Aerial of solar panels in field

Leading the charge to Solar-powered cars

Dr Jamie Foster's research is exploring how solar energy can be captured more effectively – and help increase the efficiency of electric car batteries  

As we move towards becoming a zero carbon society, pressing questions need answers. Our Senior Maths Lecturer Dr Jamie Foster is exploring two of these:

How can we make electric car batteries better? And how can we capture solar energy more effectively? 

Applying maths to real world problems is what it’s all about.

Keeping cars moving

A longer life, higher capacity and faster charging. That’s the goal for electric car batteries. Widespread use of electric cars is on the horizon. But they can’t currently compete with petrol and diesel alternatives for distance or convenience.

Electric cars use lithium ion batteries. They’re ideal because they’re light. But they need to store enough power for long enough, not just drain away. They also need to be able to charge quickly. Nobody wants to be at the services for 8 hours while their car charges. These are the major stumbling blocks to widespread adoption of electric cars.

The gold standard of what car manufacturers want is to be able to fully charge a battery in 15 minutes. But the state of play at the moment is if you charge quickly, battery life is reduced.

Dr Jamie Foster, Senior Lecturer in the School of Mathematics & Physics

Using maths, Jamie is researching how to increase the capacity of these batteries. His goal is to find out how to store more watts of energy per kilo of battery. Achieve this and mileage per charge will improve.

Charging time is a major hurdle for electric cars. Jamie explains:

‘The gold standard of what car manufacturers want is to be able to fully charge a battery in 15 minutes. But the state of play at the moment is if you charge quickly, battery life is reduced.’

If you could make a battery last 2,000 cycles, instead of 1,000, effectively your battery cost is halved. So longer life is cheaper cost.

Dr Jamie Foster, Senior Lecturer in the School of Mathematics & Physics

So longevity is yet another challenge for Jamie. Currently an electric car battery has approximately 1,000 charge/discharge cycles. After that, the battery becomes less reliable. Which is not great in a car.  

‘You want to extend that. If you could make a battery last 2,000 cycles, instead of 1,000, effectively your battery cost is halved. So longer life is cheaper cost.’ 

Capturing the sun

The perfect solar cell would look black - because it’s absorbing all the light and so is 100 per cent efficient. But they aren’t black. And they aren’t 100 per cent efficient.

Existing solar cells, often installed on house roofs, look blue. This is because blue light from the sun is reflected off them instead of being captured. Jamie says:

‘You can’t make a solar cell that’s 100 per cent efficient. There’s a theoretical upper boundary. But you could improve them by putting another layer on the solar cell which absorbs the blue light. The light that’s currently reflected rather than absorbed.’  

Jamie is working with a material which does exactly that. It’s called perovskite. It’s a fairly recent discovery that it can be used as a photovoltaic material - in other words, a material that converts energy from the sun into electrical power. Perovskite shows great promise.

You can’t make a solar cell that’s 100 per cent efficient. There’s a theoretical upper boundary. But you could improve them by putting another layer on the solar cell which absorbs the blue light. The light that’s currently reflected rather than absorbed.

Dr Jamie Foster, Senior Lecturer in the School of Mathematics & Physics

Jamie’s work on perovskite solar cells involves trying to work out how you can build the material into a commercially viable cell. There are hurdles. The biggest being that while the cells work, right now they don’t last very long. They last for just a matter of months, rather than the years that they need to. But Jamie is working on it. 

These are some of the big challenges of becoming a zero carbon society. Using maths is helping to unlock the answers. In the hands of researchers like Jamie, maths is a key weapon in the fight against climate change.

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