June 10, 2015 | By Barbara Vergetis Lundin

High penetrations of variable renewable generation can be manageable without compromising reliability. In fact, it's been proven in Texas and Colorado.

Big Spring Texas Wind Farm. Credit: David Scott/Wikimedia Commons

A new report conducted by the Brattle Group for the Advanced Energy Economy Institute (AEEI) finds that high penetration levels of renewable generation are not only technically feasible but are already being managed in these states without sacrificing electric reliability -- suggesting that an increasing share of renewable energy can be integrated into the nationwide electricity system going forward.

The report, Integrating Renewable Energy into the Electricity Grid, consists of two in-depth case studies -- one of a grid operator (Electric Reliability Council of Texas or ERCOT) and the other a vertically integrated utility (Xcel Energy Colorado) -- both of which highlight high levels of variable renewable energy, comparable to the extent the North American Electric Reliability Corporation (NERC) has indicated it is concerned about under CPP compliance, are being managed successfully today by means of established operational and technological tools.

In 2014, 10 percent of total electricity demand in ERCOT was met by wind power, with wind's contribution reaching nearly 40 percent at certain times. Xcel Energy Colorado gets nearly 20 percent of its electricity from wind.

"The success to date of ERCOT and Xcel Energy Colorado shows that integrating variable renewable energy at penetration levels of 10-20% on average and at times above 50% -- i.e., high relative to the current levels in most of the United States -- is feasible," the report states.

The report notes that use of variable renewable energy resources, primarily wind and solar, is on the rise around the country, independent of the Clean Power Plan, due to falling prices and increasing demand, including state requirements for renewable power. In terms of handling issues around variability and reliability, the success to date of ERCOT and Xcel in accommodating ever higher shares of variable resources shows that integrating renewables at relatively high levels "is feasible and generally involves relatively modest additional cost," according to the report.

"Ongoing technological progress and ongoing learning about how to manage the operations of the electric system will likely allow the integration not only of the levels of variable renewable energy capacity now in places like Texas and Colorado but even significantly larger amounts in the future," the report concludes. "Specifically, integration of variable renewable energy at levels of penetration as high as those reliably managed by ERCOT and Xcel Energy Colorado, if not higher, should not be seen as a significant obstacle to compliance with EPA's proposed Clean Power Plan. Rather, carefully examining the lessons learned in states and regions such as the ones examined here should help [Independent Systems Operators] and utilities ensure that significantly larger amounts of variable renewable energy can be integrated while maintaining high levels of reliability in a cost-effective manner."

As seen in Texas and Colorado, tenewable energy resources are already being integrated into the power grid at ever higher levels based on price and performance., and utilities and grid operators have shown they can manage variable resources without impacting reliability.

"Based on this experience, we have confidence that these fuel-free, inexhaustible resources can be used to meet electric power needs going forward at even higher levels without concern about keeping the lights on," said Malcolm Woolf, senior vice president, Policy and Government Affairs for Advanced Energy Economy, a national business association.

For more:
- download the report 

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http://www.fierceenergy.com/story/living-proof-high-levels-renewables-can-be-part-grid/2015-06-10