The California Independent System Operator Corp. (ISO) has released a study examining the integration of renewable energy under a renewable portfolio standard (RPS).
The ISO and its study partners, including GE Energy Consulting, gained insights about grid dynamics through the study, which assumes California will add 2,246 MW of solar and 6,686 MW of wind resources by 2012.
The study found that renewable energy can swing in output by several thousand megawatts in as little as 20 minutes, but wind and solar power can offset each other's variable output. Wind is often plentiful at night and during early mornings, when the sun is not in full force. On the other hand, solar power generates best on hot, sunny afternoons when the wind often eases up, the ISO says.
In addition, the study found that efficiencies could be gained if there was more participation in the ISO's new market, which allows the ISO greater dispatch flexibility for meeting real-time needs of the grid. Flexibility is important, and conventional power plants are needed to provide quick ramp-up and ramp-down capabilities to compensate for intermittent resources, according to the ISO.
New operational tools for ISO dispatchers are required to stay a step ahead of fluctuations in generation. Advanced weather-forecasting tools, for instance, are needed to anticipate variable output, the report found.
"This study provides a thorough analysis of the capability of the power grid to effectively manage an oncoming wave of highly intermittent energy resources and confirms the ISO is ready to manage the grid reliably under a 20 percent RPS,’ says Keith Casey, vice president of market and infrastructure development at the ISO. ‘However, the study also affirms the critical role the ISO market and the existing fleet of conventional resources will need to play in balancing the variable output of renewables.’
SOURCE: California ISO