In December 2023 a new record of 3.86GW was set for renewables generation in the State. The previous month, renewable sources including wind, solar and hydro generated approximately 43 per cent of grid electricity. At present, up to 75 per cent of the State’s electricity generation can come from variable renewables, such as wind and solar, at any one time. The ambition is to increase that to 95 per cent by 2030.
Those statistics represent remarkable progress over a relatively short period. There is a problem, however, and that is the intermittency of renewable energy. Although it might not feel that way, the wind doesn’t blow all the time.
“In Ireland, we have good wind about 40 per cent of the time but that’s not every day,” says Stephen Prendiville, sustainable infrastructure leader with Deloitte. “We can go for several days without wind. And solar is better in summer and in the south of the country.”
In essence, that means the power system has to be designed to have enough fossil fuel generating capacity to meet peak demand at any given time, with renewable energy being used as and when it is available. But that can mean that there is a surplus of renewable power on the system at times and it effectively goes to waste.
The solution is to find some way of storing that excess power to allow it to be used when needed.
According to Prendiville, power demand in the Republic varies between around 4GW and 6GW at peak.
“The holy grail is to be confident that you can meet the 4GW base demand from renewables all the time and deal with the 2GW spike with fossil fuel generation,” he says. “At the moment that is inverted and we use fossil fuels for the base load, with renewables coming in as available.
“With enough storage on the system, we could deploy power when we need it instead of using fossil fuel generation. That would require lots of batteries and having the renewable power available to charge them.”
Of course, it’s not quite as simple as that. A few days without wind would quickly exhaust battery storage and we would be back to the situation where fossil fuel generation would have to meet total demand. That explains why batteries are seen as just part of the overall storage solution.
“There will be a bit of a technology tussle between hydrogen, fuel cells, batteries and other storage technologies,” says Prendiville.
Notwithstanding those issues, battery storage does have a big role to play in the decarbonisation of our power system.
“The potential is huge,” says Chris Collins, country president Ireland at Schneider Electric. “It will contribute enormously to a more sustainable power supply that will dramatically reduce Ireland’s dependence on foreign gas imports.
“Storage facilities will allow Ireland to harness offshore and onshore wind and solar energy, adding capacity to the grid for immediate domestic use, while creating an energy surplus. Reserve supplies will help to ensure stability and energy security, driving prices down but also creating a surplus that can be exported to other markets.”
While the State has 1GW of battery storage connected to the grid at present, there is also scope for the technology to contribute in other ways.
“We’re already seeing some impressive innovations in the development of battery technology, especially in EV batteries, which constitute a huge amount of stored electricity,” says Collins. “In fact, we’ve only begun to scratch the surface of what opportunities EVs can offer as part of a new sustainable energy mix.”
He points out that EV batteries store electricity that can support different energy use cases through bidirectional charging.
“The residual energy contained in EV batteries can be used to power localised electricity before it goes back into the grid, leading to new charging models,” he says. “For example, you could have a hub where solar power is used to charge EVs during the day but residual power from parked EVs can help to power a residential building overnight. That’s just one scenario.
“The same model can be applied to an office building, factory or a farm, powered by infrastructures that facilitate bidirectional charging, vehicle-to-grid and vehicle-to-building transfer.”
He also notes that batteries installed in homes to store solar energy can not only provide backup power for the householder but can also deliver surplus electricity to the grid.
“We need to think about the demand side,” says Prendiville. “When smart meters are fully rolled out we will see EVs, home solar, home battery packs, community generation and so on all having roles to play.”
With smart meters connected to smart devices, the grid will be able to signal when there is a surplus of power for people to use for the likes of EV charging.
“Smart monitoring systems can be used to let us know when the grid or microgrids are experiencing a surplus in solar or wind power, encouraging businesses and households to use more or less power, or even store power, depending on their requirements,” Collins adds.
“Data-led systems can be used across the grid network to inform constituents when batteries and storage systems are at capacity, so that we can consume and store energy more efficiently.
“This aligns with broader national ambitions to create a more sustainable infrastructure based on renewable energy that charges and stores battery power, using solar power by day and wind power by night.”