Disputation i elektronik med Stefani Rydblom

Välkommen till disputation i elektronik med Stefani Rydblom som ska försvara sin sin avhandling "Development and Test of an Imaging Instrument for Measurement of Water Droplets in Icing Conditions". Disputationen är på engelska.

Stefani Rydblom BAnner 1600x900_EU.png

Date: Thursday December 5, 2019 at 10.00
Place: Campus Sundsvall, C building room C326
Main supervisor: Associate Professor Benny Thörnberg
Co-supervisor: Professor Mattias O’Nils

Opponent and examination committee:

Professor Aimé Lay-Ekuakille, University of Salenty, Italy

Professor Mikael Sjödahl, Luleå University of Technology
Associate Professor Jörgen Ahlberg, Linköping University
Associate Professor Andrey Koptyug, Mid Sweden University


The research is part of the project MiLo - funded by the EU European Regional Development Fund. Read more: https://www.miun.se/milo

Abstract Development and Test of an Imaging Instrument for Measurement of Water Droplets in Icing Conditions

Structural icing is a persistent challenge for the production of renewable energy from wind. It is mainly caused by supercooled atmospheric droplets of water, which are very common in cold climates. In the most exposed wind parks in Sweden, more than 10 per cent of annual energy production can be lost. Some properties of liquid water are included in current Numerical Weather Prediction (NWP) models and are used as input parameters for the estimation of icing, but they are rarely measured in-situ for verification or validation.

To address this problem, a new instrument was developed. The new instrument, called Droplet Imaging Instrument (DII), is based on shadowgraph imaging using LED light as background illumination and digital image processing. The components were selected with the possibility of low-cost volume production in mind. The applications of a commercial instrument based on this technique include, for example, real-time in-situ icing condition measurements and assimilation and verification of data in NWP models. The instrument, alongside a reference instrument, was tested in two locations with different icing conditions. Shadowgraph imaging and its limitations as a measurement method for droplet size and concentration were investigated.

The work presented shows that measurements of the size and concentration of water droplets using shadowgraph images can be used for the comparison and validation of NWP models and other instruments. The accuracy of the sampling volume can be improved by measuring the background light intensity in the position of the measured droplet.

With a limited amount of data, multivariate data analysis can be used to estimate the level of ice accretion. Together with a heuristic model of erosion/ablation, the resulting figures can be used to simulate the ice load.