Renmvab/e F.ne~y, Vol.$, Pm't L pp. 718--'/29, 1994 Elsevie="Science Lt(I Printed in C_=rcatBdtain 0960-1481/94 $7.00+0.00
Pergamon
WIND ENERGY PROSPECTS FOR THE FUTURE by
Dr. lan D. Mays Director & General Manager Renewable Energy Systems Limited
.
INTRODUCTION Since the dawning of civilization man has relied upon the earth's natural renewable resources as a source of power.
Only relatively recently have
we turned to using our fossil fuel reserves of coal, oil and gas.
But these
reserves are finite and are being used up at an increasingly rapid rate as the economies of the western world have developed and as demand grows quickly from the developing economies of the East and other parts of the world.
Even if one ignores concern over pollution and climate change
brought about by the products of combustion, the era of fossil fuels may be remarkably short, with some estimates anticipating constraints on supply as early as 2050 (Ref. 1).
The long term future for energy supply to meet the
world's expanding demand can only be a return to renewable sources, or nuclear or, in my view the most likely, some combination of the two.
Many countries around the world are now investing in renewable energy projects to encourage their development for the future.
In the UK, the government has recognized the desirability of supporting the development and commercial deployment of renewable energy technology "wherever they have prospects of being economically attractive and environmentally acceptable to contribute to
diverse, secure and sustainable energy supplies reduction in the emission of pollutants encouragement of internationally competitive industries"
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It is pursuing these goals through support mechanisms known as the Non Fossil Fuel Obligation (NFFO) and the Scottish Renewables Obligation.
As the UK has a substantial wind energy resource it is perhaps not surprising that a significant proportion of projects developed under the NFFO have been wind farms.
There are now 22 wind farms either generating or under construction in different parts of England and Wales.
In total they supply approximately
370 GWh of electricity to the Regional Electricity Company's network (enough to supply power to the houses of 2 5 0 , 0 0 0 people) and save 3 7 0 , 0 0 0 tons of carbon dioxide being emitted from conventional power stations each year (Table 1).
Table 1 Current Wind Farm Capacity Built or Under Construction
22 wind farms
Total installed capacity
-
141 MW
Annual Energy Yield
~
370 GWh/yr
Number of people served
~
250,000
CO2 saving
-
3 7 0 , 0 0 0 tons/yr
SO2 saving
-
1,000 tons/yr
NO X
~
500 tons/yr
Whilst it is clear from public opinion surveys that the vast majority of the general public support the deployment of wind turbines (Section 7), there has been considerable controversy in the media centred upon the visual impact of wind farms in our countryside.
Clearly the extent to which wind
energy is able to make a contribution to our electricity supply and to
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reductions in greenhouse gas emissions will depend not only upon its cost but also upon the acceptability of its local environmental impact.
The
challenge is to minimize both.
2.
THE WIND ENERGY RESOURCE The UK has a particularly good wind regime.
It has been estimated that the
total accessible resource from wind turbines sites on land is some 340 TWh/yr, marginally in excess of our total electricity demand of around 300 TWh/yr (Ref. 2).
If the offshore potential is added, the resource more than
doubles to 720 TWh/yr. and
habitation
On land, constraints of siting, e.g. avoiding towns
however
bring
approximately 50 TWh/yr (Ref. 3).
the
practical
realizable
resource
to
It would seem therefore, subject to
integration issues discussed in Section 8, quite feasible that 10% of our electricity could be supplied from the wind by the early part of next century.
The wind resource in the UK is enhanced by the country's topography. Wind speeds increase with height by as much as 10% per 100 metres elevation, such that whereas at a sea level, coastal site, annual mean wind speeds may be 6.5-7.0 m/s at a typical wind turbine hub height of 30 metres, on an elevated hill of 300 metres, this may rise to 8.5 - 9.0 m/s. The best wind resource is therefore in upland areas and hence the first wind farms in the UK have been concentrated in Wales, in the Pennines and Cornwall.
Scotland has around 50% of the UK's accessible resource but
almost 70% of the practical resource although this has yet to be utilized as, until now, there has been no NFFO in Scotland.
.
THE TECHNOLOGY The development of modern wind turbine technology started shortly after the oil price rises of the early 1970's which demonstrated the fragility of reliance upon fossil fuels.
A number of western governments initiated
programmes of development of renewable energy technologies and wind energy in particular.
Attention focused upon large machines having ratings
721
of up to 3 M W as it was believed that concentrations of large machines as power stations would be necessary if significant contributions to electricity need could be achieved.
A number of large prototype machines were built
in different parts of the world from which important data was gathered, but none of these were commercialized.
The path to current wind turbines
was, rather, an evolutionary one via a different route, driven by market demand stimulated by tax incentives in the United States and Denmark.
At
the time the market was created in 1980 in the United States, the only machines which could realistically be put into production were small, having ratings of around 50KW.
Large numbers were produced, some more
successfully than others, and developed pragmatically through experience. Sizes gradually increased, assisted by data resulting from the large machine programmes, such that by 1986 when the tax incentives were withdrawn, the largest machine produced in quantity was 250-300 KW.
Since 1986,
machine size has continued to increase to improve cost effectiveness such that the largest size of turbines now available commercially are 500-600KW.
Larger machines allow more cost efficient use to be made of the civil and electrical infrastructure of a wind farm and hence reduces energy costs. also allows a greater energy yield from a given site area.
It
As sizes increase
further however there will come a point at which relative costs start to rise; the energy produced changes with the square of the linear dimension whereas the mass of certain components rises with the cube.
There is
some debate over where the optimum size lies but is likely, for land based installation in Europe to be somewhere close to 1MW.
In the United States
where the ratio of infrastructure to turbine cost is lower, the optimum will probably be smaller.
The international market is dominated by Danish manufacturers who have developed their industry through a strong home market, created initially by subsidies. The three major Danish companies, Vestas, Bonus and Nordtank are all developing megawatt class machines as is Renewable Energy
722 Systems in the UK, Enercon in Germany and HMZ in the Netherlands.
A
one megawatt turbine would generally have a rotor diameter of 50 metres and a tower height of approximately 45 metres.
The majority of wind turbines installed worldwide are 3 bladed machines although an increasing number of 2 bladed machines are being produced by, for example, Wind Energy Group in the UK, J. Carter of the USA and the UK and HMZ of the Netherlands.
Whilst technology and innovation has it place in further reducing the cost of wind turbines and their environmental impact, the largest potential for further cost reduction comes from the benefits of scale that the growing world market will bring both in terms of quantity of units produced but also through the application of volume production techniques.
.
ECONOMICS Over the past 15 years of commercial development, the cost of wind generated electricity has dropped substantially due partly to reductions in the installed cost of turbines but also to greater levels of energy production per installed kilowatt due to improvements in reliability and hence availability of the plant.
The installed cost of wind farms varies from site to site and will depend principally upon:-
the turbine selected the size of the wind farm the distance from the grid the voltage at which the connection is made to the grid the ground conditions at the site the a~cess to the site
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but on typical site one might expect to install a wind farm now for approximately £1,000 per KW including all development, financing and legal costs.
As the world market grows and turbine prices continue to fall
combined with the increased efficiency in installation and infrastructure provision which will come from a continuous rather than discontinuous installation programme, it is reasonable to expect that the overall cost will fall to £750 per installed KW over the next decade.
In Europe the cost of turbines is currently approximately t w o thirds of the total cost of the wind farm.
A typical breakdown of the cost of a wind
farm into its components is given in Table 2.
Table 2 Wind Farm Cost Breakdown Typical 10 M W Project
%
Wind Turbines
64
Civil Works
13
Electrical Infrastructure
8
Grid Connection
6
Project Management
1
Installation
1
Insurance
1
Insurance
1
Legal Costs
2
Bank Fees
1
Interest During Construction
2
Development Costs
1
100
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The other major factors affecting the cost of wind generated electricity are the energy yield from a wind farm project the cost of the capital required to build it and the cost of operating and maintaining it.
Energy yield will depend upon five principal considerations:-
the wind speed at the site the efficiency of the turbines the reliability of the turbines the interaction between turbines (array effects) the efficiency of the electrical infrastructure
The cost of capital will vary depending upon the investor and prevailing interest rates, but can be expected to be in the range 10-15%.
Investor's
expectations should reduce as experience with the technology increases and perceived risks reduce.
Whilst there is no fuel cost for wind farms once built, there are certain ongoing operational costs:-
operation and maintenance land rental insurance management and administration electricity consumed and standing charges local taxes
These may typically total 1.3 to 2.0p per KWhr depending upon the size of the installation and the wind speed at the site.
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With an increasing number of wind farms in operation it is reasonable to expect these costs to reduce due to economies of scale and mature operational costs of 1p/KWh should be achievable.
The current and projected mature costs for wind energy are summarized in Table 3 showing that whilst the price is now around 6.2p/KWh over the 20 year life of the plant above ground for the windier sites where the mean wind speed is 8m/s at 30 metres, this is likely to reduce to only 4.25p/KWh as the technology matures on a broader range of sites where the mean wind speed is lower at 7.5 m/s.
Table 3 Costs of electricity from Wind Farms Current
Mature
1000
750
(m/s) at 30 metres
8
7.5
3.
Energy Yield (KWh/KW/yr)
2850
2700
4.
Cost of Capital (%)
12
10
5.
Operational Cost (p/KWh)
1.5
1.0
6.
COST OF ENERGY p/KWhr
6.2
4.25
1.
Capital Cost (£/KW)
2.
Site mean wind speed
Comparative costs (Ref. 4) for new coal fired plant built now, assuming a 10% cost of capital, range from 4.6 - 5.1 p/KWh and for new nuclear PWRs 4.2 - 6.6p/KWh. 2.8p/KWh.
New combined cycle gas fired plant costs range from 2.4-
If one considers that the price of fossil fuel will inevitably rise
with demand against a limited supply it is clear that wind energy costs will eventually converge with those from conventional power stations.
The
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precise date will depend upon the rate of growth of the world market for wind turbines and the rate of growth of fossil fuel demand, but a period of less than ten years would not seem unreasonable.
These cost comparisons ignore, however, the external and social costs of fossil and nuclear power generation which if taken into account make wind energy one of the cheapest sources of electricity available to us.
.
ENVIRONMENTAL BENEFITS AND ISSUES Deployment of wind turbines to replace fossil fuel generation reduces emissions of carbon dioxide, sulphur dioxide, nitrous oxides and obviates the need to dispose of the slag and ash which is a byproduct of coal fired generation.
If a level of 10% of the UK's electricity from the wind were
achieved the following savings would be made each year:-
3 0 , 0 0 0 , 0 0 0 tons 2 , 0 0 0 , 0 0 0 tons
carbon dioxide slag and ash
80,000 tons
sulphur dioxide
4 0 , 0 0 0 tons
nitrous oxides
This would require an installed capacity of 12,000 MW of wind turbine capacity which would mean wind farms dispersed over approximately 1200 square kilometres of land or 0.3% of the UK land area (an area about the size of the Isle of Arran).
Of this area only 1% or 12 square kilometres is
actually used by the turbine foundations and access roads, the balance remaining available for agriculture or recreation.
If this is to be achieved, however, the wind farms must be developed sensitively
in consultation
with
local communities.
The scale of
developments should be in keeping with the nature of the landscape and the distribution of habitation within it.
Some sites
larger wind farms, others only for smaller ones.
may be appropriate for
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A number of local environmental
issues need to be addressed and
considered proposals set out in an Environmental Impact Assessment for each wind farm.
In particular the visual impact from key vantage points
should be assessed and the distance of dwellings from turbines carefully planned, taking account of terrain, to ensure that noise levels at residences will be within agreed criteria.
The effect upon television reception,
microwave links and air traffic control radar must all be assessed and siting adjusted where necessary or other provisions made.
Whilst the effect upon flora and fauna is small during construction consideration should be given to any special habitats.
Wind turbines do not
appear to pose a major threat to local bird populations but migration route should be carefully assessed.
Clearly local archaeology must be taken into account in planning a wind farm.
The wind industry has to date worked with communities in developing wind farms and in applying government planning policy guidance but is now proposing to go further and introduce, through the British Wind Energy Association, Best Practice Guidelines.
These will be available to both
developers and planning authorities.
Active consideration is also being given to ways in which people local to a wind farm can take some financial interest in it.
7.
PUBLIC ATTITUDES It is clear that wind energy enjoys the support of the vast majority of the general public, including those living close to wind farms.
A number of
public attitude surveys have been undertaken around the country giving consistent results of between 70% and 96% of people in favour of wind
728
energy.
At open days at 7 wind farms at the end of March 1994, visitors
were asked to complete questionnaires giving their impressions of wind farms.
The result was 92% in favour of wind energy and 9 6 % of people
living within 1 mile of a wind farm in favour (Ref. 5).
In a study undertaken
at Delabole wind farm, (Ref. 6) the first in the UK, the number of people in favour rose after the wind farm was built, such that only 4 % disapproved whilst 85% approved.
.
INTEGRATION
The UK electricity network can accept up to 15% of demand from the wind without the need for major changes to the system and without the need to provide additional storage facilities (Ref. 7).
Studies have also been
undertaken in a number of European countries to assess to what extent wind generating capacity requires back up plant for when the wind is not blowing. It has been concluded that at modest penetrations of up to 10% any new wind generating plant installed can be credited as firm capacity up to approximately its average output i.e. installing wind turbines means that installation of conventional plant can be deferred up to the average output of the wind plant installed.
The major wind resource is, however, in the
remoter parts of the UK and whilst the existing grid network can support a limited number of wind farms, if a 10% penetration is to be achieved then grid reinforcement will be necessary in certain areas, in particular for the collection and export of power from Scotland.
.
OPPORTUNITIES
AND
INITIATIVES
In conclusion, the UK is well placed to utilize its rich natural wind resource to provide diversity of electricity supply and to reduce the emission of carbon dioxide and other pollutants.
It is quite feasible that 10% of our
electricity supply could come from the wind by the early part of the next century.
To achieve this will require the wind industry to work with
communities to ensure that developments are sensitive to local needs and that wind energy continues to enjoy majority public support,
It will also
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require continued support for the industry through the NFFO mechanism, effectively an environmental credit, for the next few years to provide the equitable market place necessary to allow the industry to develop and for convergence with conventional electricity prices to be achieved.
With a
firm home market UK industry would be well placed to take a share of an expanding world market for wind farms which may total as much as 20,000 MW by the year 2000 thereby creating a new export industry and new jobs.
10.
REFERENCES
1.
Jeffesorj, M, Energy in Tomorrow's World Proc. BWEA 15, York, October 1993.
.
Renewable Energy Advisory Group, Report to the President of the Board of Trade, November 1992.
.
Energy Paper 62, New and Renewable Energy; Future Prospects in the UK, DTI, March 1994.
4.
Milborrow, D.J, Energy Generation Costs - Now and for the Year 200, Proc. BWEA 15, York, October 1993.
.
Public Support for Wind Power, BWEA Press Release, 30th March 1994.
.
Young, B, Attitudes towards Wind Power : A Survey of Opinion in Cornwall and Devon, ETSU Report W/13/OO354/O38/REP, 1993.
7.
Holt, Milborrow and Thorpe, Wind Energy Penetration Study in the case of the UK, for DG12 CEC, 1990.