Oscillating water column (OWC) wave energy converters (WEC) are the most extensively studied and possibly the most reliable of all WEC devices.
The OWC is an artificial blowhole consisting of a chamber that is open beneath the waterline. The action of the waves moves the water column and, alternately, compresses and decompresses the entrapped air resulting in a bi-directional flow through an air turbine, which generates electricity. Due to the oscillatory flow characteristics, bi-directional (or self-rectifying) air turbines are generally adopted.
A fundamental step in turbine development is to conduct model-scale performance tests, however facilities that accurately simulate bi-directional, or oscillatory, air flows are relatively rare.
In 2018, AMC commissioned a bespoke test facility to generate high volume oscillating air flow. The main parameters of the AMC oscillating air flow test rig are:
- Chamber length: 3 m
- Chamber internal diameter: 1.5 m
- Ball screw driven by a 32 kW Servo motor
- 3 x linear bearings
- Piston working travel (maximum): 2 m
- Piston velocity (maximum): 1.25 m/s
- Constant velocity profiles
- Sinusoidal profiles
- Programmable profiles based using position way points and velocity
A system controller monitors the active piston position and velocity. Other measurements acquired with the dedicated data logging system include pressure and temperature sensors.
The air flow exit can be adapted to suit specific applications. Examples include: (1) a flange can be fitted to investigate the performance of flap/check valves; or (2) air turbine performance can be assessed by mounting an adaptor to the exit flange or via a bypass pipe. Orifice plates or venturi can measure bypass flow.
Key words: Wave energy; Oscillating water column; Turbine test-rig; Bidirectional air flow; Reciprocating air flow; Oscillating air flow; Self-rectifying air turbines; Experimental testing.
We gratefully acknowledge the valuable contribution from our research collaborator, Wave Swell Energy, in the development of this test rig.