NREL Study Shows US Grid Can Accommodate Large Amounts of Solar

The National Renewable Energy Laboratory (NREL) has released the Western Wind and Solar Integration Study, an initial study assessing the operational impacts and economics of increased contributions from wind and solar energy producers on the power grid.

The study specifically focuses on the operational impacts of photovoltaics, concentrating solar power (CSP) and wind on the power system operated by the WestConnect group of utilities in the Mountain and Southwest states. WestConnect is a group of transmission providers including Arizona Public Service, El Paso Electric Co., NV Energy, Public Service of New Mexico, Salt River Project, Tri-State Generation and Transmission Cooperative, Tucson Electric Power, Western Area Power Administration, and Xcel Energy.

The study examines the benefits and challenges of integrating enough solar and wind energy capacity onto the grid to produce 35% of its electricity by 2017. This target is technically feasible and does not necessitate extensive additional infrastructure, but it does require key changes to current operational practice, NREL says.

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 solar and wind plants into the power grid.

Technical analysis performed showed that it is operationally possible to accommodate 30% wind and 5% 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, NREL notes.

Currently, generators provide a schedule for a specific amount of power they will provide in the next hour. More frequent scheduling would allow generators to adjust that amount of power based on changes in system conditions, such as increases or decreases in solar or wind generation.

The study also finds that if utilities generate 27% of their electricity from wind and solar energy across the Western Interconnection, it would lower carbon emissions by 25% to 45%. It would also decrease fuel and emissions costs by 40%, depending on the future price of natural gas.

Other key findings from the study include the following:

- 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 solar and wind energy, coordinating the operations of utilities can provide substantial savings by reducing the need for additional backup generation, such as natural gas-burning plants;

- Use of solar and wind forecasts in utility operations to predict when and where it will be sunny and windy is essential for cost-effectively integrating these renewable energy sources.

The full study can be downloaded at www.nrel.gov/wwsis.