STATCOM – Working Principle, Design, and Application
What is SATCOM?
STATCOM or Static Synchronous Compensator is a power electronic device using
force-commutated devices like IGBT, GTO, etc., to control the reactive power flow
through a power network, thereby increasing the power network's stability.
STATCOM is a shunt device i.e. it is connected in shunt with the line. A Static
Synchronous Compensator (STATCOM) is also known as a Static Synchronous
Condenser (STATCOM). It is a member of the Flexible AC Transmission System
(FACTS) family of devices.
The terms Synchronous in STATCOM mean that it can either absorb or generate a
reactive power in synchronization with the demand to stabilize the voltage of the
power
network.
Working Principle of STATCOM:
To understand the working principle of STATCOM, we will first have a look at the
reactive power transfer equation. Let us consider two sources V1 and V2 are
connected through an impedance Z = Ra + jX as shown in figure below.
In the above reactive power flow equation, angle δ is the angle between V1 and V2.
Thus if we maintain angle δ = 0 then Reactive power flow will become
Q = (V2/X)[V1-V2]
and active power flow will become
P = V1V2Sinδ / X =0
To summarize, we can say that if the angle between V1 and V2 is zero, the flow of
active power becomes zero and the flow of reactive power depends on (V1 – V2).
Thus, for the flow of reactive power, there are two possibilities.
1) If the magnitude of V1 is more than V2, then reactive power will flow from
source V1 to V2.
2) If the magnitude of V2 is more than V1, reactive power will flow from source
V2 to V1.
This principle is used in STATCOM for reactive power control. Now we will discuss
the design of STATCOM for a better correlation between the working principle and
design.
You may like to read Reactive Power and Voltage Control of a Transmission Line
Design of STATCOM:
STATCOM has the following components:
1) A Voltage Source Converter, VSC
The voltage-source converter is used to convert the DC input voltage to an AC
output voltage. Two of the common VSC types are as below.
a) Square-wave Inverters using Gate Turn-Off Thyristors: In this type of
VSC, output AC voltage is controlled by changing the DC capacitor input
voltage, as the fundamental component of the converter output voltage is
proportional to the DC voltage.
b) PWM Inverters using Insulated Gate Bipolar Transistors (IGBT): It uses
the Pulse Width Modulation (PWM) technique to create a sinusoidal
waveform from a DC voltage source with a typical chopping frequency of a
few kHz. In contrast to the GTO-based type, the IGBT-based VSC utilizes a
fixed DC voltage and varies its output AC voltage by changing the
modulation index of the PWM modulator.
2) DC Capacitor
DC Capacitor is used to supply constant DC voltage to the voltage source
converter, VSC.
3) Inductive Reactance
A Transformer is connected between the output of VSC and the Power System.
The transformer basically acts as a coupling medium. In addition, Transformer
neutralizes harmonics contained in the square waves produced by VSC.
4) Harmonic Filter
The harmonic Filter attenuates the harmonics and other high-frequency
components due to the VSC.
A simplified diagram along with the equivalent electrical circuit of STATCOM is
shown in the figure below.
Now we will understand how the STATCOM works though we have discussed the
basic operating principle of STATCOM. As can be seen from the figure above,
source V1 represents the output voltage of the STATCOM. In case of reactive power
demand increases in the power system, STATCOM increases its output voltage V1
while maintaining the phase difference between V1 and V2 to zero (it shall be noted
here that there will always exist a small phase angle between V1 and V2 to cater for
the leakage impedance drop in the interconnecting Transformer). As V1 > V2,
reactive power will flow from STATCOM to the power system. Thus, STATCOM
supplies reactive power and acts as a reactive power generator.
Again, if the voltage of the power system increases due to load throw-off,
STATCOM will reduce its output voltage V1 and therefore will absorb reactive
power to stabilize the voltage to normal value.
The above mode of operation of STATCOM is called Voltage Regulation Mode.
But as we know every piece of equipment has got its own limitations, so STATCOM
must also have some limitations in supplying or absorbing reactive power. Yes, there
exists a limitation and this limitation is imposed by the current carrying capacity of
force-commutated devices like IGBT, GTO, etc. Therefore, if the operation of
STATCOM reaches its limitation, it does not further increase or decrease its output
voltage V1 rather it supplies or absorbs fixed reactive power equal to its limiting
value at a fixed voltage and current and acts like a constant current source. This
mode of operation of STATCOM is called VAR Control Mode.
Thus, from the above discussion, the operation of STATCOM can be classified into
two modes:
1) Voltage Regulation Mode
2) VAR Control Mode
The figure below well explains the above two modes of operation of STATCOM.
The figure above is the Voltage Current Characteristics of STATCOM. As can be
seen, the voltage regulation capability of STATCOM is from V1 (on the lower side)
to V2 on the upper side of the power system. If the voltage of the power system goes
below V1 or above V2, STATCOM acts in VAR Control mode. Here V1 and V2 are
just taken, for example, it should not be confused with the V1 (used for the output
voltage of STATCOM) and V2 (Voltage of power system) used in the discussion
above.
Application of STATCOM:
Voltage stability is one of the biggest problems in power systems. Engineers and
researchers are trying to consolidate a definition regarding to voltage stability,
besides proposing techniques and methodologies for their analysis. Most of these
techniques are based on the search of the point in which the system’s Jacobian
becomes singular, this point is referred as the point of voltage collapse or maximum
load ability point. (we will discuss point of voltage collapse in next post) The series
and shunt compensation are able to increase the maximum transfer capabilities of
power network .Concerning to voltage stability, such compensation has the purpose
of injecting reactive power to maintain the voltage magnitude in the nodes close to
the nominal values, besides, to reduce line currents and therefore the total system
losses. Today due the development in the power electronics devices, the voltage
magnitude in some node of the system can be adjusted through sophisticated and
versatile devices named FACTS. One of them is the static synchronous compensator
(STATCOM).
Usually a STATCOM is installed to support electrical networks that have a poor
power factor and often poor voltage regulation. The most common use of
STATCOM is for voltage stability. A STATCOM is a voltage source converter
(VSC) based device, with the voltage source behind a reactor. The voltage source is
created from a DC capacitor and therefore a STATCOM has very little active power
capability. However, its active power capability can be increased if a suitable energy
storage device is connected across the DC capacitor.
How does STATCOM work?
The STATCOM regulates voltage at its terminal by controlling the amount of
reactive power injected into or absorbed from the power system. When system
voltage is low, the STATCOM generates reactive power (STATCOM capacitive).
When system voltage is high, it absorbs reactive power (STATCOM inductive).
What are disadvantages of STATCOM?
Unlike static var compensator (SVC), the STATCOM does not employ capacitor or
reactor banks to produce reactive power. The major disadvantage of a traditional
STATCOM (with no energy storage) is that it has only two possible steady-state
operating modes, namely, inductive (lagging) and capacitive (leading).
Why
is
STATCOM
used
in
load
flow?
It converts the dc input voltage into ac output voltages to compensate the active and
reactive power of the system. STATCOM has better characteristics than SVC and it
is used for voltage control and reactive power compensation.
What is the difference between STATCOM and SVC?
The main difference between a STATCOM and an SVC is the way they operate: a
STATCOM works as a controllable voltage source while an SVC works as a
dynamically controllable reactance connected in parallel.
What are the applications of STATCOM?
It provides voltage support by generating or absorbing reactive power at the point of
coupling. Thus, a STATCOM may be used for voltage control, reactive power
compensation and damping oscillations.
What are the functions of STATCOM in the improvement of power system
performance area?
It can be concluded from the simulation results that the proposed STATCOM can be
used to improve the performance of the voltage stability, transient stability, rotor
angle deviation, transmission line to power grid under different operating conditions.
How does STATCOM compensate reactive power?
OPERATION
OF
STATCOM
The STATCOM is connected as shunt device which is used for compensation. By
using STATCOM, reactive power can be compensated by either absorbing or
injecting. Voltage profile and power factor of the transmission system is also
improved by using STATCOM.
How is STATCOM connected in a system answer?
Explanation: The two areas are connected by two parallel connected long
transmission lines. The direction of real power flow is from area-1 to area-2. The
STATCOM is placed on one of the transmission lines and near to the generator being
analyzed (area-1).
What is STATCOM Why is STATCOM used in load flow briefly explain the load
flow analysis incorporating STATCOM?
STATCOM is FACTS device used to maintain the bus voltage at designated bus of
the transmission line. The performance of STATCOM is studied and analyzed with
six bus system which shows the absorption of reactive power when connected to bus
number 5.
Why are onshore wind turbines better than offshore?
An onshore wind farm's construction and operation creates significantly less
emissions than other energy sources, while the sites they're placed on can still be
farmed. It's one of the least expensive forms of renewable energy (along with solar
PV) and significantly less expensive than offshore wind power.
Onshore vs offshore wind energy: what’s the difference?
From the wind farms that dot our landscapes to the vast installations off our
coastlines, both offshore and onshore wind power play a central role in the
transition to a carbon-free electricity system.
The technology that onshore and offshore wind turbines use to generate
electricity is essentially the same. Where the two differ is in their position, size,
scale and how the electricity they generate is transferred.
What is onshore wind energy?
Simply put, onshore wind energy is the power that’s generated by wind turbines
located on land driven by the natural movement of the air. You’ll often see
onshore wind farms in fields or more rural areas, as they’re usually constructed
in less-populated areas where buildings and obstacles don’t interrupt the air.
Onshore wind has been capturing and converting wind power in some form
since the 1880s (to make corn or drive pumps), but the opening of the Delabole
wind farm in 1991 heralded the commercial era of onshore wind in the UK.
Today there are more than 1,500 operational onshore wind farms across Great
Britain, generating over 12 gigawatt hours (GWh) of electricity for the national
electric system. In 2020 onshore wind contributed 11% of the UK’s electricity
needs, with a total 34.7 terawatt hours (TWh) generated – more than enough to
power
18.5
million
UK
homes
for
an
entire
year.
Advantages of onshore wind power




Reduced
environmental
impact
An onshore wind farm’s construction and operation creates significantly less
emissions than other energy sources, while the sites they’re placed on can still
be farmed.
Cost
effective
It’s one of the least expensive forms of renewable energy (along with solar PV)
and significantly less expensive than offshore wind power. Cheaper
infrastructure and costs to run means onshore farms can help lower electricity
bills.
Quicker
installation
and
easier
maintenance
Onshore wind farms can be constructed in months, at scale, and are relativel y
cheap and cost-effective to maintain compared with offshore.
Job
creation
Our own analysis in the Job That Can’t Wait report reveals that 400,000 jobs
are needed in the energy sector to deliver net zero by 2050 – the creation of
both onshore and offshore wind farms in that period could create up to 60,000
jobs.
Disadvantages of onshore wind power




Changing
wind
speeds
The consistency of electricity generation from wind farms can be challenged by
varying wind speeds and changes in wind direction.
No
wind
or
intermittent
generation
When the wind is intermittent (or non-existent) electricity can’t be generated
using wind power. To meet our energy requirements we’ll need a mix of
solutions to rely on, including other renewable energy sources, as well as
receiving clean energy through interconnectors and improved management of
energy demand.
Effects
on
people
and
nature
Some people complain about the appearance of wind farms on the landscape
and noise. There are also some worries that onshore wind turbines may pose a
threat to birds (find out more about this in our article How does a wind turbine
work?)
Lesser
power
generation
Onshore wind farms produce less energy than their offshore counterparts
(called their ‘capacity factor’) because onshore planning often limits the
turbines' ‘tip heights’, which doesn’t apply to offshore turbines. An average
onshore wind turbine produces around 2.5 to 3 megawatts (MW), in comparison
to
the
offshore
average
of
3.6
MW.
What is offshore wind energy?
Offshore wind farms generate electricity from wind blowing across the sea.
They are considered more efficient than onshore wind farms, thanks to the
higher speed of winds, greater consistency and lack of physical interference that
the land or human-made objects can present.
The UK is the world leader in offshore wind. As of 2020 there were nearly
2,200 wind turbines across 35 offshore windfarms off the coast of England,
Scotland and Wales. In the same year they produced 40.7 TWh – up 27% from
2019 – and contributed 13% of the UK’s electricity needs.
Advantages of offshore wind power



Offshore
wind
turbines
are
more
efficient
Higher wind speeds and consistency in direction means offshore installations
require fewer turbines to produce the same amount of energy as onshore wind
farms.
Reduced
environmental
impact
Being miles out from the coast, offshore turbines are further away from th e
local population. Restricted access to their sites may even help to protect the
surrounding marine ecosystems.
More
space
to
construct
in
Oceans provide the perfect location to build wind farms in terms of scale and
openness. More wind farms being built means more clean, sustainable energy
can
be
produced.
Disadvantages of offshore wind power



Higher
cost
Offshore wind farms require more complex infrastructure to support them and,
as a result, are more expensive to construct.
Maintenance
and
repairs
Higher wind speeds, strong seas and accessibility issues makes offshore wind
farms more challenging to maintain.
Less
local
involvement
While onshore wind turbines can be owned or operated by local cooperatives,
or even by individuals, offshore wind turbines require a considerable scale of
investment that means they’re usually corporately owned. However, they do
provide significant employment for the development and working life of the
wind
farm.
Full
power:
the
world’s
largest
wind
farm
The Hornsea Phase 2 offshore wind farm will become the largest wind farm in
the world, when operational in 2022. It will generate 1.3GW of green energy
from 165 8MW wind turbines, which is enough to supply 1.4 million homes.
The future of wind energy in the UK
According to the Climate Change Committee’s Sixth Carbon Budget, by 2050
the UK will consume more than twice the amount of electricity than today,
driving the need for four times more clean generation and leading to double the
grid capacity.
The UK government has outlined ambitious plans to increase current offshore
wind capacity to 40GW by 2030, which would triple the current output.
Revolutionary ‘floating farms’ could provide more than 1GW of power to the
national grid, while more onshore wind farms are planned or in production.
As the nation’s cleanest, most reliable renewable energy source, our ability to
reach
net
zero
will
depend
on
it.
The future of offshore energy
The windiest part of the UK is offshore, out at sea, so putting windfarms out
there is the perfect source of renewable energy for us. Find out more about the
advances being made in offshore energy and how we'll be using it to generate
much more clean energy for a net zero future.
Introduction
(Name: Joel Jacob Colby, Last 3 Digits of Student Number: 791)
Wind energy has increasingly been utilized for the growing need for reliable and
renewable energy (Zheng, Li, Pan, Liu, & Xia, 2016). In a world that is seeking for
green alternatives, wind energy has been championed as a safe and renewable energy
option for many countries (Zheng et al., 2016).
Figure 1. A photo of the Rampion Offshore Wind Farm located in the United
Kingdom. Photo by Nicholas Doherty on Unsplash (2019).
Wind energy today typically comes in two different “types”: onshore wind farms
which are large installations of wind turbines located on land, and offshore wind
farms which are installations located in bodies of water (see Figure 1).
Both onshore and offshore wind farms provide two options for bulk wind electricity
generation, and there exist different trade-offs for both types of installations.
Onshore wind farms are the most popular type of wind farm in the world today, but
there is growing interest in the developed countries to construct offshore wind farms
(Zheng et al., 2016).
This story map will explore the differences between onshore and offshore wind
farms as it relates to efficiency and capacity, their potential impact on the health and
environment, and the economic differences between the two types of wind farms.
Efficiency and Capacity
Efficiency and capacity for wind farms is most heavily impacted by wind forces,
which can vary quite heavily across several different geographic areas (Possner &
Caldeira, 2017). A key difference between onshore and offshore wind farms is the
consistency that they are able to generate energy. Notably, due to higher and more
consistent wind speeds, offshore wind farms have the potential to generate more
electricity at a steadier rate than their onshore counterparts (Kaldellis & Kapsali,
2013).
In comparison, onshore wind farms require careful analysis when selecting a
development space to ensure that wind speeds are sufficient, the impact is reduced
to humans and the nearby environment, and that they can be easily hooked into
power grids (see Figure 2 below).
Figure 2. A web map application of a wind turbine selection site study in Colorado.
This onshore wind farm development had a number of criteria, including that the
new wind farm be located next to existing power grid infrastructure. Application
by Joel Colby on ArcGIS Online (2019).
Some benefits of onshore wind farms is that they are more easily accessible than
those placed in offshore environments, they can be more easily be connected directly
to local power grids (Zheng et al., 2016). The abundance of mature onshore wind
farms also provides several resources for the development of more efficient wind
farms, and improving the precision of wind farm simulations (Zheng et al., 2016).
Health and the Environment
Figure 3. Dave Lusk of Wallaceburg, Ontario, holds a jar of water drawn from his
home's water well. Dave says that his water well began running murky after the
construction of wind turbines near his home in October 2017. Photo by Mary
Baxter on TVO (2018).
One of the most common complaints associated with the construction of new
onshore wind farms is the introduction of noise pollution and its effect on human
beings and the surrounding environment (see Figure 3) (Nissenbaum, Aramini, &
Hanning, 2012). Some have dismissed the adverse health effects attributed to
onshore wind turbines due to lack of evidence (Rubin, Burns, & Wessely, 2014) but
it’s not uncommon to see these types of complaints raised by “wind concern” groups
before and after the construction of onshore wind farms.
Conversely, as offshore wind farms are located far away from humans, there are
typically far less complaints about their construction than their onshore counterparts
(Zheng et al., 2016).
There is evidence that suggests that wind farms located onshore can an impact on
the patterns of surface air and surface air temperatures in areas that are downwind
(i.e. in the direction that the wind is blowing) from a wind farm (Baidya Roy &
Traiteur, 2010). Minor adverse effects to land and marine animals and their habitats
have also been attributed to the operation and construction of some onshore and
offshore wind farms (Leung & Yang, 2012).
When comparing a life cycle assessment of onshore and offshore wind farms, there
has been evidence that onshore wind farms tend to lead to an overall more adverse
environmental impact (in terms of their materials used to construct them, installation
and operation processes, and maintenance) than offshore wind farms (Piasecka et
al., 2019).
One major area of environmental impact for wind farms is the manufacturing and
recycling of rotor blades at the end of a wind turbine’s life cycle. Rotor blades
designed for offshore wind farms have been shown to last longer (Zheng et al.,
2016), but they also emit more air pollution during the manufacturing and recycling
processes than rotor blades for onshore wind farms (Tomporowski et al., 2018).
Economics
Figure 4. A collection of offshore wind turbines in New Shoreham, United States.
Some offshore wind turbines are very difficult to access as they are located in deep
water. Photo by Shaun Dakin on Unsplash (2017).
One of the most significant points of comparison between onshore and offshore wind
farms is their cost (at least for the time being). Currently, onshore wind farms are far
cheaper to build and maintain that offshore wind farms (Blanco, 2009). This makes
sense, given that turbines located on land are far easier to access than turbines located
out in the water (see Figure 4).
Technologies are improving, however, and it is likely that at some point offshore
wind farms will be similar or cheaper than onshore wind farms, at which point their
higher capacity will likely make them more appealing (Kaldellis & Kapsali, 2013).
Offshore wind farms are also a somewhat new technology. In rapidly developing
countries such as China, there is an obvious interest in constructing more offshore
wind farms, but many supply chain gaps and lack of infrastructure is preventing
these projects from getting started (Poulsen & Lema, 2017). In some cases such as
EU, legislative restrictions are holding back progress on offshore developments
(Poulsen & Lema, 2017).
Unfortunately for both types of wind farms, there are still many fossil fuel
alternatives which are far cheaper than wind power in the short term (Li, Peng, &
Sun, 2014), but the development of new technologies should help to make it a
competitive, clean, safe, and renewable energy option (Zheng et al., 2016).
Conclusion
Offshore wind farms are currently lagging behind onshore wind (see Figure 5)
developments primarily due to economic factors (Blanco, 2009), but it is clear that
these differences will not be as significant for much longer. As technologies
improve, offshore wind developments in areas with stronger and more stable winds
are likely to become more common when it becomes cheaper to build and maintain
them (Kaldellis & Kapsali, 2013).
The adverse health and environmental effects of onshore wind farm developments
are likely to be a key factor in influencing countries to explore offshore wind
developments as the cost of these two different types of wind farms becomes more
comparable (Nissenbaum et al., 2012).
The global eolic energy industry had its second-best year in 2021, according to
the Global Wind Energy Council (GWEC), with almost 94 GW of capacity added
globally, trailing behind the 2020’s record growth by only 1.8%. The total global
wind power capacity is 837 GW.
Europe, Latin America, Africa & Middle East had record years for new onshore
installations. Whereas 2021 was the best year in offshore wind history, bringing its
market share in global new installations to 22.5%. China installed 80% of the new
offshore wind capacity in 2021.
Onshore wind energy and offshore wind energy have similarities and differences.
Their share of total energy production is steadily rising (in the next five years, wind
power capacity is expected to increase by 557 GW). At Crosby Airpes, we have
been helping to build wind farms, both on land and at sea, for almost 20 years. We
are going to analyze the challenges involved in working in each environment.
Discover our Wind Energy solutions
Onshore and offshore wind energy: growing markets
Did you know that the average power produced by an onshore wind turbine is
between 6 and 7 MW, while offshore wind turbines can reach 10 MW?
This difference is due to the environment in which the wind farms are located. The
offshore wind’s speed is higher as there are no natural barriers to stop it, which
allows the wind turbines to be bigger.
Still, the main difference between onshore and offshore energy is their uneven
market penetration.
Both markets are increasing every year, making working on new projects possible,
both offshore and onshore. What challenges do we face at Crosby Airpes when
working on each one?
Offshore wind farms: the challenge of working at sea
Offshore wind farms are mega-structures built at an average distance of 41
kilometers from the coast and settled at an average depth of 27.5 meters (source:
WindEurope).
This means several engineering challenges: How are the wind turbine parts
transported to the wind farm? How is the nacelle placed on the tower? And how are
the blades assembled?
Having the right lifting equipment is essential for the success of the project. For
example, one of the biggest challenges is placing the nacelle on the tower. Weather
conditions at sea can be complicated: waves, wind, etc. That is why precision is vital.
Look at how we designed, tested, and implemented a specific lifting system for these
situations: Handling and transport of nacelles in WTG Towers.
Onshore wind farms: the challenge of facing gravity
An average onshore wind turbine produces around 2.5 to 3 megawatts (MW)
compared to the offshore average of 3.6 MW. But onshore wind farms are much
more extended.
Onshore wind farms don’t have to face the waves, but they account for more than
90% of the world’s wind energy production. That is why their equipment’s
maintenance is vitally important.
Setting up an onshore wind farm presents many challenges. Some of the most
important are:
 Adapting the construction to the orography
 Having the equipment always ready.
Onshore vs. Offshore Wind: What Are the Differences and Facts?
The wind is a natural source of energy and, one of the most reliable ones. As long as
there is wind, it means that we have a source of renewable power. Therefore, today,
we will focus on onshore vs. offshore wind, to help us understand what their
difference is and which one is best for wind power harvesting.
AD
As more effort is being put to increase the use of renewable energy sources, as well
as finding ways to preserve our environment, wind plays a major role. The wind
energy industry has again and again proven to be a significant player in offering
energy to many people.
Since the first onshore wind turbine was built in the late 1800s, up to the time when
offshore harvesting was established in 1992, much development has taken place in
this industry.
However, there is still much to do if we want to see this industry grow and to supply
electricity to even more people.
But firstly, let see the definitions of onshore vs. offshore wind, to understand the
distinction.
AD
Onshore vs Offshore Wind
Onshore wind is the one that blows from the sea towards the land. On the other
hand, offshore wind is the type of wind that blows from the land towards the sea.
The winds usually occur due to differences in pressure, in the atmosphere. For
example, when there exists a difference in pressure within the atmosphere, air will
shift from areas with higher pressure to areas with lower pressure. This, in return,
results in the creation of winds at various speeds.
AD
These effects are what takes place during the sea breeze and land breeze. For
instance, if the atmospheric pressure is high, and with a clear sky, the land warms
up in the daytime and gets cold by nighttime. The result of this is that wind will blow
from the sea at daytime towards the land, while at night, it will blow from the land
towards the sea.
Since our planet is also in constant rotation, the Coriolis effect also deflects the air.
The deflection can take place in any part of the globe with the exception of places
on the equator.
Wind Power Harvesting
For the longest time, onshore wind turbines have been dominant in the wind power
harvesting process. This is because the offshore turbines were just introduced almost
a century later in 1992, with the first offshore wind farm being set up in Denmark.
AD
The introduction of offshore turbines was a result of necessity which was brought
about by the effect we refer to as wind shadow. This occurs when turbines reduce
the wind’s strength as it travels downstream. Therefore, there was a need to find an
alternative source of stronger winds, and offshore winds became a target.
The winds out in the ocean are much stronger and consistent that the winds on land.
This made it necessary to improve the wind turbines technology and use it in the
ocean where they can produce more power. Many more countries now make use of
offshore wind farms since its initial introduction in Denmark.
However, although numerous nations have embraced the use of offshore technology,
most of the offshore farms are still found in Europe. Based on a report by Global
Wind statistics in 2014, Europe holds around 90% of these offshore wind farms.
AD
In the United States, onshore wind energy is more prevalent in the Midwest region
of the US. On the other hand, offshore wind energy has become more dominant in
the coastal states of the US.
Use our wind turbine calculator to determine the power of a each turbine and how
many turbines you would need for a particular project.
And, although many may assume that when looking at onshore vs. offshore wind,
the difference is only in where we set up the turbines, there is much more than that.
The two types of wind power sources are different in multiple ways, with each
having their own pros and cons.
Onshore Wind Overview
How Onshore Wind Energy Works
Just as the name goes, wind energy is energy that results from the transformation of
air currents, into electricity. To utilize the wind that blows over the land, we must
build wind farms that can extract optimum power from the wind. Wind farms found
on the land are what we refer to as onshore wind farms.
AD
To enable this, the wind farms consist of large wind turbines that will help to
transform the wind’s kinetic energy into electricity. This is how an onshore wind
turbine works to produce electricity.






The first step in this process is where the wind makes the blades of the turbine
to rotate. These blades connect to the turbines through a hub.
The blades, together with the blades, rotate at a similar speed of seven to
twelve turns every minute.
A gearbox, on the other hand, increases this speed to over 100 times. From
there, it also transforms the speed into a high-speed shaft.
With a speed of over 1500 revolutions every minute, this high-speed shaft
transmits the speed to a generator.
When this speed gets into the generator, the generator works to convert the
mechanical power from the shaft into electrical power.
Since the power is in a direct current form, a converter then transforms this
DC into AC.




From there, a transformer then increases the voltage to between 20 and 66 kV,
which makes it possible to transmit this current through the onshore wind
farm.
The next step is to transport the electricity through medium voltage cables and
take it to a substation.
After reaching the substation, the energy is again transformed into a highvoltage current of +132 kV.
From here, an evacuation line transports the electricity to the distribution
network, which in turn carries it to the consumption points (homes).
Pros of Onshore Wind Energy







Since onshore wind energy has been in use for the longest time, people have
grown more familiar with it. For this reason, many nations still prefer to use
onshore wind energy. For example, even Denmark, which established the first
offshore turbines, still get the majority of their wind power from onshore
farms (75% of their total wind energy).
In terms of cost, the infrastructure necessary for electricity transmission in
onshore is significantly cheaper than that in offshore turbines. Due to the
affordable cost, offering the power to the consumers is also cheap, which
makes it a more popular source of renewable power.
Companies producing onshore turbines are located in the land, and therefore,
if wind farms are set up near the companies, it can be economical. These
companies will also boost the economies of the areas they are situated at.
There will be fewer emissions as a result of transporting the wind structures
in onshore farms. This is because most farms can be set up near the
manufacturing companies.
Onshore wind, in most cases, will attract investment in the area. This is
because various projects will be started near the wind farm, which will, in
turn, create a chain of other businesses.
Onshore wind is a source of renewable energy, and unlike many other power
generation plants, this one doesn’t consume water.
The onshore wind turbines have minimal maintenance costs.
Cons of Onshore Wind

The speeds of onshore wind are unpredictable, more than in offshore. The
inconsistencies in the wind speeds will cause inefficiency with the turbines,
especially when the speeds are too low, or even too fast.



Not only does onshore wind differ in speeds, but the directions also vary more
often. For the turbines to function efficiently, they should face the direction
of the wind. If the direction keeps on changing, it will negatively affect the
efficiency of the turbines.
Some people work against the growth of onshore wind farms claiming they
are a danger to birds, or that they are a noise nuisance. However, there is little
or no evidence to support these claims.
They generate lesser energy than their offshore counterparts. For example, an
average onshore wind turbine produces around 2.5 to 3 megawatts while an
offshore one produces an average of 3.6 megawatts.
Offshore Wind Overview
This type of wind harvesting came into existence nearly 100 years after the invention
of onshore wind energy. For this reason, technology is yet to gain as much popularity
as its predecessor.
AD
However, after their first establishment in Denmark, multiple other nations have
made significant strides towards its development.
How Offshore Wind Energy Works
Wind harvesting here is done through erecting offshore wind turbines deep into the
ocean. The process is as follows:
The initials steps of offshore wind energy, are similar to the ones of the onshore
wind energy. The differences arise almost in the middle of the process.






The first step in this process is where the wind makes the blades of the turbine
to rotate. These blades connect to the turbines through a hub.
The blades, together with the blades, rotate at a similar speed of seven to
twelve turns every minute.
A gearbox, on the other hand, increases this speed to over 100 times. From
there, it also transforms the speed into a high-speed shaft.
With a speed of over 1500 revolutions every minute, this high-speed shaft
transmits the speed to a generator.
When this speed gets into the generator, the generator works to convert the
mechanical power into electrical power.
From here, the electricity generated is taken down using the interior of the
tower.





Since the power is in a direct current form, a converter then transforms this
DC into AC.
After the conversion into alternating current, a transformer increases the
voltage to between 33 kV and 66 kV, to enable transportation across the
offshore wind farm.
The electricity is then carried to a substation, by the use of underwater cables.
After it reaches the substation, this electricity is again transformed into a highvoltage current of over 150 kV.
The last step is to transport the electricity through a distribution network up
to the consumers’ homes.
To better comprehend the topic on onshore vs. offshore wind turbines, here are some
advantages and disadvantages of offshore wind.
AD
Pros of Offshore Wind





Offshore wind turbines have proven to be more efficient as compared to the
onshore turbines. This is because the speed of these winds is high, and they
are consistent in terms of direction. For this reason, you will require fewer
turbines to produce the same capacity of energy than through onshore
turbines.
Offshore wind turbines are far away into the ocean. This means that they don’t
cause any disruption in human activities. They are miles away from the coast,
such that you can’t see them, leave alone feel their existence.
They don’t interfere in any way with the land as they are set up far away from
coastlines.
The offshore wind farms can, in some instances, help to protect the
inhabitants of that area (marine life). Since they restrict access to areas where
they are set up, they tend to protect the marine ecosystem around.
Just like with the onshore wind farms, they are a source of renewable energy.
Also, they do not use up water like other power plants, and they provide job
opportunities.
Cons of Offshore Wind

Although the turbines are more efficient, the process through which the
electricity reaches the land and to the public is expensive. The necessary
technology for the transportation of electricity from the turbines is way costly
than in onshore turbines.





Due to strong winds and waves, the offshore turbines have to endure more
wear and tear. The result of this is a high cost of maintenance which continues
to increase the gap between offshore and onshore wind costs.
Because offshore turbines are harder to get to, it could take longer to fix
problems and restore them to function properly.
Unlike in other new energy developments which through Renewable energy
cooperatives, minor-town citizens can invest in, offshore farms don’t allow.
Although not necessarily a disadvantage, the effects the offshore wind farms
have on marine life, as well as birds are not comprehensively understood. This
brings uncertainty on whether the project is the better option.
When we build offshore wind farms near to the coastline even up to 26 miles,
they might be visible from the coast. This may affect tourism and other
activities. They may be unpopular to investors which may affect the property
prices of the area.
These pros and cons helps to bring more clarity on the issue of onshore vs. offshore
wind. we cannot understand the two concepts without looking at their strong points,
as well as their weak points.
AD
Conclusion On Onshore Vs. Offshore Wind
From the much research done to come up with this article, it’s evident that onshore
wind energy is still widely used than the offshore wind. Even with the numerous
advantages that come with offshore wind, onshore is still the preferred choice. I hope
that from this article about onshore vs. offshore wind, you can clearly see the
distinction between the two.
How do offshore and onshore wind farms work?
First of all, it’s useful to go back to basics and explain how a wind turbine works.
As the wind turns the carbon-fibre blade on the unit, a motor turns, which
transforms kinetic energy into electricity. This energy is transferred to the gearbox,
which converts the slow speed of the spinning blades into higher-speed rotary
motion—turning the drive shaft quickly enough to power the electricity generator.
Wind farms can be based onshore (on land) or offshore (sea or freshwater), with key
differences between the two. Below, we take a look at some of the advantages and
disadvantages of each.
What is offshore wind?
Offshore wind power, also referred to as offshore wind energy, is when wind over
open water, usually in the ocean, is used to generate power. Wind farms are
constructed in bodies of water where higher wind speeds are available.
Advantages of offshore wind:





Windmills can be built that are larger and taller than their onshore
counterparts, allowing for more energy collection.
They tend to be far out at sea, meaning they are much less intrusive to
neighbouring countries, allowing for larger farms to be created per square
mile.
Typically out at sea, there is a much higher wind speed/force allowing for
more energy to be generated at a time.
Wind farms seem to have a relatively neutral impact on their surrounding
environment. They are not built in shipping lanes, fishing areas or in delicate
environments.
There are no physical restrictions such as hills or buildings that could block
the wind flow.
Disadvantages of offshore wind:



The biggest disadvantage of an offshore wind farm is the cost. Offshore wind
farms can be expensive to build and maintain and because of their hard to
reach locations, they are susceptible to damage from very high-speed winds
during storms or hurricanes which is expensive to repair.
The effect of offshore wind farms on marine life and birds are not yet fully
understood.
Offshore wind farms that are built closer to coastlines (generally within 26
miles) can be unpopular with residents as it can affect property values and
tourism.
What is onshore wind?
Onshore wind power refers to turbines that are located on land and use wind to
generate electricity. They are generally located in areas where there is low
conservation or habitat value.
Advantages of onshore wind:



The cost of onshore wind farms is relatively cheap, allowing for mass wind
turbine farms.
The shorter distance between the windmill and the consumer allows for less
voltage drop off on the cabling.
Wind turbines are very quick to install. Unlike a nuclear power station, which
can take over twenty years, a wind turbine can be built in a matter of months.
Disadvantages of onshore wind:



One of the biggest issues of onshore wind farms is that many deem them to
be an eyesore on the landscape.
They don’t produce energy all year round due to often poor wind speed or
physical blockages such as buildings or hills.
The noise that wind turbines create can be compared to that of a lawnmower,
often causing noise pollution for nearby communities.
Which is best, onshore or offshore wind?
When deciding between onshore or offshore wind, there are many variables as to
which type of wind farm is chosen by energy suppliers, including political, financial,
and geographical factors. Generally, whether one or the other is used is assessed on
a case by case basis.
What is clear is that wind power is increasing in popularity around the world as the
technology becomes more financially sustainable and global policies and targets on
climate change are created. At the end of 2018, the installed wind capacity across
the world reached 597 GW which was an increase of 18% compared with 2017.
Once more, many countries outside of the traditional energy markets of Europe and
North America are driving the trend. At the end of 2018, China accounted for
roughly 34% of global installed wind power capacity, roughly the same as the whole
of Europe.
NES Fircroft and wind power
NES Fircroft is an experienced staffing provider to the renewable energy
industry and we are currently solving staffing challenges for our clients all across
the globe. If you have an onshore or offshore wind energy staffing requirement, get
in touch with our experts today.
We are already working on some of the world’s most exciting renewables projects
and we’re experts at finding the right placements for the right candidates. Wherever
your expertise lies, we have plenty of renewable energy job opportunities for skilled
engineers looking to enhance their career.
Wind power is one of the fastest-growing renewable energy technologies. Usage is
on the rise worldwide, in part because costs are falling. Global installed windgeneration capacity onshore and offshore has increased by a factor of almost 75 in
the past two decades, jumping from 7.5 gigawatts (GW) in 1997 to some 564 GW
by 2018, according to IRENA's latest data. Production of wind electricity doubled
between 2009 and 2013, and in 2016 wind energy accounted for 16% of the
electricity generated by renewables. Many parts of the world have strong wind
speeds, but the best locations for generating wind power are sometimes remote ones.
Offshore wind power offers tremendous potential.
Wind turbines first emerged more than a century ago. Following the invention of the
electric generator in the 1830s, engineers started attempting to harness wind energy
to produce electricity. Wind power generation took place in the United Kingdom and
the United States in 1887 and 1888, but modern wind power is considered to have
been first developed in Denmark, where horizontal-axis wind turbines were built in
1891 and a 22.8-metre wind turbine began operation in 1897.
Wind is used to produce electricity using the kinetic energy created by air in motion.
This is transformed into electrical energy using wind turbines or wind energy
conversion systems. Wind first hits a turbine’s blades, causing them to rotate and
turn the turbine connected to them. That changes the kinetic energy to rotational
energy, by moving a shaft which is connected to a generator, and thereby producing
electrical energy through electromagnetism.
The amount of power that can be harvested from wind depends on the size of the
turbine and the length of its blades. The output is proportional to the dimensions of
the rotor and to the cube of the wind speed. Theoretically, when wind speed doubles,
wind power potential increases by a factor of eight.
Wind-turbine capacity has increased over time. In 1985, typical turbines had a rated
capacity of 0.05 megawatts (MW) and a rotor diameter of 15 metres. Today’s new
wind power projects have turbine capacities of about 2 MW onshore and 3–5 MW
offshore.
Commercially available wind turbines have reached 8 MW capacity, with rotor
diameters of up to 164 meters. The average capacity of wind turbines increased from
1.6 MW in 2009 to 2 MW in 2014.
Wind Energy Data.
According to IRENA's latest data, the production of wind electricity in 2016
accounted for a 6% of the electricity generated by renewables. Many parts of the
world have strong wind speeds, but the best locations for generating wind power are
sometimes remote ones. Offshore wind power offers tremendous potential.
Wind energy
Wind energy is a form of solar energy.[1] Wind energy (or wind power) describes the
process by which wind is used to generate electricity. Wind turbines convert the
kinetic energy in the wind into mechanical power. A generator can convert
mechanical power into electricity[2]. Mechanical power can also be utilized directly
for specific tasks such as pumping water. The US DOE developed a short wind
power animation that provides an overview of how a wind turbine works and
describes the wind resources in the United States.
Contents
[hide]








1Wind Energy Basics
o 1.1Equation for Wind Power
2DOE Wind Programs and Information
3Worldwide Installed Capacity
o 3.1United States Installed Capacity
4Wind Farm Development
5Necessary Services to Avail
6Land Requirements
7Related Links
8References
Wind Energy Basics
Wind is caused by the uneven heating of the atmosphere by the sun, variations in the
earth's surface, and rotation of the earth. Mountains, bodies of water, and vegetation
all influence wind flow patterns[2], [3]. Wind turbines convert the energy in wind to
electricity by rotating propeller-like blades around a rotor. The rotor turns the drive
shaft, which turns an electric generator. Three key factors affect the amount of
energy a turbine can harness from the wind: wind speed, air density, and swept
area.[4]
Equation for Wind Power

Wind speed
The amount of energy in the wind varies with the cube of the wind speed, in
other words, if the wind speed doubles, there is eight times more energy in the
wind (
). Small changes in wind speed have a large impact
on the amount of power available in the wind [5].

Density of the air
The more dense the air, the more energy received by the turbine. Air density
varies with elevation and temperature. Air is less dense at higher elevations
than at sea level, and warm air is less dense than cold air. All else being equal,
turbines will produce more power at lower elevations and in locations with
cooler average temperatures[5].
Swept area of the turbine
The larger the swept area (the size of the area through which the rotor spins),
the more power the turbine can capture from the wind. Since swept area

is
, where r = radius of the rotor, a small increase in blade length
results in a larger increase in the power available to the turbine[5].
DOE Wind Programs and Information

DOE's Wind Energy Technologies Office works to improve the
performance, lower the costs, and accelerate the deployment of
innovative wind and water power technologies. Greater use of the
nation's abundant wind and water resources for electric power
generation will help stabilize energy costs, enhance energy security,
and improve our environment[6].

WINDExchange is a nationwide initiative designed to increase the use
of wind energy across the United States by working with regional
stakeholders.
The WINDExchange program
illustrates
the Department of Energy's commitment to dramatically increase the
use of wind energy in the United States. The WINDExchange
website provides a wide range of wind-related information, including:
State-by-state breakdowns of wind resource potential, success stories,
installed wind capacity, news, events, and other resources, which are
updated regularly[7].

The National Wind Technology Center (NWTC) is the nation's
premier wind energy technology research facility. The goal of the
research conducted at NWTC is to help industry reduce the cost of
energy so that wind can compete with traditional energy sources,
providing a clean, renewable alternative for our nation's energy needs.
Worldwide Installed Capacity
Country
Total Capacity,
end of 2014
(MW)[8]
Total Capacity,
June
2010
[9]
(MW)
Total Capacity,
end of 2009
(MW)[10]
U.S.
65,900
36,300
35,159
China
114,600
33,800
25,853
Germany
40,000
26,400
25,813
Spain
23,000
19,500
18,748
India
22,500
12,100
10,827
France
9,300
5,000
4,775
Country
Total Capacity,
end of 2014
(MW)[8]
Total Capacity,
June
2010
[9]
(MW)
Total Capacity,
end of 2009
(MW)[10]
U.K
12,200
4,600
4,340
Portugal
4,953
3,800
3,474
Denmark
4,883
3,700
3,408
United States Installed Capacity
In the U.S., installed wind energy capacity has advanced significantly over
the past ten years. As of the third quarter of 2017, the U.S. now has an
installed wind capacity of 84,944 MW with over 29,634 MW of wind
currently under construction or in advanced development—a 27% yearover-year increase, the highest since the American Wind Energy
Association began tracking the categories.[11].
Wind Farm Development
Siting a wind farm varies from one location to another, but there are some
important matters for land owners to consider:[12]
1. Understand your wind resource
2. Evaluate distance from existing transmission lines
3. Determine benefits of and barriers to allowing your land to be
developed
4. Establish access to capital
5. Identify reliable power purchaser or market
6. Address siting and project feasibility considerations
7. Understand wind energy’s economics
8. Obtain zoning and permitting expertise
9. Establish dialogue with turbine manufacturers and project
developers
10.Secure agreement to meet O&M needs
Necessary Services to Avail
Wind power project or WPP involves development through own resources
and manpower or by availing the technical services from consultant
organisations:[13]
1. SITE IDENTIFICATION: The process starts with regional
overviews and precision GIS mapping, through which the specific
opportunities are determined at a feasible site. This also involves
mapping of project boundaries, turbine micro-siting and
optimisation.
2. WIND RESOURCE ASSESSMENT: Accurate Wind Resource
Assessment of a widely variable resource is the most critical
feature for success of a WPP. Meso-Scale and then Micro-Scale
Wind Power Density/Wind Speed Map is produced for the site
location through input of accurate contour/terrain data. Ideal spot
is selected to install Anemometry System. The recorded wind data
is critically analyzed and formatted to represent wind
characteristics. A preliminary wind resource assessment can be
carried out by using the freely available Global Wind Atlas.
3. MICRO-SITING & ENERGY ESTIMATION: This constitutes the
foundation of a Wind Power Project. Wind Resource data is
formatted in terms of Speed and direction. The characteristic power
of selected Wind Electric Generator (WEG) is formatted. Detailed
Contour data at close interval is prepared indicating roughness and
terrain features. WEG layout is optimised and Micro-siting Map is
prepared using software and then estimated is energy generation.
4. DETAILED PROJECT REPORT: Once the site, make and rating
of WEG and the selling option are finalized, detailed survey and
field study is conducted. Comprehensive layout design is prepared
with optimization of generation along with detailed design for
approach road and grid evacuation. Detailed costing and financial
analysis is carried out to establish overall viability.
5. PROJECT MANAGEMENT: Implementation and Management of
Wind power project, WPP, calls for Multi-disciplinary activities
related to Technical, Financial and Commercial aspects. Not only
quality of works needs to be checked, it is equally important to
ensure close co-ordination and monitoring for timely
commissioning.
6. MONITORING: Energy generation with respect to wind resource,
frequency and type of machine and system failures needs to be
critically monitored and analyzed to optimize generation. Income
from WPP can be optimized only if break down and failure of
WEG and evacuation system is avoided particularly during the
limited high wind months.
7. PERFORMANCE IMPROVEMENT: For the existing Wind
Power projects also there is often need to ensure its performance
improvement, which goes down with time. Critical analysis of
monitoring reports along with on-site observations and in depth
study immensely help in performance improvement through
reduction in break-down time and interval losses. Due to seasonal
availability of wind resource, generation increasing in cubic
proportion of wind speed and overall low Plant Load Factor,
parameter setting and operational/control logic needs to be site
specific.
8. LENDER'S ENGINEERS: To meet the need of expert engineers to
serve a project especially for a definite term or contract, where the
task may not be managed with the available resources, the clients
are provided Lenders Engineer’s services as per the requirements
assessed mutually with the client. This involves serving through
deputing or appointing suitable personnel and thus meeting the
need of the project at a given point of time of various technical
types.
Land Requirements
The amount of land required for a wind farm varies considerably, and is
particularly dependent on two key factors: the desired size of the wind
farm (which can be defined either by installed capacity or the number of
turbines) and the characteristics of the local terrain[14]. Typically, wind
turbine spacing is determined by the rotor diameter and local wind
conditions. Some estimates suggest spacing turbines between 5 and 10
rotor diameters apart. If prevailing winds are generally from the same
direction, turbines may be installed 3 or 4 rotor diameters apart (in the
direction perpendicular to the prevailing winds); under multi-directional
wind conditions, spacing of between 5 and 7 rotor diameters is
recommended
Abstract
Wind energy, which is produced by wind power, refers to the process of creating
electricity using the wind, or air flows that occur naturally in the earth's atmosphere.
Modern wind turbines are used to capture kinetic energy from the wind and generate
electricity. A windmill converts the energy in wind into electrical energy or
mechanical energy to pump water or grind cereals. The most common windmills in
operation today generate power from three-blade, horizontal-axis windmills with the
nacelle mounted on steel towers that can be cylindrical steel plate or lattice towers.
This modern windmill concept has grown since 1977 and has become the industrial
standard.
4.12 Advantages and disadvantages
4.12.1 Advantages
 Wind energy is environment friendly as no fossil fuels are burnt to
generate electricity from wind energy.
 Wind turbines take up less space than the average power station.
 Modern technologies are making the extraction of wind energy much
more efficient. Wind is free, so only installation cost is involved and
running costs are low.
 Wind energy is the most convenient resource to generate electrical
energy in remote locations, where conventional power lines cannot be
extended due to environmental and economic considerations.
4.12.2 Disadvantages
 The main disadvantage of wind energy is varying and unreliable wind
speed. When the strength of the wind is too low to support a wind
turbine, little electricity is generated.
 Large wind farms are required to generate large amounts of electricity,
so this cannot replace the conventional fossil fueled power stations.
Wind energy can only substitute low energy demands or isolated low
power loads.
 Larger wind turbine installations can be very expensive and costly to
surrounding wildlife during the initial commissioning process.
 Noise pollution may be problem if wind turbines are installed in the
densely populated areas.
The power generating technologies
Wind energy is the second most significant renewable technology after hydropower
in terms of electricity production. Global output from onshore wind turbines in 2019,
according to the IEA, was 1202 TWh while offshore wind farms provided a further
66 TWh, for a total of 1268 TWh. Meanwhile figures from the Global Wind Energy
Council (GWEC)12 indicate that total installed capacity for wind energy in 2018 was
591 GW, of which 568 GW was onshore and 23 GW was offshore. The total
capacity rose to 651 GW at the end of 2019.
Wind energy, the energy contained in a mass of moving air, is available in most parts
of the world but the size of the resource will vary from place to place depending on
the wind regime. Wind energy can be harvested on land and at sea. The offshore
resource is generally the most consistent, the most reliable and able to supply the
highest energy intensity. Onshore wind resources are more variable because the wind
must travel over a land mass and it will be affected by the contours of the land and
by the ground cover. However all wind is dependent on the prevailing weather
conditions and this leads to considerable variations in availability. Sometimes the
wind blows intensely and sometimes it does not blow at all. This means that wind
power is probably the most variable and the most unpredictable of all the renewable
energy sources. Wind output reliability can be improved by coupling wind farms
that are widely spaced geographically, in effect averaging output over a large area.
Even so it is still possible for a whole region to become becalmed at times. Wind
energy must therefore be supported by other forms of generation or by energy
storage in order for it to provide a manageable resource. Wind and solar power can
be complementary since the wind blows more strongly during winter while solar
power is most intense during the summer. The management of wind output is one of
the most challenging aspects of grid management today.
Wind energy is captured by wind turbines. When the wind industry was young, in
the 1980s and early 1990s, there were a variety of wind turbine designs in use but
the range has gradually narrowed so that today the market is dominated by a single
type, the three blade horizontal axis wind turbine, with the turbine and its generator
sitting on top of a tall tower. Wind strength increases with height so the higher the
tower, the more energy can be collected at any given site. The sophistication and
reliability of wind turbines has increased enormously since the pioneer days and new
wind turbines can be expected to deliver power over a lifetime similar to that of other
types of power generation.
There are two branches or families of wind turbines, onshore turbines and offshore
turbines. Today the differences between the machines used for each are slight. Most
significant is size, with offshore turbines tending to be larger than those used
onshore. This is partly a matter of practicality. Transporting and erecting a very large
turbine onshore can be very challenging in many locations whereas the are no limits
offshore, provided only that vessels are available that can carry and install them.
However, installation of turbines offshore is much more difficult than onshore and
more costly. It is therefore more cost effective to install the largest turbine possible
at an offshore site. Typical onshore wind turbines have generating capacities of up
to 4 MW. Offshore, 6–8 MW is more typical of the capacity range, while turbines
with generating capacities of 10–12 MW are expected to enter the market for the
beginning of the third decade of the century. The main market for offshore wind is
in European waters but China has been expanding its offshore wind capacity in
recent years too.
The cost of wind energy has fallen dramatically over the last decade and over the
5 years to the end of 2019, the cost of both onshore and offshore wind had fallen on
average by more than 50%, according to the GWEC. This has made onshore wind
generation easily competitive in terms of cost with fossil fuel generating
technologies and offshore wind is likely to be in the same position in the near future.
Unfortunately the unpredictability of wind power often still leaves it at a
disadvantage. One potential means of remedying this is to combine wind power with
some form of energy storage. This will increase the overall capital cost of a facility
but by increasing its reliability, makes the energy it produces more valuable. Various
schemes are being explored including using offshore wind power to produce
hydrogen which can then be shipped ashore and used as a green energy source.
The green environmental credentials of wind power make it attractive as a means of
combatting global warming and most countries are building up wind capacity, some
faster than others. However, it is not entirely benign. Onshore wind turbines are large
additions to any landscape and they are not always welcomed by their human
neighbours. This can be problematic when obtaining permits to construct wind farms
onshore. There has also been an issue in the past with the danger of wind turbines to
birds. However, the slow rotational speed of large modern wind turbines makes this
less of a problem today. Noise, too, can be a problem onshore so it is not usually
possible to erect wind turbines close to dwellings. Onshore construction is less of
a problem in countries such as the United States and China where are wide expanses
of uninhabited territory that can be used for wind generation. Offshore wind
experiences few problems in this respect.