A turbine twist to catch energy from the wind

A wind turbine that is helical instead of bladed is found to quieter, more efficient, and does not have to have its blades feathered and be stopped in high winds. Coupled with eddy current couplings to turn flywheels, developed by an inventions company on the other side of the world, such devices can be used to deliver power or torque relatively evenly despite variations in wind speed. Both developments are presently sized for the isolated home or farm rather than major power generation, but nonetheless can easily be scaled up. There is also a strong case to be made for having individual small wind turbines on all homes. Small turbines are no more obtrusive than satellite dishes, and would seem to us to be a more aesthetic option than attempting to cover the green hills of England with big machines, in order to try to meet the 10% from renewables by 2010 goal set by government, plus acres more offshore. The helical wind turbine has been given the name the Wind Wandler and has been developed by a small German company called MatroW, based in Ladenburg which is between Heidelberg and Mannheim. Company managing director Wilhelm Hermann Josef told us when we met him at the Hannover Fair that he and two colleagues were looking for something that would allow wind turbines to be made more efficient than blades, taking advantage of modern advances in materials. Conventional wind turbines have straight, almost flat blades because they are essentially derived from windmills, descended through aircraft propellers. The form the developers picked was, apparently, originally conceived to work in water, but the availability of modern composites allowed it to be made somewhat larger and lighter than would previously have been possible. The first production units consist of two spiral vanes of glass fibre reinforced materials. They are 1m in diameter, 1.39m long and sit in a hemispherical yoke so they are supported at both ends. Output at 14m/s is about 1kW. The disk armature generator is rated at 3.5kW, and unlike bladed turbines, they do not have to be stopped in high winds. Rotation speed at 24m/s wind is 1400 rpm, but remains the same at 30m/s because surplus high speed air then tends to spill round the rotating turbine. The turbines turn naturally into the wind. Herr Josef told us that they are 53% efficient, as opposed to 46% for conventional bladed turbines, and the theoretical maximum efficiency that can be attained is 59%. They are certainly very quiet when they rotate, which he says, is because they have no blade tips to shed vortices. Total weight of turbine and generator without mast is 39kg. Noise level at 1400 rpm is 42 dBA. The company had just sold eight units when we met them, at a price of 6300 euros each. It would also like to produce large units, and has a design for a 1MW machine, with a 29m diameter turbine, and is currently looking for the 5 million euro estimated development cost. At the other end of the exhibition ground, and based at the opposite end of the world, so that the two companies were totally unaware of each other, was the Giant Lion Know How company, based in Taiwan. Its proprietor, Tai-Her Yang is the inventor of what he describes as a "Flexible and Rigid Bi-Status Coupler". This is an eddy current and one way clutch coupled flywheel device, which is primarily intended to function as an energy accumulator for wind pumps and wind power electric generators. The input shaft is connected to a copper ring armature and to the output shaft through the one way clutch. The armature interacts with field produced by the permanent magnets inside the flywheel. When the turbine is going fast, the turbine both turns the load and increases the flywheel speed through the eddy current coupling. However when the flywheel is going faster than the turbine, the flywheel continues to turn the load through the eddy current coupling, but the mechanical clutch is disengaged so that it does not try to turn the turbine as well. Coupling the flywheel through an eddy current coupling greatly reduces peak loads on input and output shafts and gears. The proprietor described the two units on show as, "Working models in steel". One was configured to drive an electric generator at relatively constant speed, and the other to drive a reciprocating water pump. A patent has been applied for which covers various variations on the basic idea, including use of fluid couplings instead of eddy currents. While German and Danish companies have come to dominate the manufacture of large wind turbines, and there were some very large examples of their machinery on show at Hannover, the leading installer of inter turbine and shore connection cabling for offshore wind farms is a British Firm. Global Marine Systems is a direct descendant of the company that laid the first international submarine telegraph cable to link Britain to France using the ship Goliath in 1850. It has dominated the underwater cable business ever since, and more than 50 per cent of the world's buried fibre optic cables have been installed by the company which also undertakes between 30 and 40 per cent of all cable repairs and maintenance. At present in the UK, there are two offshore turbines operational at Blythe and 30 at North Hoyle. About 180 are in advanced stages of planning and design and sites have been approved for 330 more. Wind Wandler Giant Lion Know-How Global Marine Systems Eureka says: There is a lot to be said for small, quiet efficient wind turbines on houses, as opposed to the large numbers of monstrosities with which some propose to cover the hillsides of England's green and pleasant land Pointers * New Wind Wandler turbine is much quieter and more efficient than conventional wind turbines. It also orientates itself into the wind, and requires no mechanics to shut it down in high winds. It is no more obtrusive than a satellite dish. * A novel flywheel coupling looks to be a promising way of easing out energy fluctuations in the output from small turbines and would appear to be particularly suitable for use with wind pumps