Data Collection and Handling: The meteorological department of Bangladesh collects 3-hourly wind speed data with the help of vertical axis cup type anemometers. These wind data for the period 1981-1996 of 20 stations were taken and monthly average speeds were computed for all the 20 stations. The wind power per unit area of approach is proportional to the cube of wind speed (Beurskens, 1978) and can be expressed as P/A = 0,6V3(watts), where,P/A is in W/m2 and V is in m/s. The available wind power represents the strength of wind and theoretically 59% of this power may be extracted but in reality maximum 45% can be extracted approximately. Practically, extractable power by any type of windmill can be written approximately as (Beurskens, 1978), Pe = 0,1 AV3 (watt), where A is the total swept area of the rotor blades and V is wind speed (m/s). Theoretical available power of different locations at 20 meter height in Bangladesh. Extracted power per square meter of swept area for different months for 20 locations in Bangladesh is shown , From this figure it can be seen that wind energy can be used in the months of March, April and May for irrigation purposes, '
Experimental Procedure:The experiment was carried out in an open circuit subsonic wind tunnel with an outlet test section of (490 mm x 490 mm) cross-section. The central longitudinal axis of the wind tunnel was maintained at a constant height from the floor. Average wind tunnel air velocity was measured directly by an electrical anemometer, which was placed in front of the rotor blades at different locations and average velocity was measured directly, Non-contact electrical tachometer was used to measure the speed of the model wind turbine at different loading. The hub was designed to give zero coning angle and it permitted variation of blade pitch several degrees above and below the nominal setting, The hub and the blades of the model were manufactured from plastic and aluminium, respectively.
Sizing the Wind Pump For Patenga, Bangladesh: Empirical equation developed for wind pump rotor sizing for Patenga, Bangladesh is given below: HQ = C x 02 X V3 (2) where,
C = Constant (here, 8.47), HQ = Volume-Head product (m4/day), Q = Water requirement per day (m3/day), H = Water tank height (m), D = Diameter of the rotor (m), V = Average wind velocity (m/s)
Sizing the wind pump for Patenga, Bangladesh: can be calculated by using equation (2), or more easily from the nomogram given in Figure 2 from the following steps. 1): Locate the volume-head product along the Y-axis on the graph on the left side. For an example, the volume-head product is 7480 m4/day. 2): Move horizontally right to intercept the line for the average wind velocity 5.91 m/s. 3): Move downward to intercept the X-axis referring to the rotor diameter. This results in D = 2.07 m. When selecting a 2.07m wind pump from available commercial designs, it might become necessary to alter the hub height to conform to standard designs.