Yesterday I saw a United Kingdom Independence Party's (UKIP) political propaganda slot on Channel4. The UKIP politician (I don't remember his name) spent the whole slot discussing about how useless and inefficient wind farms are. I want to underline that I don't have any particular political bias, so my argument is not against the UKIP but rather against the actual content of the speech I heard on TV.

The main points used by the politician were as follows:

  • Wind farms are highly inefficient since in winter they need to be switched off most of the time because of the cold weather and the average annual operational rate is 30%
  • Britain should invest in building new coal and nuclear power stations to satisfy the energy demand

These two assertions are highly questionable and were clearly used just for propaganda.

People often think wind farms are inefficient. The term "inefficiency" here is inadequate, since in the case of wind power we should rather talk about intermittency. Wind is an intermittent source of energy simply because it doesn't blow all the time at the same speed. When the wind is too weak or too strong, wind turbines must be gradually switched off, stopping their electricity production. The operational range of wind turbines has been increasing during the last few years. For example, for a Vestas V80 2MW turbine, the cut-in wind speed is 4 m/s and the cut-out is 25 m/s. The operational range is therefore fairly wide. What about the operating temperatures? The Vestas V80 turbine has a standard operating range of -20C/+40C. This proves that the temperature itself is not a real problem in the UK.

What can be a problem is the fact that under exceptional severe whether conditions, like heavy snow falls or persistent icy conditions, the turbine must be switched off for safety reasons (ice and snow can get shot away by the turbine blades). Even if it is true that this fact reduces the operational time of wind turbines, there are many solutions to take the wind farm intermittency into account. In fact, the electricity system of a country must be thought as a whole and a good grid management plan assures that shortfalls in the electricity supply will be avoided. A good explanation of this fact is available on the British Wind Energy Association (BWEA) web site where the intermittency problem is addressed in details. An other way of coping with intermittency is to put in place electricity storing techniques, like those explained by David MacKay of Cambridge University in Sustainable Energy - without the hot air. An other interesting analysis of this problem is the study undertaken by the European Wind Energy Association (EWEA) about the wind power variability and its impacts on power systems. This study is very detailed and there are multiple solutions even for systems with a high level of penetration of wind power.

Furthermore, I have recently analysed the issue of renewable energy fluctuation in micro-generation systems in the articles "The problem of renewable energy fluctuation" and "Storing up electricity in a micro-generation system", where I propose possible solutions to cope with intermittent electricity generation.

The fact that the average operational rate of a wind farm is 30% is just normal. Because wind is intermittent, the actual load factor (ratio of the average power to the peak power) is less then 1. But it is possible to set up a good power production plan taking this into account.

On the other hand there are many benefits that wind systems bring along which were not mentioned by the UKIP politician. Let's highlight some, comparing wind power with traditional fossil fuel power plants:

  • wind power is distributed across the country and for this reason, if some turbines stop working, there will be others operational somewhere else. If a big coal power station turns off, the impact on the power system is much higher.
  • the fuel for wind farms (aka the wind) is free, while coal, oil and gas are not free and in the UK at least part of the supply must be bought from other countries
  • we should remember that the efficiency of fossil fuel power station is around 33%. The second law of thermodynamics states that systems like thermal power plant can only convert a fraction of the heat produced during combustion into mechanical work. The rest of the heat (waste heat) must be released into a cooler environment, which is usually a cooler tower. Typical thermal efficiency for electrical generators in the electricity industry is around 33% for coal and oil-fired plants.

Another point worth noting is one that should be very important to the UK Independence Party. They say that we should build more coal power plants to address the UK power demand. OK, let's do it, but where do we get the fuel, i.e. the coal? They say that the UK has mined coal for 200 years, why should we stop now? The reason is very simple: the UK is running out of coal.

Figure 1 - World and UK coal production, source Cambridge University

Figure 1 shows that the UK coal production peaked in 1910 and then declined. The strong and steady coal production that backed the British industrial revolution in the the 18th and 19th centuries is over. The world coal production is still growing though, which means that if Britain wanted to live on coal in the long term, it would be more and more dependent on other countries. For oil production the story is the same. Figure 2 is a diagram provided by the energy company EDF which describes the so called "British energy gap".

Figure 2 - British energy gap, source EDF

The energy gap is created by the closure of power plants in recent years and by closures projected for the future. It is clearly visible the big gap created by massive decommissions of oil and coal power stations in 2015.

The same trend is in process in the EU area. Figure 3 illustrates the net increase/decrease in power capacity in the EU over the period 2000-2007 (in MW). Oil and coal are giving their way to natural gas and wind power. The only problem with natural gas is that a big part of it must be purchased from countries outside the EU, mainly Russia. Wind is property of the countries where it blows and it is free.

Figure 3 - net increase/decrease in power capacity in the EU over the period 2000-2007 (in MW), source EWEA

The conclusion is that, even if wind alone can't be the definitive solution for the British energy mix, at least Britain should try to exploit its potential as much as possible. If the UK Independence Party really cares about the "independence" of the UK from the rest of the world, they should at least not be against the development of new wind farms.

47GW of wind power capacity has been installed across Europe over the period 2000-2007 and this is a reality. Wind is making its way in the world energy mix, since the costs are relatively low, the fuel is free and it makes countries less dependent from other countries' energy sources.