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Denmark: good or bad for wind power?

Wind power enthusiasts sometimes point to Denmark as a good example of what can be done- claiming that it gets around 20% of its electricity from wind. Wind opponents also sometimes point to Denmark, claiming that in fact not much of this is actually used in Denmark since it’s often available at the wrong time, when demand is low, and so has to be exported. Worse still, Denmark has to import power (mainly from hydro) from Norway and Sweden, to back up it’s wind plants when they can’t deliver enough and demand is high. This costs them more than they get from their exported wind. So wind is a net financial loss, and a drain on the Danish economy. A debate on this issue has been raging on the Claverton Energy Group website and e-conference over the past year.

Some say it’s all because Denmark has a small, inflexible energy system. It’s been pointed out that a major effort was made in Denmark to move away from oil over to coal. Much of the coal capacity consists of large centralised Combined Heat and Power (CHP) plants, which although more efficient that conventional electricity plants, can’t easily be used to balance the variable wind output. Worse still, heat is often needed when there is no major demand for electricity. In these circumstances some CHP electricity has had to be exported, along with any excess from wind. Unfortunately this will be when there is likely to be a surplus of wind power in the surrounding countries, so the price which is offered is quite low.

Against that, these exports will be reducing the amount of fossil fuel which is used in places like Germany. In Norway and Sweden though this electricity may sometimes only be replacing (zero carbon) hydro, but that depends on the timing – if their hydro reservoirs are low, it can be used to pump them up, in effect storing wind power and excess CHP power for later use. On this view all is well in climate terms, though it does cost the Danes more: what’s really needed is a pan-EU balancing system, with perhaps a Cross Feed tariff to ensure that using stored power in not prohibitively expensive. More flexible generation/load management in Denmark would be good too. Along with better interconnections- and an economically synchronised market system covering all the participating and connected countries (e.g. the Baltic states and Germany). Certainly, some say that Denmark is too small to be treated as a coherent energy system, but others say that being small is actually a great advantage for them, it means that wind can be backed-up (via interconnectors) by larger grid neighbours – something that would be much more difficult in UK’s case.

Lessons for the UK

Some argue though that, being larger with a range of flexible back up plants, the UK could in fact do much better than Denmark – although they accept that it must strengthen its grid and interconnections. But even without much of that, there should be no need for extra backup for some while: you could add 30 GW wind and use existing UK fossil plants as back up – you don’t need to build 30 GW of new plant and therefore “pay twice”, as some anti-wind people claim. We already have it – and have paid for it. And some of it is already used as back-up – for conventional and nuclear plants, and to deal with the daily demand peaks. On this view, basically, when available, what wind power does is replace some output from the existing power system – so you don’t need to build any extra back-up for when wind is not available.

Although the probability of zero wind output is relatively low, as things stand at present, we would have to retain all, or most of, the existing system – wind has a low capacity credit, perhaps 15% depending on the total capacity. However, more existing capacity could be retired if we had a more flexible system, with more load management, more storage and more interconnections, plus inputs from firm non variable renewables like biomass and geothermal, though the optimal mix is as yet undetermined. There is also the problem that operating fossil plants occasionally at lower power means they are run inefficiently, part loaded, which adds to costs. But they may not have to run often and the cost penalties will therefore be low. Inputs from other renewables could also help (e.g. although they are variable/cyclic, wave and tidal availabilities are phased differently from wind). Inflexible nuclear however just gets in the way. At least Denmark doesn’t have that problem!

You can join the debate at www.claverton-energy.com.

Posted by Dave Elliott on September 17, 2010 2:19 PM | Permalink