Energy Institute

Are there times when we produce too much wind?

On very windy days there can be more wind power available than the system can accept. This is because it would displace conventional power plants below the minimum level needed for certain grid stability services. On a windy night when power demand is low the electricity System Operator may have to limit the priority access to the grid that wind enjoys. When this happens, the wind generator is dispatched down or “curtailed off” i.e. blocked from supplying electricity to the grid.

Wind generators are currently financially compensated for such curtailment, but this compensation will end from 2017.  This “curtailment” is different from “constraining off” where generators are switched off to avoid overloading the local grid. Unlike curtailment, generators will continue to be financially compensated for being constrained off due to local issues. Generators pay for “firm access” – to use the transmission grid to sell electricity – and if they are constrained off due to a local grid problem, the generator is paid compensation for not being allowed to generate as much electricity as they could.

Figure 3. Annual wind energy contribution to gross electricity generation

EirGrid/SONI (2015) All-Island Generation Capacity Statement 2014-2024. Available Online

  • Onshore wind as share of gross electricity

Figure 4. Renewable energy contribution to gross electricity consumption 1990 – 2014

SEAI (2016) Energy Security in Ireland 2015. Available Online

  • Renewables of Gross Electricity (normalised)
  • Hydro
  • Wind
  • Biomass
  • Landfill Gas
  • Biogas

In 2013 the total wind energy generated in Ireland and Northern Ireland was 5,872GWh, around 3.2% of which was dispatched-down (blocked off the grid) for one reason or another. In 2014 the total wind energy generated in Ireland and Northern Ireland was 6,436 GWh, while 4.1% was dispatched-down 1.

The development of the East-West interconnector allowed the amount of wind coming onto the system to increase and 50% less wind was curtailed mainly by sending the extra electricity across to Britain 2.

The total constraint payments for 2013 increased on 2012’s total of €123 million. With 40% more wind capacity expected to qualify in 2017 compared to 2016, the share of the PSO going to renewable energy is estimated to increase (from 56% in 2015/16 to 76% in 2016/17).3 However, the cost of guaranteeing the price for onshore wind is expected to be partially offset by the reduction in the wholesale market price of electricity in Ireland as a result of greater wind generation. 4 While the extra costs of the PSO fall directly on the consumer, the expectation is that competition in the market will cause lower wholesale prices to pass though and be reflected in lower retail prices for electricity.

In 2014 wind energy accounted for 18.2% of electricity generated in Ireland. By the end of that year the installed capacity of wind generation was 2,211MW (Figure 3.)5. The Commission for Energy Regulation is forecasting a significant increase in capacity in 2016/2017, with up to 2,943 MW planned to be supported under the PSO 6.