ExRo promises more efficient wind turbines

2008-11-19

in Canada, Economics, Science, The environment

A new type of generator for wind turbines promises to increase the range of wind speeds across which they generate electricity efficiently. The system, developed by ExRo Technologies of Vancouver, uses stacks of copper coils that can be activated and deactivated individually. That means the generator is capable of deriving small amounts of power from slow winds and larger amounts from faster winds. Crucially, the system also allows that to occur without the use of any moving parts: decreasing the cost and increasing the reliability.

For now, the company has only tested a laboratory-scale prototype. They are now aiming to scale up the technology for use in large multi-megawatt wind turbines. In some cases, it may even be economically efficient to install the new generators in existing wind turbines.

One reason for which the technology looks promising is that it could decrease the variance in power output from wind farms, decreasing the need to balance times of low output using energy storage or alternative forms of generation.

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{ 5 comments… read them below or add one }

Tristan November 20, 2008 at 8:04 am

This really demands the question, have these guys ever heard of alternators? They seem to achieve the same purpose as this switchable generator, but instead of switching coils off and on they simply vary the field voltage.

http://en.wikipedia.org/wiki/Alternator

Milan November 20, 2008 at 9:18 am

If it was as simple as dropping in an existing piece of technology, you would expect that someone would have already used it. I am not sure if these technologies, described in this Wikipedia entry, are comparable:

“Newer wind turbines often turn at whatever speed generates electricity most efficiently. This can be solved using multiple technologies such as doubly fed induction generators or full-effect converters where the variable frequency current produced is converted to DC and then back to AC, matching the line frequency and voltage. Although such alternatives require costly equipment and cause power loss, the turbine can capture a significantly larger fraction of the wind energy. In some cases, especially when turbines are sited offshore, the DC energy will be transmitted from the turbine to a central (onshore) inverter for connection to the grid.”

. November 20, 2008 at 10:22 am

From the ExRo website:

“The past 15 years have seen a number of innovations in the wind power market.The first stream of innovations focused on pitch and yaw. Literally turning the blades away from the wind, effectively reducing their area and artificially lowering available energy to the generator (shedding). This works to keep the turbine operating for a greater number of hours per year, but wastes all available energy over a given wind speed.The second stream of innovation focused on improvements to the gearbox in an effort to speed up the shaft when the wind was below the generators operating range. Again, the solution worked to widen the operating band, but gearboxes introduce friction, which reduces output (they are also prone to chronic failure).A third stream of innovation focused on varying the amount of magnetic flux in the generator, which made it easier to turn at low speeds, but also made it far heavier and less efficient than permanent magnet machines.While this tactic does allow a generator to operate over a wider band, the weight, size and inefficiencies have led most in the industry to focus their efforts on permanent magnet generators.

The most recent stream of innovation has focused on attempts to link multiple generators together, typically with mechanical gearing.A multi-generator solution allows low speed operation, by running only a single generator, and it allows the addition of additional generator capacity as available energy (wind speed) increases.The first attempts had only two generators (one small and one large) and subsequent inventions have focused on various attempts to add more generators to widen the operating band.Although this solution has to date been quite rudimentary, it has proven to provide higher output and several patents have been issued along these lines in recent years, including a recent patent which covers up to 6 generators run off a single gearbox.

ExRo’s solution follows a similar logic, but takes the concept to a much higher level by completely redesigning the electrical generator for variable input sources. Rather than layering individual legacy machines one on top of the next, the VIEG uses a series of coils, configured in “balanced stages”.The magnetic balancing allows the use of permanent magnets, yet still reduces cogging torque to a bare minimum, which allows the VIEG to operate at extremely low wind speeds (near zero).As available energy increases, the VIEG matches generator resistance to source energy by electronically adding generator stages. Conversely, the VIEG is able to drop stages as available energy (wind speed) drops, cycling up and down without hesitation and without mechanical friction.The need for a gearbox is eliminated, and a single VIEG generator scales up and down with available energy in a way that would take almost 70 individual generators to match.”

Tristan November 20, 2008 at 4:20 pm

This really demands the question, have these guys ever heard of alternators? They seem to achieve the same purpose as this switchable generator, but instead of switching coils off and on they simply vary the field voltage.

Milan November 20, 2008 at 4:21 pm

Why don’t you call them and ask? Their website includes contact information.

The media relations contact (Lisa Ann Pinkerton – 1-415-977-1916) might be able to answer your question or put you in touch with someone who could.

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