Author(s): Jorgen Sahlberg
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Keywords: No Keywords
Abstract: At Stornorrfors water power plant in the Ume river there are Frazil Ice problems, more or less severe, every winter. They occur normally in November before the river freeze up. Frazil Ice stick to the intake gates, grow and prevent the water through flow. In order to minimize Frazil Ice problem at Stornorrfors and to help in the energy production planing, forecasts of water temperature and Frazil Ice concentration are performed. The forecasting model is based on a two dimensional dynamical model coupled to a surface heat flux model. Calculations are performed over the total area from the power plant and 13 km upstream. The heat flux model takes all four mayor heat fluxes, e. g. the sensible and latent heat fluxes and the net long wave and the short wave radiation, into account. The meteorological forcing, which enters in both the dynamical and the heat flux model, consists of air temperature, relative humidity, wind velocity and amount of clouds. One forecast yields for the following three days. The forecast is performed every day as long as the intake area is open water. Another part of this project deals with the ice cover formation in front of the intake gates. The winter 1989/90 three "ice nets" were hanging from a wire 60 m in front of the gates. They consist of plastic ropes floating on the surface and they are catching Frazil Ice helping to build a strong ice cover. The purpose with the "ice nets" is to speed up the ice cover formation. Once there is an ice cover it reduces the water supercooling and hence reduces Frazil Ice problems at the gates. This paper describes both the forecasting model and the "ice-nets".
Year: 1990