Integrating renewable electricity on the grid

George Crabtree, Jim Misewich, Ron Ambrosio, Kathryn Clay, Paul Demartini, Revis James, Mark Lauby, Vivek Mohta, John Moura, Peter Sauer, Francis Slakey, Jodi Lieberman, Humayun Tai

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The demand for carbon-free electricity is driving a growing movement of adding renewable energy to the grid. Renewable Portfolio Standards mandated by states and under consideration by the federal government envision a penetration of 20-30% renewable energy in the grid by 2020 or 2030. The renewable energy potential of wind and solar far exceeds these targets, suggesting that renewable energy ultimately could grow well beyond these initial goals. The grid faces two new and fundamental technological challenges in accommodating renewables: location and variability. Renewable resources are concentrated at mid-continent far from population centers, requiring additional long distance, high-capacity transmission to match supply with demand. The variability of renewables due to the characteristics of weather is high, up to 70% for daytime solar due to passing clouds and 100% for wind on calm days, much larger than the relatively predictable uncertainty in load that the grid now accommodates by dispatching conventional resources in response to demand. Solutions to the challenges of remote location and variability of generation are needed. The options for DC transmission lines, favored over AC lines for transmission of more than a few hundred miles, need to be examined. Conventional high voltage DC transmission lines are a mature technology that can solve regional transmission needs covering one- or two-state areas. Conventional high voltage DC has drawbacks, however, of high loss, technically challenging and expensive conversion between AC and DC, and the requirement of a single point of origin and termination. Superconducting DC transmission lines lose little or no energy, produce no heat, and carry higher power density than conventional lines. They operate at moderate voltage, allowing many "on-ramps" and "off-ramps" in a single network and reduce the technical and cost challenges of AC to DC conversion. A network of superconducting DC cables overlaying the existing patchwork of conventional transmission lines would create an interstate highway system for electricity that moves large amounts of renewable electric power efficiently over long distances from source to load. Research and development is needed to identify the technical challenges associated with DC superconducting transmission and how it can be most effectively deployed. The challenge of variability can be met (i) by switching conventional generation capacity in or out in response to sophisticated forecasts of weather and power generation, (ii) by large scale energy storage in heat, pumped hydroelectric, compressed air or stationary batteries designed for the grid, or (iii) by national balancing of regional generation deficits and excesses using long distance transmission. Each of these solutions to variability has merit and each requires significant research and development to understand its capacity, performance, cost and effectiveness. The challenge of variability is likely to be met by a combination of these three solutions; the interactions among them and the appropriate mix needs to be explored. The long distances from renewable sources to demand centers span many of the grid's physical, ownership and regulatory boundaries. This introduces a new feature to grid structure and operation: national and regional coordination. The grid is historically a patchwork of local generation resources and load centers that has been built, operated and regulated to meet local needs. Although it is capable of sharing power across moderate distances, the arrangements for doing so are cumbersome and inefficient. The advent of renewable electricity with its enormous potential and inherent regional and national character presents an opportunity to examine the local structure of the grid and establish coordinating principles that will not only enable effective renewable integration but also simplify and codify the grid's increasingly regional and national character.

Original languageEnglish (US)
Title of host publicationPhysics of Sustainable Energy II
Subtitle of host publicationUsing Energy Efficiently and Producing it Renewably
Number of pages19
StatePublished - 2011
Externally publishedYes
EventPhysics of Sustainable Energy II: Using Energy Efficiently and Producing it Renewably - Berkeley, CA, United States
Duration: Mar 5 2011Mar 6 2011

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


OtherPhysics of Sustainable Energy II: Using Energy Efficiently and Producing it Renewably
CountryUnited States
CityBerkeley, CA

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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  • Cite this

    Crabtree, G., Misewich, J., Ambrosio, R., Clay, K., Demartini, P., James, R., Lauby, M., Mohta, V., Moura, J., Sauer, P., Slakey, F., Lieberman, J., & Tai, H. (2011). Integrating renewable electricity on the grid. In Physics of Sustainable Energy II: Using Energy Efficiently and Producing it Renewably (pp. 387-405). (AIP Conference Proceedings; Vol. 1401).