Solar/wind combo project in Arizona
The first utility scale solar/wind
combination project in the U.S.—the 10.5 MW Kingman
project—has started up in solar-rich Arizona, and there are
already plans to potentially doublethe size of the project.
The renewable energy industry has taken a page from conventional energy
industry's playbook by aiming to capture more commercial value from a
single location. Case in point: Western Wind Energy recently started
producing power from its combined solar and wind power project in
The 10.5 megawatt installation is the
first utility scale renewable energy project in the United States that
combines both wind and solar power production under one Power Purchase
Agreement. Located on 808 acres owned by the company near Kingman,
Arizona, and costing in the neighborhood of $28 million, the project
involved Western Wind Energy signing a Power Purchase Agreement to
provide energy to customers of Unisource Energy Services (UES), a
subsidiary of Unisource Energy Corporation of Arizona.
Through its utility subsidiaries, UES
and Tucson Electric Power, Unisource Energy Corporation serves more
than 630,000 customers across Arizona.
Initiated by UES, the size of the
project was dictated by the Arizona Corporation Commission's mandated
renewable portfolio standard.
Typically when a petroleum company
identifies a commercially viable underground energy source, it will
target the highest volume and most valuable commodities, which in most
cases are oil, gas, or a combination of both.
However, in the process of capturing
the highest volume product, the company will extract or 'strip' other
gases like propane, butane, and ethane from the production stream,
which adds to its profit margin from that site. By combining solar and
wind on a single site, Western Wind Energy is mimicking that same
The combined wind and solar approach
in Kingman was pursued by UES because it wanted to study the power
generation profile of wind and solar on a single site and how it would
fit into the utilities' power scheduling. UES wanted to see if wind and
solar were compatible for the Kingman site and when there might be a
curtailment of power generation from either source in relation to the
"We were interested in seeing the
integrated approach because it will give us some experience with the
different performance characteristics of wind and solar energy," says
UES spokesman, Joe Salkowski. "We're interested in seeing when the
power will peak relative to our own system peak, and that will help us
determine how to integrate these resources in the future as we develop
additional systems. We're looking to see what the benefit might be of
having those resources on the same site."
Until now, the company's primary
alternative energy investments have been in solar power because of its
location in Arizona, with a small wind component.
Salkowski says UES has, until this point, provided the renewable energy
component of its power supply primarily from market purchases. The
Power Purchase Agreement UES signed with Western Wind Energy is its
first dedicated renewable energy resource.
The solar component of the
Kingman project is made up of solar panels capable of producing a total
of 500 kilowatts of solar power. The solar equipment was installed by
American Capital Energy and features 1,824 Suntech Reliathon 275-watt
modules mounted on an Array Technologies single-axis tracking system.
"We believe that it's worthwhile to dip our toes in the water through
contracts that give us an opportunity to purchase renewable power
generated from a variety of technologies, and in doing that,
determining which of those technologies might be best suited for our
business and our customers," says Salkowski.
Site selection for this type of combined project depends on topography
and traditional wind patterns. Mike Boyd, Western Wind Energy executive
vice-president of development, says that some areas of the Western
United States are particularly suitable for developing sites that
integrate different power generation technologies.
"There are some geographical areas where the wind blows at a totally
different time than when the sun shines," says Boyd. Typically in the
Western U.S., the sun shines during the day, and the wind picks up in
the late afternoon.He adds that this scenario also raises the overall
capacity of a single location where there are two different power
generation sources producing at different times of the day.
"So let's say, hypothetically, if a wind project has a 30 percent
factor and a solar power installation on the same site has a 25 percent
factor, and the output from both sources is the same, you could
basically double the output of that site," says Boyd.
He gave the example of the company's 120 megawatt Windstar wind energy
project in Tehachapi, California, where solar power generation peaks
from 10 a.m. until 4 p.m., whereas peak wind power generation occurs
later, from about 4 p.m. to late at night. Given the experience that
Western Wind Energy has gained by constructing the integrated site in
Kingman, it is considering a similar integrated approach by adding a
solar component to the Tehachapi project.
"This is a situation where the power generation sources are compatible
and there wouldn't be a lot of overlap," says Boyd. "This is a good
situation, since you can maximize transmission capacity under those
kinds of circumstances, and you would not have to employ some type of
curtailment program on one or the other resource."
He adds that sites demonstrating this wind and solar power generation
profile would be potential winners if a power company were interested
in pursuing an integrated approach. However, what may discourage
utilities and developers from adopting this approach in the short term
is how much more expensive it is at the present time to install solar
power infrastructure compared to infrastructure for wind power
generation. Also, while the Western United States seems a likely target
for an integrated approach, Boyd says what they have discovered in
reality is that optimum sites (where it is easy to tie in to the
existing power grid) are not all that common. What made the Kingman
site ideal was its combination solar and wind potential as well as an
existing 69-kilovolt (kV) transmission line that runs within a mile of
the project boundary. This existing infrastructure made it inexpensive
and easy for the company to tie into the power grid.
"We have done a little homework, and we have not found another site
where there is this combination of wind and solar on the same property
that can be fed into the same sub-station," says Boyd. "It's a good
site for integrating wind and solar because it has a combination of
very steep, tall ridges and reasonably flat land where you could
incorporate the solar aspect. On the high ridges, we have the wind
turbines and on the flats, we have the solar, and it has worked out
The fact that Western Wind Energy purchased the property makes the
project even more unique, as wind power projects go. As a smaller
company, Boyd says purchase of the Kingman property versus some type of
lease and royalty agreement with the previous property owner gave the
company more credibility with UES, which was looking for bidders on its
Request for Proposals (RFPs) on an integrated project. Outright
purchase of the site took the potential issue of long-term property
access out of the equation, and the price was so attractive that it was
actually a better deal than to pay the previous landowner a royalty.
What helped move the project forward on the financial end was the 30
percent funding support offered by the federal government as well as
the accelerated depreciation benefit. State and local government
representatives were also highly supportive of the project.
"It was a pleasure to do business with Mohave County," says Boyd. "They
were very eager to establish a renewable energy industry and
consequently were receptive to how we proceeded on the project."
The site consists of five 2-megawatt Gamesa wind turbines and solar
panels capable of producing a total of 500 kilowatts (kW) of solar
So the ratio is 20:1 wind to solar. Most of the project was constructed
by Wisconsin-based, RMT Energy Construction and Engineering, a
wholly-owned subsidiary of Alliant Energy Corporation. The solar
equipment was installed by American Capital Energy and features 1,824
Suntech Reliathon 275-watt modules mounted on an Array Technologies
single-axis-tracking system. Conversion of the solar AC power to DC was
accomplished with the installation of a Solaron 500 kV inverter ahead
of the 34.5 kV step up transformer manufactured by Cooper Power
Systems. The wind and solar power are tied into the transformer
"What created a challenge is that the topography is very steep," says
Boyd. "RMT needed to be clever and creative about engineering roads to
get the heavy equipment up to the ridge tops." The solar panels are
positioned on flatter ground far enough away so that there are no
shading issues from the wind turbines.
The turbines are visible to only a small percentage of the surrounding
population as the project is about two miles from Kingman. Mohave
County already had a general plan to establish the land as heavy
industrial. All that was required was a modest zoning code change to
allow for the wind turbines. Plans are already in place to potentially
double the size of the project, but it would be strictly wind energy.
"We are working feverishly to acquire a lease on an adjacent section of
land with the State of Arizona, which has been a very, very willing
partner in this project," says Boyd. "We think that there is a chance
that we could get another 10 megawatts up and running on an adjacent
piece with either Tucson Electric Power or Mohave Electric."