Content
- Traction phase (velocity & force triangles) for non-crosswind case
- Retraction phase (velocity & force triangles)
- Depower
- Steady-state retraction as an idealization
- Transition phases
- Operational strategies (Luchsinger 2013)
Airborne Wind Energy
Energy harvesting with kites
Roland Schmehl
11 October 2024
Outline
Max DeretaLearning objectives
The focus of this lecture is on the pumping cycle operation that most of the currently implemented AWE systems use. Operational strategies are discussed, including now also winch control. Relevant literature sources are Vlugt et al. (2019), Schelbergen and Schmehl (2020) and Luchsinger (2013).
Pumping cycle operation
Pumping cycle simulation
Simulation results by Fechner (2016).
Pumping cycle visualization
Courtesy of Kitepower B.V. (2018)
Pumping cycle idealization
Pumping cycle two-state approximation
Further reading
Energy harvesting with kites is described in much detail in a draft chapter of the emerging course reader.
The accompanying Python code to compute the powercurve and operational data is available from a GitHub repository.
The powercurve and operational data is computed for the system described in this book chapter. Figure 23.15 in this chapter shows the experimentally derived powercurve.
Expanding the theory
- Account for a two-stage depowering strategy during reel-out in wind speed regime 3. The continuous increase of the reel-out elevation angle (stage 1) is already coded but commented out. Stage 2, which is currently coded and used, would be an active depowering of the kite by changing its aerodynamic properties.
- Account for gravity and a non-zero mass of the kite, by iteratively solving the quasi-steady force equilibrium equilibrium. The approach is explained in Vlugt et al. (2019).
- Remove the assumption of infinitely fast transition phases and account for a numerically integrated flight path during the reel-in phase. The approach is outlined in Section 14.2.4 “Simulating the reel-in phase” of Fechner and Schmehl (2013) and also explained in question 3 “Retraction of a kite with non-vanishing tangential motion” of this exam solution.
References
Fechner, U.: A methodology for the design of kite-power control systems.
Delft University of Technology (2016). doi:10.4233/uuid:85efaf4c-9dce-4111-bc91-7171b9da4b77
Fechner, U., Schmehl, R.: Model-based efficiency analysis of wind power
conversion by a pumping kite power system. In: Ahrens, U., Diehl, M.,
and Schmehl, R. (eds.) Airborne wind energy. pp. 249–269. Springer,
Berlin Heidelberg (2013). doi:10.1007/978-3-642-39965-7_14
Luchsinger, R.H.: Pumping cycle kite power. In: Ahrens, U., Diehl, M.,
and Schmehl, R. (eds.) Airborne wind energy. pp. 47–64. Springer, Berlin
Heidelberg (2013). doi:10.1007/978-3-642-39965-7_3
Schelbergen, M., Schmehl, R.: Validation of the quasi-steady performance
model for pumping airborne wind energy systems. Journal of Physics:
Conference Series. 1618, 032003 (2020). doi:10.1088/1742-6596/1618/3/032003
Vlugt, R. van der, Bley, A., Schmehl, R., Noom, M.: Quasi-steady model
of a pumping kite power system. Renewable Energy. 131, 83–99 (2019).
doi:10.1016/j.renene.2018.07.023