Archive → August, 2011

Troubleshooting Tips for Small Wind Turbines

30 August, 17:55, by homemadejoe Tags: , ,

Wind turbines generate clean electricity and provide a cost-effective way to go off the grid. However, building homemade wind turbines through the help of manuals is different from troubleshooting certain natural problems generated by wind turbines like heat and noise issues. Here are some ways to reduce the noise produced by the turbines, as well as other concerns that you may find helpful in the future.

Noisy gearboxes

Modern wind turbine gearboxes are designed for quieter operation. However, if you still find it noisy, you must first identify if it’s mechanical or aerodynamic noise.

Here are some steps that you can follow to avoid and reduce mechanical gearbox noise:

•    Before purchasing industrial gearboxes, make sure that the gearbox has steel wheels with slightly soft and flexible core. The surface must be hard and durable for longevity.

•    Make sure that the metal wheel’s surface has high carbon content. This can be done by heating the gear wheels and letting them cool slowly while the surface and core are packed with a powder with high carbon content. This carbon should migrate to the metal’s surface while leaving the interior soft and flexible.

Aerodynamic noise of homemade wind turbines

Aerodynamic noise can be an effect of surface vibrations made by rotor blades. To transfer energy from the rotor blades, the blades must break the wind, which in turn causes a white noise. Most rotor blades are very smooth for aerodynamic purposes and must emit minimal noise.

Noise increases with the speed of the blade. Reducing aerodynamic noise can mean sacrificing rotational speeds and energy generation. Aerodynamic noise is a minimal problem compared to mechanical noise that can lead to mechanical failure as well.

Temperature problems

Wind turbines have minimum temperature operating limits. It must be protected from icy weather as the auto sensors can be damaged and work inaccurately. Low temperature can also cause mechanical damage.

•    Lubricate gears and bearings regularly especially during cold weathers

•    Check for bacterial growth, oil and water emulsions, and other solid contaminant that can induce mechanical failure

•    Electricity loss

To make the power generated by the wind turbines usable, it must first be inverted to match the frequency and voltage of the grid. However, inverting electricity amounts to 10% of electricity loss. If the line is farther from your home, there is also electricity that will be loss in transmissions. The farther the system is, the higher the transmission loss. This is due to the wire resistance. The longer the wire and the higher the resistance, the higher the electricity loss would be.

While transmission loss also applies to electricity from the grid, the rate of electricity loss in wind turbines is quite high considering the energy generation and storage of the wind turbines.
Aside from electricity loss, there can also be a case of excess of electricity. Here is what you can do the excess energy generated by your homemade wind turbines:

•    Sell excess electricity to electric companies

•    Store excess energy in batteries for future use

•    Connect it to your hot water storage tank or hot press tank. This is especially useful in cold weather

•    Install an internal heating system to protect the sensitive power electronics in the gearboxes and CPU

Number of Wind Turbine Blades

22 August, 17:52, by homemadejoe Tags: , ,

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.