DEAR EDITOR,

Why does expanding wind and solar power make electricity more expensive and less reliable

The official narrative is that the way to reduce the cost of electricity is to build more wind and solar farms. It would seem intuitive that wind and the sun are free sources of energy and that they should make electricity cheaper.

This may have some validity up to a point, but in practice more wind and solar drives the price of electricity up instead of down. I will explain this engineering conundrum as simply as I can. I will refer to wind, but the same principle applies to solar power, which is less favourable than wind under Irish conditions.

Firstly, even though wind is free, there is a price for converting it to electrical energy. That is mainly the capital cost of a wind turbine, annualised over its lifetime and divided by the number of electrical units delivered over a year. An accountant would refer to this as the fixed price of a unit of wind-generated electricity.

Next, it is necessary to say something about ‘synchronous generation’. We would already have enough wind and solar power to supply 1.5 times our average demand in Ireland on a windy day, except this does not generate ‘synchronous’ electricity.

Synchronous generation refers to machines that rotate at exactly the right speed to produce electricity at the required frequency, namely 50 cycles/second.

Wind turbine blades go at speeds that vary with the force of wind, and so this is ‘non-synchronous’ generation. There is a rule that the percentage of non-synchronous generation on the grid is not allowed to exceed 75% at any point of time.

Beyond 75%, there is an increasing risk of blackouts – as happened in Spain in April 2025. So even though there is a capacity to generate 150% of demand, as non-synchronous, generation has to be curtailed to 75%, this means curtailing half of the available wind power.

In practice, the balance is met mostly by natural gas. On windy days you will see some turbines spinning and others idle. That is curtailment, and the idle turbines represent excess generating capacity that is not used but yet has to be paid for, in addition to paying for the natural gas that fills the gap. That is already pushing up the price of electricity.

Under the Climate Action Plan, it is proposed to over-build wind and solar capacity in order to harness as much renewable energy as possible during light winds and cloudy days. The plan is to treble the amount of intermittent (wind and solar) renewable capacity.

Because this extra utilisation of wind energy follows a law of diminishing returns, with increasing amounts of lost excess capacity, this hikes the price of electricity by a factor of three or more under a constant demand scenario.

In addition, the prioritisation of intermittent renewables constrains the utilisation of natural gas plants, which must have the capacity to supply almost the entire demand on calm nights.

The intermittent constraints on gas plants increase the fixed cost of gas-powered generation, further adding to the price of electricity. One further point.

The power from a wind turbine is more variable than the wind itself because the power generated is proportional to the cube of the wind speed. So if the wind speed drops by half in the course of an hour, the power generated falls by a factor of eight.

This variability requires a large amount of ‘spinning reserve’ – gas turbines that are running offline and available to be switched on at any time and varied up and down to accommodate the wind.

This also adds to the price of electricity.

With regard to the notion that net zero can be achieved by storing the excess capacity of wind power using either batteries or hydrogen, those are not realistic, tried and tested solutions. Wind studies have shown that we can expect sustained low-wind periods of up to 10 days in the course of 10 years. Even one day without power would be a catastrophe.

If relying mainly on wind power and battery storage, we would need long-duration energy storage capacity of perhaps 20 days of demand to deal with a worst-case scenario.

The cost of batteries to handle this is estimated at €1,000 bn and therefore not an option. Besides, batteries only supply non-synchronous power. As for hydrogen, that has never been demonstrated as feasible for large-scale energy storage on a sustainable basis.

This explanation shows the main flaws in the narrative that building more wind and solar farms will reduce the price of electricity and improve reliability.

Further details can be found in the Pollock Report which can be downloaded at www.icsf.ie.