Systems Prepare for Renewables Integration

What will it take to accommodate wind and solar?

Nov. 11, 2011 - Bill Opalka - renewablesbiz.com

Increasing amounts of renewable energy are being integrated into the nation’s power systems, but the impacts are not uniformly understood. So, the Department of Energy set out to identify best practices as it performed a worldwide survey of operators.

The result was a new study that will be released soon. In the meantime, “Successful Strategies for Renewable Integration - A Groundbreaking Global Study” was the subject of a recent webinar. The study was led by Lawrence Jones, vice president, regulatory affairs, policy & industry relations, Alstom Grid and funded by the Recovery Act.

This study is based on specific information provided by the system operators, which have not previously been gathered in one document, said Charlton I. Clark of the DOE office of Energy Efficiency and Renewable Energy.

The report was mostly focused mostly on wind because of the larger penetration, although some applications will apply equally to solar generation.

With significant expansion of wind generation expected worldwide, the reliability issue becomes critical. Some estimates put global wind at 500 gigawatts by 2030. There was a mere 2 gigawatts in 1990. The current worldwide tally is 194 gigawatts.

The study was conducted over 12 months and involved a survey of grid operators, six in-depth visits to control centers and a literature survey.

One point gleaned in the survey was that large operators don’t necessarily have the most experience with wind while some smaller operators with higher penetration have valuable insights.

No surprise, but accurate forecasting is paramount as well as support tools to help integrate renewables. Those would include voltage stability analysis and optimal power flow with wind forecasts.

“Policies and grid code changes are needed to support large-scale wind integration,” Jones said.

With lower penetration levels, some common practices coalesced over the past decade.

“Around 2000 to 2003, there seemed to be a convergence of similar policies around the world. From then on, a lot of utilities seemed to see a lot of penetration of wind energy,” he added.

As might be expected, the flexibility needed, as enabled by the smart grid, would support the further integration of renewable energy.

Perhaps in a surprise, survey respondents said wind integration has had little or no impact on reserve requirements. 52 percent said there were no additional reserves required and another 30 percent said the impact was slight.

Those areas least affected had lower penetration levels, however.

A series of recommendations were included in the report.

Those include the implementation of a centralized wind forecasting program. “Different grid operators seem to have different perspectives on the level of data required,” Jones noted.

However, the study suggests a yearly review of data to see what the most critical data needed to maintain a high level of performance.

Control rooms of the future will even look different, as the researchers noted in a study of Spain, which had a separate site for renewables integration.

“With increased penetration of wind and impact of variability, the time to make decisions seems to be getting shorter and shorter,” Jones said. With those demands on the operators’ attention, it would be especially difficult to have the same controllers managing variable and conventional generation simultaneously.

And one of the main sticking points for integration – not unique to this study – is a plea to provide policy measures that accelerate building more transmission capacity.

And there’s a large constituency for that policy, not limited to renewables integrators.

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