Over 40% of Wind Energy Shutdown Last Night

by OWEN MARTIN

Last night, over 40% of wind energy produced was shutdown or curtailed during a spell of gale force winds across the island of Ireland. This episode clearly shows the limitations of relying too much on an intermittent source of energy like wind. Billions of euros worth of turbine installations become worthless at both low wind and at high wind.   

Figure 1

The reason for the shutdown of so many wind turbines can be clearly seen in the System Frequency charts before and after the wind shutdown. 

As the gales gathered in strength on Sunday evening, maintaining the frequency of the grid became more difficult :

Figure 2

The zig zag patterns in the Figure 2 show how frequency fluctuated between 49.9 and 50.1 Hz. The dips represent periods of too much wind when system inertia drops (due to lack of conventional generation such as coal or gas). Should frequency drop below 49.7 Hz then a blackout may occur, so Eirgrid rectified this by shutting down some of the wind and allowing more conventional generation into the system. The frequency then rises again to 50Hz. Gas turbines are forced to ramp up and down more often to maintain system stability during such periods thus pushing emissions up and negating some of the benefits of  having all the wind in the first place. 

Figure 3

Figure 3 shows what happened when over 40% of the wind output was shutdown and there was more manageable levels of wind, in this case about 1,500MW. The frequency is very stable and there is little risk of blackouts. This has been normality in the grid for many years. Compare it with Figure 2. This is the future. It will certainly test engineering skills to it's limits. Gas turbines will have to function under greater strain than before. It will cost a lot of money. There can no longer be a guarantee that the electric kettle will boil when you want it to. 

The other option Eirgrid have to maintain a stable frequency in these situations is to cut demand - which is in effect a blackout under another name. The future is renewable. The future is green. I'm at a loss to figure out how this is "progress".

Are blackouts on the way in West Ireland ?

High risk to security of electricity supply in South West Ireland

A couple of weeks ago, I wrote on this blog about Unit 3 in Moneypoint coal power station in Clare. It was clear that this generator was been ramped up and down to accommodate large amounts of wind penetration in the system. The effects this ramping has on equipment designed to run at full load i.e on or near 100% output, are not made available but Eirgrid do publish weekly outage reports. Last week, on Saturday 13th September, Moneypoint 3 suffered a forced outage i.e it broke down unexpectedly, the same day that Moneypoint 1 was due to come back online (Itself suffering a forced outage a month ago). 

Also, on the same day and just across the Shannon River in Co.Kerry, a 243MW heavy fuel oil generator at Tarbert suffered a forced outage, as presumably it was brought in as reserve for the loss of Moneypoint 3.

As if this wasn't bad enough, there are two other plants in the South West region out of action for scheduled maintenance - Whitegate, a 444MW gas unit and Aghada a 258MW gas unit. So in total this is a loss of 1,500MW of generating capacity, roughly half of the thermal plant capacity in the region. There is of course some hydro and variable wind generation. 

In Eirgrid's Operational Constraints 2014 Report, they state that :

There must be at least one Moneypoint unit on load at all times Required to support the 400kV network.

So if the last Moneypoint unit breaks down at the present time, then the lights in the South West region may be going out....