Is hydro inflow forecasting an oxymoron?
The 1992 hydro shortage and the December 1995 high inflow sequence recorded in the southern catchments were timely reminders of the importance of seasonal climate for electricity supply in New Zealand. New Zealands electricity generation network has several characteristics that make it susceptible to inflow variation. These include the relatively low contribution made by thermal generation, the low proportion of hydro storage relative to hydro generation and the physical separation of the majority of demand near the top of the North Island from the major South Island hydro lakes. A series of initiatives have been undertaken in recent years to improve ECNZs ability to manage this seasonal inflow risk. Following the 1992 hydro shortage a climate advisory group was assembled and has met two or three times a year to test ideas and provided expert advice to assist ECNZ to better manage its hydro generation. One of the more useful operational tools to have emerged from this process has been a South Island snow storage model developed within the University of Otago. The group also has enabled a wide range of climate indices to be examined for inflow forecast potential. The fundamental objectives are to maximise the reliability of supply and to allow for economic generation scheduling. The emergence of a wholesale electricity market fundamentally changes how these key objectives are delivered.