Integrating Renewables: Storage Capacity of a Smart Grid

A major component of the nationwide push to upgrade our aging electric grid is the integration of renewable generation resources on a larger scale.  Noncombustible renewables, such as wind and solar, fluctuate with environmental conditions, thus producing an intermittent power source rather than a constant flow of electricity.  The intermittent nature of these resources challenges the existing electric grid, which was designed to move a steady, dispatchable flow of electricity.  One way to reduce the impact that renewables may have on the stability of the grid is to integrate energy storage functionalities and backup generation capacity into the host of grid upgrades expected over the next several years.

In addition to smoothing out electricity flow, storage capacity allows for the generation of electricity when it is cheapest and the ability to store and use it when it is needed.  For example, for solar power, generation capacity is highest during the day, while consumption, especially in residential areas, is highest during the evening hours.  Storage of solar generation would allow for distribution of the power at the time it is needed.  Currently, there are very few grid-integrated energy storage facilities, though several are expected to come on line in the next couple of years.  A significant challenge is determining which method is the best for storing the electricity: stand alone batteries, electric car batteries, flywheels, compressed-air, pumped hydro or (more likely) some combination.  The battery storage market is growing but some of the technology is very new and largely untested.  Also, similar to any high-tech market,  divergent technologies are not always compatible and it is not clear which technology will eventually  dominate.  Aside from the diverse storage options, utility-scale storage facilities are very costly and it is not clear whether such storage facilities are more affordable than backup generation sources such as coal or biomass, or other options such as natural gas.