Professor Barry McMullin:

I completely understand.

If we want an energy system that is delivered, as much as possible, from wind and solar resources, we need to be able to move that energy around in time. At the moment, that is not too big a problem, given that a large proportion of our electricity is still coming from other sources and the vast majority of our heating and transport energy comes from other sources. That is not too big a problem right now, but as we try to build out as fast as possible to get rid of those fuels from our system, we will reach the point where it is essential to be able to move that energy around in time at a very large scale. The biggest storage facility on the island is the Turlough Hill pumped-storage hydro station, which has a capacity - I apologise for the technical numbers - of about 2 GWh of storage. We need terawatt hour-scale storage to successfully deploy, year round, 70%, 80% or 90% of our energy from variable renewables. That is 1,000 times larger. We are not going to do that with pumped hydro. The only practical way of achieving that kind of scale of energy storage is with chemical forms of energy. The starter for all chemical forms of energy, if we are starting with electricity, is hydrogen.

Hydrogen storage would be the first preferred option. Hydrogen can be stored in very large quantities but the best option for doing that is in so-called salt-cavern geological formations, and on the island of Ireland they only exist in Northern Ireland. There is a project already under way looking at natural gas storage with a possible migration route to hydrogen storage there. On an all-island basis, that should be a high priority for moving along as quickly as possible and understanding what are the limits and what is the capacity there - whether we can reach terawatt hour scale or whether that will not hack it for terrawatt hour scale. Clarifying that would be really important.

The other technology needed is electrolyzers to convert electricity into hydrogen and generators to convert hydrogen back into electricity. One would not use all electricity back in hydrogen but would use some directly in heating and in transport.

Of those technologies, electrolyzer technology is developing very rapidly. It is certainly ready for medium-scale buildout already but it would need incentive schemes to make it work. It would need something like the renewable electricity support scheme, RESS, auction-type process to get much faster buildout of electrolyzer capacity. Similarly, gas turbines for electricity generation are already available in similar scales to natural gas for using hydrogen instead of natural gas but it would require explicit structured incentive schemes to ensure that any new construction of gas-fired generation was capable of migrating to hydrogen combustion.

Those technologies are there. We are much more exposed and reliant on them than many other countries but, conversely, that is an opportunity for us to push the technology profile. However, it would require, as I say, things like auctions.