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Research Papers

# Performance Characteristics of a 1 kW Scale Kite-Powered System

[+] Author and Article Information
David J. Olinger

Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609olinger@wpi.edu

Jitendra. S. Goela

Optical and Ceramic Technologies, Dow Chemical Company, Marlboro, MA 01752jgoela@dow.com

J. Sol. Energy Eng 132(4), 041009 (Oct 04, 2010) (11 pages) doi:10.1115/1.4002082 History: Received February 06, 2009; Revised April 27, 2010; Published October 04, 2010; Online October 04, 2010

## Abstract

A 1 kW scale kite-powered system that uses kites to convert wind energy into electrical energy has been studied to determine its performance characteristics and establish feasibility of steady-state operation. In this kite-powered system, a kite is connected to a tether that transmits the generated aerodynamic forces on the kite to a power conversion system on the ground. The ground-based power conversion system consists of a rocking arm coupled to a Sprag clutch, flywheel, and electrical generator. Governing equations describing the dynamical motion of the kite, tether, and power conversion mechanism were developed assuming an inflexible, straight-line tether. A steady-state analysis of the kite aerodynamics was incorporated into the dynamical equations of the kite-powered system. The governing equations were solved numerically using a Runge–Kutta scheme to assess how performance parameters of the system such as output power, cycle time, and tether tension varied with wind speed, kite area, and aerodynamic characteristics of the kite. The results showed that a 1 kW scale system is feasible using the proposed design concept with a kite area of $25 m2$ and wind speeds of 6 m/s. Preliminary efforts to build and test a working 1 kW scale kite-powered demonstrator are also reported.

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## Figures

Figure 1

The kite-powered system. (a) The system in the power configuration when the Sprag clutch and flywheel are engaged. In the idle configuration, the Sprag clutch and flywheel are disengaged, and the system splits into the two subsystems shown in (b) and (c). The structure C in (a) consists of a constant radius (RC) arc that ensures that the tension force in the chain connecting gear G to point C always acts perpendicular to the rocking arm at point C.

Figure 2

Parameter definitions for the kite and tether

Figure 3

(a) Rocking arm motion versus time. (b) Angular velocities of the rocking arm, gear G, and the flywheel versus time.

Figure 4

Time variation of rocking arm and power mechanism parameters. (a) γ, ωF, and ω. (b) Ft. (c) PK(t) and PLOAD(t).

Figure 5

Time variation of kite parameters. (a) θ, β, and αeff. (b) VR, VK, and L/D. (c) Kite position showing stable oscillation. The kite position is shown for times after initial transients have died out. The numbered times are defined in Table 1 and Fig. 3.

Figure 6

Power coefficient versus wind velocity

Figure 7

Effect of wind velocity on power output. (a) Power coefficient versus normalized load weight. (b) Power coefficient versus average flywheel angular velocity. V¯=8.31, 9.96, 11.6 m/s for V0=5.0, 6.0, 7.0 m/s cases, respectively.

Figure 8

Effect of kite area on power output. (a) Power coefficient versus normalized load weight. (b) Power coefficient versus average flywheel angular velocity. V¯=9.96 m/s.

Figure 9

System period TC, engagement time T2−4, and disengagement time T4−2 versus normalized load for the baseline run of Table 2.

Figure 10

Effect of counterweight on power output. Power coefficient versus normalized load weight. V¯=9.96 m/s.

Figure 11

Effect of kite airfoil camber on power output. Power coefficient versus normalized load weight. V¯=9.96 m/s.

Figure 12

Effect of kite aspect ratio on power output. Power coefficient versus normalized load weight. V¯=9.96 m/s.

Figure 13

The kite-powered demonstrator. The rocking arm structure, kite, power conversion system, battery bank, and electrical system are shown.

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