Integrating Renewable Electricity on the Grid

By the American Physical Society Panel on Public Affairs

The United States has ample renewable energy resources. Land-based wind, the most readily available for development, totals more than 8000 GW of potential capacity. The capacity of concentrating solar power is nearly 7000 GW in seven southwestern states.

To date, 30 states plus the District of Columbia have established Renewable Portfolio Standards (RPS) to require a minimum share of electrical generation produced by renewable sources. In addition to state policies, federal policymakers have put forward proposals to establish a national RPS which would make the need for technological developments more urgent.

However, developing renewable resources presents a new set of technological challenges not previously faced by the grid: (1) the location of renewable resources far from population sources, and (2) the variability of renewable generation. Although small penetrations of renewable generation on the grid can be smoothly integrated, accommodating more than approximately 30% electricity generation will require new approaches to extending and operating the grid.

The report’s specific recommendation follow:

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

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.

Forecasting

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.