Hi, 

Not sure what you mean with the fact that you have wind at 2.8 m/s and need it to produce like you have 7 m/s. Wind energy is kinetic energy from wind, and that depends on a few factors, one being wind speed, so if your wind speed is lower, then your mechanical available power is less and consequently your electrical power will also be less, you cannot create out of nothing some extra energy. A wind speed of 2.8 m/s is indeed fairly low, so your overall output will be rather low.

With regards to the question on materials, they should preferably be strong and light, but that is already the case, if you need to build you own prototype that may be a bit of a problem though, as some of this works better/easier for large scale production. Your easiest factor to influence is probably the design, and there are quite a few factors there that you can play with. We did some work on turbines for urban setup, and you can find the results in our paper: "Energy Gathering by Micro Turbines for Low Voltage Appliances". 

Hope this helps,

Hi,

Increasing the potential 2.8m/s wind speed up to 7m/s seems impossible. In order to use increase it, you must use some special tools or systems like wind tunnels which are consuming energy.

But if you want to build a wind turbine which is able to reach at its rated power values aound 10-11 m/s. You must start with designing an effective wind turbine generator, PM synchronous alternators are quite effective for low power wind turbine applications.

Hope this helps,

Regards,

According to the  Office of Industrial Technologies, US Department of Energy, a  wide range of materials are used in wind turbines.  There are substantial differences between small and large machines and there are projected changes in designs that will accommodate the introduction of new material technologies and manufacturing methods.  To arrive at a total, the material usage is weighted by the estimated market share of the various manufacturers and machines types.

Wind Turbine – Materials and Manufacturing (Table)

The trends in design and manufacturing differ between small and large turbines.  Small machines tend to use lighter weight castings in an effort to reduce costs.  Many parts are die cast aluminum in small turbines, while in large machines steel castings or forgings are needed to meet strength and structural fatigue requirements.  The size of steel castings for large turbines, especially the blade hub units, is one of the manufacturing challenges.

Material fatigue properties are an important consideration in wind turbine design and materials selection.  During the expected 30-year life of a wind turbine, many of the components will need to be able to endure 4 x 108 fatigue stress cycles.  This high cycle fatigue resistance is even more severe than aircraft, automotive engines, bridges and most other man-made structures.

Future Component Development Trends

There are new component developments underway now that will significantly change the materials usage patterns.  Generally, there are trends toward lighter weight materials, as long as the life-cycle cost is low.  Specific development trends in turbine components are discussed below:

Rotors Most rotor blades in use today are built from glass fiber-reinforced-plastic (GRP). Other materials that have been tried include steel, various composites and carbon filament-reinforced-plastic (CFRP).  As the rotor size increases on larger machines, the trend will be toward high strength, fatigue resistant materials.  As the turbine designs continually evolve, composites involving steel, GRP, CFRP and possibly other materials will likely come into use.

Gearboxes: The step-up gearbox used on large turbines today is expected to be replaced in many future machines.  Most small turbine designed for battery charging use a variable speed, permanent magnet, variable frequency generator connected to a rectifier.  As high power solid state electronics are improved, larger and larger machines are likely to use AC-DC-AC cyclo converters.  This is the case on turbines being developed by Northern Power Systems (100 kW), the ABB (3 MW), and in some commercial machines.  This trend will increase the use of magnetic materials in future turbines. Large epicyclic gear boxes used in large ships, may continue to be the drive system for some large turbines.

Nacelles: The nacelle contains an array of complex machinery including, yaw drives, blade pitch change mechanisms, drive brakes, shafts, bearings, oil pumps and coolers, controllers and more.  These are areas where simplification and innovation can pay off.

Towers Low cost materials are especially important in towers, since towers can represent as much as 65% of the weight of the turbine.  Pre-stressed concrete is a material that is starting to be used in greater amounts in European turbines, especially in off-shore or near-shore applications.  Concrete in towers has the potential to lower cost, but may involve nearly as much steel in the reinforcing bars as a conventional steel tower.

Material Usage Trends though 2010

The component development trends described above are reflected in the following material use projections.  The overall annual material usage trends are shown in the following figure for two periods, from now through 2005 and for 2006 through 2010.  The introduction of much of the new technology discussed above is expected to be incorporated in commercial machines during the later period.  Materials used in machines installed in the U.S. are included as part of the global totals.

The following observations are based on the results of the material usage analysis:

• Turbine material usage is and will continue to be dominated by steel, but opportunities exist for introducing aluminum or other light weight composites, provided strength and fatigue requirements can be met.

• Small turbine production volume is increasing rapidly which can be accommodated by manufacturing mechanization and innovation that will lower costs.

• Elimination of the gearbox by using variable speed generators will increase through use of permanent magnetic generators on larger turbines increasing the need for magnetic materials.

• New high power electronics will help reduce the need for gearboxes and also decrease losses occurred during transmission of wind power to distant load centers.

• Simplification of the nacelle machinery may not only reduce costs, but also increase reliability. • Blades are primarily made of GRP, which is expected to continue.  While use of CFRP may help to reduce weight and cost some, low cost and reliability are the primary drivers.

• Increasing the use of offshore applications may partially offset this trend in favor of the use of composites.

• Prestressed concrete towers are likely to be used more, but will need a substantial amount of steel for reinforcement.

 • Wood epoxy, used in early blade production, is not expected to be a material of choice despite excellent fatigue properties.

• Wind turbine component and materials manufacturing are major and expanding business opportunities for at least the next 10 years.

• The largest market for wind turbine systems and materials in the future will be outside North America and Europe, but this market will be slower in development.