Our systems for creating, conveying and using energy are full of nooks, crannies, odd corners and unexpected cul-de-sacs. The wholesale electricity system that includes large generators and the wires and associated hardware that moves power to the local distribution system where energy is transmitted to homes, offices, factories, streetlights and your cell phone charger is a great example of this reality. However, the regulatory system we have developed over the last 15 years means that much of the information about that system is available online with some notable exceptions like specific maps, apparently on the theory that terrorists would have trouble finding massive power plants and giant transmission towers if they only had Google Earth and their eyes to guide them.
One such odd corner is the fact that the wholesale electricity system sometimes runs into problems during periods when electrical demand gets very low. These moments, which tend to happen at night when there are very moderate spring or fall temperatures and our air conditioners and heaters are idle and the majority of the population is asleep with their lights off. As explained by the New England System Operator in a newsletter article these moments are known as Minimum Generation Emergencies.
As an electricity system approaches this kind of condition it becomes hard to maintain the frequency of the power, an obscure but important function of a grid operator. The operator will begin to order the shut down of power plants but some plants (like many coal fired power plants) simply can not switch off on a moments notice and others (like nuclear power plants) are pretty much always allowed to run. In this kind of situation wind turbines are “curtailed” (turned off).
None of this makes anyone happy. Wind facilities that could be generating electricity with no effort are being curtailed. Some powerplants continue to operate, generating pollution from smokestacks and creating dangerous waste products for even less good reason than usual and in fact some power plants are given special payments to turn themselves down or off. And it happens more than you might think, this morning (December 22, 2012) we approached this condition reports the New England Independent System Operator (ISO-NE), triggering the first steps and measures taken to deal with this kind of condition.
As described in the recent ISO-NE wind integration study (previously discussed on this blog) we do not need to deploy new technologies to store electricity any time in the near future as we ramp up our use of naturally variable energy resources like wind and solar. However, the fact that (even today) these kind of minimum generation emergencies can happen illustrates the value that storage can have. Energy storage, whether it is in the form of batteries, heat or mechanical energy in a flywheel, can help to create a resilient and flexible system that efficiently meets our needs will minimizes the pollution we put out into the environment.