Given that meeting peak power demand is the determinant of the amount of power capacity that needs to exist within a system, it’s important to ask the question: how often is this expensive infrastructure actually needed?
In most cases, the answer is: surprisingly infrequently!
Which means that a power system can have a significant amount of power generation capacity (i.e. power plants), which is being called on very rarely. However although they may lie around idle for much of the time, power plants still need to be maintained and kept ready for the rare occasions when they are called on to generate. Alternatively, if they generate but at well below their maximum capacity, they will tend to be operating rather inefficiently. We’ll talk about efficiency in a later lesson, but suffice to say that it’s a bad thing if you’ve had to pay for fuel with which to operate the plant.
Either way, whether unused or inefficiently used, it’s not great from an economic perspective.
As explained in this video, when faced with a huge amount of data for a system, the easiest way to analyse how often peak power demands occur – and hence the size of this capacity dilemma – is to view the data differently. Rather than view and plot it in time order, as a demand curve, we can instead view it in size order and plot a “load duration curve“.
You might find the results quite alarming!