Load shapes, reflecting daily variations in electricity demand, are now more meticulously forecast by US power grid operators. Balancing requirements, based on hourly load forecasts, are used to develop resource schedules and anticipate dispatch of power plant assets – key to meet energy needs at time of peak demand.
Actual demand for electricity can differ from the day-ahead forecast and can vary within the hour, so balancing authorities work with power generators to make them swiftly adjust plant dispatch and power output match real-time demand.
In case of ‘system stress’, balancing authorities call upon generating capacity held in reserve – bearing in mind that if the grid has over-committed generation capacity this can be costly for consumers, as this incurs hefty capacity payments.
In some areas, TSOs can enforce demand-response programs to reduce electricity demand, typically at large industrial facilities, to maintain the supply-demand balance.
Isolate potential problems
In the US, alternating current (AC) power system operates at or 60 Hertz – if supply and demand fall out of balance and AC frequency increases or decreases substantially, the entire system can collapse and cause widespread blackouts. To prevent permanent damage, the grid is designed to isolate any problems.
As for balancing purposes, operating load levels tend to be recorded as hourly averages instead of as instantaneous values. Based on these numbers, total system demand is calculated by adding the net generation while factoring any flow of electricity into or out of the area (interchange).
The EIA as of July 25 is providing hourly electricity operating data, including actual and forecast demand, net generation, and the power flowing between electric systems. The U.S. Electric System Operating Data tool can be accessed at: http://www.eia.gov/beta/realtime_grid