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More sun, more wind - But will their success hurt the power grid?

A look at intermittent power sources and reliability

Feb 16, 2018 at 5:30 am
    Snow covers some of the panels on a 72.5kW solar field at Farmers' Electric Cooperative in Kalona on Friday, Dec. 22, 2017. (Stephen Mally/The Gazette)

    North of Kalona, near the unincorporated Johnson County community of Frytown, a small electric cooperative has established itself as a solar energy leader.

    Farmers Electric Cooperative’s 3,373 cumulative watts of local solar power per customer ranks first in the state and third in the nation.

    The co-op, which began investing in solar about a decade ago, now generates about 20 percent of its power from solar panels. The cooperative’s entire grid can be fueled by solar on a sunny Sunday afternoon.

    With solar making up less than 1 percent of state or national power generation, Warren McKenna, general manager of the co-op, said there’s room for more.

    “For the entire state of Iowa, it would take probably three gigawatts of solar to get to 20 percent to match us,” McKenna said. “There’s a lot of growth potential in Iowa.”

    But as cooperatives and utilities expand their renewable portfolios, and businesses and homeowners explore the possibility of adding solar panels to their rooftops, how does that growing solar network — and the intermittent power it generates — affect the state’s power grid?


    This past April, U.S. Energy Secretary Rick Perry requested a study to examine U.S. electricity markets and reliability, specifically regarding the impacts of growth and trends in the market.

    According to the nearly 200-page report, growth in wind and solar has negatively influenced the economics of baseload plants, which largely include coal, natural gas and nuclear generation.


    Solar and wind generators cost less to operate and are dispatched first, which displaces baseload generators, the study states.

    The study notes that accelerated wind and solar growth has been spurred by state renewable portfolio standards, which have been adopted by more than half of all U.S. states and require utilities to sell a specified percentage of renewable electricity.

    “Competition from resources that benefit from such policies reduces revenues for traditional baseload power plants by lowering the wholesale electric prices they receive and by displacing a portion of their output,” the report says.

    The report argues that adding renewables while simultaneously closing baseload plants increases risks to the reliability and resilience of the grid.

    However, a separate independent report by economic and financial consultant Analysis Group — commissioned by Advanced Energy Economy and American Wind Energy Association — released in June contradicts the U.S. Department of Energy’s staff report.

    “Recently some have raised concerns that current electric market conditions may be undermining the financial viability of certain conventional power plant technologies (like existing coal and nuclear units) and thus jeopardizing electric system reliability. In addition, some point to federal and state policies supporting renewable energy as a primary cause of such impacts,” the Analysis Group report states. “The evidence does not support this view.”

    This report also counters that declining natural gas prices and advancements in technology have been the biggest factors contributing to the retirement of aging coal plants, rather than growth in renewable power sources.

    “This is a natural consequence of market competition. The result is a more diverse set of energy resources on the grid that is being capably managed in a way that provides reliable electric power,” Analysis Group senior adviser Susan Tierney said in a June news release regarding the report.

    In January, the Federal Energy Regulatory Commission dismissed Perry’s request to subsidize baseload power plants, which the energy secretary had said was necessary to enhance grid resilience. Commission members, while saying they were unconvinced of the need, also announced plans to evaluate the grid’s resilience.


    Back at Farmers Electric Cooperative, McKenna said solar power has been a dependable energy source.

    “I think reliability is a big misnomer. People say you’re going to sacrifice reliability, which is not the case with the model that we’re using,” he said.

    With a practice called load-tagging, two of the co-op’s solar farms are located near industrial buildings with a higher power usage, which reduces infrastructure needs, he said.

    “You put these larger units maybe next to manufacturing, or a lot of cities are doing it near their water treatment or sewer facilities,” McKenna said. “You put solar near where you need it.”

    Nathaniel Baer, energy program director with the Iowa Environmental Council advocacy group, said there is potential within the cooperative’s approach. By locating larger solar installations near the user, energy travels a shorter distance and the need for large infrastructure upgrades or additional substations could be significantly reduced.

    “When solar comes on, it can reduce stress in the grid. It can provide clean energy when it’s most expensive. Both wind and solar, they’re very complementary.”

    - Nathaniel Baer

    Energy Program Director, Iowa Environmental Council


    What’s more, solar can provide cheap power when it’s needed the most, he added.

    “Solar can help meet customer needs when the demand is at its highest,” Baer said. “Most utilities in Iowa are summer peaking. They have their highest usage periods in the summer, during the day and afternoon — at times when solar is producing well.”

    Iowa’s wind industry — which makes up more than one-third of the state’s energy generation — is another story, Baer added.

    Wind turbines traditionally exist in wind farms, generating large-scale energy in open fields. The power is transported to the larger grid through high-voltage transmission lines — called multi-value projects.

    But Krista Tanner, president of ITC Midwest, which operates more than 6,600 circuit miles of transmission lines in the state, said wind farms have grown faster than the transmission lines.

    In some cases, wind farms can produce more power than the infrastructure can handle.

    “We’re able to connect the wind — but on days when the wind is blowing a lot and transmission cannot handle it, then that wind has to be curtailed. That’s investment that is just wasted,” she said.

    Adding energy projects to the Midcontinent Independent System Operator — the not-for-profit, member-based organization that regulates what power sources are deployed and when — requires a level of planning and approval, which can take years and can create logistical challenges.

    “We have seen a big increase in generation that’s connected to our system,” said Dan Barr, planning engineer supervisor with ITC Midwest. “It’s difficult to coordinate all of those interconnection requests and find out what’s actually needed for the system.”

    Barr added that the large majority of the state’s big renewable power projects — both planned and present — are wind projects. So far, solar has not lent itself to large-scale applications.


    But what does adding solar and wind power to the market mean for the grid, or transmission lines, substations and circuits that carry energy from solar panels and wind turbines to homes and businesses?

    Earlier this year, as the Iowa Utilities Board debated potential amendments to state interconnection rules, some utility providers argued that solar projects, particularly single-customer rooftop arrays, put added strain on the infrastructure. Officials with Alliant Energy last year cited recent investments in renewables as one reason for customer rate increases.

    However, Andy Johnson, director of Winneshiek Energy District in Decorah in northeast Iowa, which has between four and five megawatts of locally owned solar, argued that Iowa still has a long way to go until solar becomes a big enough piece of the power grid to have any major effects on infrastructure.

    In Iowa and nationwide, solar is at a mere 1 percent of all power generation.

    “At the levels of penetration we’re at — at well under 1 percent — it’s irrelevant, largely,” Johnson said. “You have to deal with it more at the high single digits. But at 1 percent, it doesn’t matter.”

    While solar has grown to the mid-single digits of Winneshiek County’s energy production, Johnson said he hasn’t witnessed any major impacts on infrastructure needs so far,

    If growth in solar will put strain on the system, it likely will be at connection points between producers of solar and the grid.


    The issue with solar, Johnson said, is it can become an intermittent power source if, for example, homeowners install more solar than they use. Power traveling back and forth on a system can put added wear on some components, he said.

    “Circuit by circuit is really where the action is at, I think,” he said. “In a given circuit, if you end up installing a certain amount that ends up becoming as much or more than those consumers use, then that circuit needs to be able to flow backward through the substation.”

    Johnson added he is not aware of solar causing any large-scale issues on the grid so far.

    Iowa Environmental Council’s Baer said state rules for on-site generation — regulated by the Iowa Utilities Board — provide the framework for statewide solar growth.

    To connect solar to the grid, customers first have to determine the impacts of such an addition. The process — which was developed a few years ago and adopted in 2017 — helps ensure that such connections are done in a safe and efficient manner, Baer said.

    But most importantly, Baer said, is that wind and solar work together. With a diverse energy portfolio, utilities can dispatch the cheapest option available as conditions and energy prices fluctuate.

    “When solar comes on, it can reduce stress in the grid. It can provide clean energy when it’s most expensive,” he said. “Both wind and solar, they’re very complementary.”

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