Pairing Wind + Solar for Cheaper, 24-Hour Renewable Energy

Along a country road east of Lima, Ohio, a company is preparing to build one of the world’s largest renewable energy projects that pairs wind and solar to create a hybrid power source. It’s a rare combination now, but one that’s expected to become more common because of its potential to cut costs while providing a more consistent flow of clean energy.

Invenergy is starting with a 175 megawatt wind farm. Within the wind farm, it plans to build a 150 megawatt solar farm. Together, they would produce enough electricity for about 75,000 homes.

The wind and solar energy complement each other. They hit their peaks at different times of day and night, allowing them to provide a steadier output together than if each was alone. And they save money because they can share equipment, power lines and workers.

The consistency is increasingly important as renewable energy replaces coal-fired plants, which can provide 24-7 power but that also create pollution and contribute to climate change.

Most renewable energy development so far has targeted either the sunniest or the windiest areas, without considering locations that could be good for both solar and wind.

That’s changing as wind and solar costs decrease and the technology advances. Today, there are many parts of the U.S. where both wind and solar can be profitable, said Vahan Gevorgian, a chief engineer at the government’s National Renewable Energy Laboratory in Colorado. “It will create economic opportunities for wind in parts of the U.S. where wind [farms are] not present,” he said.

In the Midwest, where wind farms are more common than solar, it’s the other way around, with opportunities to put solar panels alongside wind turbines. One example is the Grand Ridge Energy Center in northern Illinois, also operated by Invenergy, which has 210 megawatts of wind, 20 megawatts of solar and 33 megawatts of energy storage.

Wind-Solar Hybrids Keep Power Flowing

The benefits of wind-solar hybrids start with a simple idea: Solar power is strongest when the sun is brightest, often in the middle of the day. Wind power is stronger at night in many areas of the U.S. By combining the two, a hybrid project has the potential to produce power around the clock.

This is important because one of the challenges of managing a power grid is dealing with the intermittent nature of renewable energy.

Power grids have to provide the right amount of electricity to match customers’ power demand moment-to-moment, so natural gas power plants are often kept at the ready to power up when needed. That could include being used on a cloudy day when a region’s solar power output is down.

The ability of a gas plant to quickly ramp up and down helps keep the grid reliable, but it’s harmful in terms of emissions, said Joshua Rhodes, an energy research associate at the University of Texas at Austin. The plants emit more pollutants per megawatt-hour when increasing or decreasing their output than they do when running at a steady rate.

If wind and solar plants built together can provide a more consistent power supply, other power plants could run on a more predictable schedule, with lower emissions and lower costs.

In addition, operators of solar-wind hybrids can save money by sharing assets. With the Ohio project, wind and solar will be located right next to each other and feed power into the same equipment that connects to the grid, with a single substation. They likely also will share a maintenance building and other operations.

The Australian government estimated in a 2016 report that integrating solar and wind energy would cut costs by 3 to 13 percent. 

Other countries have embraced wind-solar hybrids, too. In India, the government released a draft policy in May that encourages their construction. Bloomberg New Energy Finance, which tracks energy developments, also lists small wind-solar hybrid projects in Wales and Chile, among other locations.

Renewable Energy Grows in Ohio

In Ohio, the first wind turbines of the new project are scheduled to be built next year, followed by construction of the solar farm soon after.

Gabe Klooster, a project analyst for Invenergy, said his Chicago-based company was attracted to the Hardin County site because it is right next to a transmission line that can transport power to the grid, and land in the area is some of the most affordable to develop within the PJM Interconnection grid region, a territory that stretches from Chicago to the Atlantic Coast.

The community has also been welcoming, he said, which is not always the case when companies want to build energy infrastructure. “We have great relationships there,” he said. 

There is no comprehensive international list of hybrid wind-solar projects, but Klooster believes the Invenergy project would be the largest in the world to have such a level of integration and both sides with at least 150 megawatts.

Invenergy’s 150 megawatts of solar would also be one of the largest solar arrays in Ohio, adding to a statewide total that was 182 megawatts as of June, according to the Solar Energy Industries Association. Even though state lawmakers in Ohio have pushed back on renewable energy targets in recent years, it’s clear that utilities are still moving ahead. AEP also announced plans last week for an even larger solar-only farm in Appalachian Ohio.

Local residents stand to benefit. Invenergy is leasing the land and will provide royalties to the landowners and taxes to local governments. The county got its first wind farm in December when another developer finished a 66 megawatt project a few miles to the north of the Invenergy project.

Next Step: More Solar + Wind + Storage?

Invenergy is looking at options for selling the electricity from the project, a key step toward securing all the financing for construction.

The company says its typical model is to own and operate its projects, but that it will consider selling projects and remaining as the operator. It had explored the possibility of selling the wind farm portion of the Ohio project to a subsidiary of American Electric Power, but that was rejected by West Virginia regulators.

Asked about the status of finding buyers for the power, Invenergy spokeswoman Beth Conley said the project continues to move forward.

The likely next step for wind-solar hybrids in the broader market is that developers will begin to consider adding wind or solar to existing renewable energy sites, Rhodes said.

Energy storage is also likely to become a key part of the mix as renewable energy projects increasingly operate like traditional power plants.

Wind-solar hybrids “should be a part of the conversation for every project that comes up,” Rhodes said. “It’s not going to make sense everywhere, but at some price point it will make sense.”

Editor’s note: This story was updated to correct the total number of homes expected to be served by the new project to 75,000.