Electrical energy cannot easily be stored.It has the troublesome feature that production and consumption need to be almost simultaneous or there will be problems.

There are storage technologies (reservoirs above hydro stations) which have long been available, and others are in development (industrial-scale batteries), but they are costly and not readily deployable at scale. Without extensive storage the high variability of demand needs highly responsive production or there will be system failures, including blackouts.

The (almost) simultaneous equation of production to demand is not a feature of the markets for other important goods and services. If the market for bread had this feature, the bakeries would have to run, at variable speed throughout the day and night, somehow delivering the product instantaneously to the fickle customers, who consume the non-storable product at a fluctuating pace. But bread stays fresh for a day or two and can be stored cheaply on supermarket shelves or in a cupboard.

Production must be agile, capable of swift ramp-up or ramp-down, in response to demand fluctuations which are not easily predicted

To meet the demand variations, hourly electricity production needs to include a significant component which will always be available, since off-peak demand must be met and never falls to zero. It rarely falls below one-half of the hourly peak level in many countries. But production must also be agile, capable of swift ramp-up or ramp-down, in response to demand fluctuations which are not easily predicted.

Flexibility

The traditional solution has been to design a generation system with flexibility.

Some plants produce day and night to meet base-load demand, others are capable of intermittent production at the flick of a switch. The system operates most of the time below capacity, but production is always, or nearly always, adequate.

Unfortunately, this is not possible when a large portion of electricity production comes from intermittent and weather-dependent sources, such as wind and solar. There must either be extensive storage or a continued reliance on predictable production from traditional generation.

Since everyone agrees that turf, coal and oil stations will have to be phased out due to high carbon emissions, there will need to be something else in the generation mix to replace their predictability.

Unless someone can deliver cheap and very plentiful storage, or sharp reductions in demand variation, it will not be possible to rely entirely on wind and solar

Gas stations also have serious emissions, about half those of coal per unit of electricity produced and it would be nice to phase them out too. But gas has an extra feature which matters.

Gas stations can be brought on the system, or switched off, quite quickly, which cannot so readily be done with coal or with nuclear.

Advances

While great advances have been achieved in the integration of intermittent power onto national systems, there is a limit and accordingly a future for electricity production which offers either always-on base-load power with low emissions, or flexible, fast-response power with modest emissions.

Unless someone can deliver cheap and very plentiful storage, or sharp reductions in demand variation, it will not be possible to rely entirely on wind and solar.

Prudent planners are thus targeting increased renewable, low- or zero-carbon, generation, but with a continuing role for base-load power which is always-on, and for flexible power with the lowest emissions that can be achieved.

Within the horizons of existing or prospective technologies, this means that some gas stations will always be needed, and that all base-load options, including nuclear generation, need to be considered.

Existing interconnection with the power system in the United Kingdom and the planned link to France will mean imports of nuclear power anyway – the plans for a replacement nuclear station on Anglesey island in north Wales, 90km from Dublin, have been revived and there is already an expansion of base-load electricity demand driven by the data centre boom which will not be met by press releases about their contracts with windfarms.

Heavy cost

Traditional nuclear plants have had two things in common. They have been large-scale and have imposed heavy capital cost.

The largest Irish station, the Moneypoint coal plant in Clare, likely to close soon, is the biggest on the system at about 900 megawatts in 3 x 300 configuration.

Single nuclear units have heretofore been even larger, and seen as too big for the Irish system, as well as too costly. This may be about to change, according to a study just released from a group of engineers and downloadable at www.18for0.ie.

New technologies are emerging which, it is hoped, will make smaller nuclear units available at a scale which would suit the Irish market, roughly the 300 megawatts of the three due to close at Moneypoint.

These new nuclear units could be more predictable in cost too, although it would be wise to wait and see.

It is time for the Government to acknowledge that nuclear is a legitimate long-term option and that some gas units will also need to be retained.

It is unrealistic to plan for reliance exclusively on wind and solar.