Instream generation using tethered kites in the carousel configuration
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Date
31/07/2021Author
Luttik, Kristin Nicole
Metadata
Abstract
In recent years, kites are beginning to be considered as viable alternatives to oshore
wind turbines, due to the potential reduction in levelised cost of energy and the increase
in exploitable resource due to versatility of kite based generators. This thesis focuses
on the kite carousel design, which consists of a ground based vertical axis generator
with a number of kites attached. The kites are flown in a pattern that induces motion
in the generator and thus produces power. This method of energy harvesting allows
substantial scaling of devices. Device output depends not only on the available ow
and kite size, but is further influenced by the length of the kite tether, the radius of the
carousel structure, and the number of kites attached.
Although kites have been studied extensively in recent years, there is no consensus on
the optimum design and configuration of the carousel. The thesis presents a minimum
order model of a kite carousel. This numerical model is used to indicate the driving
principles of the carousel and the importance of flightpath design on output. The presented model can be applied to various ow conditions. However, due to the definition
of dimensionless power used, there is a scaling dependency of the model outputs regarding the kite tether length. An alternative method of describing the swept area of
the carousel, based on the swept area of the kite flightpath, is used to mitigate this and
indicate device efficiency in power extraction.
The flightpath optimisation and parameter study illustrate this scaling dependency and
highlight the effect of the carousel radius and tether length on the optimized flightpath.
These results then inform a case study for a carousel placed in a representative tidal
flow. The case study describes a device with 8 kites attached to a 5 m diameter carousel
that produces 64 kW over a representative tidal cycle with a peak flow of 2.2 m/s.