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Reduction in Carbon Dioxide Emissions: Estimating the Potential Contribution from Wind Power

In the UK, the parallel objective is to generate 10% of the UK’s electricity from renewable sources by 2010. Renewable electricity has become synonymous with CO2 reduction. However, the relationship between renewables and CO2 reduction in the power generation sector does not appear to have been examined in detail, and the likelihood, scale, and cost of emissions abatement from renewables is very poorly understood.

The purpose of this report is to analyse a wide range of technical literature that questions whether the renewables policy can achieve its goals of emissions reduction and power generation. To some, renewable energy has the simple and unanalysed virtue of being “green”. However, the reality of this quality is dependent on practical issues relating to electricity supply.

......In conclusion, it seems reasonable to ask why wind-power is the beneficiary of such extensive support if it not only fails to achieve the CO2 reductions required, but also causes cost increases in back-up, maintenance and transmission, while at the same time discouraging investment in clean, firm generation.


Executive Summary

• Climate change has risen to the top of the political agenda. The Prime Minister has presented it as a topic on which his views might be seen to differ from those of President Bush, and the government’s Chief Scientific Advisor, Professor David King, expressed the view that global warming posed a greater threat to the world than terrorism, while Michael Howard claimed his Party was giving it high priority.

• The UK Government’s Energy White Paper has one clear objective: i.e. to reduce CO2 emissions by 10% from the 1990 base by 2010.

• In the UK, the parallel objective is to generate 10% of the UK’s electricity from renewable sources by 2010. Renewable electricity has become synonymous with CO2 reduction. However, the relationship between renewables and CO2 reduction in the power generation sector does not appear to have been examined in detail, and the likelihood, scale, and cost of emissions abatement from renewables is very poorly understood.

• The target date chosen, 2010, leaves inadequate time to examine the full range of renewable options: for example, wave, tidal, tidal stream, solar and biomass. The Government created the New and Renewable Energy Centre (NaREC) in 2002 to study these options but before any considered evaluation has been made, policy has effectively constrained the marked to select wind-power.

• The purpose of this report is to analyse a wide range of technical literature that questions whether the renewables policy can achieve its goals of emissions reduction and power generation. To some, renewable energy has the simple and unanalysed virtue of being “green”. However, the reality of this quality is dependent on practical issues relating to electricity supply.

• Wind turbine technology has been developing in Europe for nearly twenty years, and ample experience has been gained to show wind generated power to be variable, unpredictable, and uncontrollable. In fact, the European experience shows conclusively that the annual production is routinely disappointing, and this does not augur well for the UK’s chances of achieving significant emissions abatement.

• Denmark’s wind density is striking (0.88 kW of wind-power per head of population, the highest level of any country in the world2), and it is credited with supplying 20% of the country’s electricity. The fact is that this is a speciously impressive half-truth, and results from an arithmetical calculation putting Danish demand in relation to installed wind production. It is not an accurate representation of daily operation. In fact, 80% of this Danish wind power is exported to neighbouring countries, Norway and Sweden for example.3 In order to absorb the random intermittency of wind power, Denmark operates this system in conjunction with its neighbours’ hydroelectric systems via cable inter-connections which exceed the current installed wind capacity, a unique geographic annexation which provides the operating flexibility that is essential to absorb full wind power output. Island power systems such as those of the UK or Ireland, by contrast, must balance their grid systems internally. It should be noted, also, that Denmark achieves little or no direct reduction of emissions, because CO2-free wind power is working alongside CO2-free hydro-power.

• The key lesson learnt by the Danish and German utilities is that wind does not generate as much power as anticipated (typically an 18-20% annual load factor – not the 30% assumed for UK onshore wind turbines) and production does not match the daily and seasonal fluctuations of demand. Both countries have experienced consistently low annual load factors that have led various commentators to articulate concern about the cost and the level of subsidy needed to approach the targets set for renewable energy by the European Union. These low annual load factors do not bode well for the performance of wind farms in the UK where, with the exception of North-west Scotland, the wind conditions are similar to those experienced in Denmark and Germany.

• The CO2 emissions reduction from renewable energy in an island power system must be assessed on the basis on the impact that the accommodation of wind power into the grid will have on the whole supply chain. Electricity differs from other forms of energy, and cannot be stored directly on an industrial scale. Consequently, generation and demand have to be balanced on the grid continuously, and second by second. Policy-makers appear to have only a weak grasp of this critical fact and its implications. Indeed, the accommodation of the variable output from wind turbines into the transmission system is complex and the technical challenges are barely understood outside professional circles. Fossil-fuelled capacity operating as reserve and backup is required to accompany wind generation and stabilise supplies to the consumer. That capacity is placed under particular strains when working in this supporting role because it is being used to balance a reasonably predictable but fluctuating demand with a variable and largely unpredictable output from wind turbines. Consequently, operating fossil capacity in this mode generates more CO2 per kWh generated than if operating normally. This compromising effect is very poorly understood, a fact acknowledged recently by the Council of European Energy Regulators.

• Thus, the CO2 saving from the use of wind in the UK is probably much less than assumed by Government advisors, who correctly believe that wind could displace some capacity and save some CO2, but have not acknowledged the emissions impact of matching both demand and wind output simultaneously. As a result, current policy appears to have been framed as if CO2 emissions savings are guaranteed by the introduction of wind-power, and that wind power has no concomitant difficulties or costs. This is not the case.

• Even amongst government bodies there is uncertainty as to the emissions abatement effect of randomly intermittent renewables, and the DTI, DEFRA, and the Carbon Trust all offer different methods for calculating the CO2 savings resulting from the introduction of wind power.

• DEFRA employ a fixed emissions factor figure based on a grid average, while the DTI recognise that the precise fuel type and generating technology displaced by wind must play a key role in the level of emissions that could be saved. However, even the DTI’s figures overstate the likely emissions savings because of the frequency with which conventional plant must start-up and shut-down in the course of matching demand and ensuring that wind power is absorbed as smoothly as may be into the grid.

• Still more strikingly, the British Wind Energy Association (BWEA) has prominently and consistently claimed a 17 Mt CO2 saving from 3,500 wind turbines projected by 2010.5 This is twice the level of saving suggested by DEFRA, and appears highly unlikely since it assumes the displacement of coal-fired capacity only. However, the BWEA’s guideline figure is being used to support planning applications around the UK.

• With this level of disagreement between governmental authorities and trade bodies it is hardly surprising that there is general public confusion over the issue. This uncertainty is most undesirable, not least because of the economic implications of an erroneously reasoned choice of carbon abatement technology.

• The current renewables programme is being driven by substantial financial incentives created through the Climate Change Levy and the Renewable Obligation. Both sources of funding result in significant increases in the price of electricity, penalising industry and causing a domino effect on the rest of the economy. Electrical power is, for example, the major cost to the water and sewage industries. Ultimately, a commitment to wind on the scale proposed seems guaranteed to force up power price in the domestic sector, the very sector the Government’s Energy Policy is designed to protect. Bluntly, it is not clear that wind power is compatible with the White Paper’s aim “to ensure that every home is adequately and affordably heated”.

• It is for, example, well known that power from wind turbines is more expensive than that from other generating technologies such as combined cycle gas turbines. Onshore wind turbines cost £650 per kW while offshore installations are about £1,000 per kW. In comparison, the estimated cost of Combined Cycle Gas Turbine CCGT is around £270–350 per kW,6 a fact which becomes particularly salient when we recall the Danish/German annual load factor of around 20% for wind and put it alongside the typical 85–90% load factor for CCGT plant. These low load factors for wind obviously illustrate a very poor utilisation of high cost assets, particularly so when we bear in mind that gas turbines can now guarantee CO2 emissions reduction of around 60% in comparison with coal generation. If these comparative costs are applied in conjunction with the need for continuous fossil-fuelled back-up and its associated CO2 emission, the cost of using wind turbines as a method of CO2 avoidance is very high. In fact, it emerges as the highest cost option.7

• While no one is opposed to the encouragement of renewable energy, a controlled learning programme as set up under NaREC would appear to be the prudent approach. Trials for offshore wind would be justified to assess load factors in UK waters, and could make a valuable contribution when suitable methods of electricity storage can be developed, for example, the reversible fuel cell. However, the sheer numbers of turbines needed to approach the 10% of generated power (not installed capacity) set as the Government’s target would have a colossal impact on the UK, penalise electricity consumers with higher prices, and lead to only modest CO2 reduction. Indeed, the knock-on effect of wind on emissions is unclear, and deserves serious consideration.

• Market forces will fix wholesale electricity prices at a level that discourages new investment in modern plant, and the focus on wind power for new generating capacity is likely to lead to the retention of old, low efficiency, coal-fired plant for an extended period. But an increase in wind capacity will have to be matched by new conventional capacity required to cover winter peak demand when there is no wind. This new capacity would be under-utilised, again raising the unit cost and deterring investment. UK demand will continue to grow, as forecast by National Grid Transco, and power shortages seem inevitable in the medium term if the “secure” generation capacity needed to replace obsolete plant is not forthcoming.

• In conclusion, it seems reasonable to ask why wind-power is the beneficiary of such extensive support if it not only fails to achieve the CO2 reductions required, but also causes cost increases in back-up, maintenance and transmission, while at the same time discouraging investment in clean, firm generation.

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Renewable Energy Foundation

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About David White

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Source: http://www.ref.org.uk/image...

DEC 1 2004
http://www.windaction.org/posts/115-reduction-in-carbon-dioxide-emissions-estimating-the-potential-contribution-from-wind-power
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