The Cost of Energy

Are a few extra turbines in a large wind farm really worth their price?

You have a huge stretch of land that would be ideal for a wind farm. Some spots are windier than others, so you’ll just stick the turbines in those windy areas and everything will work out great.

Not so fast. What if an exceptionally windy area is on the backside of a large hill, separated from the rest of the turbine clusters? Then you have to figure the costs for access roads and extra cabling, not to mention the already expensive tasks of transporting turbines, construction, permitting, insurance, O&M and taxes, among others.

Is increasing your wind farm by a few turbines on the back of a hill really worth it?

AWS Truepower tries to make this decision easy to come by. AWS provides renewable energy consulting and information services, including the openWind program. The design and optimization software application allows users to design and estimate the energy production of wind projects. The program is offered free, but an Enterprise version includes more advanced elements.

“The traditional approach [to wind farm development] is just to place turbines in the locations where they produce the greatest energy production so it maximizes the energy production,” says Michael Brower, chief technical officer at AWS Truepower. By inputting a wind resource map and defining what size project you’re working with, openWind can shoot back turbine locations that will generate the most energy. It takes into account wake losses between turbines and spaces them out accordingly.

“The problem that often comes up though is that particular layout may be quite expensive to build. There may be a small hill or similar terrain feature that’s off from the rest of the turbines,” Brower says. “The program sees that that is a windy spot and decides to put two or three turbines there. Those are called ‘stranded turbines’ because they’re quite a distance away from the rest of the layout, and if you were to put them there, you would have to build a road specifically to service those turbines. You’d also have to put in cabling specifically to bring in the power from those turbines. So you’d be putting in a lot of extra road and a lot of extra cabling just to serve two or three turbines.”

That’s where one of openWind’s modules — the Cost of Energy Optimizer — comes in. It determines whether those stranded turbines are worth it. With a traditional program, you would make adjustments and manually move turbines to better locations. But with openWind, this process is imbedded within the program, using the Cost of Energy Optimizer.
“Every time the program makes a new layout, it will also estimate the cost of the roads and cabling required to serve that layout and estimate the cost of energy,” Brower says. “So rather than maximize the energy production, it will minimize the cost of energy, and that gets rid of the problem of stranded turbines.”

Considering the different access road requirements (turn radius, terrain, etc.) and cabling options, developing a wind farm layout can get complicated. Brower says more large developers benefit from the openWind program because the more turbines you have, the more complicated problems you run into. And AWS tries to make the task of designing wind farms as simple as possible.

“There are different ways you can design a layout. All of these options need to be considered, and they each have their own cost. It’s quite an involved process,” Brower says. “We’re very pleased that we’ve come up with what we think is a very efficient and useful tool for doing that.”