Bridging the gap to a sustainable future: Underground Hydrogen Storage

To decrease emissions of greenhouse gasses into the atmosphere, we have to move away from fossil fuels into a green and sustainable society. Hydrogen can play a big role in this, as it is a universal energy carrier and can be used to fuel cars or ships, heat buildings, melt steel or make electricity. When it burns mostly water comes out.

For this transition, we will need a lot of hydrogen throughout the year. But where can we store all this hydrogen during the summer days when we do not need as much? Underground hydrogen storage, or UHS as it`s called for short, offers us the possibility for storing energy in the subsurface at a very large scale.

For Norway, UHS is a big opportunity to use existing know-how and infrastructures from the oil and gas industry and move into a green future, protecting jobs and our environment!

In this text we will explain what UHS is and put a light on some of our major research goals on the topic.

What is underground storage and how does it work?

UHS is a concept for large-scale energy storage where excess hydrogen is pumped and stored in different deep geological formations. Salt caverns, aquifers and depleted hydrocarbon deposits (gas reservoirs) in the North Sea can be used for this type of storage. There the hydrogen can stay for days, weeks or months, until it is needed. When it is pumped back, it can be either directly used or transformed into electricity later. This means, UHS is like a big battery in 1000-meter depth! Also, it is very safe because the storage formations are so deep and oxygen-free, there is no risk for humans or nature.

Why do we need UHS?

Our energy demand is pretty steady with some annually variations. Renewable energy like electricity from wind, water or solar is, however, a very variable resource. What can we do when we need energy but there is no wind? Going for 100% renewable energy will not work without energy storage where surplus electricity is used to produce hydrogen by electrolysis. Hydrogen can then be pumped and stored and when the energy production is low, hydrogen can be used to again produce electricity. This will give us a steady energy production throughout the year.

Is UHS ready?

Although there a handful UHS sites in the world already, there are still open questions we have to resolve first before we can start employing UHS in Norway. These research question span from basic knowledge on physical properties to site-specific questions on hydrogen movement and -loss.

Here are some examples we are working on:

• Hydrogen is a very small particle, which might diffuse through the rock. This could cause hydrogen loss during storage over time. This potential diffusion and general subsurface movement must be experimentally tested under the relevant pressure and temperature conditions. The results can further be used for large-scale modelling studies.
• As hydrogen is in contact with ambient rocks and minerals, it may chemically react with them. The result can be reduced gas purity and hydrogen loss. The extent and speed of this reactions must be understood better.
• The storage sites in the subsurface often contain microorganisms and there are some known, which can feed on hydrogen. What types of microbes are triggered by hydrogen storage, their growth behavior and possible inhibition must be studied in more detail.
• Gases and water in the subsurface will also influence hydrogen. At the interface between hydrogen, other present gases (for example methane or CO2) and water/brine different mixing effects can happen. Until now it is not clear how this mixing will affect the hydrogen purity or lead to potential loss.
• There are still some uncertainties on the best suitable geological areas in the subsurface, which could be used for hydrogen storage. Geological mapping specifically for hydrogen is needed.

Because hydrogen has unique properties and behavior in geological formations, experiments must be performed at high pressures, temperatures or salinities. This can be quite difficult but in NORCE we have all needed interdisciplinary competence and year-long experience in subsurface processes to be able to do this. Our goal is to promote and help UHS to become a secure and reliable technology for Norway and the world, so we can take the next step in the transition into a carbon-emission-free world!

Contact us, if you want to collaborate with us on this fascinating topic!