Repowering and Used Wind Turbines

REPORT - Repowering and Used Wind Turbines
Walter Hulshorst
Econ International
April 2008
www.leonardo-energy.org 1 / 27
REPORT
REPOWERING AND
USED WIND TURBINES

Summary
In countries that started early with wind energy, old wind turbines were placed at locations
where the wind is often very good. Since the best locations for wind in these countries are
occupied by old wind turbines with lower energy outputs compared with new wind turbines,
programmes were started to replace the old turbines with new ones. With repowering, the
first-generation wind turbines can be replaced with modern multi-megawatt wind turbines. In
general, many factors speak in favour of repowering programmes:
• more wind power from the same area of land: wind power generation is multiplied
without the need for utilising additional land;
• fewer wind turbines: the number of turbines can be reduced, enhancing the natural
landscape. The construction height can be raised;
• higher efficiency, lower costs: modern turbines make better use of available wind
energy. The cost of production is significantly lowered;
• better appearance: modern turbines rotate at much lower speeds and are thus more
visually pleasing than older, faster-rotating turbines;
• better power grid integration: modern turbines offer much better grid integration, since
they use a connection method similar to conventional power plants and also achieve
a higher utilisation degree;
• wind speed and direction are known: at an existing wind turbine location, wind speed
and direction are already known, so it is easy to calculate the expected annual energy
production for an existing location.
Since Germany is the largest wind energy user, it is reasonable to expect that Germany will
provide the major market for repowering. About 90% of the wind power capacity in Germany
is located in suitable turbine areas. The German Wind Energy Association (BWE) calculated
that up to 2020, with a realistic approach, the on-shore repowering potential in Germany will
be about 15.000 MW. As a result of repowering, there is a growing interest around the world
in used wind turbines that still have several years’ remaining service life.
Growing energy demand in developing countries stimulates the use of renewable energy
sources, such as wind power, to provide a sustainable and environmentally-friendly power
supply. For most of these countries, projects with new wind turbines have proven to be
unaffordable: that is why using cheaper second-hand turbines may be an option. Utilising
used wind turbines instead of new ones offers several benefits:
• lower capital expenditure saves the investor’s capital resources and reduces the
efforts involved in collecting borrowed capital;
• shorter project duration reduces the investor’s financial risk, especially valuable in
politically and economically unstable conditions;
• turbines from 150 to 600 kW can be transported and erected without major problems.
However, larger turbines often require specialist equipment that is not available in
many parts of the world, while smaller turbines may not be economical to place. Many
manufacturers are no longer fabricating turbines of this size. Therefore, buying used
turbines is the most common way of obtaining a wind turbine that can be shipped and
installed easily;
• maintenance work on used turbines can be conducted easily, compared with the
latest technology turbines that require both a sophisticated infrastructure and
specialists to carry out routine work. Using used turbines means that it is not
necessary to make high demands on qualified personnel;
• a substantial overhaul and adaptation to regional requirements can take place while
the used turbine is being dismantled. This is cheaper than overhauling while the plant
is in operation.

CONTENT
1. INTRODUCTION....................................................................................................................................... 4
2. CHARACTERISTICS OF THE WIND MARKET ................................................................................. 5
3. REPOWERING........................................................................................................................................... 8
3.1. AVERAGE WIND TURBINE SIZE CONTINUES TO GROW YEAR ON YEAR.................................................... 8
3.2. WHY REPOWERING ............................................................................................................................. 10
3.3. WHAT IS THE POTENTIAL OF REPOWERING.......................................................................................... 14
3.4. WHAT INCENTIVES ARE NEEDED FOR REPOWERING ............................................................................ 15
3.4.1. What incentives are there in Europe ............................................................................................. 15
3.4.2. What incentives are promising for the repowering of wind energy............................................... 18
4. USED WIND TURBINES......................................................................................................................... 21
4.1. WHY BUY USED WIND TURBINES......................................................................................................... 21
4.2. WHEN BUYING USED WIND TURBINES ................................................................................................. 23
4.2.1. Grid integration of used wind turbines ......................................................................................... 24
4.2.2. General overhaul and maintenance of used turbines.................................................................... 24
4.3. WHAT IS THE POTENTIAL OF USING USED WIND TURBINES .................................................................. 25
5. CONCLUSIONS........................................................................................................................................ 26
6. APPENDIX A - TRADING COMPANIES FOR USED WIND TURBINES....................................... 27

1. INTRODUCTION
In countries like Germany, Denmark, or the Netherlands, wind power is already so
widespread that few on-shore sites are left on which new units can be built. Two main paths
are being followed to further increase the electrical power generated by wind: building off-
shore wind parks, and replacing existing wind turbines with new and larger types (3 to 5
MW). The older, replaced types are appearing on the second hand market and will allow
other (developing) countries to start using wind power at lower costs.
The second booming development in wind energy technology particularly affects countries
like Denmark and Germany that are running short of productive sites. In these countries, it is
more efficient for investors to replace smaller and middle-sized turbines on highly productive
sites with new and larger turbines, rather than just building the new turbines on less
productive sites. This process is known as “Repowering”.
The successful implementation of wind energy in Europe during the past decade and the
continued economical support offered in national legislation has led to a developing market
for second-hand wind turbines. Repowering of plant after 5 to 15 years of operation releases
a large number of turbines into the market.
For developing countries, this is an opportunity to gain experience in working with renewable
energy sources, to establish their own wind energy industries and to profit from technology
transfer with low capital expenditure.
In Chapter 3, this document describes the principle of repowering (as performed in Germany
and Denmark), while Chapter 4 focuses on the developing market for used wind turbines. But
first, in Chapter 2, this document describes the status quo regarding wind power for several
regions and countries in the world, as at the end of 2007,

2. CHARACTERISTICS OF THE WIND MARKET
The Global Wind Energy Council calculated that, at the end of 2007, the worldwide installed
capacity of wind energy was 94.112 MW1
. Wind energy contributes to the energy mix in more
than 70 countries across the globe. Figure 2.1 shows the development in the growth of wind
energy across the world.
Global cumulative installed capacity 1996 - 2007
6.1007.60010.20013.600
17.400
23.900
31.100
39.431
47.620
59.091
74.133
94.122
0
10.000
20.000
30.000
40.000
50.000
60.000
70.000
80.000
90.000
100.000
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
MW
Figure 2.1 Global cumulative installed wind energy capacity
The installed capacity per region is shown in figure 2.2
Annual installed capacity by region 2003-2007
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
Europe Asia North
America
Latin
America
Africa &
ME
Pacific
MW
2003
2004
2005
2006
2007
Figure 2.2 Annual installed wind energy capacity by region
1
Article on www.gwec.com: continuing boom in wind energy, 20 GW of new capacity in 2007.

While Europe remains the leading market for wind energy, new installations in 2007
represented just 43% of the global total, down from nearly 75% in 2004. For the first time in
decades, more than 50% of the annual wind market comes from outside Europe, and this
trend is likely to continue in the future. While Europe, North America and Asia continue to
see the most valuable additions to their wind energy capacity, the Middle East/North Africa
region, increased its wind power installations by 42%, reaching 534 MW by the end of 2007.
New capacity was added in Egypt, Morocco, Iran and Tunisia.
The countries with the highest total installed capacity are given in Figure 2.3. The countries
with the largest growth in 2007 are given in Figure 2.4.
Top 10 total installed capacity [MW]
Germany; 22247
US; 16818
Spain; 15145
India; 8000
China; 6050
Denmark; 3125
Italy; 2726
France; 2454
UK; 2389
Portugal; 2150
RoW; 13008
Figure 2.3 Top 10 countries’ installed wind energy capacity (end 2007)
Top 10 new capacity [MW]
US; 5244
Spain; 3522
China; 3449
India; 1730
Germany; 1667
France; 888
Italy; 603
Portugal; 434
UK; 427
Canada; 386
RoW; 1723
Figure 2.4 Top 10 countries development of new capacity wind energy in 2007.
Based on these figures, it can be expected that the US will overtake Germany as the leader
on wind energy by the end of 2009. The tremendous growing market for wind power in China

has encouraged domestic production of wind turbines, and within China there are more than
40 domestic companies involved in turbine manufacture. In 2007, Chinese domestic
production accounted for 56% of the annual market compared to 41% in 2006.
It is expected that the worldwide market will exceed 200 GW2
in 2011. Europe will remain the
largest market in 2011, with an installed power of 108 GW (Germany and Spain will remain
the major markets). North America will be second with 47 GW (USA will be the major
market). Asia will be third, with 37 GW (China and India will be the major markets). The
installed power of the Rest of the World will be about 11 GW. Asia will have the strongest
growth.
Despite double digit growth in the wind turbine market, the main challenge for wind turbine
manufacturers and their suppliers is to cope with the growth in demand for wind turbines.
The main bottlenecks have been in the supply of gear boxes and large bearings. Gearboxes
are supplied by a relatively small list of companies. As in the manufacture of wind turbines,
there have been few new entrants to this market as, historically, the technology risks have
been perceived as high. In addition, turbine manufacturers try to avoid using those new
suppliers who can demonstrate only limited industry experience, or who do not have
established track records. Over 80% of the profit warnings in the wind turbine manufacturing
industry relate to gearbox issues, primarily malfunctioning bearings, but also unforeseen
issues with various gearbox designs.
Fig 2.5 Example of a wind park3
2
Wind turbine manufacturers, here comes pricing power; Merril lynch, August 2007
3
Windpark Hartel; www.eneco.nl

3. REPOWERING
The first generation of wind energy generating projects that were installed in the US and
Europe in the 1980s, have only recently begun to reach the end of their use life. The older
technology used in these projects has generally proven to be more durable and longer
lasting than was originally anticipated. However, at some older projects, repowering has
taken place. Repowering refers to the refurbishment of older wind turbines, or to their
removal and replacement with newer, more efficient turbines. Where older turbines have
been removed and replaced with newer turbines, this has generally been accomplished by
installing fewer, larger turbines.
3.1. Average wind turbine size continues to grow year on year
Generally, the size of wind turbines keeps on growing4
. Figure 3.1 shows the development
of technology in Germany since 1980.5
Rotor
diameter
Hub
height
Rotor
diameter
Hub
height
1980 1985 1990 1995 2000 2005
Nominal power 30 kW 80 kW 250 kW 600 kW 1.500 kW 5.000 kW
Rotor diameter 15 m 20 m 30 m 46 m 70 m 115 m
Hub height 30 m 40 m 50 m 78 m 100 m 120 m
Annual energy yield 35 MWh 95 MWh 400 MWh 1.250 MWh 3.500 MWh 17.000 MWh
Figure 3.1 Development of wind turbines in Germany
4
Wind Energy Barometer EurObserveER; Systemes Solaires no 177. February 2007.
5
Renewables made in Germany, Deutsche Energie Angentur (DENA). www.renewables-made-in-
germany.com/en/wind-energy/

The average size of wind turbines has been increasing with rapidly growing demand for
turbines in the 1.500 – 2.500 MW size range, and less demand for smaller sized turbines
(see table 2.1).6
Table 2.1 Distribution of wind turbines
Size 2004 2005 2006
Small WT < 750 kW 5,4% 3,6% 2,4%
One MW 750 – 1500 kW 50,9% 48,2% 43,3%
Mainstream 1500 – 2500 kW 42,8% 45,8% 49,9%
Multi MW > 2500 kW 0,9% 2,4% 4,3%
There are two main reasons for this:
• for utilities trying to scale-up their wind portfolios and achieve critical mass quickly,
there has been a preference for larger turbines. This is also for practical reasons, as
the power potential of a wind turbine is determined by the square of the rotor
diameter: a large turbine, therefore, delivers much more power than two separate
turbines of half the size;
• in addition, for off-shore markets to minimise installation costs per MW, a significant
proportion of which is the cost of foundation, the largest possible capacity is installed
on each foundation unit.
In the German market, the average machine size increased by 125 kW between 2005 and
2006, i.e. a mean unit capacity of 1.849 kW. The German market is calling for more and
more powerful wind turbines, in order to ensure that the areas that are available for wind park
installations as profitable as possible. This evolution is reinforced by the rise in the
importance of the market for repowering (136 MW in 2006) on the most attractive sites, those
on which the first wind turbines were installed.
This evolution is even more significant in the UK where wind turbine size reached 2.103 kW
in 2006 (+ 371 kW). This growth is further explained by the very favourable climatic
conditions found in the UK. High capacity wind turbines are particularly well adapted for sites
with higher average wind speeds. The development of the UK off-shore market in 2006, has
also reinforced this evolution with the connection of thirty 3 MW wind turbines at the Barrow
off-shore park.
The new (2006) French wind farms have also used more powerful wind turbines with an
average power of 1.689 kW (+557 kW compared to 2005). The increase in wind turbine size
has been lower in Spain (2006), + 33 kW with respect to 2005, bringing the average size of
the wind turbines up to 1.375 kW. This can be explained by the less significant constraints
and restrictions in terms of the availability of land. It is also explained by the strategic choice
made by Spanish industrialists, who are very present on their domestic market, to limit the
capacity ranges by proposing, as Gamesa does, either 850 kW wind turbines or 2 MW wind
turbines.
It is worth noting that, although the average wind turbine size is increasing, for logistical
reasons, there are real limits to the size of turbines that can be transported, particularly in on-
shore markets. This is particularly true in Asia, where logistical and grid connection issues
will mean that the preference for smaller sized turbines will continue in these markets.
6
Wind turbine manufacturers, here comes pricing power; Merril Lynch, August 2007.

However, once the repowering market takes off in more mature markets, a trend for utilising
larger turbines will become even more marked, as developers replace small turbines with
larger units on the same sites.
3.2. Why repowering
In countries that started early with wind energy, old wind turbines were placed at locations
where the wind is often very good. Since the best locations for wind in these countries are
occupied by old wind turbines with lower energy output compared with new wind turbines,
programmes were started to replace the old turbines with new ones. With repowering, the
first-generation wind turbines can be replaced with modern multi-megawatt wind turbines. In
general, many factors speak in favour of repowering programmes7
:
• more wind power from the same area of land: wind power generation is multiplied
without the need for utilising additional land;
• fewer wind turbines: the number of turbines can be reduced while enhancing the
natural landscape. The construction height can be raised;
• higher efficiency, lower costs: modern turbines make better use of available wind
energy. The cost of production is significantly lowered;
• better appearance: modern turbines rotate at much lower speeds and are thus more
visually pleasing than older, faster-rotating turbines;
• better power grid integration: modern turbines offer much better grid integration, since
they use a connection method similar to conventional power plants and also achieve
a higher utilization degree;
• wind speed and direction are known: at an existing wind turbine location wind speed
and direction are already known, so it is easy to calculate the expected annual energy
production for an existing location.
Additionally, it is often easier to get licences to build a wind turbine (farm) on an existing
location than on a new location. However, it should be mentioned that, in Germany, there are
some bottlenecks with licenses, because of the height increase of larger wind turbines
compared with old wind turbines.
But also for government and local authorities, the results of repowering can be positive:
• additional wind energy power will create a larger basis for wind energy;
• although the wind turbines are higher after repowering, the quality of the landscape is
often perceived as being improved, since the number of wind turbines is reduced;
• replacement can be used to achieve national (or local) targets for renewable energy
or for CO2 reduction.
But there are also practical reasons for repowering;8
for example, in situations in which the
manufacturer of the wind turbine no longer exists, and no other company can carry out the
refurbishment of the wind turbine.
Replacement of old turbines with new ones can be done in several ways. According to
research performed by Grontmij,9
five alternatives can be used:
7
http://www.wind-energie.de/en/topics/repowering/
8
Repowering of wind farms in practice, Essent Wind Nederland B.V.

1. 1-to-1 up-scaling of solitary wind turbines;
2. 2-to-1 replacement, replacement of two smaller wind turbines by one large wind
turbine;
3. clustering of solitary wind turbines into farms; e.g. replacement of 20 solitary wind
turbines by clustering 6-10 wind turbines at one location;
4. 1-to-1 replacement of wind turbines with similar rates but with newer machines;
5. 1-to-1 up-scaling of wind farms.
Each of these alternatives has it own pros and cons. Alternative 1 has the largest electricity
production and alternative 4 the lowest. For alternatives 1-3 and 5, grid capacity can be a
problem and investment for the grid connection may be required, while for alternative 4 it is
not necessary. For each alternative there is a positive impact on the landscape: the best one
being alternative 3. However, the following conclusions are presented:
1. Energy: when old installed wind turbines are replaced by larger ones, the total
installed wind turbine capacity will increase;
2. Financial issues: in most cases, replacing an old wind turbine with a larger one is
economically profitable;
3. Environment: replacing already installed wind turbines has advantages for the quality
of the landscape, including:
o unity of appearance of the wind turbine;
o decrease in the number of wind turbines with a high rpm;
o possible decrease in the number of wind turbines;
o possible decrease in concentration of visual intrusion and noise;
o possible concentration of hindrance by installing wind turbines at locations
where they are accepted.
The environmental impact of a repowering project is visualised in Figure 3.2.10
Although the
wind turbines after repowering are higher, the quality of the landscape after repowering is
often perceived as being improved compared with that prior to repowering.
9
Replacement of existing wind turbines (in Dutch); Grontmij, Advies en Techniek B.V. 2000
10
German Wind Market and Industry – Current Developments and Perspectives; German wind energy
association (BWE), March 2007.

Before
Windfarm Bassens
(Lower Saxony)
Figure 3.2 Example of environmental impact before and after repowering
An example of repowering in Germany11
where twenty 200 kW turbines were replaced with
seven 2 MW turbines, indicates that the investment was tripled, but the annual energy
production increased fourfold, while the installed capacity increased by a factor of 3,5 as
shown in Figure 3.3. As can be seen, production increases more than proportionally with
installed capacity. This is because the taller turbines access the increased wind speeds
present at higher altitudes, and new wind turbines have better P-v curves.
After
11
German wind market and industry: Current developments and perspectives; German Wind Energy
Association (BWE), April 2006.

Figure 3.3. Example of repowering in Germany
A study of the effects of repowering projects in three regions in Germany is given in Figure
3.4.12
This study clearly shows that the height increases by approximately a factor of 2, while
the number of turbines was only half down to one fifth. The installed capacity increased by
12
Repowering: Weniger ist Mehr (in German); Bundesverband Windenergie E.v. June 2007
20 turbines
4 MW
10 millionkWh
6 million Euro
7 turbines
14 MW
16 MW
Reduction 70%No of turbines
Installed capacity
Yield
Investment
20 turbines
4 MW
10 millionkWh
6 million Euro
7 turbines
14 MW
16 MW
Reduction 70%20 turbines
4 MW
10 GWh
6 M€
7 turbines
16 M€
3 fold increase
40 GWh
4 fold increaseInvestment
Yield
14 MWInstalled capacity 3,5 fold increase
No of turbines Reduction 70%
Effects of repowering
Decrease Increase4 43 Factor 2 Factor 2 3
Example
Schleswig Holstein
Example
Niedersachsen
Example
Mecklenburg-Vorpommern
Energy
Height
Power
Number of turbines
Energy
Height
Power
Number of turbines
Energy
Height
Power
Number of turbines
Effects of repowering
Decrease Increase4 43 Factor 2 Factor 2 3
Example
Schleswig Holstein
Example
Niedersachsen
Example
Mecklenburg-Vorpommern
Energy
Height
Power
Number of turbines
Energy
Height
Power
Number of turbines
Energy
Height
Power
Number of turbines

between 1,5 up to 3,5 while the annual energy produced increased by between 2,2 and 4,3.
Figure 3.4 Overview of effects of repowering at locations in Germany
The overall conclusion of repowering projects performed by Essent in the Netherlands was
that good locations for wind farms in the Netherlands are limited.13
Wind turbines were
installed at the most windy locations, some 15 years ago. Several of these old wind farms
require new solutions, because of technical problems, and new subsidy schemes in Holland.
Essent was confronted with the need to find solutions for its existing wind farms. The result
shows that good opportunities for repowering or retrofit, at reduced costs are available.
Restrictions, regarding permits, grid conditions, technical possibilities and others, require
customised solutions for each situation. In general it can be concluded that cost reductions of
10% - 30% can be achieved by repowering, compared with new solutions (green field
solutions).
3.3. What is the potential of repowering
Countries that started early with promoting wind power are now facing the problem that the
land with good wind opportunities is occupied by older types of wind turbines. New locations
for wind turbines may meet increasing resistance from local residents and local councils, as
well as from environmental action groups. Assuming that all parties concerned accept new
modern large wind turbines on existing turbine locations, repowering can contribute to the
realisation of national targets. Since the new wind turbines have become larger and land with
good wind opportunities are rare, the most efficient option could be to replace the old wind
turbines with new wind turbines.
In Europe, it can be expected that wind turbines older than 10-15 years, either on sites with
good wind opportunities or in countries in which no new locations for wind turbines can be
found, will be replaced with new types of wind turbines. It can be expected that the countries
that first started with wind energy will also be the leading countries concerning repowering, if
there are good incentives.
It can also be expected that wind turbines will develop during the next 10 years. Knowing that
the first off-shore wind farms are built or are planned to be built, it can be expected that these
wind farms could also be repowered after 10 to15 years.
Since Germany has the largest market for wind energy, it is reasonable to expect that
Germany will be the major market for repowering. About 90% of the wind power capacity in
Germany is located in suitable turbine areas.14
The German Wind Energy Association (BWE)
calculated that, with a realistic approach, the on-shore repowering potential in Germany up to
2020 is about 15.000 MW.15
Figure 3.5 shows the potential for repowering (on and off-shore)
for each year up to 2030.16
13
Repowering of wind farms in practice; Essent Wind Nederland BV
14
More wind with fewer wind turbines, German Wind Energy Association (BWE), August 2005.
15
Windenergie in Deutschland, actueller Stand und künftige Entwickelung; BWE, October 2007 (in German)
16
German Wind Industry: Market Development and Perspectives; Verband Deutscher Maschinen- und
Anlagenbau - German Engineering Federation (VDMA) March, 2005.

0
1000
2000
3000
4000
5000
6000
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
2016
2018
2020
2022
2024
2026
2028
2030
InstalledMWperyear
onshore onshore repowering offshore offshore repowering
Figure 3.5 Potential repowering German wind market (on and off-shore).
3.4. What incentives are needed for repowering
Incentives are needed to promote the repowering wind turbines. Several papers discussed
and compared the different types of incentives for Renewable Energy Sources (RES) used in
several countries.
3.4.1. What incentives are there in Europe
In 2005, The Fraunhofer institute investigated the different policy instruments used in
Europe17
. Promotion instruments can be classified according to different criteria (i.e. whether
they affect demand for or supply of RES or whether they support capacity or generation). So
that a common terminology can be applied, at least within this thesis, Table 3.1 provides a
classification of these instruments, covering all the currently applied strategies referring to
the promotion of RES deployment. A brief explanation of the terminology is provided
underneath the table for instruments of high relevance.
17
Monitoring and evaluation of policy instruments to support renewable electricity in EU Member States,
Fraunhofer Institute, 2005.

Table 3.1 Classification of promotion strategies
Direct Indirect
Price-driven Quantity-driven
• Investment
incentives
• Tendering systemInvestment-
focused
• Tax
Incentives
• Feed-in tariffs • Tendering System
Regulatory
Generation-
based • Rate-based
incentives
• Quota obligation
based on TGCs
Environmental
taxes
• Shareholder
programmes
Investment-
focused
• Contribution
programmes
Voluntary
Generation-
based
• Green tariffs
Voluntary
agreements
Investment incentives establish an incentive for the development of RES projects as a
percentage above total costs, or as a predefined amount of € per installed kW. The level of
incentive is usually technology-specific.
Feed-in tariffs (FITs) are generation-based price-driven incentives. This system determines
the price per unit of electricity that a utility, supplier or grid operator is legally obliged to pay
for electricity from RES. Thus, a national (or provincial) government regulates the tariff rate. It
usually takes the form of either a total price for RES production, or an additional premium on
top of the electricity market price paid to RES producers. Apart from the level of the tariff, its
guaranteed duration represents an important parameter for assessing the actual financial
incentive. FITs allow technology-specific and band-specific promotion as well as an
acknowledgement of future cost reductions by implementing decreasing tariffs (see, e.g. the
German Renewable Energy Act).
Quota obligations based on Tradable Green Certificates (TGCs) are generation-based
quantity-driven instruments. The government defines targets for RES deployment and
obliges the parties involved in the electricity supply-chain (e.g. generator, wholesaler, or
consumer) to meet these targets. Once defined, a parallel market for renewable energy
certificates is established and their price is set according to demand and supply conditions
(which is forced by the obligation to achieve the targets). Hence, for RES producers, financial
support may arise from selling certificates, in addition to the income from selling electricity on
the power market.
Tax incentives are generation-based, price-driven mechanisms that work by offering
payment exemptions from the electricity taxes applied to all producers. This type of
instrument thus differs from premium, feed-in tariffs solely in terms of the cash flow for RES
producers: it represents an avoided cost rather than additional income.
Tendering systems are quantity-driven mechanisms. The financial support can either be
investment-focused or generation-based. In the first case, a fixed amount of capacity to be
installed is announced, and contracts are given following a predefined bidding process which
offers the winners a set of favourable investment conditions, including investment subsidies
per installed kW. The generation-based tendering systems work in a similar way. However,

instead of providing up-front support, they offer support in the size of the ‘bid price’ per kWh
for a guaranteed duration.
As well as the regulatory instruments described above, on-going market liberalisation has led
to the appearance of an increasing number of voluntary approaches. They are mainly based
on the willingness of consumers to pay premium rates for renewable energy. However, in
terms of effectiveness so far – i.e. actual installations resulting from their appliance – their
impact on total RES employment is negligible. Figure 3.6 gives an overview of the renewable
electricity support systems used in the EU.
CZ LV EE
HU CY RO BG SI
DE DK LT LU
PT ES GR
AT FR SK NL
PL
IT
BE UK
SE
IE
UK
NL
FI
MT
SL
Quota
Tax measuresTender
Feed in Tariff
Certificate Systems
CZ LV EE
HU CY RO BG SI
DE DK LT LU
PT ES GR
AT FR SK NL
PL
IT
BE UK
SE
IE
UK
NL
FI
MT
SL
Quota
Tax measuresTender
Feed in Tariff
Certificate Systems
Figure 3.6 Overview of the renewable electricity support in Europe
A research study performed by the Anglo-German foundation for the study of industrial
society18
tried to find an answer to the question as to why wind power in Germany is
considered to be a major success story (Germany has the largest operating capacity in the
world and enjoys world leadership in terms of its turbine manufacturing base), while the UK
has the best wind resource in Europe, but has little installed capacity and underdeveloped
manufacturing.
This question was tackled by comparing the energy sector issues, policy dimensions and the
factors related to local implementation that affect the industry in the both countries.
According this study, it was clear that the German “feed-in tariff” has proved a highly flexible
18
Wind power in Britain and Germany: explaining contrasting development paths, 2006.

and manageable policy instrument. In contrast the UK’s Renewable Obligation (RO) has
proved more costly but less productive. Moreover, the RO is making wind power
progressively more expensive to the UK consumer at a time when regressive feeding rates
are making it cheaper in Germany. Where German policy makers had recognised the need
to adjust the levels of feed-in tariffs to changing circumstances, their British counterparts
drew few lessons at that time from national experience or international comparison. The
effectiveness of renewable energy ‘feed-in tariffs’ in the promotion of wind power is now
widely recognised (Commission of the European Communities, 2005).
3.4.2. What incentives are promising for the repowering of wind energy
To combat barriers against repowering, it is necessary and useful to consider a proactive
policy to encourage repowering; one which would offer an explicit incentive for the
repowering of aging wind projects. There are many ways that such a policy might be
designed. Since Denmark and Germany currently have successful proactive policies
intended to directly encourage repowering, this report summarizes related efforts in both
countries.
Germany
Germany’s wind power boom started later than Denmark’s. Repowering is expected to constitute
a major part of the wind market in the years ahead, especially as available new sites for wind
development diminish. Stumbling blocks include local government restriction on hub height or total
turbine height, and setback requirements between installations and residential areas. Despite
these barriers, the wind repowering opportunity in Germany in enormous.
Before 2004, German feed-in tariffs provided some encouragement for wind repowering, by
offering new wind projects a higher payment than existing projects that had been operating for
some time. Since 2004, the feed-in tariff has offered a longer and higher payment level to wind
turbines that replace/modernise existing project built before Dec 1995 and that are at least three
times the capacity of the repowered turbine.
Despite this incentive, repowering has just begun and, given the regulations on siting and the
barriers to repowering identified above, the wind industry argues that the feed-in tariff repowering
incentive is insufficient.

It must be noted that the German repowering programme is starting slowly compared to the
Danish programme. Although it is obvious that Germany has a good potential for repowering,
a study performed in 2005 showed that there were some obstacles in the repowering
programme.19
The main conclusions were:
Denmark
Denmark was the first country to actively support wind repowering, in part because wind turbine
installation began in the early 1980s, so a large number of aging, small (< 75 kW) wind turbines
exist throughout the country. Denmark recognized that these smaller, aging turbines were an
obstacle to new project development, and that removing and repowering those turbines would
require an overt and explicit incentive. Denmark’s repowering programme has led to repowering
two-thirds of the oldest turbines in the country.
Denmark’s first incentive programme for repowering wind turbines operated from April 2001 –
December 2003. For turbines smaller than 100 kW, “repowering certificates” allowed owners to
install three times the capacity removed, and receive an additional feed-in tariff price of 2,3
cents/kWh for the first 12.000 full load hours (about 5 years) of the enlarged wind project. For
turbines in the 100 – 150 kW size range, owners could install twice the capacity removed, and
receive the same treatment.
As a result of this programme, 1480 turbines totalling 121,7 MW were replaced with 272 new
turbines totalling 331,6 MW. Some owners of older wind projects also decided to decommission
their projects and sell their repowering certificates to other wind developers.
Denmark has continued to encourage wind repowering through a policy enacted via the energy
policy agreement of March 2004. This new programme intends to repower another 175 MW of
aging wind turbines. Under the programme, an extra surcharge is paid for new, on-shore wind
turbines on the condition that the owner has a repowering certificate for a 450 kW wind turbine or
less, decommissioned between Dec 2004 and Dec 2009. The surcharge is paid for factory new
wind turbines connected to the grid between Jan 2005 and Dec 2009. The surcharge amounts to
1,6 cents/kWh and is paid for electricity production corresponding to 12000 full load hours for up
to twice the decommissioned wind turbine installed power. The surcharge is regulated in relation
to the market price of electricity, and the total of the surcharge and market price must not exceed
a specified level. Because of the current low price of wholesale electricity, wind industry
stakeholders in Denmark are concerned about the adequacy of this incentive and are calling for a
larger incentive.
• the current spacing requirements lowered the potential yield increase when emission
control requirements are fulfilled;
• if the spacing requirements are ignored while the height limit is maintained, the yield
increase lowers even more;
• if both the spacing requirements and the height limit are maintained, the potential yield
does not increase at all in extreme cases.
These results are remarkable for a number of reasons:
• they show that spacing requirements and height limits result in the loss of enormous
economic potential for wind energy;
• spacing requirements and height limits make small turbine areas completely unsuitable
for modern wind turbines, given the current state of technology;
19
"The Limitations of Repowering With Regard To The Legal Requirements and Procedures for Approval";
Hermann-Föttinger Institute of Fluid Mechanics at the Technical University of Berlin, in cooperation with
Ecofys; 2005

• the repowering incentive offered has no effect, since the spacing requirements and height
limits make it impossible to achieve the required tripling of installed nominal capacity;
• if yields cannot be increased by a factor of 2.5, then repowering turbines before their
technical service life ends (usually 20 years), no longer offers an economic advantage to
wind farm operators. It should be noted here, that more than 50 percent of the wind
power capacity in Germany was installed after 2000. Maintaining the current spacing
requirements and height limits actually preserves the number of existing wind turbines.
From the above it is obvious that the repowering of wind energy needs to be supported by
the government. To encourage repowering it seems that feed-in tariffs are in favour, and
strict height and spacing limitations should be limited, otherwise the necessary increase in
installed power cannot be achieved.
Figure 3.7 Eneco wind park, Slufter20
20
www.eneco.nl

4. USED WIND TURBINES
Many wind turbines are designed to achieve a service of 20 years or longer. Over the last
decade, wind turbines have become larger. Politicians in many countries have focused their
attention on up-scaling wind turbines at existing locations. As a result of repowering, interest
in used wind turbines with a remaining service life of several years is growing across the
world. A fledging new business is now showing signs of gaining sophistication.
In the early 1990s, reaction to the efforts of selling used Californian wind turbines to
developing countries was decidedly mixed. A strong body of opinion argued forcefully (and in
the end successfully) that dumping outdated technology on an inexperienced yet potentially
large new market was morally questionable, and likely to be bad for long-term business.
Nowadays in Europe, the body of opinion is arguing that sales of well-maintained, older
machines, allows new markets to gain positive experiences with wind power at lower
commercial risks than the far greater investment needed to buy state-of-the-art technology.21
Replacement turbines are not always installed on the same site as the old machines, with the
result that old turbines can either be sold for erection elsewhere, or for continued operation
on the existing site by a new owner, who accepts that the output no longer attracts a
subsidised price. Others are dismantled entirely and are sold for scrap, recycling, or for their
parts.
4.1. Why buy used wind turbines
Growing energy demand in developing countries stimulates the use of renewable energy
sources, such as wind power, to provide a sustainable and environmentally-friendly power
supply. For most of these countries, projects with new wind turbines have proven to be
unaffordable: that is why using cheaper second-hand turbines may be an option. Utilising
used wind turbines instead of new ones offers several benefits22
:
• lower capital expenditure saves the investor’s capital resources and reduces the
efforts involved in collecting borrowed capital;
• shorter project duration reduces the investor’s financial risk, especially valuable in
politically and economically unstable conditions;
• turbines from 150 to 600 kW can be transported and erected without major problems.
However, larger turbines often require specialist equipment that is not available in
many parts of the world, while smaller turbines may not be economical to place. Many
manufacturers are no longer fabricating turbines of this size. Therefore, buying used
turbines is the most common way of obtaining a wind turbine that can be shipped and
installed easily;
• maintenance work on used turbines can be conducted easily, compared with the
latest technology turbines that require both a sophisticated infrastructure and
specialists to carry out routine work. Using used turbines means that it is not
necessary to make high demands on qualified personnel;
• a substantial overhaul and adaptation to regional requirements can take place while
the used turbine is being dismantled. This is cheaper than overhauling while the plant
is in operation;
21
The art of selling repowered turbines; Wind Power Monthly, May 2004.
22
Perspective of reusing wind energy converters in developing countries; N. Peterschmidt, Technical University
of Clausthal.

• for developing countries, it is an opportunity to contribute to sustainable development
and the reduction of CO2 emissions;
• for European investors, it is an opportunity to make connections with a potential
future wind power market, and to gain experience of the social and economic
environments in developing countries.
But disadvantages will also arise:
• more efforts will be required to select suitable turbines for specific projects e.g. each
used turbine has different characteristics, including such things as equipment and
defects that have occurred. These characteristics should meet regional requirements
in order to minimize the costs of adaptation. To determine the price of used plant,
dynamic measurements can be conducted during operation;
• the life expectancy of overhauled used wind turbines cannot be satisfactorily
predicted. For this reason, all results of economic analyses are based on
assumptions;
• the procurement of spare parts may also become an obstacle, as most
manufacturers’ technical support expires after 20 years. Centralised storage of spare
parts may help to overcome this obstacle.
In some cases, dependent on the site and on the plant used, the advantages outweigh the
disadvantages, and the utilisation of used wind turbines is advisable. Because of many of the
benefits mentioned above, developing countries lend themselves to realising projects with
used turbines.
Despite increased repowering activities, the demand for used turbines in Europe is estimated
to remain low, which means consequently that prices will also follow this trend. In Figure 4.1,
representative quotations of used turbines in Germany were plotted in order to give a
description of current rates, referring to slightly overhauled plant at the place of storage in
Europe without transportation and installation.
0%
10%
20%
30%
40%
50%
60%
70%
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Age [years]
Priceoftheusedturbinecompared
tothepricewhennew
Figure 4.1 Age dependent prices of used wind turbines
To demonstrate the profitability of a wind farm project with used wind turbines, the
profitability of a project using four 10 year old 500 kW turbines is compared with a project

using three new 600 kW turbines. The different number of turbines was chosen to get an
equivalent amount of generated power per year for both options. The economic analysis was
carried out on the assumption of single payments and periodic expenditures displayed in
Figure 4.2. Furthermore the life expectancy after erection was assumed to be 15 years for
the used wind turbines and 25 years for the new turbines. The cost of electricity generation
was approximately 0,079 Euros for the used turbine and approximately 0,086 Euro for the
new turbine, showing the used wind turbine to be more profitable. Of course, this result is not
generally applicable for all projects, and an individual approach to the purchase of used or
new turbines is necessary.
€ 0
€ 500.000
€ 1.000.000
€ 1.500.000
€ 2.000.000
€ 2.500.000
Starting
capital
annual
costs
Starting
capital
annual
costs
3 new turbines 4 used turbines
other annual costs
Annual maintenance
Reserves
Mains Connection
Foundation
Transport
Overhaul
Converter
Figure 4.2 Comparison of costs between new and used wind turbines
4.2. When buying used wind turbines
Successful utilisation of wind turbines is always dependent on sufficient wind energy
potential. This is the basis for both new and used wind turbines. Electrical stability in weak
grids with stochastic feeders, limits the permissible load of wind turbines. That is why only
small generators in the 150 to 600 kW class are suitable for simple grid connections.
Turbines of this size are no longer being manufactured and are only available on the second-
hand market. This option allows lower initial expenditure costs, resulting in a shorter project
duration, favourable for countries without long-term planning reliability in the initial
implementation period23
.
Additionally, a certain technical infrastructure is required (cranes, roads, companies for basic
maintenance) and access to the national grid should be supported by a sufficient buyback
price.
23
Repowering – New changes for wind power implementation; H. Peters, WWEA.

4.2.1. Grid integration of used wind turbines
In most developing countries the operating conditions of turbines are different from those in
Europe. Not only will climate changes have an impact on the turbines, but also connection to
the grid. In contrast to highly populated industrial countries, electrical power in developing
countries is often supplied via long transmission lines of low capacity with large fluctuations.
To avoid expensive applications for stabilising the voltage level, it is necessary to choose a
site with transmission lines of adequate capacity. Highly productive sites may also be
dismissed because of concerns of frequent black outs, that are a strain for wind turbines and
diminish the energy supply.
4.2.2. General overhaul and maintenance of used turbines
Climate or geographical changes will have impact on the turbines. In general, in
temperatures above 35°
C, an advanced cooling system for the gearbox and the generator is
required; an extra ventilator for the generator and additional cooling for the gear oil or the
whole system are possibilities.
To avoid erosion of the blade surface as a result of high fluctuations in temperature (e.g.
sandy deserts) the application of special protection-films against erosion is recommended. In
the event of sandstorms it is necessary to use sand filters to protect the equipment inside the
nacelle.
Low air density at high altitude sites reduces the energy output of wind turbines, compared
with sites at sea level. The limitation of power generated at high wind velocities takes place
at lower output. In order to improve the output, the blade angle can be adjusted.
To enable an adaptation to different power frequencies, a wind turbine with generator and
electrical converter should be chosen. It can be adapted to 60 Hz easily, just by adjusting the
control system of the converter. By contrast, wind turbines with induction generator need to
be altered; either the gear transmission ratio has to be adjusted by alternation of the whole
gearbox, or an external converter has to be applied to change the frequency. Both solutions
are expensive. Different voltages also have to be covered, e.g. by adjustment or even by
replacing the transformer.
For the project planning of a wind farm or an individual wind turbine with used wind turbines,
it is vital to know the performance and the technical condition of a machine, since ultimately
the technical condition is the criterion for the financial success of the project. A plant that is
permanently generating costs can be hardly profitable. It is, therefore, recommended that the
technical condition be verified prior to purchase, preferably before dismantling has started on
the original site.
There are no one hundred percent damage-free wind turbines. The goal is to keep the
number of problems low, and to identify and address existing damage on time. Measures
introduced on time ensure maximum life expectancy of the turbine. The actual damage
potential of a problem can only be evaluated by specialists. Prior to purchasing a used wind
turbine, it is recommended that a status-oriented survey of the wind turbine be carried out.
This survey also includes a review of the available documentation, which is designed to give
a complete overview of the structure, operation and history of the turbine. As a minimum, the
following documents must be available:

• Building permission
• Operating instructions
• Circuit diagrams and hydraulic diagrams
• Commissioning record
• Results of former oil analyses
• Maintenance specification, including all maintenance and service reports
• Logbook with all the service team calls.
4.3. What is the potential of using used wind turbines
In countries where repowering programmes have started, different companies have entered
the market for selling used wind turbines. If owners of wind turbines decide to go for
repowering, in most cases the price of selling the used wind turbines is not important, since
they do not depend on the sale of the used turbines. If the fate of the old machines is not
economically relevant to the repowering, the owner can try to find buyers, or may eventually
sell them for scrap. As mentioned earlier, wind turbines between 150 up to 600 kW offer the
best possibilities for re-utilisation in developing countries.
Selling older machines can be done by the owner, but this can also be done by the
manufacturer of the used machine. Some of the wind turbine manufacturers do have a
department for re-selling used wind turbines. Also, new players have entered this market
who are focusing entirely on selling used machines. They have become specialists in the
market and in inviting potential customers to select their preferred wind turbine, once their
project begins to takes shape.
Selling used wind turbines to developing countries offers opportunities for all countries
concerned. Utilising used turbines in developing countries offers an opportunity to gain
experience in working with wind energy technology with low capital expenditure. Establishing
their own wind energy industries, assisted by technology transfer from Europe, may help to
improve the labour market in these countries. If used turbines find a market in developing
countries, repowering activities may increase, and European countries can then extend their
wind power generation capacity. This would also contribute to a double reduction in CO2
emissions, (at the location of the repowering, and at the location at which the turbines are re-
used).

5. CONCLUSIONS
The recycling of wind turbines preserves the amount of energy and material invested in the
equipment itself. The unique combination of increased supply from European countries,
coupled with increased demand for smaller and middle sized turbines in developing
countries, offers opportunities for exporting reliable wind turbines. The reduced remaining
life-expectancy of such turbines does not present significant disadvantages because, in
these countries, such turbines fill a niche in their developing and partly insecure markets.
Most of the turbines currently placed in Europe need a general overhaul after 6 to 10 years.
For the former operator, selling the plant at this age and replacing the existing wind turbines
with larger ones, offers the opportunity to avoid overhead costs; which also results in energy
gains at the same location. The new investor of the used turbines can carry out all necessary
work at the disassembled plant (thus reducing costs).
Projects utilising used wind turbines, that have already been realised in several countries,
represented the initial step for the long-term alteration of these countries’ energy sectors
regarding the introduction of wind-power technology. These projects differ from projects that
utilise new equipment, in that certain aspects need to be taken into consideration and
evaluated during the project planning. In summary, any project with either new or used
turbines can only be undertaken profitably if a number of different crucial basic requirements
are met regarding: the existence of sufficient wind speeds; a stable grid; minimum buyback
prices; technically qualified personnel; spare parts; and reliable economical and political
conditions. In going for the option of re-using second-hand turbines, the main difference
concerns simplifying financing, because of the lower initial expenditure.

6. APPENDIX A - TRADING COMPANIES FOR USED WIND TURBINES
This Appendix provides a list of some companies that sell or offer advice regarding wind
turbines in Europe. This list is not a complete list of all companies in Europe. Most of the
companies listed below are companies operating in countries in which repowering has
already started.
Company Country Website Description
Windpartnersbg Bulgaria www.windpartnersbg.com Consultancy
in used wind
turbines from
225 kW to
1,5 MW
Windbrokers Netherlands www.windbrokers.com Supplier of
used wind
turbines from
150 kW and
upwards
Repowering
solutions
Spain www.repoweringsolutions.com Supplier of
used wind
turbines from
150 kW and
upwards
Dansk Vindenergi
ApS
Denmark https://dansk-vindenergi.dk Sales of used
wind turbines
between 150
– 250 kW
BSgreen Germany http://gebrauchtewindkraftanlagen.com
www.usedwindturbine.com
Consultancy
& installation
Dansk
Vindmoelleformidling
Denmark www.danishusedwindturbines.com Export of wind
turbines from
30 kW to 1
MW
GFW Germany www.neic.de/wind/gfw-e.htm Sales of used
wind turbines
P&J Windpower ApS Denmark www.pjwindpower.com Supplier of
second hand
wind turbines
MainWind Netherlands www.mainwind.nl Sales of used
wind turbines
Bettink Netherlands www.bettink.nl Sales of used
wind turbines
Immobilen Service
Lothar Müller
Germany www.wind-park-power.com Sales of used
wind turbines

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