Simplified electrical grid with energy storage. Simplified grid large scale power generation using fuel cell pdf download flow with and without idealized energy storage for the course of one day.
Thus, renewables in the absence of storage present special challenges to electric utilities. While hooking up many separate wind sources can reduce the overall variability, solar is reliably not available at night, and tidal power shifts with the moon, so slack tides occur four times a day. How much this affects any given utility varies significantly. While hydroelectric and natural gas plants can be quickly scaled up or down to follow the wind, coal and nuclear plants take considerable time to respond to load.
Utilities with less natural gas or hydroelectric generation are thus more reliant on demand management, grid interconnections or costly pumped storage. At present this storage serves only to shift consumption to the off-peak time of day, no electricity is returned to the grid. As well commercial and industrial users will take advantage of cost savings by deferring some processes to off-peak times. Historically this was only done in cooperation with large industrial consumers, but now may be expanded to entire grids. For instance a few large scale projects in Europe link variations in wind power to change industrial food freezer loads, causing small variations in temperature. Modernizing the electric system will help the nation meet the challenge of handling projected energy needs—including addressing climate change by integrating more energy from renewable sources and enhancing efficiency from non-renewable energy processes.
Advances to the electric grid must maintain a robust and resilient electricity delivery system, and energy storage can play a significant role in meeting these challenges by improving the operating capabilities of the grid, lowering cost and ensuring high reliability, as well as deferring and reducing infrastructure investments. Finally, energy storage can be instrumental for emergency preparedness because of its ability to provide backup power as well as grid stabilization services. Where AC grid power was not readily available, isolated lighting plants run by wind turbines or internal combustion engines provided lighting and power to small motors. The battery system could be used to run the load without starting the engine or when the wind was calm. A bank of lead-acid batteries in glass jars both supplied power to illuminate lamps, as well as to start an engine to recharge the batteries. Battery systems connected to large solid-state converters have been used to stabilize power distribution networks. Contrary to electric vehicle applications, batteries for stationary storage do not suffer from mass or volume constraints.