2 Taking action – energy management systems
2.1 The need to monitor energy use
In this section we look almost entirely at energy, as it is the main contributor to CO2 emissions, either directly (through burning fuels on site or in vehicles) or indirectly (through purchasing electricity, heat or steam that has come from fossil-fuel sources).
‘If you don’t measure it, you can’t manage it’ sums up the first stage of good energy management – as a prerequisite you need to monitor and report energy consumption on a regular and timely basis. This is not quite the same as calculating your carbon footprint – that may be done on an annual basis; energy needs to be monitored monthly, weekly or daily (or per batch of product) if it is to be effectively controlled. This process is known as monitoring and targeting (M&T). Plotting energy use on a regular time series allows small variations in demand to be seen more clearly – and a cusum (cumulative sum of differences) chart can be used to plot variations against average consumption, normalised for production volumes or temperature differences.
You can see some real-life examples of cusum charts in this slide show.