Embark IEI Research Achievement Awards

Wave energy is the most abundant source of renewable energy in the World. For the last two decades,engineers have been investigating and defining different methods for power extraction from wavemotion. The concept of harnessing the power from ocean waves has resulted in the design of manydevices. Some of these devices utilize the principle of an Oscillating Water Column (OWC), which extractsenergy from water waves and converts it into low-pressure pneumatic power in the form of bi-directionalairflow. The impulse turbine for wave energy applications presented here is one of a class of turbinescalled self-rectifying turbines, that is, turbines that rotate in the same direction no matter what thedirection of the airflow is. Self-rectifying air turbines convert this energy due to this reciprocatingmotion into mechanical shaft power, which in turn is converted into electrical power by a generator.To validate the design, the turbine is tested experimentally in the Wave Energy Research Team’s (WERT)turbine test rig, but within the limitations of existing experimental facilities. However the real workingconditions of the turbine are different from those posed by the experimental facilities. In the real seaconditions, the airflow generated by the OWC is irregular because of irregular waves. Therefore it is veryimportant for the designers to understand the behaviour of these devices, under irregular airflow, beforebuilding prototypes and deploying them physically in the real sea conditions. To test the turbineexperimentally under those conditions the limitations of the experimental facilities have to be extendedto simulate the similar conditions.This paper presents the work undertaken in order to simulate sinusoidal flow conditions and irregularreal wave conditions in the turbine test rig of WERT. By using instrumentation and control techniques adata acquisition system was designed and implemented to speed up the task, and improve the accuracy,of testing by illuminating the human element. A full set of tests have been carried out using the newacquisition system on 0.6m diameter impulse turbine, with hub to tip ratio of 0.6, under steady flowconditions. Results show a maximum efficiency of 47%. To allow any required flow pattern to be created in the test section of the turbine test rig, a new valvewas designed and manufactured. This valve has an independent control system that is linked with thedata acquisition system. These new modifications allow performance evaluation to be carried out on thecurrent design of impulse turbine with guide vanes under unidirectional irregular flow conditions.Performance testing is started on the 0.6m diameter impulse turbine, with hub to tip ratio of 0.6, undervarious unidirectional flow conditions. Further modifications will be undertaken to create bi-directionalairflow in the current rig to allow performance evaluation of a given turbine under similar flowconditions to what will be experienced at a give wave site. The ultimate goal of this work and the workof WERT is to optimise the performance of the impulse turbine under actual sea conditions.