Environmental Engineering Reference
In-Depth Information
analysis presented in Sect. 8.4 shows this noticeable variation of required heat
power for different locations, with the highest value at the leading edge of the tip of
the blade (Fig. 8.5 ). These calculations show that heating the entire blade using this
locally adjusted heat flux consumes approximately 7-10 % of the rated power of
the wind turbine [ 14 ]. Equally heating the entire blade, such as using a hot air
technique, consumes even more power (about 15 % of the rated power) as reported
in Refs. [ 17 ] and [ 24 ]. Many active and passive anti/de-icing methods are in
development, but few are available on the market. Active heating of blades using
resistive thermal heaters is the most tested, used, and reliable way to prevent icing
effects [ 8 ]. It is often used in parallel with a passive hydrophobic coating to lower
energy consumption. While accurate and direct ice sensing and distributed resistive
thermal actuation have not yet been tested on wind turbines, it is now a growing
research area because it could significantly reduce de-icing energy consumption by
providing locally adjusted thermal power only in the regions where ice exists.
In our preliminary experimental test bed, we use flexible resistive thermal
heating elements with a maximum heating capability of 10 W/in 2 . A similar
thermal resistor has also been used by a wind energy research laboratory at the
University of Quebec in Canada for their preliminary study of electrothermal de-
icing of wind turbine blades [ 25 ]; however, these are large heaters which heat the
bulk of the blade based on coarse environmental conditions. We use many small
local heaters on the surface of the blade, capable of heating in short time frames by
heating only a thin layer and not the bulk material. This allows to enhance the
intelligence of the control system while using established thermal actuation
technologies. In Sect. 8.7 , we explain our fabricated experimental setup for active
de-icing using distributed ice and temperature sensors and resistive heaters.
8.7 Experimental Setup
We have built an experimental setup to create different types of ice on a blade and
to implement active de-icing using combined optical ice and temperature sensors
and distributed resistive heating with adjustable heat flux in different blade loca-
tions using feedback control. This section describes the components of the
experimental setup, including resistive heaters, optical ice sensors, custom fabri-
cated icing chamber, and amplifier circuit board.
De-icing is investigated under a fixed blade pitch angle for a non-rotating
blade inside a thermally insulated custom cooling chamber (Fig. 8.10 a). Different
types of ice can be created by controlling temperature, humidity, and wind speed
inside the chamber. The benefit of this custom cooling chamber over an icing wind
tunnel is that it is less expensive to operate. However, there are some limitations
such as stationary blade installation and longer time for ice creation inside the
chamber compared to an icing wind tunnel. The experimental results of de-icing
for a stationary blade can be extended to a rotating blade using further compu-
tational simulations. Wind is generated by a box fan installed inside the test
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