Power grid could accommodate "large increase" in solar generation

The findings of the Western Wind and Solar Integration Study assess the operational impacts and economics of increased contributions from solar and wind energy producers on the power grid. It also examines the benefits and challenges of integrating enough solar and wind energy capacity into the grid to produce 35 percent of its electricity by 2017.

The study concludes that this target is technically feasible and does not necessitate extensive additional infrastructure. It does, however, require key changes to current operational practice. Additionally, it was found that if utilities generate 27 percent of their electricity from wind and solar energy across the Western Interconnection grid, it would lower carbon emissions by 25 to 45 percent. It would also decrease fuel and emissions costs by 40 percent, depending on the future price of natural gas. The results offer a first look at the issue of adding a significant amount of variable renewable energy in the West and will help utilities across the region plan how to ramp up their production of renewable energy as they incorporate more wind and solar energy plants into the power grid.

"If key changes can be made to standard operating procedures, our research shows that large amounts of wind and solar can be incorporated onto the grid without a lot of backup generation,” said Dr. Debra Lew, NREL project manager for the study. “When you coordinate the operations between utilities across a large geographic area, you decrease the effect of the variability of wind and solar energy sources, mitigating the unpredictability of Mother Nature.”

The study focuses on the operational impacts of wind, photovoltaics, and concentrating solar power on the power system operated by the WestConnect group of utilities in the mountain and southwest states. Though wind and solar output vary over time, the technical analysis performed in this study shows that it is operationally possible to accommodate 30 percent wind and 5 percent solar energy penetration.

To accomplish such an increase, utilities will have to "substantially increase" their coordination of operations over wider geographic areas and schedule their generation deliveries, or sales, on a more frequent basis. Currently generators provide a schedule for a specific amount of power they will provide in the next hour. More frequent scheduling, says NREL, would allow generators to adjust that amount of power based on changes in system conditions such as increases or decreases in wind or solar generation.

Other key findings from the study include:

  • Existing transmission capacity can be more fully utilized to reduce the amount of new transmission that needs to be built.
  • To facilitate the integration of wind and solar energy, coordinating the operations of utilities can provide "substantial savings" by reducing the need for additional back-up generation, such as natural gas-burning plants.
  • Use of wind and solar forecasts in utility operations to predict when and where it will be windy and sunny is "essential" for cost-effectively integrating these renewable energy sources.

The study was undertaken by a team of wind, solar and power systems experts with across both the private and public sectors.

More information can be found at www.nrel.gov/wwsis