And why Curtailment of Wind Power will become substantial by 2020
We currently have over 2,000MW of wind. Theoretically, we are at the stage where it should be easy to export some of our excess wind energy, which we can't use, to the UK as curtailment levels are still relatively small (in 2013 we curtailed about 3.5% of our wind) and should not pose problems to the UK system which is 11 times greater than ours. When we reach really high levels of wind, we will want to export a lot more surplus wind energy to our neighbours.
When you extract the data from Eirgrid's website (See here) for the year 2014, electricity exports to the UK amounted to just 6.5% of what we imported. So for every 1MW of electricity that we import, we export just 0.065 of a MW. So what is going on ?
Days like the 23rd February 2015, give us a clue because large levels of wind penetration occurred. Figure 1 shows wind output which remained unusually high throughout the day - between 1,500MW and 1,969MW which is a record for Ireland (A similar analysis was done for 30th March here).
|Figure 2: EW Interconnector Flows 23/02/15 - we were importing close to 500MW of electricity from UK from 8am till 10pm|
So the fact is that we are not able to export wind energy except at night. This means that a large proportion of our wind cannot be exported and the situation is exacerbated by the fact that high wind speeds tend to occur during daylight hours (as wind is a function of heat).
When we get to higher levels of wind at 4,000MW or more, we will be at a stage where wind will sometimes exceed even the daily demand. Taking into account all the constraints in the system - baseload plant that must be running, 50% limit on wind and interconnection etc - this means substantial amounts of wind will have to be curtailed (i.e wind farms will be shutdown) unless it can be exported - currently this is not the case for around two thirds of each day on average and we have no reason to believe this will change in the future.
This presents a problem for the Irish renewable experts because Denmark is often held up as an example of what Ireland can do. But Denmark has 6GW of interconnectors and can export wind at any time to Sweden and Norway. These countries have a lot of hydro which can be switched on and off at the flick of a switch to facilitate the intermittency of Danish wind. This then, perhaps, gives us a clue as to what is going on in the UK.
The UK has only around 900MW of hydro which is kept running as baseload power regardless of what wind is doing. Figure 3 shows an example of a day with large levels of wind penetration in the UK system. Like Ireland, it is CCGT (gas plant) which is ramped down to accommodate the wind. The CCGT fleet in figure 3 has very low output which means they are running very inefficiently, like a car running in 1st gear. The UK do not want our wind at this time because, frankly, they do not have space for it. Nuclear must be kept running at baseload level and cannot be ramped down. There is a little more freedom with a coal plant but they too are designed mainly for baseload. An interconnector to France won't alleviate the situation as 80% of their electricity is powered by nuclear which cant be ramped down either.
And I might add that windy days in UK tend to occur at the same time as windy days in Ireland (see previous articles on this blog).
|Figure 3: The UK system on a windy day|
It will become all too clear in the coming years as to how this situation pans out but the phrase "badly thought out" springs to mind. Denmark, we are not, and can never be.
What this means is that it will be very difficult for us to achieve our renewable targets. The only way the UK will take our wind is if we compensate them for their CCGT running more inefficiently. This might sound like a mad idea (and yes it is) but the regulations already facilitate for such an arrangement - see here, its called negative pricing.
What this means for consumers is higher bills - either more payments to shutdown wind farms or payments to compensate the UK grid to take our wind (negative pricing).
By the looks of it, most likely Ireland will overtake Denmark in one aspect - as the country with the most expensive electricity in Europe by 2020.