Category Archives: Power Generation
Monster Wind Turbine Blades Could Help Offshore Wind Compete with Fossil Fuels | MIT Technology Review
Offshore wind is a huge resource, but it can’t yet compete with fossil fuels.
Big blade: The forms for the 80-meter turbine blades that Vestas is developing stretch into the distance.
Blade Dynamics, a six-year-old company that’s partly owned by American Semiconductor, a wind turbine designer and supplier of wind farm electronics, says that it has developed technology that will make possible the world’s largest wind turbine blades. It’s demonstrated the technology by manufacturing 49-meter blades, and now the Energy Technologies Institute, a partnership between the U.K. government and major corporations such as BP, Shell, and Caterpillar, has given the company nearly $25 million to build 100-meter blades. They could enable 250-meter-tall wind turbines that would tower over the Washington Monument, which stands a mere 169 meters tall. The largest wind turbine blades now are 75 meters long (see “A Mighty Wind Turbine ”).
The effort is no mere record-setting spectacle. Finding affordable ways to make the enormous wind turbine blades is one of the biggest challenges to making offshore wind competitive with fossil fuels, and leading wind power companies, including GE and Vestas, are developing technology to solve the problem.
Some of the best winds for generating power are found offshore, where wind can be steadier, faster, and less turbulent than on land. Wind turbines only make up about a third of the cost of offshore wind farms—installation costs are the major expense, as they involve enormous, specialized ships and are subject to delays from bad weather. Using larger wind turbines reduces the number of wind turbines needed, decreasing installation and maintenance costs (see “Building Bigger, Better Wind Turbines ” and “The Great German Energy Experiment ”).
One problem with building very large wind turbines is that the cost of making the blades is skyrocketing. As wind turbines get bigger, the loads on the blades, and therefore their weight, goes up exponentially. The conventional way for making blades involves forms that are as long as the blades themselves. The forms and other equipment needed to make them are becoming so big and specialized that there are few suppliers, which increases prices for manufacturing equipment. Making sure the blades are formed accurately also gets more and more difficult as blades get longer.
Some major wind turbine manufacturers are sticking with the large forms, but are adopting carbon-reinforced fiberglass blades and new blade designs to offset some of the manufacturing cost increase. They’re also counting on savings in installation and other costs to make the business case for larger wind turbines. Siemens, for example, is using large forms for its 75-meter blades, as is Vestas, which is developing 80-meter blades for a wind turbine that will be available next year.
While manufacturers like Vestas are using carbon-reinforced blades, Blade Dynamics is making blades entirely out of carbon fiber. The company has developed proprietary ways to make 12- to 20-meter sections of carbon fiber blade and then splice them together seamlessly—eliminating the need for large forms. Some previous attempts at modular blades involved bolting blade sections together, but this created stress points within the blades that make them too weak.
Carbon fiber is more expensive than fiberglass, so for a given length, the blades will be more expensive. But David Cripps, senior technical manager at Blade Dynamics, says the use of carbon fiber can improve the overall economics of wind turbines in several ways. By making the blade in smaller sections, it’s possible to make more precise aerodynamic structures, improving performance, he says. Also, because the blades weigh much less than fiberglass ones, it’s possible to put longer blades on existing wind turbine designs. For example, the company’s 49-meter blade weighs no more than a conventional 45-meter blade specified by a wind turbine’s original design. Longer blades gather more wind, allowing the turbines to generate more power at lower wind speeds, increasing revenue.
The lighter blades also make it possible to design new wind turbines that have lighter and less expensive components, such as the drive shaft, tower, and foundation. “Instead of a 24-ton rotor, you might have a 15-ton rotor. That’s substantial weight to save on the end of a long cantilevered tower,” Cripps says.
The development effort is part of American Superconductor’s strategy of bringing 10-megawatt wind turbines to market (offshore wind farms typically use 3.6-megawatt turbines or, more rarely, six-megawatt ones). It’s reducing the weight of the wind turbine generator with the help of superconductor materials, and is developing a 10-megawatt turbines that it says will weigh about as much as five-megawatt ones, to keep installation costs down.
Posted January 23, 2013 – 03:33 by Kate Taylor
Super-small particles of silicon react with water to produce hydrogen almost instantaneously, University at Buffalo researchers have discovered.
It means that soldiers or campers, for example, need only take a small hygrogen fuel cell and a bag of the powder to power electronics and other devices on the move.
“It was previously unknown that we could generate hydrogen this rapidly from silicon, one of Earth’s most abundant elements,” says research assistant professor Folarin Erogbogbo.
“Safe storage of hydrogen has been a difficult problem, even though hydrogen is an excellent candidate for alternative energy, and one of the practical applications of our work would be supplying hydrogen for fuel cell power. It could be military vehicles or other portable applications that are near water.”
Spherical silicon particles about 10 nanometers in diameter combine with water and react to form silicic acid – which is non-toxic – and hydrogen, a potential source of energy for fuel cells.
The reaction doesn’t require any light, heat or electricity – and also creates hydrogen about 150 times faster than similar reactions using silicon particles 100 nanometers wide, and 1,000 times faster than bulk silicon.
The reason’s down to to geometry. As they react, the larger particles form nonspherical structures whose surfaces react with water less readily and less uniformly than the surfaces of the smaller, spherical particles.
Though it does take significant energy and resources to produce the powder, the particles could help power portable devices in situations where water is available and portability is more important than low cost.
“Perhaps instead of taking a gasoline or diesel generator and fuel tanks or large battery packs with me to the campsite (civilian or military) where water is available, I take a hydrogen fuel cell (much smaller and lighter than the generator) and some plastic cartridges of silicon nanopowder mixed with an activator,” says Professor Mark Swihart.
“Then I can power my satellite radio and telephone, GPS, laptop, lighting, etc. If I time things right, I might even be able to use excess heat generated from the reaction to warm up some water and make tea.”
MIT researchers at the David H. Koch Institute for Integrative Cancer Research have developed a new material that changes its shape after absorbing water vapor. (Credit: MIT)
Jan. 10, 2013 — MIT engineers have created a new polymer film that can generate electricity by drawing on a ubiquitous source: water vapor.
The new material changes its shape after absorbing tiny amounts of evaporated water, allowing it to repeatedly curl up and down. Harnessing this continuous motion could drive robotic limbs or generate enough electricity to power micro- and nanoelectronic devices, such as environmental sensors.
“With a sensor powered by a battery, you have to replace it periodically. If you have this device, you can harvest energy from the environment so you don’t have to replace it very often,” says Mingming Ma, a postdoc at MIT’s David H. Koch Institute for Integrative Cancer Research and lead author of a paper describing the new material in the Jan. 11 issue of Science.
“We are very excited about this new material, and we expect as we achieve higher efficiency in converting mechanical energy into electricity, this material will find even broader applications,” says Robert Langer, the David H. Koch Institute Professor at MIT and senior author of the paper. Those potential applications include large-scale, water-vapor-powered generators, or smaller generators to power wearable electronics.
Other authors of the Science paper are Koch Institute postdoc Liang Guo and Daniel Anderson, the Samuel A. Goldblith Associate Professor of Chemical Engineering and a member of the Koch Institute and MIT’s Institute for Medical Engineering and Science.
The new film is made from an interlocking network of two different polymers. One of the polymers, polypyrrole, forms a hard but flexible matrix that provides structural support. The other polymer, polyol-borate, is a soft gel that swells when it absorbs water.
Previous efforts to make water-responsive films have used only polypyrrole, which shows a much weaker response on its own. “By incorporating the two different kinds of polymers, you can generate a much bigger displacement, as well as a stronger force,” Guo says.
The film harvests energy found in the water gradient between dry and water-rich environments. When the 20-micrometer-thick film lies on a surface that contains even a small amount of moisture, the bottom layer absorbs evaporated water, forcing the film to curl away from the surface. Once the bottom of the film is exposed to air, it quickly releases the moisture, somersaults forward, and starts to curl up again. As this cycle is repeated, the continuous motion converts the chemical energy of the water gradient into mechanical energy.
Such films could act as either actuators (a type of motor) or generators. As an actuator, the material can be surprisingly powerful: The researchers demonstrated that a 25-milligram film can lift a load of glass slides 380 times its own weight, or transport a load of silver wires 10 times its own weight, by working as a potent water-powered “mini tractor.” Using only water as an energy source, this film could replace the electricity-powered actuators now used to control small robotic limbs.
“It doesn’t need a lot of water,” Ma says. “A very small amount of moisture would be enough.”
A key advantage of the new film is that it doesn’t require manipulation of environmental conditions, as do actuators that respond to changes in temperature or acidity, says Ryan Hayward, an associate professor of polymer science and engineering at the University of Massachusetts at Amherst.
“What’s really impressive about this work is that they were able to figure out a scheme where a gradient in humidity would cause the polymer to cyclically roll up, flip over and roll in the other direction, and were able to harness that energy to do work,” says Hayward, who was not part of the research team.
The mechanical energy generated by the material can also be converted into electricity by coupling the polymer film with a piezoelectric material, which converts mechanical stress to an electric charge. This system can generate an average power of 5.6 nanowatts, which can be stored in capacitors to power ultra-low-power microelectronic devices, such as temperature and humidity sensors.
If used to generate electricity on a larger scale, the film could harvest energy from the environment — for example, while placed above a lake or river. Or, it could be attached to clothing, where the mere evaporation of sweat could fuel devices such as physiological monitoring sensors. “You could be running or exercising and generating power,” Guo says.
On a smaller scale, the film could power microelectricalmechanical systems (MEMS), including environmental sensors, or even smaller devices, such as nanoelectronics. The researchers are now working to improve the efficiency of the conversion of mechanical energy to electrical energy, which could allow smaller films to power larger devices.
The research was funded by the National Heart, Lung, and Blood Institute Program of Excellence in Nanotechnology, the National Cancer Institute, and the Armed Forces Institute of Regenerative Medicine.
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Replacing flat panels with three dimensional structures can significantly change the economics of solar power generation, say engineers
The Sun sends some 87 Petawatts of power our way and converting some small fraction of this into usable power is one of the key battlefronts in the fight to free the world from its addiction to oil.
One way to do this conversion is to turn light into electricity using flat photovoltaic panels. This form of power generation is rapidly expanding all over the world.
But it suffers from various problems that prevent its more widespread adoption, particularly at higher latitudes where the amount of energy that can be converted varies dramatically throughout the day and by season too.
This variation can be mitigated by solar tracking mounts but these are expensive and potential points of failure.
Today, Marco Bernardi and pals at the Massachusetts Institute of Technology in Cambridge say there is a simple fix that could dramatically increase the performance of photovoltaics. Instead of two dimensional flat panels, Bernadi and co suggest using three dimensional structures.
They’ve simulated the performance of various shapes and tested several of these on the roof of a building at MIT. Their results indicate that 3D structures can increase the amount of energy that can be generated by a given footprint by as much as 20 times. These structures can also double the number of useful peak hours of generation and reduce seasonal variation to boot.
There are two effects at work. The 3D structure can pick up light when the Sun is at lower angles and internal reflections within the structure help increase the amount of captured light.
These structures needn’t be complex. A simple cube, open at the top and covered inside and out with photovoltaic cells, can generate as much 3.8 times the power of a flat panel with the same footprint. By comparison, a solar tracking mount produces an increases of only up to 1.8 times.
The ultimate test for this idea is in the economics, of course. A cube has a much higher surface area than a flat panel and is more expensive to produce in the first place. But Bernadi and co say the extra power it generates more than compensates up for this.
If the numbers work out as these guys say, 3D structures could significantly change the photovoltaics market. Bernadi and co suggest their 3D structures could be shipped as flat packages that easily “pop up” into 3D structures when assembled.
And there may be significant improvements to be had in future too. They say the inspiration for this work is “the three-dimensionality of sunlight collecting structures found in Nature.” Presumably, they mean trees and plants.
These are far from the box-like shapes studied so far. Instead, nature seems to rely on fractal structures for solar energy capture. Just how much better these shapes are needs to be established. Copying these shapes will also be difficult with today’s methods of manufacture so advances will be needed in this area too.
But clearly, there’s plenty of potential for further work here. .
Ref: arxiv.org/abs/1112.3266: Solar Energy Generation in Three-Dimensions
New thermoelectric materials will be tested in BMW, Ford, and Chevrolet vehicles by the end of summer.
At least two-thirds of the energy in gasoline used in cars and trucks is wasted as heat. Thermoelectrics, semiconductor materials that convert heat into electricity, could capture this waste heat, reducing the fuel needs of the vehicle and improving fuel economy by at least 5 percent. But the low efficiency and high cost of existing thermoelectric materials has kept such devices from becoming practical in vehicles.
Now researchers are assembling the first prototype thermoelectric generators for tests in commercial cars and SUVs. The devices are a culmination of several advances made independently at thermoelectric device-maker BSST in Irwindale, California, and at General Motors Global R&D in Warren, Michigan. Both companies plan to install and test their prototypes by the end of the summer—BSST in BMW and Ford cars, and GM in a Chevrolet SUV.
BSST is using new materials. Bismuth telluride, a common thermoelectric, contains expensive tellurium and works at temperatures of only up to 250 °C, whereas thermoelectric generators can reach 500 °C. So BSST is using another family of thermoelectrics—blends of hafnium and zirconium—that work well at high temperatures. This has increased the generator efficiency by about 40 percent.
At GM, researchers are assembling a final prototype based on a promising new class of thermoelectrics called skutterudites, which are cheaper than tellurides and perform better at high temperatures. The company’s computer models show that in its Chevrolet Suburban test vehicle, this device could generate 350 watts, improving fuel economy by 3 percent.
Story Continues -> Powering your car with waste heat