Scheduling of heating load

Since 1989 Northern Ireland Electricity (NIE) has had the capability to schedule heating load. The system relies on phase modulation of the BBC´s 198-kHz Radio 4 signal. This facility is known as `radio teleswitching´. NIE is responsible for the operation of the radio teleswitching scheme. This provides an opportunity to co-ordinate the scheduling of heating load with generation. The approach has been to segregate heating from the rest of the off-peak load. The nonheating component is supplied during traditional off-peak times. Heat load may then be scheduled in such a way as to minimise operating cost. The flexibility of this approach leads to a challenging optimisation problem. It is necessary to derive a switching schedule for each of a number of heating blocks. The general approach to date has been to fill the off-peak `trough´. As a result, an almost flat off-peak demand has been achieved. However, it has been realised that the `trough filling´ objective may not be the most economic option. Also, the scheduling process has lacked transparency. This contribution describes progress with a more formal method for heat load scheduling. Firstly, it is shown how an optimum heat load profile may be obtained. Then a load block scheduling process based on dynamic programming is described. A case study is used to compare the trough filling and the optimum profile approaches. Finally, prospects for integrated scheduling of generation and heat load are discussed