WIND ENERGY CONVERSION SYSTEMS TECHNOLOGY AND TRENDS PDF

Preface
The renewable energy penetration rate to the power grid is increasing rapidly nowa-days. Wind, solar, biogas/biomass, tidal, geothermal, etc.
are considered as the
renewable sources of energy and among those the wind is playing the major role in
world’s energy market along with conventional sources of energy.
The wind
energy sector has already reached a matured stage due the contributions from
many engineering and science disciplines in the last few decades, mainly from
mechanical, electrical, electronic, computer, and aerospace.
Each discipline has its
own beauty and the combined efforts from scientists from different disciplines are
the secret of the success of wind industry.
In this book, the present future development schemes of wind turbine generator
systems are depicted based on the contribution from many renowned scientists and
engineers from different disciplines.
A wide verity of research results are merged
together to make this book useful for students and researchers.
The chapters of the book are organized into three parts.
In part I, wind energy
conversion systems using different types of wind generator including necessary
control schemes, are presented.
Efficiency analysis of commercially available wind
energy conversion systems, large scale wind generator, using superconducting
material and high efficient power converter technology are the key features of this
section.
Part II is focused on several important issues for wind industry and
transmission system operators.
Grid interfacing issues, grid code, lightning strike
and protection, use of energy storage options are highlighted in this section. And in
the part III, the focus is given only to offshore wind power technology.
Offshore
wind speed observation from the space, HVDC based transmission scheme to
interconnect offshore wind farm into onshore grid, hybrid offshore wind farms and
marine current farms are the key issues discussed in this section.
A general
overview and essence of the chapters can be obtained from
Chap.1 of the book.
Chapter 1
Introduction
S. M. Muyeen
Abstract In this chapter, first, the global wind power scenario is depicted
followed by the market forecasting upto the year 2030.
Then the current technology
and the future trend of wind energy conversion system are discussed where the
development of wind generator, blade designing, lightning protection, installation,
commissioning, operation and maintenance of wind turbine generator unit are
briefly stated.
Some important issues such as variability and predictability of wind
power, energy storage options and grid interfacing techniques are discussed as well.
Prime offshore wind farm technology issues in terms of feasibility study, bulk
power transmission scheme are discussed in detail.
Finally, the highlights of all the
chapters are given from where the flavor of the book can be obtained at a glance.
1.1 Global Wind Power Scenario
Wind energy is becoming one of the mainstream power sources in many countries
around the world.
According to Global Wind Energy Council (GWEC) statistics,
global wind power installations increased by 35.8 GW in 2010, bringing the total
installed wind energy capacity upto 194.4 GW, a 22.5% increase on the 158.7 GW
installed at the end of 2009.
GWEC is one of the few organizations doing an
excellent job by broadcasting and forecasting regional wind power development
throughout the world. In the following section, the present wind power installation
scenario at the end of 2010 and some future predictions are demonstrated in light
of GWEC reports [1, 2].
1.1.1 Asia
The growth in Asian markets has been breathtaking, as more than 50% of the
world’s wind energy in 2010 was installed in Asia and it is the 3rd year in a row
where Asia is leading the regional market on the globe.
China was the world’s
largest market in 2010, adding a staggering 16.5 GW of new capacity, and slipping
past the USA to become the world’s leading wind power country. The Chinese
market more than doubled its capacity from 12 GW in 2008 to 25.8 GW in 2009
and added 16.5 MW in 2010 to reach 42.2 GW at the end of 2010 [1]. The
planning, development and construction for the ‘‘Wind Base’’ programme, which
aims to build 138 GW of wind capacity in eight Chinese provinces, is well
underway. It is expected that in its twelfth Five-Year Plan, which is expected to be
adopted in March 2011, the Chinese government will increase its official target for
wind power development to 200 GW by 2020.
1.1.2 North America
According to American Wind Energy Association (AWEA) statistics the U.S.
wind energy industry installed 5,115 MW in 2010.
This is barely half of 2009s
record pace, but the fourth quarter was strong, showing new momentum for 2011
1.1.3 Europe
During 2010, 9,883 MW of wind power was installed across Europe, with
European Union countries accounting for 9,259 MW of the total. This represents a
decrease in the EU’s annual wind power installations of 10% compared to 2009.
1.1.4 Latin America
Brazil and Mexico are the leading countries in Latin America in wind power generation as can be seen from the GWEC report [1]. In 2010, Brazil added 326 MW of
new capacity, slightly more than in 2009, and is now host to 931 MW of wind power.
Mexico’s installed wind capacity more than doubled for the second year in a row,
with 316 MW of new capacity added to the existing 202 MW operating at the end of
2009. The total installed wind power capacity now amounts to 519 MW.
1.1.5 Pacific Region
At the end of 2010, 1,880 MW of wind capacity was installed in Australia, an
increase of 167 MW from 2009.
There are now 52 operating wind farms in the
country, mostly located in South Australia (907 MW) and Victoria (428 MW).
1.1.6 Africa and Middle East
In North Africa, the expansion of wind power continues in Morocco, Egypt and
Tunisia.
Egypt not only saw the largest addition of new capacity in 2010 (120 MW),
bringing the total upto 550 MW but also continues to lead the region. Morocco
comes in a distant second with a cumulative capacity of 286, 30 MW of which was
added in 2010. Tunisia added 60 MW of new capacity in 2010, taking the total to
114 MW.
1.2 Market Forecast
GWEC predicts that at the end of 2015, global wind capacity will stand at
449 GW, up from 194 GW at the end of 2010 [1].
During 2015, 60.5 GW of new
capacity will be added to the global total, compared to 35.8 GW in 2010. These are
shown in Fig. 1.9. The annual growth rates during this period will average 18.2%
in terms of total installed capacity, and 11.1% for annual market growth.
GWEC also estimates that Asia will remain the fastest growing market in the
world, driven primarily by China, which is set to continue the rapid upscaling of its
wind capacity and hold its position as the world’s largest annual and cumulative
market. For Asia as a whole, the annual market is expected to increase from
19 GW in 2010 to 26 GW in 2015, which would translate into a total of 116 GW
of new capacity to be added over this period—far more than in any other region.
In 2013, Asia is expected to overtake Europe as the region with the largest total
installed capacity, and it will reach a cumulative wind power generation capacity
1.3 Technological Aspects—Present and Future
Though wind energy conversion system has reached to a mature stage it is still
going through a continuous development program by researcher and industry
peoples from different disciplines for the improvement in both component
1.3.1 Wind Turbine Generator Unit
Wind turbine manufacturers are trying to incorporate the recent technology in drive
train layout, turbine blade design and structural improvement to reduce the total mass
and net cost and to increase energy extraction efficiency and lifetime as well.
Gearbox
is one of the components that causes the downtime of wind turbine generator systems
the most, and therefore, gearless or one or two gearing stage with multi-pole generator
based scheme is going to be a popular trend in the wind industry.
Elimination of
carbon fibre reinforcement from turbine blade might be a good attempt which is under
consideration by blade manufacturers.
Lightning protection scheme including eddy
current loss minimization should be focused more in future blade designing. This is
because the lightning strike in one wind turbine may not only hamper wind power
extracting from that unit, but the nearby units as well
1.3.2 Power Electronic Converter Technology
The issue of energy conversion from wind power nowadays involves the presence
of power electronic devices.
In a power electronic inverter and converter the
commonly used devices are the diode, thyristor, gate turn-on thyristor (GTO) or
insulated gate turn-on thyristor (IGBT) and in some cases the integrated gatecommutated thyristor (IGCT). The conduction and switching losses in these device
modules have been reduced greatly and therefore the losses in high power converters/inverters have also reduced significantly.
As a result, the full rating
inverter/converter-based wind energy conversion system using permanent magnet
synchronous generator is becoming popular.
The same reason is behind the popularity of HVDC-based offshore wind farms.
However, the wind power industry
is looking forward to further loss reduction of high power converters and the
discovery of a silicon carbide (SiC) power switch has added extra pace in this
development.
1.3.3 Offshore Wind Farm
In the recent years offshore wind farms show the most prominent market opportunities, since they are likely to offer comparatively higher productivity than projects
based on onshore wind turbines, due to the higher speed of offshore wind. It is
expected that while the average wind speed on the shore is 7 m/s, offshore speed
ranges between 9 and 10 m/s.
The average size of the offshore wind farm is increasing
e.g., the average offshore wind farm size in Europe in 2010 exceeds 150 MW [4],
therefore, the total accumulation will be on a big scale.
Many large-scale offshore
wind farms are under construction and many more are in the planning stage.
Numerous technological challenges exist for successful installation, commissioning and operation of offshore wind farms.
The average distance from the shore
is increasing compared to previous years. As per the EWEA report [4], the average
distance from the shore increased in 2010 by 12.7–27.1 km, substantially less,
however, than the average of 35.7 km for projects currently under construction.
As a consequence, the average water depth is increasing, e.g., Average water depth
in 2010 was 17.4 m, a 5.2 m increase from 2009, with projects under construction
in water depth averaging 25.5 m.
These raise the issues of foundations, installation
methods, bulk power transmission system, etc.
1.3.5 Moderate and Bulk Power Transmission
Economical feasibility is one of the key issues behind the selection of transmission
technology (HVDC or HVAC) for grid interconnection of offshore wind farms.
The distance of the offshore wind farm from the shore is an important factor to
determine the transmission system as transmission line loss has a direct relation
to it.
High power converter technology has progressed tremendously, losses in
converter have reduced significantly, and therefore, big companies are offering
complete packages for bulk offshore power transmission using HVDC technology.
There is a chance that future offshore wind farms will move to the HVDC-based
transmission system, especially with the spread of the supergrid concept these
days.
Some of the other issues like multi-terminal scheme for offshore wind farm,
loss minimization in HVDC stations, control scheme including fault ride-through
capability augmentation should be focused more to make this technology viable.
Moderate level DC-based onshore wind farms may attract the grid operator where
full-bridge DC–DC converters can help in boosting the generator side voltage to
higher levels using high frequency transformers.
1.3.6 Variability and Predictability
There is no argument about the variability of wind power but about intermittency!
Wind power is often described as an ‘‘intermittent’’ energy source, and therefore
unreliable.
In fact, at the power system level, wind energy does not start and stop at
irregular intervals, hence the term ‘‘intermittent’’ is misleading. The output of
aggregated wind capacity is variable, just as the power system itself is inherently
variable.
Since wind power production is dependent on the wind, the output of a
turbine and a wind farm varies over time, under the influence of meteorological
fluctuations.
These variations occur on all time scales: by seconds, minutes, hours,
days, months, seasons and years.
Understanding and predicting these variations is
essential for successfully integrating wind power into the power system and to use
it most efficiently [6].
1.3.7 Energy Storage Option
To cope with the variability of wind power and to meet the requirement of
transmission system operators (TSO) or grid companies,the wind industry is
extensively dependent on energy storage options.
There is increasing interest in
both large-scale storage implemented at transmission level, and in smaller scale
dedicated storage embedded in distribution networks.
The range of storage technologies is potentially wide.
For large-scale storage, pumped hydro accumulation
storage (PACPACPAC) is the most common and best known technology, which
can also be done underground. Another technology option available for large scale
is compressed air energy storage (CAES).
On a decentralized scale storage options
include flywheels, batteries, possibly in combination with electric vehicles, fuel
cells, electrolysis and super-capacitors.
Furthermore, an attractive solution consists
of the installation of heat boilers at selected combined heat and power locations
(CHP) in order to increase the operational flexibility of these units.