Policymakers must focus more on developing new energy storage technologies as they consider a national renewable electricity standard, recommends the American Physical Society’s (APS) Panel on Public Affairs (POPA) in a new report that examines scientific and business perspectives on how to best integrate renewables into the U.S. grid.

The society, whose membership of physicists in academia, national laboratories, and industry exceeds 48,000, endorses the establishment of a national renewable electricity standard (RES) in its report, “Integrating Renewable Electricity on the Grid,” arguing that an RES will help unify the fragmented grid system. But without focus on storage devices, it will be difficult to meet proposed standards, the report says.

To date 30 states, plus the District of Columbia have established Renewable Portfolio Standards. However, “although small penetrations of renewable generation on the grid can be smoothly integrated, accommodating more than approximately 30% electricity generation from these renewable sources will require new approaches to extending and operating the grid,” the report asserts.

One reason for this is that variability of renewable resources, due to weather fluctuations, introduces uncertainty in generation output on the scale of seconds, hours, and days. “These uncertainties, affect up to 70% of daytime solar capacity due to passing clouds and 100% of wind capacity on calm days for individual generation assets,” the report says. “Although aggregation over large areas mitigates the variability of individual assets, there remain uncertainties in renewable generation that are greater than the relatively predictable uncertainties of a few percent in demand that the grid deals with regularly.”

Another challenge facing the grid involves the long-distance transmission of renewable electricity from places that receive a lot of wind and sun to those that do not. “We need to move faster to have storage ready to accommodate, for example, 20 percent of renewable electricity on the grid by 2020,” said George Crabtree, co-chairman of the POPA study panel and a senior scientist at Argonne National Laboratory. “And, by devoting the necessary resources to the problem, I am confident that we can solve it.”

The report addresses variability and transmission issues by urging the U.S. Department of Energy (DOE) to increase research on materials to develop energy storage devices and by encouraging the DOE to focus on long-distance superconducting direct current cables to bring renewable electricity to load centers, lessening the chance that power will be disrupted. The report also calls for “examining renewable electricity in light of a unified grid instead of one that is fragmented and improving the accuracy of weather forecasts to allow for better integration of renewable electricity on the grid.”

Specifically, the report recommends:

Energy Storage
The U.S. Department of Energy (DOE) should:

  • Develop an overall strategy for energy storage in grid-level applications that provides guidance to regulators to recognize the value that energy storage brings to both transmission and generation services on the grid;
  • Conduct a review of the technological potential for a range of battery chemistries, including those it supported during the 1980s and 1990s, with a view toward possible applications to grid energy and storage; and
  • Increase its research and development in basic electrochemistry to identify materials and electrochemical mechanisms that have the highest potential use in grid-level energy storage devices.

Long-Distance Transmission
The DOE should:

  • Extend the Office of Electricity program on High Temperature Superconductivity for 10 years, with a focus on direct current superconducting cables for long-distance transmission of renewable electricity from source to market;
  • Accelerate research and development on wide band gap power electronics for controlling power flow on the grid, including alternating to direct current conversion options and development of semiconductor based circuit breakers operating at 200 kilovolts and 50 kilo amperes.

Business Case
The Federal Energy Regulatory Commission and the North American Electric Reliability Corporation should:

  • Develop an integrated business case that captures the full value of renewable generation and electricity storage in the context of transmission and distribution; and
  • Adopt a uniform integrated business case as their official evaluation and regulatory structure, in concert with the state Public Utility Commissions.


The National Oceanic and Atmospheric Administration, the National Weather Service, the National Center for Atmospheric Research and private vendors should:
Improve the accuracy of weather and wind forecasts on time scales from hours to days.
Forecast providers, wind plant operators and regulatory agencies should:

  • Develop uniform standards for preparing and delivering wind and power generation forecasts.
  • Wind plant operators and regulatory agencies should:
  • Develop operating procedures to respond to power generation forecasts.
  • Develop criteria for contingencies, the response to up-and-down-ramps in generation and the response to large weather disturbances.
  • Develop response other than maintaining conventional reserve, including electricity storage and transmission to distant load centers.

Sources: APS, POWERnews