Tag → wind turbine design

Number of Wind Turbine Blades

22 August, 17:52, by homemadejoe Tags: , ,
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One of the most asked questions prior to building homemade wind turbines is the number of blades to be used. For the last 50 years, wind energy system manufacturers have used two to three blades. However, the third blade was not much of an option if the priority is to increase aerodynamic efficiency.

During tests, it is found out that increasing the number of blades from one to two increases aerodynamic efficiency by 6%. However, when two blades are increase to three, there is only a 3% increase of efficiency. Minimal improvements are yielded from additional blades. Furthermore, as the number of blades increases, the thinner the blade gets, sacrificing blade stiffness and power generation.

The cost is also affected by the number of wind turbine blades. In general, fewer blades mean less manufacturing and material cost. A wind turbine with fewer blades is also able to build up higher rotational speed with reduced peak torques, allowing lower generator and gearbox costs.

Number of blade concepts

1-bladed concept

It may look pretty unbalanced and strange but a one-blade wind turbine save an entire cost of a rotor blade. Although more economical with regards to manufacturing costs, one-blade wind turbines suffer from aesthetic and noise problems. A counterweight on the other side of the hub needs to be placed to balance the rotor and keep it from rotating.

Teetering or 2-bladed concept

Some wind turbines have only two rotors to save up on the cost of a third blade. However, 2-blade wind turbines are being overtaken by 3-blade wind systems due to aesthetic and noise issues. Rotational speeds also generate less energy, making it a poor second to third-bladed wind turbines.

3-bladed Danish concept

Modern homemade wind turbines have three-bladed designs, also referred to as the Danish concept. This design provides a smoother operation during turbine yaw due to symmetrically balanced cyclic loads. While two-bladed concepts allow less manufacturing, materials, and maintenance costs, three-bladed wind turbines are considered by some people to be more balanced and pleasant to look at compared to one or two bladed turbines.

Old and modern wind turbines differ in speed and materials use. Modern small wind turbine blades are mostly made from aluminum because of its low density and resistance to corrosion. When combined with composite materials, it allows the blades to gain speed as the winds pick up. Commercial wind turbines use a variety of materials that require composite fabrication techniques to ensure the durability and longevity of the blades.

If you are building homemade wind turbines, consider a two-blade concept for easy installation and construction. However, if you want a quieter wind turbine operation, higher efficiency, and do not mind spending for an additional rotor, go for three-bladed wind turbines. Residential wind turbine blades do not have to be made from expensive materials. Look for lightweight glass-enforced plastic or even laminated wood to reduce material costs. If budget is not an issue, use graphite-fiber in epoxy for specific load-bearing parts of the rotor blades.

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How do you make a homemade wind vane?

30 July, 17:29, by homemadejoe Tags: , ,
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Wind vanes are mechanical devices showing wind’s direction. Though the weight is evenly distributed, the surface area of a wind vane is designed unequally distributed so that the pointer can move freely on its axis. It is the larger surface area that is being blown away from the winds direction. The smaller area where the pointer is located then points towards the wind direction.

Though wind vanes can basically give idea about wind’s direction this may not be accurate especially when there are too many interferences around such as trees, buildings and other objects. For this reason, these mechanical devices are sometimes use for decorative purposes. Earlier wind vanes even had ornamental pointers but nowadays, they are usually found with simple pointers.

There are many materials from which a wind vane can be constructed. However, the design has to consider the main purpose of these instruments – to tell the wind direction as accurate as possible. Wind vane can be an important tool for those with homemade wind turbines.

Using this device, the owner can always have a way of tracking wind direction. Moreover, wind vanes can also be used by those planning to build homemade wind turbines to properly select the best location for these electricity generators.

One of the simplest ways to make a home-made wind vane is by using plastic materials, cardboards and some markers. The first part that should be done is the base or the stand of the vane. A plastic soda bottle will do. Fill this with dirt, sand and pebbles. It is important to make sure that this will be stable enough to hold the vane as it follows the wind direction.

Near the top of the bottle, mark four points of equal spaces. These points will represent the four directions: north, east, west and south. Cut out two pieces of cardboard for the tail and for the point. A recommended measurement for the tail is 3 inches long by 3 inches wide. The other piece of the cardboard should be in the shape of a triangle that is 2 inches high at the wide end.

Lay the tail and the pointer on the table and lay a straw over them. Tape these two cardboards on each end of the straw. It is important to ensure that the tape will be long and strong enough to hold these cardboard pieces on both ends.

Find the exact middle of the straw and push a straight pin. The end of the pin is then push in a pencil eraser. Let the pencil stick into the dirt or pebbles inside the base bottle. Take note that after accomplishing these steps, you now have a wind vane and that the straw should move freely to serve its function.

The final step is doing some calibration. Find the true north using a compass. Upon locating, position the wind vane such that the N or the north markings on the bottle is in line with the same north as with the compass direction. Unlike the homemade wind turbines, making a home-made wind vane is definitely much easier with no so much money involved. Scrapped materials can even be used.

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