conservation of solar energy inside the system was tackled by scientists at the Chalmers University of Technology, Sweden, with a specialized solar thermal fuel.
Dynamic Liquid Batteries
The solar thermal fuel is developed to store and utilize solar energy for up to 18 years. These liquid batteries are a more efficient alternative to their regular lithium-ion counterparts in ways that
- They cost less
- Last longer
- Safer than the otherwise exploding lithium-ion batteries
Jeffrey Grossman of MIT defined the solar thermal fuel as “a rechargeable battery, but instead of electricity, you put sunlight in and get heat out, triggered on demand”.
The fluid, as a matter of fact, is a molecule in liquid form that is composed of carbon, hydrogen, and nitrogen.
The interaction of sunlight with the liquid triggers an isomeric reaction in the system. On being exposed to sunlight, the atoms in the liquid rearrange themselves to form, what is called, an isomer. Isomers are two different forms of the same compound made by the rearrangement of atoms. Basically, when introduced to sunlight, the solar thermal fuel converts into an ‘energized version of itself’.
This conversion of isomers leads to the entrapment of energy in between the atomic bonds of the liquid. The energy stays there even after the liquid is brought down to room temperature.
This stored energy can be brought out using a catalyst. The catalyst converts the isomer back to its original form and the energy trapped is released as heat. Whether nightfall or a cold winter evening, the efficiency of the solar thermal fuel is maintained.
The leader of the team, Kasper Moth-Poulsen, Professor at the Department of Chemistry and Chemical Engineering at Chalmer, said, ”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.”
Installation of Prototype and Possible Applications
A prototype of the system was installed on the roof of the university and has since caught the attention of prospective investors.
The system works as a loop. The fluid is pushed through tubes where it is heated by the sunlight. This interaction converts the liquid, norbornadiene, to its isomer, quadricyclane.
Whenever energy is required, the fluid is pumped through a catalyst that brings the molecules back to their original form, warming the liquid in the process to 113 degrees Fahrenheit.
Possible applications for this liquid are domestic heating systems, water heaters, dishwashers, clothe dryers amongst many others.
The loop ends with the liquid being pushed back to the roof again.
Scientists have run this cycle over 125 times and no significant damage to the molecule has been reported.
Implications of the technology is that solar thermal systems could be sized for storage capacity sufficient to meet the needs of winter energy demands using summer sunlight.
Researchers believe that significant improvements can be made to the system to increase the temperature of the liquid released. The set aim is, at least, 230 degrees Fahrenheit.
“There is a lot left to do. We have just got the system to work. Now we need to ensure everything is optimally designed,” says Moth-Poulsen.
This system is estimated to be commercially available in another 10 years.