Floating Offshore Wind Turbines

8:44 PM 3 Comments

Power targets the rapidly maturing offshore wind sector by eliminating current deep-water limitations with an innovative and economic solution.
WindFloat is a floating support structure for offshore wind turbines with a simple, economic and patented design. The innovative features of the WindFloat dampen wave and turbine induced motion, enabling wind turbines to be sited in previously inaccessible locations where water depth exceeds 50 m and wind resources are superior. Further, economic efficiency is maximized by reducing the need for offshore heavy-lift operations during final assembly deployment and commissioning. Multiple projects are in development for the installation of commercial Windfloat units in both European and US offshore wind farms.

Advantages: There are three advantages to the WindFloat foundation: first, its static and dynamic stability provides sufficiently low pitch performance enabling use of commercial offshore wind turbines; second, its design and size allow for onshore assembly; third, its shallow draft allows for depth independent siting and wet tow (fully assembled and commissioned) to sites not visible from shore. Primary markets are transitional (30-60 m) and deep ( greater than 60 m) water offshore wind sites in the US and Europe, previously inaccessible, and estimated to have greater than 2 Terawatts (TW) of resource potential. Secondary markets include sites in Asia and other Oceanic countries.

Floating offshore wind turbine 

Stability: The WindFloat is fitted with patented water entrapment (heave) plates at the base of each column. The plates improve the motion performance of the system significantly due to damping and entrained water effects. This stability performance allows for the use of existing commercial wind turbine technology. In addition, WindFloat's closed-loop hull trim system mitigates mean wind-induced thrust forces. This secondary system ensures optimal energy conversion efficiency following changes in wind velocity and direction.

Windfloat

Design: The design of the WindFloat enables the structure to be fully assembled onshore and towed to its final location. All fabrication and qualification is completed at quayside in a controlled environment. Deployment cost savings are significant when compared with monopile/jacket support structures which require offshore heavy-lift operations.
Mooring SystemThe mooring system employs conventional components such as chain and polyester lines to minimize cost and complexity. Through the use of pre-laid drag embedded anchors, site preparation and impact is minimized.

Vestas offshore wind turbine 

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Mitsubishi 7 MW Wind Turbine Blade

7:00 PM 1 Comment

This is really a competition!! The companies are trying to do their bests. The next amazing news are from Mitsubishi. They have pronounced the 81.6 meters blade was developed at Euros' production facility on the island of Rügen, Germany. It has a mass of 32.5 tons!! It will be tested in Glasgow, UK and Fukushima, Japan.

Mitsubishi offsore wind turbine

Euros announced that it will be set up series production in Rostock.

Mitsubishi Sea Angel Nacelle

They are calling this giant as SeaAngel. It uses a hydraulic drive system designed by Artemis Intelligent Power, a digital displacement hydraulics technology specialist. The full hydraulic continuously variable drive system and two conventional fixed-speed brush-less synchronous generators, eliminating the need for a power electronic converter.

Mitsubishi 7 MW blade

To read article about Siemens 6 MW wind turbine blade: http://easywindenergy.blogspot.de/2013/05/siemens-75-m-wind-turbine-blade-worlds.html

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Siemens 75 m Wind Turbine Blade( World's longest )

6:57 PM 5 Comments

Day by day wind industry is going to be massive. The next incredible new is from Siemens. They're building  the world's largest turbine with each blade 75 meters in length. Each blade is made by carbon fiber(Siemens believes the B75 blade is the world’s largest fiberglass component to be moulded in one piece.), and it will be working at coast of Britain in 2014. 

Siemens 6 MW offshore blade

The contract agreed on July 19, 2012 to supply 300 wind turbines with a capacity of 1.8 GW which will be installed between 2014-2017. The 6MW offshore prototype will be working for testing during the next year. 
This 6 MW offshore wind turbine has 154 meters diameter with a swept area of more than 18.600 square meters which is equivalent to the area of approximately two-and-a-half football fields. 6 MW offshore wind turbine can supply approximately 6000 European household with electricity. 

Siemens 6 MW nacelle

The blades will be built in factory in Aalborg, Denmark. One more important point is transporting for these giant wind blades. Normally the distance between factory and Britain is 330 km. But because of re-routing due to over size blades (bridges, roads... are considered) 575 km will be gone. 

Siemens blade transportation

Michael Suess, a board member for Siemens energy sector, said: 'Offshore wind energy has huge potential. Offshore wind conditions are strong and stable, enabling an energy yield which can be about 40 percent higher than onshore.'The United Kingdom, Denmark and Germany in particular are counting on the future of offshore wind energy. We are pleased that our long-term customer DONG Energy has chosen the latest generation of our wind turbines.'Together we are working to further reduce the levelised costs for this environmentally-friendly form of power generation.'

SWT 6.0 MW

Just to compare Airbus A 380 with Siemens 6 MW offshore wind blade !! 

Airbus A 380

Lastly, Vestas has also 8 MW offshore wind turbine with 164 meters diameter !! See: http://easywindenergy.blogspot.de/2013/05/vestas-v164-80-mw-offshore.html

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Vestas V164-8.0 MW Offshore

10:06 AM 1 Comment

Vestas calls it as V164-8.0 MW. The development of the V164-8.0 MW offshore turbine is still progressing.Main components such as drivetrain, bearings and blade are now in testing step. For the first prototype of the V164-8.0 MW offshore is expected to be installed in the second quarter of the 2014.

Vestas V164-8.0 MW Offshore wind turbine blade test

V164-8.0 MW will be worlds' biggest and most powerful wind turbine for offshore. It is said first prototype of the blade is currently undergoing testing. At the same time in the worlds' biggest test bench of Vestas testing facilities in Aarhus, Denmark, drivetrain, gearbox and generator is undergoing testing.

Vestas V164-8.0 MW Offshore wind turbine hub

Other main components such as hub, blade bearings, main shaft, main bearing have been also manufactured. It is expected the first prototype of V164_8.0 MW will be running in the second quarter of 2014. 

The gearbox is ready for testing in Aarhus, Denmark.

Vestas V164-8.0 MW Offshore wind turbine gearbox test stand

For the first prototype this shaft is also ready to test.
As a short information about Vestas' giant blade, just one blade weighs 33 tons !!

Vestas V164-8.0 MW Offshore wind turbine blade 80m

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Offshore Wind Turbine Installation

11:03 PM 3 Comments

Alstom build floating wind turbine platform in UK waters. The platform will feature a 6MW Alstom Haliade turbine. It has pretty high rated power (6 MW) with 73.5 meters LM blades that creates a swept area of 17.860 square meters. 

Alstom Offshore

Generally this type of offshore designs have a floating foundation which is fixed to the seabed using catenary cables. By positioning this floating platform in any place in water. Tanks to this property the turbine cane be moved to much more deeper waters which means less turbulent more strong wind which means less loads with high power efficiency.

Offshore transportation

On the other hand, it is a little bit hard to transport wind turbine stuffs from manufacturer to offshore area. As it seen in the following picture of nacelle, first land transportation then sea transportation is needed which costs extra money. And as a small note, it can be clearly identified with the dimensions of nacelle, direct drive wind generator technology is used. 

Alstom 6MW Nacelle

Sometimes it can cost serious amount moneys. That's why nowadays some of persons say production of off-shore wind turbines must be decreased. But some of companies which are so assertive are persistent with off-shore wind energy sector. 

Off-shore crane technology

If it is needed to compare with on-shore wind turbines, it is definitely clear that it is much much more easier to install on-shore wind turbines than the off-shore wind turbines. As it seen in the previous picture also, the crane technology must be designed in a clever way to be able to withstand with all forces during installation. 

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Wind Availability and Location Optimization for Wind Turbines

12:08 PM No Comments

Wind Availability

Whether constructing a wind turbine is economically viable at your home or farm depends most strongly on the quality of your wind resource. Generally, average annual wind speeds of at least 4.0-4.5 m/s (14.4- 16.2 km/h; 9.0-10.2 mph) are needed for a small wind turbine to produce enough electricity to be cost-effective. A very useful resource for evaluating a site for its wind energy potential is a wind resource potential map. 

Wind Map for Eastern Ontario. (a.g.l. = above ground level) 

It may be useful to check wind speed measurements that have been recorded at a local weather station. It is important to consider that sitting factors at these weather stations, such as nearby trees and buildings, might influence any wind speed measurements. Also, keep in mind that the equipment at these stations is often located close to the ground, and that weather stations located at airports are usually sheltered from the wind.

Wind Map for Southwestern Ontario. 

This means that wind speed measurements recorded at these stations might under represent the wind potential at your site.

For the most precise evaluation of the wind speed at your site, you need to purchase a wind resource evaluation system. While wind resource evaluation systems can be expensive, if your property is hilly and has unusual terrain features then it might be worth obtaining one.

The most important component of a wind resource evaluation system is an anemometer. Anemometers are typically designed with cups mounted on short arms that are connected to a rotating vertical shaft.

The anemometer rotates in the wind and generates a signal that is proportional to the wind speed. If you do purchase an anemometer, you will also need to purchase something to record the readings made by the anemometer, and a tower or tripod to mount the whole system on.

For as little as $500 you might be able to purchase a wind totalizer, which is a very simple type of wind resource evaluation system where the anemometer is linked to an odometer. The odometer is similar to those found in cars. After a period of time, the number recorded on the odometer, which represents the total "distance" the anemometer has turned, can be divided by the time passed since the odometer was last checked in order to determine the average wind speed over a period of time at a location.

If there is a small wind turbine system in your area, you may be able to obtain useful information from its owners about the annual electrical output of the system and, possibly, wind speed data. Such information could be extremely valuable as an alternative to installing a wind resource evaluation system.

 Wind turbine schematic. (Modified image from Natural Resources Canada)

Picking the Best Location for a Wind Turbine

Where you choose to build your wind turbine is important. Remember that if nearby houses, tree lines and silos obstruct the full force of the wind from your wind turbine, you will not be able to generate as much power.

Also keep the following in mind:

• Wind speeds are always higher at the top of a hill, on a shoreline, and in places clear of trees and other structures.
• Remember that trees grow over the years; wind turbine towers do not.
• Inform neighbours of your plans to avoid conflict later on.
• Be courteous. Keep the turbine as far away from neighbours as possible. 250-300 m away is typical.
• Check with the local government for any other laws and regulations about zoning.

Wind speeds tend to be higher on the top of a ridge or hill, and for that reason it is a good idea to locate wind turbines at hilly locations. Just remember to keep your turbine away from high turbulence. Neighbours must also be taken into consideration when picking a spot to build your turbine. The farther your wind turbine site is from neighbouring houses, the better.

Do not expect your wind turbine to generate the same amount of power all the time. The wind speed at a single location may vary considerably, and this can have a significant impact on the power production from a wind turbine. Even if the wind speed varies by only 10%, the power production from a wind turbine can vary by up to 25%!

 Example of wind speed distribution by hour of the day. Values shown are monthly averages of measurements made by anemometers. 

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Wind Generator

6:17 PM 1 Comment

The wind turbine generator converts mechanical energy to electrical energy.
Wind turbine generators are a bit unusual, compared to other generating units you ordinarily find attached to the electrical grid. One reason is that the generator has to work with a power source (the wind turbine rotor) which supplies very fluctuating mechanical power (torque).
These pages assumes that you are familiar with the basics of electricity, electromagnetism, and in particular alternating current. If any of the expressions volt (V), phase, three phase, frequency, or Hertz (Hz) sound strange to you, you should take a look at the Reference Manual on Electricity and read about alternating current, three phase alternating current, electromagnetism and induction before you proceed with the following pages.

Wind genearator

Generating Voltage (tension)
On large wind turbines (above 100-150 kW) the voltage (tension) generated by the turbine is usually 690 V three-phase alternating current (AC). The current is subsequently sent through a transformer next to the wind turbine (or inside the tower) to raise the voltage to somewhere between 10,000 and 30,000 volts, depending on the standard in the local electrical grid.
Large manufacturers will supply both 50 Hz wind turbine models (for the electrical grids in most of the world) and 60 Hz models (for the electrical grid in America).
Cooling System
Generators need cooling while they work. On most turbines this is accomplished by encapsulating the generator in a duct, using a large fan for air cooling, but a few manufacturers use water cooled generators. Water cooled generators may be built more compactly, which also gives some electrical efficiency advantages, but they require a radiator in the nacelle to get rid of the heat from the liquid cooling system.
Starting and Stopping the Generator
If you connected (or disconnected) a large wind turbine generator to the grid by flicking an ordinary switch, you would be quite likely to damage both the generator, the gearbox and the current in the grid in the neighbourhood.
You will learn how turbine designers deal with this challenge in the page on Power Quality Issues , later.

Small wind generator

Design Choices in Generators and Grid Connection
Wind turbines may be designed with either synchronous or asynchronous generators, and with various forms of direct or indirect grid connection of the generator.
Direct grid connection mean that the generator is connected directly to the (usually 3-phase) alternating current grid.
Indirect grid connection means that the current from the turbine passes through a series of electric devices which adjust the current to match that of the grid. With an asynchronous generator this occurs automatically.

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Wind Turbines and Power Quality Issues

11:55 AM 1 Comment

The buyer of a wind turbine does not need to concern himself with local technical regulations for wind turbines and other equipment connected to the electrical grid. This responsibility is generally left to the turbine manufacturer and the local power company.
For the people who are technically minded, we go into some of the electro-technical issues involved in connecting a turbine to the grid on this page.

Power quality

The term "power quality" refers to the voltage stability, frequency stability, and the absence of various forms of electrical noise (e.g. flicker or harmonic distortion) on the electrical grid. More broadly speaking, power companies (and their customers) prefer an alternating current with a nice sinusoidal shape, such as the one in the image above. 

Starting and Stopping a Turbine
Most electronic wind turbine controllers are programmed to let the turbine run idle without grid connection at low wind speeds. (If it were grid connected at low wind speeds, it would in fact run as a motor). Once the wind becomes powerful enough to turn the rotor and generator at their rated speed, it is important that the turbine generator becomes connected to the electrical grid at the right moment.
Otherwise there will be only the mechanical resistance in the gearbox and generator to prevent the rotor from accelerating, and eventually over-speeding. (There are several safety devices, including fail-safe brakes, in case the correct start procedure fails).

Soft Starting with Thyristors
If you switched a large wind turbine on to the grid with a normal switch, the neighbours would see a brownout (because of the current required to magnetize the generator) followed by a power peak due to the generator current surging into the grid. You may see the situation in the drawing in the accompanying browser window, where you see the flickering of the lamp when you operate the switch to start the wind turbine. The same effect can possibly be seen when you switch on your computer, and the transformer in its power supply all of a sudden becomes magnetized.
Another unpleasant side effect of using a "hard" switch would be to put a lot of extra wear on the gearbox, since the cut-in of the generator would work as if you all of a sudden slammed on the mechanical brake of the turbine.

Grid connection

To prevent this situation, modern wind turbines are soft starting, i.e. they connect and disconnect gradually to the grid using thyristors, a type of semiconductor continuous switches which may be controlled electronically. (You may in fact have a thyristor in your own home, if you own a modern light dimmer, where you can adjust the voltage on your lamps continuously).

Thyristors waste about 1 to 2 per cent of the energy running through them. Modern wind turbines are therefore normally equipped with a so called bypass switch, i.e. a mechanical switch which is activated after the turbine has been soft started. In this way the amount of energy wasted will be minimized.

Weak Grids, Grid Reinforcement
If a turbine is connected to a weak electrical grid, (i.e. it is vary far away in a remote corner of the electrical grid with a low power-carrying ability), there may be some brownout / power surge problems of the sort mentioned above. In such cases it may be necessary to reinforce the grid, in order to carry the fluctuating current from the wind turbine.
Your local power company has experience in dealing with these potential problems, because they are the exact mirror-image of connecting a large electricity user, (e.g. a factory with large electrical motors) to the grid.

Grid connection

Flicker
Flicker is an engineering expression for short lived voltage variations in the electrical grid which may cause light bulbs to flicker. This phenomenon may be relevant if a wind turbine is connected to a weak grid, since short-lived wind variations will cause variations in power output. There are various ways of dealing with this issue in the design of the turbine, mechanically, electrically, and using power electronics.

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Interesting Wind Energy Facts

8:05 PM 1 Comment

1. At the current growth rate, U.S. wind energy developers install two new wind farms per week.

2. Wind mills have been in use since 2000 B.C. and were first developed in China and Persia.

3. Wind power is currently the fastest-growing source of electricity production in the world.

4. Google has invested $5 billion in a new underwater transmission line to connect offshore wind farms in the Atlantic Ocean with 1.9 million households on the East Coast.

Offshore wind farm

5. A single wind turbine can power 500 homes.

6. Roscoe Wind Farm in Texas is the world’s largest wind farm with 627 turbines generating 781.5 MW of electricity.

7. More than one-third of all new generating capacity installed in America since 2007 is from wind power.

8. There’s enough on-shore wind in America to power the country 10 times over.

Interesting wind turbines

9. U.S. wind power produces as much electricity as nearly 10 nuclear power plants.

10. Most wind turbines (95%) are installed on private land.

11. Modern wind turbines produce 15 times more electricity than the typical turbine did in 1990.

12. At times, wind energy produces as much as 25% of the electricity on the Texas power grid.

Wind turbine and birds

13. American wind power is a $10 billion a year industry.

14. Unlike nearly every other form of energy, wind power uses virtually no water.

15. By 2030, U.S. wind power will save nearly 30 trillion bottles of water.

16. At times, wind power produces as much as 45% of the electricity in Spain.

Interesting wind farm

17.Wind energy became the number-one source of new U.S. electricity-generating capacity for the first time in 2012, providing some 42% of all new generating capacity. In fact, 2012 was a strong year for all renewables, as together they accounted for more than 55% of all new U.S. generating capacity.

18.During the fourth quarter of 2012, Texas led the nation in new wind installations (with 1,289 megawatts), followed by California, Kansas, Oklahoma and Iowa.

19. U.S. renewable energy consumption increased by 6% in 2010, with wind energy as the source of 11% of the total renewable energy consumption.

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Size of Wind Turbine

7:39 PM No Comments

Following figure shows trends by year of the typical largest turbine sizes targeted for mainstream commercial production. Megawatt turbines existed in the 1980s but almost all were research prototypes. An exception was the Howden 1 MW design (erected at Richborough in the UK), a production prototype, which was not replicated due to Howden withdrawing from the wind business in 1988. Although there is much more active consideration of larger designs than indicated in figure, no larger turbines have appeared since 2004.
To read more about new wind turbine trends see: Wind Turbine Trends 

To enlarge the figure click

Up until around 2000 an ever-increasing (in fact mathematically exponential) growth in turbine size over time had taken place among manufacturers and was a general industry trend. In the past three or four years, although there is still an interest in yet larger turbines for the offshore market, there has been a slowdown in the growth of turbine size at the center of the main, land-based market and a focus on increased volume supply in the 1.5 to 3 MW range.

The early small sizes, around 20-60 kW, were very clearly not optimum for system economics. Small wind turbines remain much more expensive per kW installed than large ones, especially if the prime function is to produce grid quality electricity. This is partly because towers need to be higher in proportion to diameter in order to clear obstacles to wind flow and escape the worst conditions of turbulence and wind shear near the surface of the earth. But it is primarily because controls, electrical connection to grid and maintenance are a much higher proportion of the capital value of the system in small turbines than in larger ones. 

To enlarge the figure click

Onshore technology is now dominated by turbines in the 1.5 and 2 MW range. However, a recent resurgence in the market for turbines of around 800 kW is interesting and it remains unclear, for land-based projects, what objectively is the most cost-effective size of wind turbine. The key factor in continuing quest for size into the multi-megawatt range has been the development of an offshore market. For offshore applications, optimum overall economics, even at higher cost per kW in the units themselves, requires larger turbine units to make up for the proportionally higher costs of infrastructure (foundations, electricity collection and sub-sea transmission) and number of units to access and maintain per kW of installed capacity.

Following figure shows the development of the average sized wind turbine for a number of the most important wind power countries. It can be observed that the average size has increased significantly over the last 10-15 years, from approximately 200 kW in 1990 to 2 MW in 2007 in the UK, with Germany, Spain and the USA not far behind.

 As shown, there is a significant difference between some countries: in India, the average installed size in 2007 was around 1 MW, considerably lower than in the UK and Germany (2,049 kW and 1,879 kW, respectively). The unstable picture for Denmark in recent years is due to the low level of turbine installations.
To learn more about Germany wind energy see: Germany wind energy potential

To enlarge the figure click

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Wind Energy

7:38 PM 1 Comment

A wind turbine is a machine made up of two or three propeller-like blades called the rotor. The rotor is attached to the top of a tall tower. As the wind blows it spins the rotor. As the rotor spins the energy of the movement of the propellers gives power to a generator. There are some magnets and a lot of copper wire inside the generator that make electricity.

Wind farm

Because winds are stronger higher up off the ground, wind turbine towers are about 30 meters tall to allow the rotor to catch more wind energy. The turbines are built with a device that turns the rotor so that it always faces into the wind.

Just one wind turbine can generate enough electricity for a single house or the electrical energy to pump water or to power a mill which grinds grain. The electrical energy can also be stored in batteries.

Wind farms

Wind farms are places where many wind turbines are clustered together. They are built in places where it is nearly always windy. The electricity that is generated at a wind farm is sold to electricity companies that provide the electricity to people living in cities and towns.

Wind farm

What are the advantages of wind turbines?

• The energy they generate is renewable. This means that as long as the winds blow there is power to turn the blades of the rotor. 
• Using wind energy means that less fossil fuel (coal and oil) needs to be burned to make electricity. Burning fossil fuel pollutes the atmosphere and adds greenhouse gases to it. 

What are the disadvantages of wind turbines?

• Some people don't like the look of the turbines. They say that they spoil the look of the natural environment.
• Wind turbines make noise.
• Turbines kill birds that fly into them. However collisions are rare and there are reports from Denmark saying that some falcons had built nests on the top of turbine towers. To protect birds however, it is important that wind farms be built away from bird sanctuaries and from the pathways of migratory birds. (Migratory birds are those that fly from cold places in winter to warmer parts of the world)

Wind farm

Here to find how to build your own wind generator?

Homemade 1 kW wind generator

Here to look more about small wind turbines.

Small wind turbine

Go here to read more about wind energy and wind farms.

Why wind energy?

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Wind Turbine Grid Connection

4:03 PM 1 Comment

The wind turbines generate power by rotating a permanent magnet generator which generates three phase AC at the frequency of the turbine's rotation. The AC power from the generator is not only the wrong voltage to be connected to the local power grid, but also, as the wind speed changes so does the rotational speed of the turbine, and therefore the frequency of the power generated. The power from the generator therefore needs to be converted to DC and then fed into a special electronic device called an inverter, to ensure that it is always at the correct frequency and voltage for the local grid. 

Grid connection

Any power you generate will be first used by your own property, thereby saving you the maximum amount possible on your electricity bill. Any excess energy your wind turbine generates, e.g. on windy days or at night, is "spilled" to the power grid and your electricity supplier pays you for it. 

Grid connection

In order to charge your electricity supplier for any energy that you export to the grid, you need to have a new bi-directional electricity meter installed which will work both when you buy (import) and sell (export) electricity. Depending upon your local requirements, there may be additional meters needed to record energy generation to enable a claim for a Government subsidy. 

Shown below is a simplified block diagram of how all the system components are connected in the EU.

Companies however shortly hope to offer an off-grid package which when combined with a battery pack, and optionally solar PV panels and/or a diesel generator will enable the generation of “mains” power where there is no grid connection. For more information on small wind turbines go to small wind turbines.

Grid conection

The inverter also provides essential safety features to control the power output from the turbine, and to automatically switch off the current if the grid connection should fail. This means that should the grid connection fail, the inverters will switch off their output and there is therefore no danger to any maintenance engineers fixing the fault. This does however mean that the wind turbine will produce no power to the property if the mains connection fails. 

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Germany's Wind Energy Potential

6:54 PM No Comments

Most of Germany’s pro-Energiewende voices think that Germany will far exceed its 2020 target of 35% clean energy. The Heinrich Böll Foundation, a Green think tank, is definitely among them. It argues that Germany could — with the right policies — go 100% renewable by 2050.

But for Germany to do it, argues the report "A European Union for Renewable Energy," there has to be greatly improved cooperation. The EU targets, road maps, and action plans are steps in the right direction, but they fall far short of a comprehensive EU common energy policy.

The report, commissioned by the Heinrich Böll Foundation European Union and prepared by independent experts, argues that most European countries' current energy grids are antiquated, nationally organized, and designed for fossil fuel and nuclear energy sources. The grids are composed mostly of one-way transmission cables connecting large production facilities, like coal-firing plants and nuclear reactors, to residential and commercial hubs.

Since the requisite storage technology is still largely undeveloped, what is needed are "smart," flexible, decentralized grids that crisscross the continent and beyond. In contrast to the "dumb" decentralized networks of the fossil-fuel age, a smart grid is a digital network that links customers with dispersed suppliers, like those operating wind parks and solar installations, through the Internet. The wider-reaching and "smarter" this network is, the better its ability to match weather-dependent supply surpluses and demand needs, both regionally and across borders.

Since grid construction needs as long as ten years to be realized, potential grid investors would need an unshakable commitment to renewable energies to invest in such a costly project. The report underscores a number of measures to get the ball on an all-European system rolling, including a "review" of the EU treaty that stipulates that the national states have full authority to determine their own energy supplies as they wish. Ultimately there must be a guarantee that nationally minded states don't obstruct plans for an European grid system.

As for Europe's current energy markets, they too tend to reflect national priorities and a fossil fuel-dominated system that the EU is supposedly committed to phasing out. The report argues that "open and hidden" subsidies for fossil fuels and nuclear must be abolished in order to even the playing field between renewable and conventional energies.

Moreover, Europe is a patchwork of diverse incentives, subsidies, and related taxes. About two-thirds of EU countries have a feed-in tariff along the lines of Germany's successful model. Its essence is that utilities are required to buy renewable energy from private producers at a higher-than-market price in order to cover the producer's investment in solar modules, wind turbines, biogas plants, or other production installations.

A key recommendation is the gradual harmonization of incentive and subsidy programs based on best practice models, including but not limited to the feed-in tariff. "To make prices within the internal energy market more transparent and attract cross-border investment," says Sascha Müller-Kraenner, the report's chief organizer, "today's systems have to be better connected, based on feed-in tariffs. Remuneration systems like tenders and auctions for big producers such as offshore wind farms can help make today's system even more competitive, but this doesn't mean replacing the most successful elements of the feed-in tariffs."

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Offshore Wind Energy in U.S.A

8:11 PM 1 Comment

The first offshore wind project was installed off the coast of Denmark in 1991. Since that time, commercial-scale offshore wind facilities have been operating in shallow waters around the world, mostly in Europe. With the U.S. Department of the Interior’s “Smart from the Start” initiative, wind power projects will soon be built offshore the United States. Newer turbine and foundation technologies are being developed so that wind power projects can be built in deeper waters further offshore.   

Wind energy has been utilized by humans for more than two thousand years. For example, windmills were often used by farmers and ranchers for pumping water or grinding grain. In modern times, wind energy is mainly used to generate electricity, primarily through the use of wind turbines. All wind turbines operate in the same basic manner. As the wind blows, it flows over the airfoil-shaped blades of wind turbines, causing the turbine blades to spin. The blades are connected to a drive shaft that turns an electric generator to produce electricity. The newest wind turbines are highly technologically advanced, and include a number of engineering and mechanical innovations to help maximize efficiency and increase the production of electricity. 

  

Offshore Wind Energy Resources

Offshore wind turbines are being used by a number of countries to harness the energy of strong, consistent winds that are found over the oceans. In the United States, 53% of the nation’s population lives in coastal areas, where energy costs and demands are high and land-based renewable energy resources are often limited. Abundant offshore wind resources have the potential to supply immense quantities of renewable energy to major U.S. coastal cities, such as New York City and Boston.  

Offshore winds tend to blow harder and more uniformly than on land. The potential energy produced from wind is directly proportional to the cube of the wind speed. As a result, increased wind speeds of only a few miles per hour can produce a significantly larger amount of electricity. For instance, a turbine at a site with an average wind speed of 16 mph would produce 50% more electricity than at a site with the same turbine and average wind speeds of 14 mph. This is one reason that developers are interested in pursuing offshore wind energy resources. The U.S. Department of Energy (DOE) provides a number of maps showing average wind speed data through its Resource Assessment & Characterization page and through National Renewable Energy Laboratory’s (NREL) MapSearch. 

United States wind speeds at 80m hub height (Credit: NREL)

Wind resource potential is typically given in gigawatts (GW), and1 GW of wind power will supply between 225,000 to 300,000 average U.S. homes with power annually.  In a July 2012 Technical Report, NREL estimates a gross wind power resource of 4,223 GW off the coast of the United States. That is roughly four times the generating capacity of the current U.S. electric grid. Even if only a fraction of that potential is developed, clearly there is enough offshore wind resource to power a substantial portion of our nation’s energy needs.

Wind speeds off the Atlantic Coast and in the Gulf of Mexico are lower than wind speeds off the Pacific Coast. However, the presence of shallower waters in the Atlantic makes development more attractive and economical for now. Hawaii has the highest estimated potential, accounting for roughly 17% of the entire estimated U.S. offshore wind resource. For additional information on NREL’s assessment of offshore wind power resource, see the publicationAssessment of Offshore Wind Energy Resources for the United States. Maps of renewable energy potential for multiple technologies, or state-by-state analyses, can be downloaded here. 

  

United States offshore wind resource by region and depth (Credit: NREL)

Transport of Wind-Generated Energy

An Electric Service Platform (ESP) for an offshore wind facility.

All of the power generated by the wind turbines needs to be transmitted to shore and connected to the power grid. Each turbine is connected to an electric service platform (ESP) by a power cable. The ESP is typically located somewhere within the turbine array, and it serves as a common electrical collection point for all the wind turbines and as a substation. In addition, ESP’s can be outfitted to function as a central service facility, and may include a helicopter landing pad, communications station, crew quarters, and emergency backup equipment. After collecting the power from the wind turbines, high voltage cables running from the ESP transmit the power to an onshore substation, where the power is integrated into the grid.  The cables used for these projects are typically buried beneath the seabed, where they are safe from damage caused by anchors or fishing gear and to reduce their exposure to the marine environment. These types of cables are expensive, and are a major capital cost to the developer. The amount of cable      used depends on many factors, including how far offshore the project is located, the spacing between turbines, the presence of obstacles that require cables to be routed in certain directions, and other considerations.

Offshore Wind Energy Technology

The engineering and design of offshore wind facilities depends on site-specific conditions, particularly water depth, geology of the seabed, and wave loading. In shallow areas, monopiles are the preferable foundation type. A steel pile is driven into the seabed, supporting the tower and nacelle.  The nacelle is a shell that encloses the gearbox, generator, and blade hub (generally a three-bladed rotor connected through the drive train to the generator) and the remaining electronic components. Once the turbine is operational, wind sensors connected to a yaw drive system turn the nacelle to face into the wind, thereby maximizing the amount of electricity produced.

For more information about wind turbine technology, see NREL’s “Wind Energy Basics: How Wind Turbines Work.”

Today’s offshore turbines have technical modifications and substantial system upgrades for adaptation to the marine environment. These modifications include strengthening the tower to cope with loading forces from waves or ice flows, pressurizing nacelles to keep corrosive sea spray from critical electrical components, and adding brightly colored access platforms for navigation safety and maintenance access. Offshore turbines are typically equipped with extensive corrosion protection, internal climate control systems, high-grade exterior paint, and built-in service cranes. To minimize the expense of everyday servicing, offshore turbines may have automatic greasing systems to lubricate bearings and blades as well as heating and cooling systems to maintain gear oil temperature within a specified range. Lightning protection systems help minimize the risk of damage from lightning strikes that occur frequently in some offshore locations. There are also navigation and aviation warning lights, regulated by the U.S. Coast Guard and the FAA. Turbines and towers are typically painted light grey or off-white to help them blend into the sky, reducing visual impacts from the shore. The lower section of the support towers may be painted bright colors to increase navigational safety for passing vessels.

The Repower 5M turbine, offshore Scotland, one of the world’s largest wind turbines. (5-MW, 126m tall, 45m depth)

To take advantage of the steadier winds, offshore turbines are also bigger than onshore turbines and have an increased generation capacity. Offshore turbines generally have nameplate capacities between 2 MW and 5 MW, with tower heights greater than 200 feet and rotor diameters of 250 to 430 feet. The maximum height of the structure, at the very tips of the blades, can easily approach 500 feet, and turbines even larger than 5 MW are being designed and tested for future use. 

While the tower, turbine, and blades of offshore turbines are generally similar to onshore turbines, the substructure and foundation systems differ considerably. The most common substructure type is the monopile—a large steel tube with a diameter of up to 20 feet. Monopiles are typically used in water depths ranging from 15 to 100 feet. The piles are driven into the seabed at depths of 80 to 100 feet below the mud line, ensuring the structure is stable. A transition piece protrudes above the waterline, which provides a level flange to fasten the tower. In even shallower environments with firm seabed substrates, gravity-based systems can be used, which avoids the need to use a large pile-driving hammer. Tripods and jackets foundations have been deployed in areas where the water depth starts to exceed the practical limit for monopiles.

  

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