Advances in solar energy shine light on renewable research

Since the sun keeps coming up everyday and is not going to leave anytime soon, a number of people have decided to turn some of that sunshine into electricity. The energy conversion aspect has been figured out, but to use it on a larger scale requires efficient storage for all that sunshine. Currently the most popular form of storage for large power grids is to use the excess energy to pump large amounts of water from a reservoir to another one that is higher up. When energy is needed, water is released back into the lower reservoir which creates hydroelectric energy.

The problem is not only that it is not the most efficient form of storage, but it is not realistic for anything smaller than an entire power grid. Fortunately, those whose work with solar energy have come up with something new. Researchers at The Chalmers University of Technology have designed what they call “molecular solar thermal energy storage,” or MOST for short. They have created a brand new molecule that can capture and store solar energy long term and on a scale suitable for private properties.

‘If MOST is successful, then solar energy will become an even better form of renewable energy.’

To understand the potential of this technology, first one needs to look at what’s currently available. The company Tesla is selling what they call the Powerwall. It’s essentially a huge lithium-ion battery that stores any excess energy captured by solar panels. The battery in most cell phones is a lithium-ion battery. The main difference between it and the Powerwall is scale. In both, there is some lithium sandwiched between two other chemicals. The two chemicals will be referred to as A and B. The lithium in the middle keeps A and B separate while letting lithium ions (very energetic bits of lithium that love to jump around) pass through. When charging the battery, lithium ions travel through this barrier and create a bond with chemical A. When one uses energy, the bond with A breaks, energy is released and the lithium ions move back to chemical B. The lithium ions can repeat this process over and over again, but it happens in slow degrades. 

Over time, the battery will hold less charge and might need to be replaced with a new battery. The battery can lose charge even when not being used. One can test this process out with an experiment. When a phone is charged to 100 percent and then is turned off, after a month, it won’t be at 100 percent anymore. For small devices, these flaws are manageable; but with the larger scale of something like the Powerwall it’s less than ideal.

The researchers at Chalmers believe that they have made something better at storing solar energy than lithium-ion batteries. Instead of being fed energy like lithium-ion batteries, MOST and the new molecule created for it (a derivative of norbornadiene) directly captures solar energy. By the researchers’ estimation, it can then store the solar energy for up to 18 years. This all works through a process called photoisomerization. Isomers are chemicals that are made of all the same pieces as the old model, but are put together differently. Photoisomerization is when one of these molecules goes from the one way it can be put together to the other because light hit it. Inside the human eye is an isomer called retinal. Just like the isomers used in MOST, retinal changes when exposed to light, and this is the beginning of all the reactions that eventually tell the brain what you’re looking at. In MOST when the norbornadiene is hit with light it captures that energy and becomes its isomer. This isomer can then hold the solar energy for an extended period of time or be forced through a catalyst that changes it back to norbornadiene and releases the energy that was stored.

Hydroelectric plants and lithium-ion batteries are a functioning solution for now, but MOST aims to improve on this method. If MOST is successful, then solar energy will become an even more reliable form of renewable energy. 

Tim Cochran is a  second-year transfer student majoring in English.

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