Photo by HENNING KAISER/AFP/Getty Images.

Photo by HENNING KAISER/AFP/Getty Images.

There’s no question that variable resources like solar PV and wind present unique grid challenges, but with the Clean Power Plan pointing to higher penetration levels, there’s a lot of debate about how big an issue integration really is. The North American Electrical Reliability Corporation set off alarms bells in late April with a report that said the CPP could bring levels of renewables (and new natural gas generation with its own infrastructure requirements) that would pose “a significant planning and operational challenge” and be expensive to manage.

Renewable energy proponents aren’t taking that assertion lying down, however, and the latest pushback comes in the form of a new study prepared for Advanced Energy Economy Institute by the Brattle Group. The report points to experiences in Texas and Colorado to demonstrate that the levels of renewable energy penetration likely under the CPP won’t be so daunting or pricey.

ERCOT (and the distribution utilities in ERCOT) and Xcel Energy Colorado have managed to successfully integrate increasing amounts of variable renewable energy resources at costs that have generally been small to modest. For example, ERCOT estimated the cost of integrating its first 10,000 MW of wind, approximately the capacity currently deployed, to be about $0.50 per MWh of wind generation. These organizations have used well-established and widely available methods and technologies…

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 possible. Integration challenges in other parts of the United States will differ due to both the mix of renewable resources and the make-up of the existing electric system. Nonetheless, by adopting approaches similar to those used (or planned) in ERCOT and Xcel Energy Colorado, ISOs/RTOs and utilities in other states should be able to integrate increasing shares of variable renewable generation using well established tools and technologies. While infrastructure changes will likely be necessary in the longer term, the shorter-term integration challenges in many cases can be addressed with modest operational changes. – “Integrating Renewable Energy into the Electricity Grid: Case studies showing how system operators are maintaining reliability

Among the practices and adaptations cited in the study:

  • changes in ancillary services, which manage short-term mismatches between electric supply and demand, with fast-ramping gas-fired generation, demand response, storage, and other technologies,
  • improved forecasting of production from wind,
  • increased flexibility of fossil power plants on the system,
  • evolving capabilities of renewable generation itself to contribute to reliability,
  • expansion of transmission infrastructure (even though not an “integration measure” according to our use of the term), and
  • newer approaches under development, which include utilizing large-scale storage, dynamically managing the capacity of transmission lines, and allowing demand response to play a bigger role in managing system variability (and emergency situations).