New innovative way to store renewable energy

Microporous materials potentially provide a new, more practical solution for using hydrogen to store sustainable power.

Limitations in generating renewable energy

Only a small percentage of energy generated in the UK comes from renewables, such as biomass, wind, wave or solar.

There are great incentives to have a higher proportion of our electricity supplied by these technologies - particularly to manage climate change.

But, unlike conventional energy production methods like coal, renewables only generate energy intermittently.

We need technology that can help us store the electricity and would allow solar energy generated during the day to be delivered in the evening, when we are more likely to be home.

Concentrated hydrogen the answer?

One potential solution to this storage problem is to use hydrogen.

Hydrogen is readily available, can be produced from a variety of sources and – as an alternative energy carrier – has the potential to redefine the UK and global economies by the replacement of carbon-based fossil fuels.

Hydrogen gas has good energy density by weight, but poor energy density by volume compared to hydrocarbons like petrol. So it requires a much larger tank to store.

In order to make hydrogen storage practical for everyday use, it needs to be concentrated in a much smaller space.

New innovative way to store hydrogen

Currently, there are two main methodologies to store hydrogen in small lightweight containers:

  • liquefying hydrogen – this has to be done at temperatures only 30 degrees above absolute zero – incredibly difficult to both achieve and maintain
  • compressing hydrogen – done at room temperature, but using pressures up to 700 times the atmospheric pressure, which can cause problems in terms of safety and management

Researchers at University of Bath are looking at a third solution – using materials with very small pores in them.

These pores may only be one thousandth millionth of a meter across. But they have very special properties that enable them to contain a lot of hydrogen.

Understanding how hydrogen behaves in these porous materials will help to develop new effective ways to store it.

By passing hydrogen gas over promising materials their hydrogen storage characteristics at different pressures and temperatures can be measured.

There are a number of materials, such as metal-organic frameworks, zeolites, polymers that are intrinsically microporous and activated carbons that are good at being able to densify the hydrogen to make it easier to carry around.

One of the biggest challenges is that it’s very difficult to probe the gas inside the solid material. Recent experiments have involved a technique that can provide information on the density and state of the hydrogen inside the pores of a solid material, known as inelastic neutron scattering.

This information can help identify what makes these materials so good at absorbing hydrogen. And help to develop better hydrogen storage materials with higher capacities for the future.

Developing higher capacity storage materials

These materials could be used to store hydrogen in motor vehicles, and electricity from renewable electricity. Both of which have really positive advantages in terms of reducing carbon dioxide emissions, which then help reduce the impact of climate change.

‘Hydrogen storage is difficult. If you’re driving 300 miles you need about 4-5kgs of hydrogen, about a third of the mass of gasoline you’d need to go that same distance. It would occupy 60 cubic metres, which is three or four times the volume of your car.’
Dr Tim Mays, Department of Chemical Engineering

Storing electricity as hydrogen