Ingenieur Vol 68 Oct-Dec 2016 | Page 32

INGENIEUR Figure 5. [Clockwise from left] CAWT model, particle streamlines and vector plots of CFD simulation (k-omega, SST) of a guide-vane structure for capturing, accelerating and deflecting the oncoming wind towards the bottom of the CAWT. between the CAWT and the VAWT. The RPM of both of the wind turbines increased linearly with time until it reached a maximum value of 609 rpm and 229 rpm at t = 223s and t = 161s for the CAWT and VAWT, respectively. From the initial test, the maximum RPM generated by the CAWT is 166% higher than the VAWT under the same experimental conditions. The increase in maximum RPM proved that the CAWT harnesses more wind energy than the conventional VAWT. A preliminary CFD simulation was also carried out on the prospect of using a guide-vane shroud structure with the CAWT (as shown in Figure 5). The concept of the omni-directional shroud used is similar to the one used by Chong et al. [5] It forms the outer covering of the turbine but directs the wind from all directions to interact with the horizontal blades. The shroud consists of a series of deflectors that are shaped to capture the wind (free stream velocity = 8 m/s) and to channel it upwards. The vector plot in Figure 5 shows that the horizontal wind is deflected far above the guide vane. Thus, this deflected wind is expected to interact with the horizontal blades and provide extra power to the CAWT. 6 30 VOL - DECEMBER 2016 VOL68 55OCTOBER JUNE 2013 Potential applications and impacts The CAWT is proposed to be used in harvesting off-shore wind power. The HAWT, VAWT and CAWT in off-shore applications are illustrated in Figure 6. The proposed CAWT is able to float on the water surface with its guide-vane serving as a buoy. The CAWT is more stable when compared to the HAWT especially during rough sea profiles in bad weather as its center of gravity is expected to be located in its lower portion. The off-shore power extraction performance of the CAWT is expected to out-perform the VAWT as higher torque is available from the guided wind produced by the omni-directional guide vane which is absent in most VAWT designs. The CAWT system can be installed as a standalone or integrated onto buildings for power generation as shown in Figure 7. The installation is easy and without wire trenching on the ground, and the electric power generated can be supplied to the user for any application. Such on-site power generation especially for urban areas and islands could be supplied to a wide market, for example, island countries such as the Philippines and