Article - Issue 24, September 2005

Responses to `The Climate for Nuclear Power` and the Reith Lectures

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The climate for nuclear power debate

The Royal Academy of Engineering has been working hard for many years to promote informed debate on all matters concerning UK energy policy. This work has included the publication of The Costs of Generating Electricity in March 2004, stakeholder discussion meetings on wind intermittency and nuclear generation costs, and the current series of seminars being run at the Academy on different aspects that need to be considered in determining energy policy.

A key issue has been the cost of wind power and in particular the cost associated with intermittency. Divergent views have arisen, often due to the different terminologies in use, and so the Academy, along with many other stakeholders, has been working to reach an agreed understanding. With this in mind, I am pleased to be involved on the steering group of the current UK Energy Research Centre (UKERC) assessment of evidence on intermittent generation, which, among other aims, will help to introduce some uniformity of definitions for the various terms in use.

It is a shame that such misunderstandings should have appeared in Tony Cooper’s article ‘The Climate for Nuclear Power’ (Ingenia 23) where erroneous statements were made concerning the performance of wind turbines on the UK electricity system. In particular the article states that the load factor (actual output divided by maximum possible output) for a wind turbine is “about 15%” whereas 30% ± 5% is a more realistic assumption. The extent to which wind turbine capacity needs to be ‘backed up’ varies according to the amount of wind power generation in the electricity system as a whole (the level of penetration). At small levels of penetration the amount of back up is small and can be ignored, but this rises at higher levels of penetration and becomes significant above 10% penetration. In addition there are costs associated with balancing the short term fluctuations in wind turbine output. The costs associated with these aspects of intermittency are still the subject of ongoing discussion.

The Academy would not wish Ingenia readers to believe that we are taking sides in the energy debate. This could not be further from the truth. The Academy continues to work to improve understanding of the issues surrounding both wind power and nuclear generation, these being the main methods for producing carbon-free energy in the foreseeable future. It is the Academy’s view that diversity is important in order to ensure security of supply and that all types of electrical generation should be valued for their own particular characteristics, whether they offer low or zero-emissions, high security or flexibility. Whilst it is recognised that cost will not be the final determinant in deciding the energy mix, we believe that a full and proper understanding of these costs is required in order to make sensible and sustainable decisions about the UK’s future energy policy.

Phil Ruffles FREng
Chairman, Engineering Policy Committee and Energy Sterring Group.


I read with surprise Tony Cooper's article ‘The Climate for Nuclear Power’ in the June issue. After starting with a request that we should avoid "simple-minded grandstanding", he proceeded to do so himself. His experience of arguing this issue means he must understand the complexities more fully than he shows in this article and so should not inadvertently fall in the trap of making such elementary mistakes, the most glaring of which are below.

Tony Cooper states that during the 2003 heatwave "demand for air conditioning was at its highest". What does this matter? He must know that overall demand is near its annual lowest level and in France was a full 40% below the winter peak. It was the combination of power stations undergoing refuelling, maintenance or repairs and the high temperatures and low river flows reducing the amount of heat that could be dumped from operating power stations that resulted in concerns about insufficient power. Wind and marine energy farms provide more power during winter when the demand is greatest.

Tony Cooper states renewables "are only available 25% of the time". This is not true.

For example, a typical windfarm will generate some power for between 70% and 85% of the time, which interestingly is more frequently than a typical nuclear power station in the UK.

Regarding the decision in Finland to build a new nuclear plant, this was actually highly contentious and a sizable minority voted against (107 for vs. 92 against). The fact that natural gas is imported from Russia, a country with whom they have had a number of wars in the last century,was probably the most important influence for the decision. That Areva has agreed to a fixedprice contract must also have helped. It is unlikely that Areva will shoulder this level of risk frequently. On a serious note, if the nuclear industry's perception of reality and analytical capability is reflected in this article,we can expect that the next generation of power stations would perform as poorly as the current.

Dr Andrew Henderson
Responsible for offshore wind energy projects at Ceasa henderson@ceasa-offshore.com


I was very surprised at the tone and many of the conclusions in Tony Cooper’s recent article in the June edition of Ingenia entitled ‘The Climate for Nuclear Power’. However I am obliged in particular to point out a number of errors in one paragraph on page 20 which reads as follows:

"The average availability for wind turbines across Europe is about 15%. Even if we assume a more charitable 25% for the windier UK, we would need to build wind capacity equal to our entire current conventional capacity, around 60,000 MW, to provide 25% of our electricity from a source available only 25% of the time."

The root of the problem with this paragraph is a misunderstanding of the difference between availability, capacity factor and the percentage of the time during which wind turbines output power. The "availability" of a wind turbine refers to its readiness to generate i.e. not on forced outage or maintenance, and is typically 98% or above (BWEA). The figures the author quotes are closer to the values for the “capacity factor" of wind turbines although they are lower than the UK figure which exceeds 27% averaged over the last seven years (DUKES). The capacity factor (also known as load factor) is calculated from the energy actually produced in a period of time (often a year) divided by the total energy which would have been produced had the generator been running constantly at rated capacity for that same period. The most serious misunderstanding however is the assertion that wind power is "available only 25% of the time". In the case of wind turbines, neither the availability nor the capacity factor bears a direct relation to the percentage of the time during which a wind turbine is producing power. In fact wind turbines will produce some power at any time the wind is above their cut in wind speed which is typically 4m/s (DWIA). For a single turbine, the percentage of the time when the turbine is operating is dependent on the site, but will obviously be far higher than the capacity factor since otherwise the turbine would be producing at maximum power all the time it was turning. In fact wind turbines output power 70–85% of the time at most UK sites, which have average wind speeds of 7.5–9m/s (BWEA). If the combined output of multiple wind turbines at diverse sites is considered, reduced wind speed correlation means that wind will produce some power for the UK almost constantly (Sinden, ECI Oxford). With these points in mind, along with a basic understanding of the difference between annual energy production and peak power capacity, it is clear that the author’s description of 60,000 MW of wind capacity is completely incorrect.

Steven Hunt MPhil candidate in Engineering for Sustainable Development, Queens' College, Cambridge University


The enduring popularity of cycles

Dr Alex Moulton riding his Series 1 Moulton Deluxe outside the specially built factory in the grounds of The Hall, Bradford on Avon, 1962 Courtesy of Alex Moulton

Dr Alex Moulton riding his Series 1 Moulton Deluxe outside the specially built factory in the grounds of The Hall, Bradford on Avon, 1962 Courtesy of Alex Moulton

In the first of this year’s Reith Lectures ‘The Triumph of Technology’ (Ingenia 23), Lord Broers stated his surprise at the result of a recent poll, which asked the public how they would rank Britain’s greatest inventions. The poll as reported in the Professional Engineer showed that over 50% of 5,000 respondents chose the safety bicycle.

Thirty years previously, in the same Faraday Lecture Theatre in which Lord Broer’s gave his BBC lecture, I gave a talk entitled ‘The Moulton Bicycle’. In this I described my endeavour to make an advance on the safety bicycle which had remained unchanged for some 60 years since it had reached the familiar form which I termed ‘the classic’. My machine, which has been available since the 1960s, has small wheels, high-pressure tyres, full suspension and a unisex open separable frame.

I showed the test results of the power required vs. speed to propel a bicycle of varying wheel size and inflation pressure under controlled condition, using for the first time a chain wheel dynamometer. These were compared with the energy required to propel other vehicles on land, sea and air in terms of energy input per passenger mile vs. speed. It showed that the human-propelled bicycle uses the least energy of any vehicle used by man and is unique in having a mass of only 1/10 of the load it carries.

It may well be that the public in their recent choice of the bicycle were intuitively realising that the bicycle in any form is a benign creation consuming no fossil fuel and making no pollution, while usefully serving mankind worldwide in vast quantities. They may not have realised that without the invention of JB Dunlop of the inflated rubber tyre for bicycles, motorised road vehicles would not be feasible and indeed are more dependent on tyres than on the internal combustion engine. Air transport would presumably have been confined to flying boats. The bicycle industry, essentially pioneered in Britain, created the demand for the manufacture of ball bearings, the roller chain and steel tubes.

The bicycle was an extraordinary creation and a very unlikely one to have been predicted in so far that a human being could readily learn to balance and control a single-track vehicle. To simulate this mathematically is formidable. Jacques Rosay, after the first test flight in the giant A380, lavished praise on his “totally perfect” aircraft, and commented: “You handle this large aircraft like you handle a bicycle, it is very, very easy to fly”.

Dr Alex Moulton CBE RDI FREng
Inventor of the Moulton bicycle

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