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Renewable Energy Integration

California’s Renewable Portfolio Standard (RPS) goals of 20% penetration by 2010 and 33% by 2020 have focused attention on the needs of the transmission system to successfully integrate these levels of renewable energy. Enhancing transmission integration of renewables has become the central focus of most current research. At a fundamental level, there are three objectives for renewable integration.

First, all central station renewable power plants must be able to connect in a timely fashion to a transmission system. Many sites favorable for renewable resources are located far from a suitable grid connection point. Increasing population densities and environmental concerns have made siting new lines increasingly difficult, expensive, and time consuming. The Electric Grid Research Program pursues research that can accelerate the planning and siting for new transmission or that will mitigate environmental, technical, or economic issues.

Second, the grid operator needs tools to manage the unique characteristics of some renewables to maintain system stability and reliability. Wind and solar are expected to form the largest portion of new renewable resources. Unlike a coal fired, nuclear, and hydropower, resource availability can vary significantly over days, hours, and even minutes. In addition, conventional sources consist of very large rotating machines which possess huge inertia, a tendency to keep rotating even when conditions change. In large measure the transmission system has evolved around this characteristic and depends on it for stability. Examples of the Electric Grid Research portfolio includes technologies such as real-time monitoring and analyses of an intermittent renewable power plant, improved wind and solar forecasting, power flow control, and the modeling of loads and large wind power plant models needed to reliability and efficiently operate the grid.

The third requirement for renewable integration is adequate capacity of the entire path from a new source to the load area where power is required. Many existing transmission lines are already operating at their limits. A number of Electric Grid Research projects focus on a variety of methods by which capacity can be increased. These include technologies as diverse as fault current limiters which limit the flow of current in the event of a fault to grid oscillation detectors which detect in real time grid instabilities that can lead to large scale blackouts.

A detailed analysis of the renewable integration needs and opportunities for emerging technologies can be found in the Electric Grid Research Program staff report Transmission Technology Research for Renewables (1.6 MB pdf).