Date: 8/12/2013

Some wind farms in the United States are nearing the end of their 20-plus-year lifetimes, increasing the possibility of re-powering the older equipment. When considering this option, wind farm owners and developers must be aware of the possible impacts and challenges of a wind farm re-power. While conducting research on this topic, Wind Powering America's Frank Oteri interviewed Neil Habig, senior developer at Iberdrola Renewables; Don Bain, president of Aeropower Services; and Mark Jacobson, senior project leader at the National Renewable Energy Laboratory and former director of business development at Invenergy LLC. They shared the following lessons learned regarding the re-powering of wind farms.

When is it appropriate to re-power?

Determining the correct time for a re-power requires analyzing many different aspects of the project. In Bain's opinion, the profitability of the project plays a role in determining when re-powering is appropriate. According to Habig, re-powering depends on particular project situations, such as the status of the turbine manufacturer and the availability of spare parts.

"If you have a turbine that you can't maintain because the company went out of business, or if you have a specific technical problem, re-powering might need to happen sooner. But other than that, the systems are designed to run for about 20 years," Habig said. "Plants that are ripe for re-powering are plants that have old turbine technology. Either that technology is working, which I would say is the minority of projects, or that technology is very problematic. So you look at operations and maintenance costs and revenues versus the costs and net profits of pulling turbines out, or a project out, and re-powering it. You get to a certain point, perhaps before the initial project's lifetime is up, where it makes sense to re-power because there's the opportunity to make a lot more money or there's the opportunity to get a lot more megawatts into the ground than you initially had, which in turn leads to higher revenues and higher profits."

Jacobson believes two additional factors determine the appropriate time for a re-power.

"It's important to remember that if you decide to put more megawatts on the line, you'll have to go through the interconnection process again. The power buyer, who's usually the same utility you're dealing with on the interconnection issues, has to want the additional megawatt-hours and be willing to modify the current power purchase agreement prior to the end of its term or renew the agreement if the re-powering option occurs at the end of the agreement's term," he said.

What are some common challenges of re-powering a project?

Two common challenges of re-power projects are land leases and permits for the project. Bain believes that these two topics were sometimes not fully considered during initial negotiations for the original plants.

"You have issues with leases, the underlying land control," he said. "You may find, in fact in my experience it is common to find, land leases that did not incorporate the re-powering of a wind project."

Bain said that often land leases only considered the initial project and land control for a period of time sufficient to install another project or two.

"You may find that a whole bunch of other re-powering issues have not been addressed in the land lease," he added.

According to Bain, another issue is that the original project permits may not include a decommissioning requirement. The decommissioning requirement did not exist as part of the earliest wind projects, which would probably be the ones that are the most ripe for re-powering today.

What are the benefits of a re-power?

There are multiple benefits associated with a re-power, including the installation of fewer machines to produce the same or more power, the potential re-use of roads or other infrastructure, the continued use of a known resource, and usually lower power costs. There's a benefit if the facility is at the end of its useful economic life and if the turbine manufacturer has discontinued the turbine or it's impossible to find service or parts. But according to Habig, the real benefit results from using new technology.

"Over time, turbine energy capture, power curves, capacity factors, and overall machine size tend to go up," he said.

Habig provided an example: a wind farm in Searsburg, Vermont, that came online in 1997 and consists of 11 600-kilowatt Zond machines. If modern 2-megawatt machines were installed instead, only three or four turbines would be needed. Some of the roads might be usable, but the foundations and pad site locations would be different.

"But you might have an available interconnection, and you already have the infrastructure for that, so that's an extended use," Habig said.

Bain believes that the primary attraction is the familiarity one has with the site.

"The attractiveness of a re-power is that not every place is windy. You know this site is windy," he said.

Can the cost of removing old equipment be offset by selling it?

Some believe that the costs of removing old equipment can be offset by selling it. This depends on the current demand for the older technology, as well as on the current costs of scrap metal. Habig believes that the cost of removal can be offset in certain situations.

"The company has to post a decommissioning bond, and if you have a used-equipment valuation, that may bring it closer to neutral," he said. "Take Searsburg as an example. You're not going to sell those turbines to anyone. It really depends on technology, how modern it is, and the size."