Hydrogen economy, hydrogen society, hydrogen fuel cells… Over the last few years, the first element in the periodic table has become a global buzzword.
This is because it has the potential to address two major challenges in the global drive to achieve net-zero emissions by 2050.
First, it can help tackle the perennial issue of intermittency. Renewables can’t provide a consistent energy supply because the wind doesn’t always blow and the sun doesn’t always shine. By converting excess power generated on windy or sunny days into hydrogen, the gas acts as a medium for temporary energy storage that we can fall back on when energy supply from renewables is low or demand higher than usual.
Second, hydrogen can help decarbonize areas where electrification alone is not enough. Good examples are domestic heating, and heavy industrial processes like steel and cement manufacturing, which are energy intensive and as such heavy emitting.
One challenge to using hydrogen in tackling climate change is that this excellent energy storage medium has itself been hard to store.
Here are four hydrogen storage solutions that could turn the tables.
1. Geological storage
The world’s largest renewable energy storage project, called Advanced Clean Energy Storage, was announced recently and will be located in Utah in the United States.
Advanced Clean Energy Storage will demonstrate technologies essential to a future decarbonized power grid.
As part of the project, hydrogen produced from excess renewable energy will be stored in a series of underground salt caverns. A single cavern will hold enough renewable hydrogen to provide 150,000 MWh of clean energy storage.
Mitsubishi Hitachi Power Systems will provide the technology for converting surplus renewable electricity into ’green’ hydrogen.
Gas storage in salt caverns is an established technology, which enables easy knowledge transfer. Other options for geological storage include depleted oil and gas fields and aquifers.
2. Compressed hydrogen
Like any gas, hydrogen can be compressed and stored in tanks, and then used as needed. However, the volume of hydrogen is much larger than that of other hydrocarbons, for example nearly four times as much as natural gas.
Therefore hydrogen needs to be compressed for practical handling purposes. For example, fuel-cell powered cars run on compressed hydrogen contained in highly pressurized large containers.
If an application requires hydrogen volume to be reduced further than compression can achieve, it can be liquefied. The two techniques – compression and liquefaction – can also be combined.
3. Liquified hydrogen
MHI Group along with the space industry as a whole, has used liquefied hydrogen to fuel rockets for many years.
But liquid hydrogen storage is technically complex and, as such, it has historically been very costly.
Hydrogen has to be cooled to -253°C – not far from absolute zero – and stored in insulated tanks to maintain this low temperature and minimize evaporation.
Complexity and cost have limited the use of liquified hydrogen to date. However, the expected proliferation of renewable hydrogen applications may generate economies of scale to make liquefaction a more viable storage option.
4. Materials-based storage
An alternative to compressed and liquified hydrogen storage is materials-based storage. This technique uses materials – solids or liquids – that can absorb or react with hydrogen to bind it, due to their chemical attributes.
At the University of California, Berkeley, research is underway to create an adsorbent that will allow a light-weight, inexpensive pressure container to be used in hydrogen-powered cars, for example, in lieu of the large, heavy containers currently in use.
Ammonia is another material that offers a path to turning hydrogen into a liquid fuel more easily than using liquefaction.
Ammonia’s energy density by volume is nearly double that of liquefied hydrogen, making it far easier to store and transport.
Where next for hydrogen storage?
It’s clear that unleashing hydrogen’s potential for delivering truly decarbonized societies and economies will depend on identifying the most suitable storage method for each application. And it’s not only about the technical possibilities – any approach has to be economically viable.
But science does not stand still: last year, a team of international scientists at Lancaster University in the U.K. discovered a new material, made from manganese hydride, which could store four times more hydrogen in the same volume as current fuel cell technologies. It also doesn’t require external heating and cooling. While the research focus was on hydrogen-fueled cars, the implications of this discovery may ultimately go further to help open up a mass market for hydrogen.
Source : https://spectra.mhi.com/4-ways-of-storing-hydrogen-from-renewable-energy