By Natasha Marino, Climate Change Thought Leadership Award winner (Master’s Category) 2022
Renewable energy technologies cannot always produce a consistent amount of energy. For example, the energy outputs from solar technologies are limited in winter, when there’s fewer daylight hours and the sky is often overcast.
Likewise, demand for energy varies throughout the year. Think of winter evenings, when households all over the country will be cooking, turning on the TV and have the heating on, creating a surge in demand for both electricity and gas during the colder months.
What is interseasonal energy storage?
Interseasonal energy storage can act as a buffer between the seasonal mismatches in demand for and availability of energy.
It provides a solution when demand for energy does not match the supply from renewables, which can prevent the need to resort to fossil fuel derived energy to plug any gaps.
How does interseasonal energy storage work?
Anyone who can cast their minds back to high school physics, will be aware that energy cannot be created or destroyed, but can be transferred from one form to another.
A battery stores energy by converting it to a chemical form, which can then change to electrical energy. Interseasonal energy storage is not dissimilar to a battery, but instead of metal casing, the storage unit is an underground cavern, and the energy is stored in the form of a gas, such as green hydrogen.
Green hydrogen can be produced by splitting water into hydrogen and oxygen when using renewable electricity from solar or wind. It is important to transition to green hydrogen, as the majority of hydrogen use comes from grey hydrogen which has high levels of greenhouse gas emissions.
Salt caverns, where salt has previously been mined, provide the best geology to securely store gases. This provides an opportunity in areas where there has historically been a lot of salt mining, as disused caverns can be readily converted for storage.
Depleted oil and gas fields can also be used – if they stored a fossil fuel for thousands of years before it was extracted – they can be adapted to securely store hydrogen.
How could interseasonal energy storage be used in the UK?
Currently, these interseasonal energy storage solutions lend themselves more readily to industrial uses. Gas powered household boilers and cookers can currently use a negligible amount of hydrogen, however testing is occurring to allow this limit to increase to a 20% blend. But, increasing the hydrogen gas blend beyond 20% into the national grid will require an update of existing infrastructure, with entire towns adapting boilers to enable more hydrogen use.
In industry, it is possible to look for closely located storage geologies to use for green hydrogen storage. Investments could be made to convert some of the more energy intensive industries to this renewable energy source, reducing pressures on harder to abate sectors.
In the UK, there are opportunities to use existing geological infrastructure for hydrogen storage. Near Southampton, for example, there is a salt formation too deep for commercial salt production that provides ideal conditions for adaptation to gas storage.
There’s also an opportunity in the Humberside area, where there’s an existing interseasonal storage unit, which was originally built in a salt formation to store natural gas to respond to fluctuations in usage in the national gas grid. There’s also an offshore wind farm, the energy from which could be used to generate green hydrogen, to be stored in the cavern.
Creating interseasonal storage capacity in areas where fossil fuels have previously been extracted creates an opportunity to upskill existing workers. The oil and gas workforce are already equipped with many of the skills needed in renewables development, making the people in these jobs an asset to the renewables industry. It is imperative that the transition from this workforce to green jobs is enacted soon to meet the net zero targets.
Could interseasonal energy storage be used for households?
Currently, interseasonal storage is best used at a national scale for industrial and network uses.
Projects like community micro-grids offering hydrogen storage may come to fruition at a large scale. However, for the time being, hydrogen projects are very much dependant on governmental subsidies and industrial project applications.
Natasha Marino won the 2022 Climate Change Thought Leadership Award, for her MSc level research into opportunities to use interseasonal energy storage in the UK. Her research identified clusters of industry activity close to potential storage caverns. She also used modelling to determine how much energy could be stored within a salt cavern. Now, Natasha is continuing research in energy solution as a PhD student at the University of Bath.