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Catch the wind; Research into renewable energy source finds possibilities and challenges

Slowly turning in the breeze, wind turbines seem an obvious solution to the nation’s energy needs. The fuel is free, and the greenhouse gases nonexistent.

But incorporating electricity produced by the wind into a power grid poses a host of challenges.

“Wind can be very intermittent,” says Nag Patibandla, director of the Center for Future Energy Systems at Rensselaer Polytechnic Institute. The Independent System Operator, which oversees the state’s wholesale electricity market, wants reserve capacity available to replace that power.

“You’re maintaining duplicate investments on the grid, which have to be paid for,” Patibandla says.

Often, these backup generators are among the grid’s least efficient providers, and they can produce more greenhouse gases.

Ken Klapp, a spokesman for the ISO, says the disruption caused by a lack of wind would become an issue were wind power to provide 10 percent or more of the state’s total power. Right now, wind provides less than 1 percent.

But with 6,000 megawatts of wind power projects planned or proposed – total state generating capacity from all sources is 39,000 megawatts – this promises to become more of an issue.

General Electric, which has made wind power a key component of its Ecomagination initiative to bring cleaner technology to market while reducing greenhouse gas emissions and improve energy efficiency, is looking for ways to resolve these and other issues.

Much of this research is being done at GE’s Global Research Center in Niskayuna.

Another challenge: upgrading the wires that will carry the power away from the wind farm, as the collection of wind turbines is called. Because these are often built in rural areas, away from major power transmission lines, connections need to be built or upgraded, said Janet Besser, vice president of regulatory strategy for National Grid. This adds to wind farms’ costs.

“National Grid is interested in encouraging wind power,” she said. “We’re very concerned about climate change.”

GE reserchers seek solutions

GE’s Global Research Center in Niskayuna hopes to improve wind power technology in the following areas:

* Blade weight: Carbon composites could replace heavier materials.

* Blade length: Blades could be shipped in pieces, assembled on site.

* Storing output: Batteries, electrolyzing water to produce hydrogen, hydraulic storage are possible solutions.

* Light winds: Better aerodynamic design would move blades at lower wind speeds.

Wind energy: Clean and plentiful, except when it’s calm

Wholesale costs are based on large-scale plants and don’t include tax incentives

Source Cost per kilowatt-hour Greenhouse gases?

Coal 5.7 cents Yes

Natural Gas 5.8 to 7.2 cents About half that of coal

Nuclear 6.4 cents No

Solar/thermal 19 cents No

Solar/voltaic 25 cents No

Wind 9.6 cents No

Source: Electric Power Research Institute

Spinning power from the breeze

The nacelle that sits atop the wind turbine tower contains the rotor and the magnets used to generate electricity. When a wire-wrapped rotor turns through the magnetic field, it triggers a flow of electrons in the wires, which is basically the electric current. This phenomenon, first discovered by Michael Faraday in 1831, is called electromagnetic induction.

Turning the rotor are the wind turbine blades. Gears, sensors and brakes are all part of the mechanism contained within the unit, which can be anywhere from 235 feet to more than 400 feet in the air. The goal is to maximize electricity output from the prevailing winds at any given point.

While the wind itself is free, the cost of construction, financing and maintenance, and the general wear-and-tear from operation all contribute to the cost of generating electricity.

But as the cost of oil rises, wind energy is getting more competitive.

The scale of wind turbines also is growing, reducing further the per-unit cost of generating electricity. Many of the largest turbines are being installed offshore.

GE seeks new ways to capture wind

GE seeks new ways to capture wind

ERIC ANDERSON Deputy business editor

General Electric Co.’s expertise in aircraft engines and steam and gas turbines is being applied to its wind energy efforts. Wind Platform Technology Leader Stephane Renou, who is based at the GE Global Research Center in Niskayuna, discussed the work now under way.

Q: What approaches are used to boost the generating output of a wind turbine?

A: In the industry, the unit rated capacity is a function of the maximum generator output. For example, GE’s 1.5MW wind turbine has a maximum output of 1.5 megawatts. Increasing the total energy production can be achieved by optimizing the energy capture vs. wind speed.

A key goal is to be able to generate more power at the lower wind speeds, which increases the annual energy production of a given turbine.

There are many approaches that can be taken to increase energy production. One approach is to increase blade length or its aerodynamic efficiency.

Incorporating better controls in the operation of the turbine also can help maximize energy production.

Q: What are the challenges of longer blades? Weight? Transport to construction site? How is GE addressing these challenges?

A: All of the above. Longer blades add more weight, which can add costs to the turbine structure. Lighter materials and better design solutions will be needed to keep these costs under control. The use of lightweight carbon fiber composites is being considered to move beyond these technical barriers.

To address the transport challenges, GE researchers are exploring how to ship the blade in pieces, which can then be assembled at the wind farm site.

Material changes like the use of carbon fiber composites to replace glass composites is one approach being explored. Lighter blades require less energy and less work to initiate the blade’s rotation and may enable a lower minimum wind speed.

Q: What approaches are being explored to store energy for times when the wind isn’t blowing?

A: Present levels of intermittent renewable power on large grids do not require energy storage. As these sources become more prevalent on the grid or applied to smaller power islands, energy storage could become an important element in managing luctuations in load and maximizing clean energy production.

GE is continually investigating technologies in hybrid systems, grid management, as well as energy storage to provide viable solutions down the road.

Q: What are the challenges?

A: The main challenge for energy storage will be economical. For instance, batteries, hydraulic storage and even combining traditional and renewable sources of energy will be challenging from a cost standpoint. But having viable energy storage solutions could be a key part in optimizing the use of clean, renewable power sources and the overall management of the grid.

Q: Are there wind speeds too great for wind turbines to operate? Are you looking for ways to make turbines operate in higher winds?

A: Yes, all turbines have a cut-out wind speed. The decision on whether to design turbines to operate at higher wind speeds is an economic trade-off of increased structural costs versus a marginal increase in energy production.

Q: What might the next generation of wind turbine look like?

A: GE Energy recently released a 2.5MW wind turbine as part of its product portfolio. With the wind industry focused on low cost energy production, we are working on fundamental research that will enable lower cost wind production.

Size is one element to achieve better economies of scale. But researchers at GE Global Research will continue to work with our Energy business on material improvements, better controls and power electronics and more aerodynamic blade designs to further reduce the cost of electricity.

By Eric Anderson
Deputy business editor

Times Union

19 November 2007