Electric load forecasting in a hydro- and renewable based power system

Electric load forecasting has for decades been an integral part of power system planning, including renewable hydro based system planning. In this paper we present load forecasting in the renewable based power system of Iceland. When load forecasting was initiated, informal forecast were made by utility companies, especially before and after establishing the main generating company, Landsvirkjun in 1965. However, in 1976, a dedicated Energy Forecasting Committee (EFC) was established by the stakeholders to carry out coordinated, system wide forecasts of annual electric load. The paper reviews the history and practice in these forecasts and, in addition, adapts them to renewable system needs, by expanding them to include different time frames, and suitable calendars for annual, weekly and hourly system wide time frames. This is done by interpolation in weekly and season-specific hourly distribution factors, from generic factors published and estimated by the EFC. The results of this paper include a load forecasting framework, applicable in three time frames and various types of power system planning and operations models. The modeling approach presented here constitutes a coordinated hierarchy with annual load forecasts at the top, then a medium term weekly model and a short term, hourly load model at the bottom of the hierarchy. These modeling approaches can be used interactively in power system modular planning and operations models.