Wind + Sun Join Forces
by Gail Kinsey Hill
A Washington wind-solar plant is testing whether two fickle sources can create one reliable supply
Puget Sound Energy has blanketed a rock quarry atop central Washington's Whisky Dick Mountain with solar modules in an unprecedented effort to test the compatibility of sun and wind energy.
More than 2,000 panels stretch squat and angular alongside the tall, sweeping turbine blades of the utility's Wild Horse wind farm near Ellensburg.
Nowhere else in the country has a utility tried to marry such different, distinctively fickle sources of electricity generation. Yet the elements' uneven temperaments are precisely what the utility finds attractive.
"We want to track the power profiles of each to see if there's a way to balance the two, to see if we can fill in the wind gaps with solar," said Steve St. Clair, PSE's manager for renewable assets.
The project is the largest solar installation in the Northwest. But it's small by industry standards: just enough to light up a neighborhood or two. The energy produced is expensive, four times that of the power from the accompanying wind turbines (see PSE's photo gallery of the wind facility).
Still, the experiment is intriguing, experts say, one that takes on wind's bugaboo -- variability -- and allows consumers to tap into another clean energy source without the expense of installing solar modules on their own at home or at a business.
"There are natural complementary patterns between wind and solar," said Elliot Mainzer, a policy manager with Bonneville Power Administration, the federal agency that markets more than a third of the electricity consumed in the Northwest.
Wind power has become the country's fastest-growing source of renewable energy, pushed by fossil-fuel concerns and government subsidies. But its up-and-down nature is a significant drawback.
To ensure that customers get uninterrupted power, wind power must be blended with electricity from more reliable energy producers, such as hydroelectric dams and coal- and natural gas-fired power plants. The integration can get complicated, and it can increase costs.
Puget Sound Energy's decision to commingle solar and wind represents a groundbreaking effort to blend two clean but unpredictable sources of energy into a renewable hybrid with more reliable generating credentials.
"It absolutely makes sense," said George Douglas, a spokesman for the U.S. Energy Department's National Renewable Energy Laboratory.
Wind tends to blow more vigorously at night as the Earth cools, and when solar fizzles to darkness. And breezes often cease on intensely hot days, leaving only the sun to provide power.
Central Washington's Kittitas Valley, which includes Whisky Dick Mountain, is known for its strong winds and an estimated 300 days of sunshine a year.
The utility acknowledges that the project is little more than a test. When adjusted to reflect solar's inconstant nature, the photovoltaic (PV) array, with its 450-kilowatt capacity, can light up the equivalent of 55 homes. The companion wind farm, with a 230-megawatt capacity (there are 1,000 kilowatts in a megawatt) can power the equivalent of 60,000 homes. A like-sized natural gas plant can power 150,000 homes.
"In truth, it would be hard to build a PV array to fully replace the output of a wind farm," St. Clair said.
Cost remains a big obstacle. Utility-scale solar only recently has attracted the attention and money that could take it mainstream. The electricity from Puget Sound Energy's project costs about 20 cents a kilowatt-hour to produce, whereas the wind farm power comes in at about 5 cents a kilowatt-hour, St. Clair said.
"There's no getting around it, solar is more expensive -- just as wind was 25 years ago," St. Clair said.
PSE is Washington's largest utility, with customers primarily in the western part of the state. It plans to recover development costs -- $4 million for the solar array and $380 million for the wind farm -- through rate increases.
The utility saved money on the solar project by hooking into the same power lines and substation that carry the wind energy to the main transmission grid and west to Puget Sound customers. But it faced particular challenges, including the wind itself.
"The panels act like huge sails," St. Clair said, prompting PSE to reinforce the structure to withstand winds up to 125 mph.
Though it may be the only utility in the United States to link wind and solar, the matchup can be found in areas unserved by utilities. In Alaska, for example, remote communities have installed turbines and modules to ease the need for backup diesel power generation.
Though Puget Sound Energy's solar array is relatively small -- it will top out at 500 kilowatts once the second phase is completed -- it's the largest in the Northwest.
The nonprofit Portland Habilitation Center had hoped to have a larger, 870-kilowatt solar array in place at its new building near Portland International Airport by the end of 2007, but financing delays pushed installation into this year. Other businesses and public agencies in Oregon are considering even larger projects.
The largest photovoltaic array in the country is a 14-megawatt project -- 30 times the size of PSE's -- at Nellis Air Force Base in Nevada. It only recently hit the grid and, with the burst in solar enthusiasm, isn't expected to hold the record for long.
Another technology, called "concentrating" or "thermal" solar, has bigger ambitions. A 64-megawatt project, composed of 184,000 mirrors and covering 300 acres, began generating electricity last year in Boulder City, Nev. A consortium of Southwest energy suppliers is talking about a 250-megawatt thermal system, and California reportedly has 900 megawatts of such projects under discussion.
Photovoltaic arrays rely on solar cells to convert the sun's light directly into energy. In contrast, thermal systems use the sun's heat to superheat a medium such as oil, which then is used to create steam to turn a turbine.
Thermal systems cost about half that of PV arrays but are best-suited to hot, desertlike climates and large-scale projects.
So far, no other utilities in Oregon or Washington are planning stand-alone solar projects, let alone a combination such as Puget Sound Energy's. The costs and the risks are too high, they say.
"We haven't found it to be economic, at this point, for our customers." said Jan Mitchell, a spokeswoman for Pacific Power, one of Oregon's largest utilities.
Pacific Power and Portland General Electric, which together account for more than 70 percent of Oregon's electricity use, have taken a more grass-roots approach. Encouraged by grants and tax breaks, customers are installing solar arrays on homes and commercial buildings at record-breaking rates. Utilities track the on-site electricity produced, so-called distributed energy, and compensate accounts accordingly.
Puget Sound Energy also promotes distributed solar. But it couldn't resist the foray onto the central Washington mountaintop.
"It seems to be such a great fit," St. Clair said.
learn more on topics covered in the film
see the video
read the script
learn the songs