The misleading measure of “household equivalents”

In last post there was a statement from a documentary maker about wind turbines that:

… each one [is] capable of powering 2000 households” …

Such statements are common in the media when alternative energy is concerned. For a country like Denmark I think this could somehow work, but other countries don’t have for example a couple of bigger neighbors that are able to absorb their overproduction or readily provide power when there is a shortage on their grid. Yet, also in Belgium this statement is used plentiful and, according to me, unwarranted.

The problem with this statement is that it has no relation whatsoever with reality. None of those households can actually rely on the supply of one or even more turbines. Those households get the average of the energy produced by it. In a way, one could say that over one year the turbine produces as much energy as the average yearly demand of those households.

What is not to like?

I think it is an illusion to think that the energy that is produced in a supply driven way, can be used without losses in a demand driven system. Our grid is demand driven. The demand is highest in the morning and the evening of a work day, less in the weekend or at night. The demand is also highest in winter and lowest in summer. With a combination of several conventional sources this demand could be followed rather well.

Now enter alternative energy sources. Wind energy is supply driven. There is a lot of supply when there is a lot of wind, less supply (or even no supply at all) when there isn’t much wind. There is no guarantee that wind is blowing hard when demand is high or wind is blowing less when demand is low.

The extent to which a supply driven energy source can successfully drive a demand driven, continuous grid depends on the ability to respond rapidly to a variable supply. When the share of alternative energy is rather low, this will not be much of a problem. Currently that share of wind energy in Belgium is only a few percent of our consumption and can be absorbed into the grid. But even with this small share, our grid took some hits in the past. In those cases there was a high production (windy and sunny days) and low consumption (weekend). Because Elia couldn’t power off conventional power plant quick enough our grid almost collapsed. The Netherlands had the same problem, so could not help us. In those cases it was France that saved us and absorbed our overproduction, although it had no need for that energy at that time. What consequences would this have when we had a share of, say 20% alternative sources or even more? What consequences would this have if all our neighboring countries were expanding wind energy as they do now?

When the share of wind and solar increases in the future it will get more important to shave off peaks in production in order to protect the grid. In our country we only have a very limited capacity to do that. We only have one pumped storage facility in Coo and it has a capacity of 1100 MW for maximum 5 hours. Additional problem is that it is in use for the nuclear power plant of Tihange for doing the opposite. So chances are that it could not be used at its maximum for alternative energy sources.

More, if we really want to “wean” off fossil fuels/nuclear, then we will not only have to shave off the peaks to protect our grid, but also need that energy to accommodate for the times that production is low or non-existent. We then should have the ability to store the energy that is produced at times when there was no need for it and use it later when there is no(t much) production and a demand for energy. It is absurd to think that we can increase the share of intermittent energy sources without having backup by alternative energy sources or expanding our ability to store energy on a large scale.

This is why I think this statement of “household equivalents” is fundamentally wrong: it is misleading because it implies things that aren’t there. It assumes that a wind turbine is the equivalent of a conventional power plant, therefor implying that the added capacity can REPLACE conventional sources. When looking at reality, that is not even remotely true and it is a dangerous assumption to make when we want to rely on a continuous working grid.