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".

News from Germany and UK

The German Association for plant construction this month have issued a warning about the damage that increased cycling of power plants, due to balancing of renewables on the grid, is having on generation equipment :

http://www.fdbr.de/fileadmin/Dateien/Pressemitteilungen/FDBR-PM_2014_03.pdf

The FBDR is the German association for process plant construction in the energy, environment and process industries. Their press release of the 6^thOctober 2014 below lays it bare in that that thermal power stations remain as a central factor for a reliable electricity supply and that existing plants are not technically laid out for the operational requirements of today, which naturally is being altered due to the highly intermittent input of increasing amounts of solar and wind energy on to the grid. As the press release points out even if Germany was to meet a 100% renewable potential, it would still need to guarantee it through a back-up performance of 80 GW by means of conventional power stations.

This rapid increase in renewables in recent years in Germany has put operational demands on existing gas and coal power plants, which are simply not technically designed for it. The plants must be more frequently switched on and off in order to be able to compensate for the fluctuations, which are associated with electrical inputs from sun, wind and water. The degree of load change is partly more than 200 times higher than that permissible for the power station. As a result the danger of lasting damage to the power  plants grows – along with increasing risks to the security of electrical supply.   On  their own the plant operators cannot come up with the necessary investment for the technical conversion of thermal power plants. Already we have reached the situation where the operation of conventional gas and coal power plants is barely profitable, even to the point that the regulated maintenance is more and more being postponed. Correspondingly the political process is being called upon, not only to promote pumped storage and transmission systems, but also to integrate the existing power stations into their planning. “If you want the Energiewende (energy transformation), you must also provide for your back-up cover”.

And the UK National Grid have issued a report stating that they are facing a capacity shortage this winter, with emergency measures including "load shedding" of heavy industrial users where factories will revert to their own sources of electricity generation i.e. diesel generators, in order to reduce peak demand (essentially a transfer from coal to diesel power) :

http://bishophill.squarespace.com/blog/2014/10/28/wheels-coming-off.html

So will the new 400 million euros East West Interconnector be lying idle over the winter as a result ?