Professor Barry McMullin:

The Cathaoirleach saved the good ones for last. We cannot run an electricity system without so-called firm generation capacity. That is capacity that can run on demand to meet peak demand. In the energy system as a whole, there has to be enough of this kind of generation capacity that can meet firm demand. Excluded from that normally are wind and solar. It might be night-time or the wind might not be blowing, so they cannot arbitrarily meet firm demand, although when we go offshore, we get a certain level of pretty well firm demand. In the Irish case, as we are electrifying other things and as we are building out more renewables, we still have to have enough firm generating capacity to meet the peak demand even when there is not any wind or solar. This means having the generating plant to do that. The preferred plant, which, arguably, is the least emissions-intensive, although it depends because it is a complicated equation, is using natural gas, maybe with some biomethane in future years. We are not going to have a huge amount of biomethane, even with the most optimistic projections. We are talking about a little bit of displacement of that gas and a certain amount of gas.

As long as we are going to be relying on natural gas generation to meet that firm demand, we have to have the plant. If we retire other kinds of plant such as Moneypoint and the oil plant at Tarbert, which is at end of life, in order to continue peak demand - and an increasing peak as we are electrifying heating and transport - we need additional generation capacity. At the moment, that needs building a new gas-fired plant. That is what we can get off the shelf to do that. I accept and endorse that this is happening and that it needs to continue to happen. However, it is not straightforward. The kind of plant we are now deploying is technically called open-cycle gas turbine plant. That is lower efficiency than so-called combined cycle gas turbine plant, which we are using in certain big gas-fired stations. The problem with the latter is that it is much more capital intensive, although it delivers much higher efficiency. It is much more expensive. If we are not running it much of the time it is harder to make the combined cycle plant economical. If we successfully decarbonise, we have to have this new plant on standby but we are trying to minimise the amount of time for which it runs.

From an economic perspective, having a really expensive capital plant for that is not very attractive. It means that some of the advantage of reducing the run hours in emissions terms, if we move the fleet towards these open-cycle plants that are less efficient, some of the advantage in reducing the run hours is evaporating because we are using less efficient plant. It is not a great trajectory. We really need other options. There are other options but they are not mature. We cannot go out in the markets or at least they would not be competitive in an auction-type system.

We definitely need more battery. By buffering short-term fluctuations with battery, we can then allow the combined cycle plants, which are slower both to start up and to shut down, to run for longer and we can get over the start-up and shut-down variations. More battery will allow us, on a 24-hour cycle, to shave the peak in order that the peak where we need another form of generation will not be the daily peak but a daily average, although there will be still a winter peak relative to a summer peak. This is something of which we need to do more, and it would reduce the need for gas plant.

The longer term picture relates to thermal plant gas turbines that do not run on natural gas but on something else, and the devil in the detail concerns what else they run on. Insofar as possible, as we are supporting the build-out of new gas turbines, we want to future-proof them such that they will be able to run on alternative fuels. The candidates in play are the direct combustion of hydrogen; ammonia, which is somewhat controversial because it tends to involves knocks, although there is no carbon in it; or synthetic methanol, a carbon-based fuel. I recently visited the technical university of Berlin, where there is a specialist the committee may want to invite before it on another occasion. He sees tremendous potential for that methanol route.

There is a new form of gas turbine of which only one scale example is operating in the world at the moment. It is a 50 MW gas turbine, operating at scale, using a new technology called Allam cycle, which allows it to operate at a higher temperature, meaning higher efficiency. We can offset the shift from combined cycle to open cycle and regain that efficiency by going to these Allam cycle gas turbines. Additionally, the secret sauce of the Allam cycle turbine is that the working fluid - I am sorry for getting technical - is mostly carbon dioxide. The net result is that we can build a closed system where methanol is taken in and combusted, water and carbon dioxide are released and, if there is a source of hydrogen, the carbon dioxide can be recycled to produce methanol again, with water. There is a closed cycle and the carbon never leaves the system, so there are no emissions. The reason I suggest this rather than the direct combustion of hydrogen is that hydrogen is difficult to store and manage in large quantities. We can produce it from renewable energy, but storing it in large quantities is difficult. I mentioned developing natural gas storage that could be repurposed for hydrogen and that is certainly a pathway, but methanol is a liquid in normal conditions, which is easy to store. At the other end of the cycle, we would have to store carbon dioxide, which is a bit more difficult to store but still much easier to store than hydrogen.

I think there is an opportunity, even as we build out new gas-fired capacity, to ring-fence some of that for trying to accelerate the deployment of these kinds of technologies that will allow us to migrate away from natural gas. As I said, there is only one Allam cycle plant in the world at the moment, but the commercial company behind it is looking for new sites to go to. It was originally focused on a so-called carbon capture and storage market for which it is also suitable, but in the Irish context it would be about demonstrating a closed cycle system. Even short of that, it would immediately deliver efficiency comparable to a combined cycle rather than to these low-efficiency open cycle systems we are currently procuring. There are already opportunities, even in the steps we are currently taking, to accelerate that development.