Capacitive Probe for Ice Detection and Accretion Rate Measurement: Proof of Concept

Abstract

Ice accretion on wind turbines is a major problem in cold climates that reduces power generation and fatigues turbine components. Effective anti-icing and de-icing strategies to manage ice accretion require reliable local assessment of icing conditions and a measure of ice accretion rate on structures. Such sensors could be located on meteorological towers near wind farms or the nacelle of wind turbines. A new concept for the estimation of atmospheric ice accretion based on the measurement of capacitance and resistance change between two charged cylinders as ice accretes on the cylinders is introduced in this study. Numerical simulation of the electric field between the charged cylinders is used to investigate the dependence of the sensitivity of capacitance to the distance between the cylindrical probes and location of ice deposits. The numerical results are validated experimentally using aluminum probes and a set of acrylic cylindrical sleeves that fit over the probes to simulate icing with accurate geometries. A charged cylindrical probes system constructed based on the numerical results is described and evaluated under controlled rime and glaze icing conditions in the University of Manitoba Icing Wind Tunnel. Test results indicate ice builds up on the cylindrical probes and the measured capacitance increases while the resistance decreases. The change in measured capacitance change correlates well with the increase in the ice mass. Rime and glaze ice are distinguishable based on the rate of change of resistance with ice accretion. The numerical and experimental results provide a proof of concept of the charged cylindrical probes ice accretion measurement concept.