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Dublin: 13 °C Friday 28 October, 2016

These five graphs dig into the figures behind wind energy in Ireland

Figures show that wind power generation did not meet forecast electricity generator 58 per cent of the time over the past five years.

Wind turbine
Wind turbine
Image: Ryan McD via Flickr/Creative Commons

EARLIER THIS MONTH, the Minister for Energy Pat Rabbitte revealed that wind energy contributed more energy than ever to the national grid one windy evening last December.

1866 megawatts, 42 per cent of our total electricity needs at the time, was generated and fed into the grid, according to the Minister. Furthermore, the Irish Wind Energy Association (IWEA) has predicted that 18 per cent of demand last year was met by wind energy.

But what do the other figures on wind energy reveal? got our the pencils and spreadsheets out and crunched some numbers…

Firstly, how much is a megawatt?

A megawatt (MW) is the main unit of measurement. At any one time in Ireland, roughly 3500MW is required to power our homes, businesses, hospitals, and everything else. This dips at night and generally reaches its peak in the evening.

It’s generally said that 1MW can power between 750 and 1000 homes.


All data is available online for wind energy production is available in precise detail. The figures below are based on either wind energy generation, wind energy generation forecast, or system demand calculated every 15 minutes and available from EirGrid.

This concerns electricity contributed to the grid, rather than the total amount of power produced by the wind turbines.

The graph below shows, unadjusted, how much wind energy was pumped into the national grid. The result is a little chaotic, as wind energy can vary between 0MW to more than 1500MW on any given day.

The information is provided, as stated, in 15 minute intervals, leading to over 35000 individual units of data.

Click here to view a larger version.

It starts to make a little bit more sense with a smoothed graph.

When an average of the megawatts contributed to the grid is calculated per every half-month, it reveals a trend loosely matched each year-on-year, but average contribution to the grid dipping as low as 200MW.

It peaks at 750MW late last year, potentially due to the weather we were experiencing.

Click here to view a larger version.

Forecasting demand

EirGird’s data also lists a forecast of how much wind energy is expected to be produced.

Over the past five years (31 December 2008 to 31 December 2013), the amount of power contributed to the grid by wind turbines missed this forecast 58 per cent of the time.

The figure was surpassed 41 per cent of the time, and in the remaining 1 per cent the demand was either met or data was unavailable.

Click here to view a larger version.

New farms and rising capacity

Between 2011 and 2013, 49 new wind farms were built, according to the IWEA.

Minister Rabbitte recently announced these are made up of 1,386 wind turbines.

The total capacity of these wind farms, or the total amount of electricity these farms have the potential to contribute, has now reached 2011 MW.

Adding up to this 2011Mw figure over recent years were 18 wind farms built last year adding 289MW, eight wind farms adding 120.49MW in 2012, and 23 adding 199.15MW the year previous.

It is extremely unlikely that our wind farms would be able to produce 2011MW. Wind turbines generally operate much lower than their stated capacity. This is revealed in the graph below.

The increase is in capacity is most noticeable in the peak output, the single highest measurement recorded each year, but less so in the average output, calculated at 486MW in 2011, dipping to 467MW in 2012 before rising to 529MW in 2013 according to EirGrid quarter-hourly figures.

Click here to view a larger version.

Meeting demand

The graph below has taken each 15-minute interval in 2013, amounting to around 35,000 individual units, and calculated how much of the total demand for electricity on the national grid was being met by wind energy at that time.

For example, less than one per cent of demand was met during 250 of these units, while during 1600 of these units 3 per cent of demand was being produced.

Click here to view a larger version.

Aata above was either provided during Dáil debates or by the IWEA, but the vast majority can found on An iPhone app is also available, and shows energy-related data in Ireland and Northern Ireland.

Read: Permission refused for Offaly wind farm >

More: IKEA to invest in Leitrim wind farm to power Irish stores >

Column: Ireland’s rural community is being ignored over wind energy concerns >

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