Dynamic demand (electric power)

Dynamic Demand is the name of a semi-passive technology for adjusting load demands on an electrical power grid. (It is also the name of an independent not-for-profit organization in the UK supported by a charitable grant from the Esmée Fairbairn Foundation dedicated to promoting this technology.) The concept is that by monitoring the frequency of the power grid, as well as their own controls, intermittent domestic and industrial loads switch themselves on/off at optimal moments to balance the overall grid load with generation, reducing critical power mismatches. As this switching would only advance or delay the appliance operating cycle by a few seconds, it would be unnoticeable to the end user. This is the foundation of dynamic demand control. In the United States, in 1982, a (now-lapsed) patent for this idea was issued to power systems engineer Fred Schweppe. Other patents have been issued based on this idea.

Dynamic demand is similar to demand response mechanisms to manage domestic and industrial consumption of electricity in response to supply conditions, for example, having electricity customers reduce their consumption at critical times or in response to prices. The difference is that dynamic demand devices passively shut off when stress in the grid is sensed, whereas demand response mechanisms respond to transmitted requests to shut off,

The power utilities are able to predict to a reasonable accuracy (generally to within one or two percent) the demand pattern throughout any particular day. This means that the free market in electricity is able to schedule just enough base load in advance. Any remaining imbalance would then be due either to inaccuracies in the prediction, or unscheduled changes in supply (such as a power station fault) and/or demand. Such imbalances are removed by requesting generators to operate in so called frequency response mode (also called frequency control mode), altering their output continuously to keep the frequency near the required value.

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