PhD Thesis - Energy Systems Research Unit - University of Strathclyde

days; one reflecting the monthly hourly variation on weekdays and the other themonthly hourly variation on weekends. This is however only possible if suitable datais available. A limitation of this research is that the original data used does notdistinguish between weekdays and weekends, hence differences between weekdaysand weekends are not taken into account.2.4.2.2 Stage 2 - Converting to 1-min time resolutionStage 2 takes on from the work done in Stage 1 to produce 1-minute time resolutionload profiles for each hour of each individual appliance. The assumptions behind thisprocess were that: Most appliances (including television sets, entertainment appliances, water heaters,fridges, cooking and lighting) can be assumed to follow a simple ‘On’/‘Off’square pulse pattern varying between zero power during its ‘Off’ state and thesteady-state operating power during its ‘On’ state [29]; and Certain appliances such as washing machines, a finite amount of energy consumedby that particular appliance over one complete utilisation cycle can be re-modelledusing a known energy utilisation pattern.In both cases switching-on transients are ignored as these are for the most part onlyseconds long [35].For an appliance App(z) with an ‘On’/‘Off’ pattern having a steady-state operatingpower P On-App(z) in Watts (W), whose electrical energy consumption during Hour (ho)was E App(z),Hour(ho) in Watt-Hours (Wh), the active time in minutes, min On(Hour(ho)) , canbe calculated using equation (2.2) below.- (2.2)If the appliance has a stand-by power, P Stand-By , in W, then, assuming that theappliance is continuously on stand-by when not ‘On’ and that the electrical energy49