FAQ (frequently asked questions)
The most asked question is how it works?
Answer: The Ettridge Wind Generator works on a spinnaker or sail principle, not as the propeller wind generators, which use an aero foil principle. We would all have seen sailing boats or yachts moving in the same direction as the wind, with a large sail puffed out to catch as much wind as possible. They can only use the spinnaker while traveling in the same direction as the wind. The normal air extractor, which is fitted to vans etc. only has two blades adjacent to one another, and relies on the fact that the curve in the blade means that one side offers more wind resistance than the other side. If both blades were flat and the same size, it would not move at all. One side of the blade is scooped, and catches the oncoming wind, while on the other side, the scoop is reversed, and deflects the oncoming wind. However it does use energy from the other side scoop to achieve this. It effectively has a power stroke for 120 degrees of one turn, while the returning scoop uses energy to be driven into the oncoming wind for 240 degrees of one turn. With the Ettridge Wind Turbine, a wind shield is positioned in the 240 degrees area, to prevent the oncoming wind acting on the turbine blade. Although this would prevent the oncoming wind acting on the returning turbine blade, the blade would be pushing the air in front of it which is trapped in the tunnel formed by the turbine blade and wind shield; so it would still be using energy in the return direction. To overcome this problem, a wind scoop is fitted above the turbine, and at the correct place, the wind is directed down into the tunnel, and forces the turbine to rotate in the direction of the wind. This means that both turbine blades are producing a power stroke, and at no time are they using up energy to be driven. It also means that more turbine blades can be fitted to give a larger surface area to resist the wind movement, providing more power to the turbine shaft. It has the same effect as the wind direction changing, and following a circular path for the sailing boat. The usual propeller used on a wind generator has two or three blades, and does not have a large surface area exposed to the wind.
Is Wind energy another form of Solar Energy?
Answer: Yes, Wind is produced by the sun heating a land mass, and the heat from the land is absorbed by the surrounding air. When the air temperature reaches a certain temperature, it begins to rise quickly upwards, this results in a low pressure area at ground level, and a higher pressure area above ground level. Remember, hot air rises, cold air falls, it is this movement of air from one place to another that we call convection currents or wind. Air naturally moves from high pressure areas to low pressure areas, trying to equalize the air pressure. Areas of the Earth closer to the sun, such as the equator, become warm quicker than areas further away, such as the poles. As the air moves over the warm areas and rises, cooler air from surrounding areas rushes in to fill the space left by the rising air, thereby creating surface winds or air movement. Due to elevation, topography, location and surface ruggedness, some locations experience more wind than other locations. Winds occur both in the day time and at night.
Solar radiation is subject to the same conditions as for winds, but has a much shorter time frame. For solar radiation to occur, it must be day time or daylight hours, there is no solar radiation at night. Solar radiation is not subject to convection currents.
How is wind used to create electricity?
Answer: The rotation movement of the turbine drives a generator, either by direct drive or through gearing, to produce electricity. This electricity can be used on-site in an automobile, for domestic uses in a home, or commercial applications in a business, farm, etc. or can be connected in to an electrical grid for transmission to others who require it.
How does the cost of wind generation compare with Photo voltaics and Solar Thermal ?
Answer: Both Wind and Photo voltaics ( solar cells, usually in sheets which convert sunlight directly into electricity ) are in commercial production, while Solar thermals ( directing the suns rays by the use of mirrors on to a central heating element, to turn water to steam which is used to drive a turbine and generator ) is still in a prototype stage with some large commercial size installations proposed. At this stage, Photo voltaics installed cost approximately $8 / watt, which it is hoped to reduce to $3 in 2010. They are typically used in Suburban sites, and naturally depend on location, intensity of sun available and duration of sunlight. Solar thermal is still in the demo stage, with the expected installed costs around $10 / watt, and is expected to be used mainly by large commercial companies, and again depend on location, intensity of sun available and duration of sun light. Wind energy for small installations is about $3.30 / watt but is expected to reduce to $1.60 by 2010; large commercial units are even lower and depending on size, can be installed in Suburban or Rural areas, and located in an area with average wind movement above 8 mph is desirable.
Does the Ettridge Wind Turbine have to be mounted on a tower ?
Answer: The Ettridge Wind Turbine is the only wind turbine that can operate at ground level, simply because it works on a sail, spinnaker principle, and as we all know sailing ships and yachts work at sea level. Naturally the clean air movement and constant direction of the wind is desirable, and a domestic unit installed on the roof of a house would be better than ground level, provided there are no tall trees planted around the house. A commercial unit located near the top or on the top of a hill would have no more visual impact than a shed or water tank. Painted in an appropriate color ( green or light blue ) it would be difficult to see. The small propeller wind turbines are mounted at the top of masts or towers, with a minimum height of 40 feet =(12 meters) and can be much higher, while commercial units, have towers 80-130 ft =( 24-40 meters).
Is the foot print ( area of the base, or mounting ) as large as a propeller wind generator ?
Answer: If you compare a small domestic wind generator on a 40 foot mast, and include the area taken by the retaining wires, the answer is No. For a domestic application, it needs about the same size as a evaporative water cooled air conditioner, which is much smaller in area than the 40 ft mast plus retaining wires. If you compare it to a commercial unit with a 80-130ft mast, it would be about the same size, but only 20-30ft high.
How much noise does the Ettridge Wind turbine make compared to propeller type wind generators ?
Answer: How much noise does a sail or spinnaker make ? There are no high surface speeds. The blades in the Ettridge Wind Turbine only move the speed of the wind or slower, unlike a propeller tip which can approach the speed of sound. I have read about people who installed a small domestic wind generator close to their house, and described the sound " like a hurricane fighter plane about to land on the house " in strong winds. That is why most domestic installations are as far away from the house as possible. The noise level using the Ettridge Wind Turbine is negligible, about the same as the surrounding wind.
How is the Generator attached to the Ettridge Wind Turbine ?
Answer: The Ettridge Wind Generator can have a Gemini Electric Generator incorporated in the base of the turbine, in line with the main shaft. The Gemini Electric Generator website is : www.geminielectricmotor.com
It is possible to run a gearbox off the base to step up the speed if using a conventional alternator.
How does the cost compare to a conventional propeller wind generator ?
Answer: The cost of a domestic installation of the Ettridge Wind generator would be less than the total cost of an equivalent propeller wind generator, especially when the cost of the tower or mast is included. The larger the unit, the greater the difference in cost, with the Ettridge Wind Turbine being the lower cost.
Is there much maintenance with the Ettridge Wind Turbine ?
Answer: There is very low maintenance with the Ettridge Wind turbine, and provided the bearings on the rotor shaft are well lubricated, and they require about the same attention as the wheel bearings on an automobile. Because the Ettridge Wind Turbine can be situated at ground level, naturally any debris from trees or vegetation needs to be kept low or clear. If vegetation builds up, apart from restricting the wind, solid vegetation could obstruct the rotor and damage the blades. It would be fairly obvious that the area around the turbine needs to be cleared or kept very short. Ideally the area would be fenced or the area on which the base of the turbine sits on, should be raised to prevent domestic animals getting near the turbine blades.