Written by Elaine Baker
Why do we need to store energy?
Switching from fossil fuels to renewables is essential for de-carbonisation. For most renewables, such as wind and solar, we can’t turn them up and down according to our needs. This is a key argument used by the fossil fuel lobby against renewables – the fossil fuel lobby try to persuade us that we still need fossil fuels for when the wind is not blowing or the sun is not shining. However, to eliminate fossil fuels, what we actually need are ways of storing energy when the wind is blowing and the sun is shining, for use when the wind is not blowing and the sun is not shining. This is energy storage.
What are the different types of energy storage?
The most promising technologies for energy storage are batteries, green hydrogen, and pumped water (like Turlough Hill). Each of these have different advantages and disadvantages, so we probably need a combination of them. Some of them are more suitable for short term storage (e.g. storing some energy daily for use during the early evening peak) and others are more suitable for long term storage (e.g. storing energy annually for use during the winter peak).
What are the pros and cons of green hydrogen relative to other energy storage?
Green hydrogen vs batteries: Hydrogen storage infrastructure lasts a long time whereas batteries wear out quickly, green hydrogen is more suitable than batteries for storing large quantities of energy for months, and currently there are human rights and local environmental issues around extractive mining for several battery minerals.
Green hydrogen vs pumped water: Green hydrogen storage can be built in many places, whereas pumped water storage can only be done in places with certain topology, and can also have negative local environmental effects.
However, when converting electricity to green hydrogen, a lot more energy is lost in the process relative to batteries or pumped storage. So each is suitable in different circumstances. Some of the problems with batteries can be reduced by better policy, recycling and technology, but green hydrogen is an important option, particularly for months-at-a-time storage.
Beware of the greenwash!
While green hydrogen energy storage is likely to be a very important piece of the de-carbonisation puzzle, there is a lot of greenwash to look out for!
- No to grey hydrogen! Hydrogen can also be produced from fossil fuels directly, or can be produced from electricity where the electricity has been produced from fossil fuels (even worse, as even more carbon emissions involved). Hydrogen produced using fossil fuels is called grey hydrogen. We need to produce hydrogen only at times when there is a surplus of renewables on the electricity grid – this is green hydrogen.
- No to blue hydrogen! The fossil fuel lobby try to get around this by saying they can capture the carbon and store it while they are producing hydrogen from fossil fuels. They call this blue hydrogen. We need to not emit carbon in the first place, not emit it and then use up lots of energy trying to capture it again! The best carbon capture technology by far is provided by nature - the tree and other natural carbon sinks. Artificial carbon capture and storage (CSS) technologies do not make any sense.
- No to new gas pipelines! The fossil gas industry argues in favour of investment in new fossil gas pipelines because they say they can also be used to transport hydrogen. We need to be very careful about this – most gas pipelines can only be used for hydrogen if the hydrogen is mixed with a lot of fossil gas! Also, it is a lot quicker and more efficient to transport energy by sending electricity via cables than by sending hydrogen via pipelines.
- Beware of “We will convert fossil gas generators to hydrogen generators later” – It may be possible to convert existing fossil gas electricity generators into hydrogen electricity generators, but we have to be really careful not to allow this to justify new fossil gas generator investment that turns out to be costly or difficult to convert – this can be a back door to fossil fuel lock-in.
Hydrogen has a lot of potential to support de-carbonisation, but also can be used by the fossil fuel lobby to greenwash fossil fuels – let’s support the move towards genuinely green hydrogen and not be tricked by the greenwash!