October 29, 2010
By: Rowena F. Caronan
The potential benefits of wind energy, such as job creation and a reduction in greenhouse gas emissions, are encouraging many countries to switch from fossil fuels to this renewable source for their power needs. The United States and Europe are just a few examples, with both regions aiming for 300,000 megawatts of wind energy supply over the next two decades.
For the United States, this entails ramping up annual installations of new wind power capacity to more than 16,000 MW to meet the target. As for Europe, this means installing about 75,000 onshore and 15,000 offshore wind turbines with a capacity of at least 2 MW and 10 MW each, respectively.
However, growing demand for wind turbines requires additional technical innovations to address existing and new challenges in wind energy development to boost overall competitiveness.
Setbacks
Alongside its environmental and economic benefits, wind energy also come with drawbacks such as high capital and maintenance costs vis-à-vis conventional generation sources.
Onshore wind farms are often located in remote locations that are far from cities where electricity is supplied. Transmission lines built to connect a wind farm to its client city are an added expenditure for developers.
Those who wish to enter the offshore wind market must shell out even more funds as offshore wind farms are 30 percent to 50 percent costlier than their onshore counterparts. However, the tradeoff is higher wind speeds at sea that lead to more energy production, offsetting offshore wind’s additional expenses.
Aside from cost-based concerns, critics also find fault in wind turbines’ deafening rotor blades, their aesthetic impact and bird deaths caused by turbine blades.
New rotor blade designs
Wind turbine operations are limited on wind speeds as those operating in lower wind speeds shut down upon reaching maximum speed, while heavier generator and blades produce lower output in the more frequent and moderate winds.
Wind manufacturers increase the pitch, or the operating angle of the rotor blade, to improve low-speed wind performance. While pitch turbines balance power production by increasing pitch as wind speeds fall, they are still limited to pitch angles possible with conventional airfoils.
New wind turbine designs aim to address three major limitations in wind power – poor reliability when winds fail, noise and poor performance in unsteady or turbulent air. One such design is the new-fangled tubercle technology, which pushes the limits of airfoil-dependent blade design.
Tubercles are installed along the edges of airfoils to help the blades cut through the air while still absorbing energy from the wind.
Canadian wind turbine manufacturer WhalePower makes tubercle-enhanced blades similar to whale fins.
The tubercle technology tilts blades to a steeper angle to cut through air, akin to humpback whales shifting its fins at a specific angle to make a better lift in the water.
Steeper-angled winds are beneficial in low wind speeds and, with a stalled angle of 40 percent, are better in moving the air around.
Wind Energy Institute of Canada concluded that tubercles not only enhance wind turbines’ operational stability and durability under varying wind speeds and turbulence, but also reduce noise and remove tip chatter through its quieter blades.
Tubercle-enhanced blades also increase annual energy production by 20 percent due to stall reduction as the air stays attached to the blade, the institute added. Whale Power said the new rotor blade design has attracted the interest of 10 large and small turbine manufacturers.
Small-wind turbine for houses
The wind turbine has a helical design resembling a jellyfish, hence the name. It can be mounted on home rooftops or existing street lights that are prewired to the grid, which is not feasible for conventional turbine designs.
The Jellyfish has a rotor design that absorbs wind energy from different directions. Its blades are also barely audible over normal sounds, such as wind blowing through trees, and spin roughly at half the speed of a typical wind turbine, reducing the probability of injuring birds that fly into them.
The wind turbine is also Wi-Fi capable, allowing homeowners to track and monitor system performance using specific desktop software. It also comes with a circuit protection that shuts off the system in case of a power outage.
Clarian Power estimated that the Jellyfish can generate 40 kilowatt-hours of energy monthly in moderate winds – the equivalent of the power needed to light an average home using energy efficient light bulbs.
Homeowners do not have to spend a lot to acquire the Jellyfish as the turbine is very affordable at under $800. The turbine also qualifies for a 30 percent federal tax credit, as well as other local and state tax credits and rebates.
However, the use of the Jellyfish wind turbine in homes requires the United States to upgrade its existing power distribution system to a smart grid. The turbine’s total generated capacity will also not satisfy all power needs of an average American home, which stands at an estimated 1.38 billion kWh, according to the Energy Information Administration.
Eliminating location-dependency
Magenn Power aims to overcome this drawback by designing a wind turbine that will complement diesel power generation. The California-based company manufactured a high-altitude wind turbine called MARS that boasts of exceptional mobility, allowing it to be easily deployed and eliminating problems with locations. MARS is a light-tethered, horizontal-axis wind turbine that contains helium, allowing it to ascent 1,000 feet above the ground – higher than conventional wind turbines.
With the ability to reach such altitude, MARS can be installed closer to the grid and in places with wind speeds ranging from 4 miles per hour to over 60 miles per hour, making its generated energy 25 percent to 60 percent efficient. It can transfer the energy down through the tether for immediate use, for storage in a battery or for connection to a power grid.
Magenn Power said that the Magnus effect of the wind turbine’s rotation provides additional lift and keeps the turbine stabilized. MARS reportedly has lower noise emissions and is less probable to cause bird and bat deaths.
Lowering capital cost
Another solution to the expensive cost of manufacturing, transporting and installing large wind farms is to generate wind energy with few materials. This can be done by putting together two to ten dozens of smaller rotors on the same shaft linked to the same generator, according to Doug Selsam, the inventor of the Selsam Sky Serpent wind turbine.
The seven-foot diameter turbine boasts of the highest generated capacity of 5,033 watts at over 31 miles per hour and the lowest capacity of 1,943 watts at more than 18 mph. During the latest testing in California in 2004, the wind turbine recorded its highest generated capacity of 6,000 watts at a wind speed of 32.5 mph. The lowest generated capacity was around 1,000 watts at winds of 16 mph.
To achieve the highest efficiency, each rotor is aligned at the optimal angle and spaced to receive its own wind. The efficiency is dependent on each rotor receiving its own wind, which is different from previous multirotor turbines. The Selsam wind turbine received $75,000 funding from California Energy Commission for component testing.
Other challenges
The United States has increased its funding on research and development particularly in wind energy. As a result, component testing of wind turbines further enhanced reliability.
About $75 million is allotted for wind and $20 million for renewable systems integration. The United States’ Department of Energy is also building major blade testing and gearbox facilities.
The American Wind Energy Association also asked for $201 million funding to meet industry needs, improve performance, lower cost and improve reliability.
Similar efforts are being taken in Europe, where a research program will allocate 50.52 billion euros ($72.72 billion) for renewable energy, including wind.
However, challenges in the wind energy industry do not end in manufacturing of new wind turbine designs and increased funding on R&D. To significantly boost the competitiveness of wind power, the cost of offshore wind must be brought down, compliance with standards in small-wind turbine technology must be ensured and risks reduced through standards reliability testing.
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