PDF《Wind Power Generators》

1 INVELOX system shown in Figure 2. Eventually, they are put through a Venturi in which an energy harvesting system (i.e. gearless turbine-generator system) is installed. Based on the Bernoulli and Venturi principals, the wind speeds will increase depending on the cross sectional differences. Since the only energy injected in the system is wind, and mass flow and energy balances, it is the pressure energy that is converted to additional kinetic energy. This process allows the WTG installed in the Venturi section to have access to much larger kinetic energy of the wind, and thus be able to generate same or more power using smaller turbines. INVELOX is based on hydro power approach used for years. The only difference is that INVELOX uses air versus water used in hydro. INVELOX uses the existing kinetic energy and pressure energy in wind while a hydro dam only uses the pressure that is based on water density and gravity. INVELOX does not require huge upfront capital cost that dams require, and INVELOX does not leave a huge negative environmental footprint that dams often build up over years of operations. But from the functionality point of view, they operate in similar manner, and that is how INVELOX can deliver a significantly lower power cost than traditional WTG mounted on a tall tower. Figure

3 shows the detailed dimensions and geometry of omnidirectional INVELOX modeled using COMSOL-CFD package. This model (INVELOX tower model number M1360- 001) uses double nested cone concept with

360 degrees wind intake capability. In addition to having no blade on the top of the tower, this model needs no yaw control to orient the intake into the wind, manually or automatically. This model is scaled to fit a 6ft diameter wind turbine at the Venturi location, and to be erected to a height of 60ft. Since INVELOX has no hub on the top, the height of the tower is measured from the center of the intake to the ground level. The speed ratio (SR=the free stream wind speed to the wind speed at the Venturi), an important design factor, is designed to be about 2. If the free-field wind speed is

15 mph, the speed at the location of the turbine (Venturi) will be equal to 2*(15 mph) =

30 mph.? 3. Use of COMSOL Multiphysics Figure

4 shows the INVELOX model created using COMSOL-CFD package. The virtual wind tunnel is the large

200 by

300 by

150 feet rectangular box. Omnidirectional INVELOX is placed at the center of the box while the bottom edge of the system is close to the bottom surface (X-Y plane) of the virtual wind tunnel. The intake is composed of two nested cones. The top cone is the guide directing wind into the lower cone. The CFD model is based on the k-epsilon turbulent flow. Figure

4 CFD model of INVELOX Figure

2 INVELOX system Figure

3 Detailed dimensions and geometry of omnidirectional INVELOX A constant velocity field, representing free stream wind, was assigned to the entire Y-Z plane at X=0. The magnitude of the velocity was set at

15 mph. The entire box was assumed to be at atmospheric pressure. All other five are considered slip walls with exception of the Y-Z plant at X=300ft. 4. Results Figure

5 shows velocity and pressure fields in the x-z plane at the center of INVELOX. The free stream wind speed is

15 mph in the direction of positive x. No blade is placed inside the Venturi. It is noted that while the maximum wind speed reaches 30.9 mph in the Venturi, the average wind speed is about 27.3 mph;

this results in an average speed ratio (SR) of about 1.82. The pressure field in the Venturi reaches a low value of (-111) Pa while the maximum pressure is