Ireland’s optimum generation mix

Ireland’s energy policy is focussed on the 3 key pillars of energy security, sustainability and competitiveness. Because energy plays an important role in driving economic activity, we must reduce our carbon foot print and our dependency on fossils fuel while also taking advantage of energy efficiency initiatives.

It is equally important to reduce our energy demand while, at the same time, ensuring that our energy supply is optimised. But what would be the optimal energy supply for Ireland?

I am unaware of any agency, State or otherwise, that is responsible for devising an optimal energy mix for Ireland. Perhaps it now falls within the remit of the Commission for Energy Regulation (CER), but no work had been done on this when last I checked.

So, let me outline my view of an optimum electricity supply mix – one that would supply electricity securely, sustainably and competitively. This mix minimises the need for additional pylons and high-voltage cables across the countryside while also reducing the visual and social impact of excessive numbers of wind turbines.

It includes a reasonable mix of intermittent and regular electricity sources to reduce system overheads while maintaining reliability of the supply.

There are, of course, no sources that are absolutely reliable – even hydro is subject to the weather.

It is important to clearly distinguish between hydro and pumped storage. Our hydro (based on a river) is effectively at maximum already (250 MW) as all the major rivers are harnessed.

There is a 70 MW pumped storage (based on two lakes) plant being built and more are likely to follow. The proposed Spirit of Ireland (SoI) scheme of 600 to 1000 MW will probably not restrict itself to wind exclusively – they will use anything from Irish thermal to British nuclear, as required, to keep the reservoirs full. If SoI can be built for its claimed costs, then this could be the best ally that nuclear power in Ireland could have – any base load generator could benefit from about 1500 MW of pumped storage.

Intermittent renewables of 2500 MW (average 600 MW output) is already built or under construction. Wind at low penetrations appears to be cost-effective but need not be replaced if proven otherwise. The national effort to produce wave and tidal may lead to the technology being developed here, so I feel we should leave these estimates in place as aspirations.

Waste to Energy (250 MW) is already under way at 2 off 70MW plants. Supply is guaranteed due to costs of other waste disposal options and will save landfill cost penalties.

Biomass (250 MW) is also already in place and can use non-food land. Again aspirational, but why rule it out at this stage?

In general, I believe there is a good fuel mix and a synergy among the participants in this outline:

  • 2400 MW of nuclear power (could be 4 NuScale modules of 12 units each. Perhaps have 2 modules at Moneypoint and 2 elsewhere)
  • 1500 MW of pumped storage capacity (perhaps Spirit of Ireland type if it ever comes about)
  • 2500 MW of intermittent renewable energy (wind, tidal, wave as it becomes available)
  • 250 MW waste to energy
  • 250 MW of biomass
  • 250 MW of hydro as exists now
  • 1000 MW of interconnection as already built
  • Some peaking open cycle gas turbines (to be determined by system modelling)
  • Coal-fired carbon capture and storage (CCS) plant – if economic – may replace an equivalent amount of nuclear plant
  • Remainder as combined cycle gas turbines (to be determined by system modelling).

Note that the average demand in the Republic of Ireland is around 3000MW while the peak demand (in mid-winter) is around 5000 MW. Minimum load (in mid-summer) is around 1800  MW.

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