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Interdisciplinary Research Centre
Solar batteries without the charger? We’re working on that - Michael de Volder - Department of Engineering

Professor Michael De Volder tells us how a Friday afternoon experiment led to research on a new low-cost battery design that can be charged directly by light without a separate solar cell or power converter.

“One area we have made clear progress in is improving the stability of the batteries as they are charged and discharged, bringing it closer to what you would expect from a commercially available battery.” Professor Michael De Volder, Department of Engineering


How does what you’re working on differ from conventional batteries?
For most of us, recharging a battery is easy. When a battery is flat, you plug it into a charger and after an hour or so you are good to go. But in a remote area, without access to mains electricity, this becomes much more complicated.

You can of course use solar power to charge batteries in off-grid locations, but this always requires a separate solar cell and a power converter, in addition to the battery, which makes solar charging systems more expensive and less robust.

What we have developed is a way to charge the battery directly from sunlight — no separate solar cell, no power converter. So we’ve reduced those three components to just one, a battery that can be exposed directly to light and recharges all by itself, without any external intervention. It’s quite neat.

We’re also using zinc-ion batteries, which are fairly cheap, so we believe that it will be possible to have the light-charging capability for the cost of a normal battery.


You’ve said that this is a proof-of-concept and that further testing is needed. But what are some of the applications that you envision?

Exactly, this is a proof of concept, and it is technology still in its very early days. One problem we still have to solve is increasing our efficiency in converting energy from sunlight to energy stored in the battery. Conventional solar cells have an energy conversion efficiency of 10–20 per cent, whereas the efficiency of our battery is still below one per cent. So we think this technology mostly has applications in situations where the energy conversion efficiency isn’t the most important criteria, as compared to the price or volume.

If we think of technologies such as the Internet of Things, or sensors that are used in smart cities which are distributed over large areas and not connected to mains power supplies, those are sometimes exposed to the sun for many hours a day but consume very small amounts of energy. Therefore, you don’t need a very high energy conversion system, but having a compact energy solution is important.

Also, for parts of the world where people are trying to fight energy poverty, having a system that is able to harvest sunlight and store its energy cost-effectively would be extremely useful. Where cost and safety might be more important considerations than energy conversion efficiency, this technology is quite promising.


Read the original Department of Engineering article.


Image credit: philriley427