New Wind Turbine Generator Ditches Mechanical Transmission, Ups Efficiency 50 Percent

[CvP]

New wind generator design takes advantage of an advanced electrical transmission to decrease cost while boosting performance

While the costs of solar power have continually dropped over the past couple decades, wind power has only decreased slightly in cost, owing to a relative lack of sources of improvement. Much of the wind power research has focused on either building larger turbines which are naturally more cost effective or trying to fit turbines into new areas. Few looked to reinvent the base structure of the turbine.

Startup ExRo is not your average wind power company, though. This think-outside-the-box firm has reinvented one of the most basic components of wind turbines -- the generator. Its new design promises up to 50 percent more efficiency and lower production costs as well.

Ordinary wind power generators have an optimal rate which is fine tuned to local average wind conditions. When the wind is blowing at this speed, the turbine produces electricity at an outstanding efficiency of around 90 percent. However, when the wind blows faster or slower the efficiency significantly decreases. This is a major cause of why wind power is more expensive than coal, which burns in plants with turbines that turn at steady rates, maintaining the higher efficiency.

In the past, some have tried blades that change pitch to catch more or less wind and maintain a steady pace. Others have used mechanical transmissions. However, these components tend to be expensive, raise maintenance costs, and only help so much.

The new generator scraps the mechanical transmission, replacing it with an electrical one. The new transmission still requires a bit of blade pitching when winds are extremely high. However, it is able to extend the peak efficiency range significantly, balancing gusts and lulls, and producing, over the course of the year, up to 50 percent more power.

Ed Nowicki, a professor of electrical engineering at the University of Calgary who consulted on the project said some locations could even see their power output double.

The generator is relatively standard in basic design, with magnets attached to a rotating shaft that create a current as they pass stationary copper coils arranged around the shaft. In a normal generator all the coils are switched on. When turning too slowly, this can cause excess resistance, decreasing the generator efficiency.

The coils on ExRo's generator are not on by default, but are controlled electronic based on wind speed. At lower speeds only a couple coils are on, producing optimal efficiency, and as speeds ramp up, more coils are turned on to harvest the energy of the wind at peak efficiency.

The generator also sports another improvement. Typically in order to generate more power at top speeds, you need more coils via a very large diameter generator. However, such generators are very hard to get moving and more expensive. The ExRo generator instead uses multiple small-diameter generators to produce an equivalent effect. It calls each of these mini-generators stacks. In addition to being able to harvest more wind power and change speed faster thanks to its small diameter, the design allows for easy customization on the production line for local wind conditions by adding or removing stacks.

While some other companies have tested multi-stack designs, these required multiple mechanical transmissions, which added too much weight and effectively negated much of the benefits. By switching to an inexpensive electric transmission, ExRo was able to finally offer an effective version of this solution.

ExRo estimates that a utility employing its new generator will make 57 percent more money from a turbine over the course of a year. These estimates come from scale models. The company plans to test a small 5 kW turbine in the field later this year. The company then plans to aggressively ramp up to megawatt-scale designs, at which point it will release finalized efficiency figures.

A prototype of one of ExRo's stacks showcases the company's new electric transmission. The improvement could make wind power 50 percent more efficient over the course of a year. (Source: ExRo)

A rendering of the stack illustrates how two rings of rotating magnets connect to the shaft (blue) generate power by passing coils (green and red). These coils can be selectively turned on and off by the electric transmission. Multiple stacks can be collected to a single shaft for better performance. (Source: ExRo)

[GG.AIM]

The max efficiency possible with a wind turbine theoretically is 59.3% neway.