ACCORDING TO THE WITTICISM and cliché, there are three levels of inaccuracy… lies, damned lies and statistics… This sounds both amusing and accurate but is somewhat unfair, since statistics by their nature are impartial, although their content can be abused selectively to present a distorted picture.
The statistics associated with nature are probably less amenable to distortion than most; for example… the hours of sunshine, annual rainfall or wind velocities. Let us consider the last. The data on wind speed variation has been studied in great detail in recent years as part of the evidence to support wind turbine park construction. The quantity of electricity and hence the income from such investments depend on the range of wind speeds over the year. Naturally, developers look for areas with more elevated wind speeds – often but not exclusively in the uplands.
The spectrum of wind speeds experienced over a year is far less random than might be expected from our everyday experience of the weather. Wind speeds have been found to follow a pattern that can be represented by a particular mathematical function – a statistical distribution called ‘Weibull’ to be precise. The ‘Weibull distribution’has been found to provide a good fit to the observations in many areas. An example is shown in the figure below. The distribution is concentrated at the low speed end and centre, with only a minority of days having high wind speeds.
Source: Garrad Hassan
Wind turbines do not perform equally well at all wind speeds. They require a ‘threshold’ wind speed of 4 or 5 metres per second before any electricity is generated. So looking at a Weibull distribution, it can be seen that for about 20 per cent of the year, the wind speed is too low to generate any exportable power.
This observation is not restricted to one single site. The conclusion has been confirmed by Dr Capell Aris in the Scientific Alliance investigation into wind power generation across the entire UK, three years ago. The most common (or mean) speed is usually 7-10 m/s but turbines need about 15 m/s to reach the output claimed in the advertising material, which ignores poor performance.
Now with electricity, consumers demand one particular quality above all others and that is continuity of supply. Electricity cannot easily be stored like water or gas so when the power goes off, appliances cease to work. One may well ask therefore why power companies are increasingly prepared to employ contrivances that produce little useful power for at least 20 per cent of the time. In fact this dilemma was examined by the nationalised electricity supply industry some thirty years ago, who concluded that investment in wind turbines could not be justified in the UK. Backup equipment equal to the wind turbine power would have to be constructed to cover for the low wind days but which would then work inefficiently on windy days. It was in fact necessary to build two sets of plants when one reliable coal or nuclear unit would suffice.
The reasoning has changed because politics has overruled these engineering decisions. Governments are influenced by the impeccable environmental virtues of pressure groups who are not sullied by the knowledge or experience of operating a synchronised grid system. Environmentalist follies can be indulged for several years, whilst the grid system still has sufficient conventional capacity (coal, gas and nuclear) to maintain supplies on low wind days.
Of course, wind and solar power are justified because of their claimed lower emissions of CO2, but that is based on doctrine not evidence. The countries in Europe with the very low per capita emissions ie less than 5 te/annum have almost no renewable generation. Sweden, France and Switzerland rely almost exclusively on a combination of hydro electricity and nuclear power. These states should have been used as the models for the low-carbon future. Renewables were a solution searching for a problem. The preference for renewables is illogical.
Wind power may have lower emissions than coal or gas, but the backup plants that support it on unfavourable days release emissions, so it can never be as low as nuclear electricity. This is the cold, objective logic that explains the failure of the green energy experience in Germany. Emissions declined from 1250 Million te in 1990, to just over 900 in 2010. Thereafter, however, they have fluctuated from year-to-year but effectively have been level for eight years during a period of massive expansion in renewables.
More recently, to comply with EU Environmental Objectives, France has committed its industry to an equally perverse strategy. In July 2015, the French parliament passed a comprehensive energy and climate law requiring 40 per cent of national electricity production to come from renewable sources by 2030. On 22nd October 2018, EU Commission cleared 200 million Euros of French state aid to support renewable energy – only a tiny fraction of the funds needed. French electricity consumers will no doubt be convulsed with paroxysms of delight at the prospect of their price per kWh doubling to match the level of German electricity as they strive to reach the 40 per cent objective. In parallel they will see emissions rise as nuclear and hydro electricity are reduced.
A few statistics from the UK serve to illustrate the scale of the challenge facing French electricity. The UK has in excess of 10,000 turbines with annual generation of 35 TWh. France would need to generate 190 TWh for 40 per cent of 2018 electricity. It might require therefore 50,000 turbines (depending if the Environment Commissioner permits large-scale hydro to be classed as acceptably green). That is eighty every week for twelve years, each costing several million Euros.
Is there any equivalent in recent world affairs of a threat like global warming being identified, but where the counter measures are doomed to be a grotesque failure because politicians have been beguiled by ossified doctrine and disregarded objective scientific evidence?
Paul Spare CEng FEI FIMechE