Expert AdviceWelcome to Energy Guru®
Oct 6, 07
Wind Energy – A Viable Source
Wind power is one of the most efficient alternative energy sources to
combine with solar, especially out in the middle of a total
self-sustainability project. Because when there is sun; there isn’t always
wind, but when there is wind, there isn’t always sun, so the two systems
(solar/wind) seem to be compliment with each other.
Wind energy is now attractive for many reasons – it is renewable, clean and scalable.
A bright future for wind energy
The
economics of wind energy are already strong, despite the relative youth of
the industry. The downward trend in costs is predicted to continue. The
strongest influence will be exerted by the downward trend in wind turbine
prices. As the world market in wind turbines continues to boom, wind turbine
prices will continue to fall.
The global wind energy market is expanding rapidly, creating opportunities for employment through the export of wind energy goods and services.
For
additional information please refer to DoE’s excellent resource on Wind
Energy: http://www1.eere.energy.gov/windandhydro/
Uses of Wind Energy Systems
Wind energy systems are a very
reliable and versatile technology which have been used for hundreds of years
for different purposes.
Water
Pumping
The wind has been used as a
reliable and inexpensive water pumping power source for generations. Either a
mechanical or electric water pumping system could be ideal for rural and
remote locations to supply livestock, a household or even a small community.
Recreation
Using the wind as an energy
source for your cottage or boat could be efficient and inexpensive when
compared to fossil fuel generators. An environmentally friendly wind energy
system could power lights, radios and small appliances.
Farm and
Ranch
Used for centuries by farmers to
pump water, today's wind energy systems can do much more for a modern
agricultural operation. Because they are ideal where remote, low voltage
power is required, wind energy electrical generators are used for such farm
systems as electric fences and yard lights.
Home Use
Rural home owners who want to
help reduce the environmental impact of their energy use can reduce their
reliance on grid power with a wind energy system. Even a mini wind energy
system saves electricity generated from fossil fuels or nuclear energy.
Remote
Communities
In remote communities where
diesel generators often supply electricity, the use of wind energy not only
makes environmental sense, it makes economic sense. Larger wind energy
systems can reduce reliance on expensive and greenhouse gas-producing
generators.
An expert on wind energy systems can help you assess your power
requirements and determine if a wind energy system is feasible for your
location.
Wind Energy Technology
Wind turbines take common wind power and convert it into electrical wind
energy. The wind turns the blades that crank the shaft which spins a magnet
inside a housing that creates an alternating electromagnetic field, and thus
electricity. The more wind the more spins and the more electricity a wind turbine
will produce. Most wind turbines used on a commercial level are built with
aerodynamics and make the most of the wind power they conduct.
Types of wind turbines
Wind turbines are categorized according to a number of criteria:
The position of the axis (horizontal or vertical) is obvious.
Horizontal axis wind turbines (HAWTs) can be further divided into those with
rotors rotating in front of the tower (windward) and those rotating behind
the tower (leeward) vis-à-vis the direction of the wind. The tip speed ratio
and the number of blades determine the response of the drive, and hence how
the wind turbine can be used.
In modern wind turbines that generate electricity, there are
different types of nacelles that turn on top of the tower to face the wind.
There are turbines with gearboxes and without and nacelles whose components
(bearings, gears, generator) are positioned separately or have multiple
functions integrated in one component (bedding of rotor shaft in the
gearbox).
Poles (generally guyed) are usually only used for small wind turbines
(up to 10 kW). Free-standing towers are either steel or concrete tubular towers
or pylons.
Economics of Wind Energy
Systems:
A
totally free market - where all methods of making electricity compete on the
same level - does not exist anywhere. In every country the price of
electricity depends not only on the cost of generating it, but also on the
many different factors that affect the market, such as energy subsidies and
taxes.
The cost of generating electricity comprises of
- capital
costs (the cost of building the power plant and connecting it to the
grid)
- running
costs (such as buying fuel and operation and maintenance) and
- the cost of
financing (how the capital cost is repaid)
With
wind energy, and many other renewables, the fuel is free. Therefore once the
project has been paid for, the only costs are operation and maintenance and
fixed costs, such as land rental. The capital cost is high, between 75% and
90% of the total for onshore projects.
The
capital cost breakdown of a typical 5 MW onshore project is shown below.
What
influences the costs?
There
are two main influences which affect the cost of electricity generated from
the wind, and therefore its final price:
- technical
factors, such as wind speed and the nature of the turbines
- the
financial perspective of those that commission the projects, e.g. what
rate of return is required on the capital, and the length of time over
which the capital is repaid.
1)
Technical factors
The more
electricity the turbines produce the lower the cost of the electricity. This
depends on:
a.
The windiness of the site
The power available from the wind is a function of the cube of the
wind speed. Therefore if the wind blows at twice the speed, its energy
content will increase eight fold. In practice, turbines at a site where the
wind speed averages eight metres per second will produce around 80% more
electricity than those where the average wind speed is six metres per second.
Figure below shows how generation cost varies with wind speed.
- Wind turbine availability
This is the capability to operate when the wind is available. This is typically 98% or above for modern European machines. - The way the turbines are arranged
Turbines in wind farms must be arranged so that they do not shadow each other.
2)Financial perspective
The economics of grid connected wind power depend very much upon the
perspective taken. How quickly investors want their loans repaid and what rate
of returns they require can affect the feasibility of a wind project: a short
repayment period and a high rate of return pushes up the price of electricity
generated, as shown below.
How the
cost of wind energy varies with wind speed and rate of return on capital
NB. The cost of wind energy has fallen since these figures were calculated,
nevertheless the graph shows an indication of how wind speed and interest
rates influence the cost.
Public
authorities and energy planners tend to assess different energy sources on
the basis of the levelised cost. These calculations do not depend upon
variables such as inflation or taxation system. However, the perspective of private
investors or utilities is different, and takes into account the variables
introduced by government policy and shifts in financial and foreign exchange
markets. These investors make decisions on project cash-flow and payback
time.
Public
authorities and energy planners require the capital to be paid off over the
technical lifetime of the wind turbine, i.e. 20 years, whereas the private
investor would have to recover the cost of the turbines during the length of
the bank loan. The interest rates used by public authorities and energy
planners would typically be lower than those used by private investors.
Why is
the cost coming down?
Although
the cost varies between different countries, the trend everywhere is the same
- wind energy is getting cheaper. The cost is coming down for various
reasons. The turbines themselves are getting cheaper as technology improves
and the components can be made more economically. The productivity of these
newer designs is also better, so more electricity is produced from more
cost-effective turbines. There is also a trend towards larger machines. This
reduces infrastructure costs, as fewer turbines are needed for the same
output.
The cost
of financing is also falling as lenders gain confidence in the technology.
Wind power should become even more competitive as the cost of using
conventional energy technologies rises.
The
figure below shows how the cost of wind energy has fallen under the
Non-Fossil Fuel Obligation (NFFO) contracts. The Renewables Obligation was
introduced in 2002, which has masked underlying trends, as a shortage of all
renewables, plus uncertainty in the market, has affected prices. However, the
figure below is a good indication of how rapidly wind energy prices fell in
the 1990's.
NB. The
actual price paid for NFFO2 contracts was 11p/kWh. The cost shown for NFFO2
on the figure below is calculated on the basis of a 15 year contract, in
order to make it comparable with the other renewables orders. For more
information on costs see page on
the
history of the Government's renewables policy.
How do
prices compare with other technologies?
It is
difficult to compare the cost of making electricity from different energy
sources because many of the benefits of renewable energy (e.g. no pollution
and never-ending supply) do not have a universally accepted price. However,
it is important to try and compare 'like with like' when contrasting wind
generation costs with those of the fossil fuel sources and so prices bid into
the Non-Fossil Fuel Obligation, which offered 15-year contracts, are a good
guide. In the last round of all, the third Scottish order, around 1000 MW of
wind was bid at 2.8 pence per kilowatt hour (p/kWh) or less - 3.2 p/kWh at
2004 prices while the minimum bid was around 2.2 p/kWh at 2004 prices.
Nevertheless,
even if some of these crucial benefits are ignored, the figure below shows
that onshore wind energy is competitive with new coal fired plant, and
cheaper than new nuclear power.
NB. The
prices for fossil-fuelled generation used in the figure below have been drawn
from recent government White Papers - except in the case of gas. In this
instance, the recent price movements have been taking into account and, as a
result, generation costs from new plant are likely to be close to 3p/kWh. In
early autumn 2004, gas prices in the futures market were moving upwards,
which could result in higher generation costs.
Offshore,
the Department of Trade and Industry (DTI) has suggested that present-day
generating costs are around 5.1 p/kWh. Although some early wind farms have
reported higher capital costs than this, experience in Denmark suggests that
the lower costs are also achievable and so a range of plus or minus 10%
around the central value has been used.
What
about the cost of pollution?
To
determine the true cost of generating electricity, the cost of pollution and
other 'external costs' should be included in the calculations. External costs
are the costs to human health and the environment which are not reflected in
the price of the electricity.
Society
bears the cost of pollution in terms of poorer health (leading to higher
health service costs funded by the taxpayer) and a degraded environment
(which increases the cost of food and farm products).
