Chapter 5
Introduction | Discussion of Chapter 1 | Chapter 2 | Chapter 3 | Chapter 4 | Chapter 5 | Chapter 6 | Chapter 7 | Chapter 8 | Chapter 9 | Chapter 10 | Chapter 11 | Chapter 12 | Conclusion | Appendix
Chapter 5: do wind turbines abate carbon emission? The chapter begins by acknowledging that society needs energy supply, including electricity, and that local opposition to new generating plant of any kind is common. Etherington then makes a fundamental error in stating* ‘despite wind power having existed as a fairly mature technology since the 1930s, it came to nothing….. until the 1970s-80s when along came the suspicion that man-made CO2 accumulating in the atmosphere might cause climate change’. Leaving aside his doubts about anthropogenic climate change, Etherington exposes here his ignorance of modern wind turbine technology and recent energy supply constraints. It was the OPEC nationalisation of oil supplies within the 1973 ‘oil crisis’ that initiated modern activity in ‘alternative’ energy supplies. Technological advances from the same period allowed wind turbines to utilise computer aided design, composite materials, solid-state digital electronics, remote monitoring and control, and a host of other benefits unknown in 1930’s engineering. The 1930s turbines mostly failed to be utilised or developed, whereas the 1980s turbines mostly succeeded in being further developed and utilised. By the 1990s, wind power became a mainstream technology for utility generation of power; a position that has been enhanced since as the technology continues to expand and develop. Of course, as well as supporting energy security and diversity of supply, wind power assists the needs of climate change abatement; a task obligated on governments and societies by both their own legislation and by international treaties and aspirations.
Etherington alleges that wind power fails to abate significant carbon emissions. In seeking to understand how energy from different sources disperses in an electricity grid, he fails to understand the basic principle of Ohm’s Law that electrical current, and hence electrical energy, flows down a voltage gradient. Thus the energy from a wind turbine enters a grid because it is at a higher voltage then the grid would be otherwise, and this energy is utilised in the nearest outlets. This principle allows the energy flow in a grid to be monitored, whereby it is apparent that wind power entering a local distribution network is utilised locally. If a windfarm is connected directly to a long-range transmission (very-high-voltage) line, then the energy again follows a voltage gradient to the next outlet. Etherington believes however, that ‘because the energy travels at nearly the speed of light it will manage [sic] the length of the British Isles’**, i.e. he believes that the electrical energy from any generating plant is equally distributed throughout the whole national network. Perhaps such understanding is not important, but Etherington should not castigate the wind industry for seeking to explain how and where its electrical energy is used. Nevertheless, Etherington correctly exposes some electricity suppliers who overstate their supply of ‘green electricity’ to their consumers with ‘green tariffs’***. It may be excusable that an ecologist does not understand electricity supply, but I agree that it is inexcusable that an electricity utility fails to explain the correct situation and uses words that mislead.
Determining what generation is not used when wind power, or any form of generation, enters the grid, is not an easy problem to solve. In principle, knowing the exact voltage gradients from every generator would allow analysis, but no such detailed measurement is made by the network operators, whose main task is to maintain voltage and frequency for all consumers within the statutory boundaries. In practice, the tariffs for paying generators allows some generators to operate at near-constant power output (e.g. nuclear and most coal plant), some to generate at their capacity and less without restriction (e.g. wind to date and microgeneration), and some to operate intermittently as required (e.g. gas turbines and managed load). However, the scientific law of conservation of energy proves that if wind energy enters a grid, and the demand does not change, then equal energy from regulated plant is not used.
However, determining exactly what sources of energy are not used when wind energy enters national and international grid is not an easy parameter to determine in the absence of accurate on-line monitoring of voltages and currents and their relative phases. Such grids have many hundreds of different generating plants, each operating at different fuel-to-electricity efficiencies. However, with sufficient instrumentation, determining the displaced energy for a single windfarm could be determined. Without such instrumentation and monitoring, it is reasonable to assume that the average output from a specific windfarm displaces energy from the nearest ‘conventional’ generating plant of larger capacity and operating optimally. If one ignores the energy utilised to produce the fuel and ancillary services, e.g. cooling water, the displaced CO2 per kilowatt hour of electricity would then be: 860g for coal (thermal station with no combined heat), 360 g for natural gas (combined cycle power with no combined heat), zero for nuclear fuels and for other renewables****. Including the energy and the losses to supply these fuels would add about 100 g for coal, about 40 g for natural gas and 100 g for nuclear and biomass*****.
Given the complex challenge of exact measurement of displaced carbon from all windfarms combined across a region or country, various authorities****** have judged it best to use nationally averaged abatement data which should allow for thermal plant on standby, e.g. as ‘spinning reserve’, and other non-linearities. Such a national average reduces year by year as more renewables come on line and as thermal plant is made more efficient. Etherington agrees with the British Wind Energy Association (now named ‘RenewableUK’) that the 2009 average of abatement is 430 g CO2 per kWh of renewables.
Although Etherington does not include the ‘embodied’ carbon emissions from the mining, extraction, processing and delivery of conventional fuels, he does comment on the accelerated carbon emissions that occur around foundation and road construction at windfarms on peat bogs. He reasonably comments that such windfarms are not common and even so the ‘carbon payback’ may be about 2.5 years*******, i.e. much less than the 20 to 25 year lifetime of the initial turbines. He quotes examples of calculations of the energy payback of wind turbines, with the longest being 1.1 years. Of course, such calculations depend on many factors, including the country of manufacture and the windiness of the site.
*Page 87, from end second paragraph
**Page 162, second paragraph and related comment.
****Etherington’s data and references, page 88 etc.
*****My estimates from literature.
******E.g the UK Advertising Standards Authority, the UK Sustainable Development Commission, pages 88 -89 Etherington
*******Page 91, last paragraph ‘3.6 years less 1.1 years for the turbines themselves; hence 2.5 years.