Environmental Engineering Reference
In-Depth Information
Ice Sensing
Actuation
Active
Passive
Indirect
Direct
Inflatable
Pneumatic
Boots
On the Blade
Actual vs.
Predicted
Power Output
Anti
Freezing
Liquid
Spraying
Resistance
Impedance
Capacitance
Inductance
Piezo-Electric
Estimation
Based on
Temperature
and
Humidity
Hot Air
Ice
Repellant
Coatings
Optical
Sensing
(OFDR)
Control
Thermal
Resistors
Our Work
Fig. 8.3 Summary of different approaches to ice sensing and anti-icing and de-icing. Among all
of the direct ice sensing methods to date, our optical ice sensing method provides the most
complete information (ice existence, type, and thickness) for local de-icing
Table
8.1
shows a high-level qualitative comparison of different active de-icing
methods on wind turbines, where the advantages and disadvantages of each
method in a number of categories are listed. There are very limited technical data
available in the literature related to the active control of icing for wind turbines.
Among all of the mentioned active de-icing techniques, only thermal resistors and
hot air techniques have been successfully tested on wind turbines in cold climates
with available commercial kits.
Different types of ice have different thermodynamic and adhesion characteris-
tics and need different amounts of heat flux for de-icing [
5
]. Direct detection of ice
on the blade, as opposed to estimating ice accumulation on the blades using
sensors on the nacelle, also provides a more accurate method for applying thermal
control for de-icing. This highlights the need for improved sensing methodologies.
We aim to demonstrate a de-icing method using combined on-the-blade opti-
cal and temperature sensors and electrothermal actuation, as shown in Fig.
8.4
.
Our de-icing experimental setup consists of a distributed optical sensor network
that allows for precise local measurements of ice existence and type. Our ice
sensors are responsive (0.5 Hz response time) and accurate in measuring ice
thickness (36 micrometer thickness resolution) and hence are able to detect ice in
the very early stages of ice formation. Leveraging the ability to quickly measure
and react to changing conditions, we then develop a suite of control solutions
optimized for any type of ice accumulation. Temperature sensors, installed close to
the blade leading edge area, are used for calculating the input thermal power for a
distributed network of heaters.
