Evaluation of wind energy pattern for Chandona-Gazipur, Dhaka

Abstract

The available wind speed data of different locations of Bangladesh so far recorded by various organizations are not adequate for designing Wind Ener6'Y Conversion System (WECS). This is because of the fact that the way of measuring them was not intended for wind energy research. Hence a wind speed data measurement, its frequency and duration etc. should be recorded in a systematic way must be carried out. This is essential for studying the effectiveness of several types of WECS. For this purpose, a wind monitoring plant is constructed at Chandona, Gazipur with modem electronic di6.;tal apparatus. A 20-m height wind monitoring plant is set-up at Chandona, Gazipur. Continuous wind speed is measured with a modem three cups and pulse counter sensor type anemometer. The wind data are stored into a digital data-logger for two years. The wind data are automatically stored into a statistical programmable software built-in digital data-logger since August 1997 to July 1999. There are three types of statistical data storing devices in the data logger, such as daily basis, weekly basis and monthly basis. Each statistical data-storing device has thirteen memory blocks. So, wind data of thirteen days, or thirteen weeks or thirteen months can be stored into the data logger. Wind data are recorded as daily basis from August 1997 to July 1998 (annual-I) and as monthly basis from August 1998 to July 1999 (annual-2). Every block gives the mean wind speed, maximum wind speed, frequency of wind speeds, frequency of lull periods and mean diurnal wind speeds for those statistical blocks. Hourly average wind speed is directly obtained from the output of the data-logger for annual-I and for annual-2, these values are calculated from the percentage of frequency table of monthly basis statistical blocks. Then the velocity frequency tables are done and histograms have been plotted for every month and year. The wind speed distribution is processed and fitted to the Weibull function to determine the nature of wind regime for that site. The shape factor (k) and scale factor (C) of Weibull function are determined and compared with standard one for each month and year. Then the Weibull functions F(v), Weibull density functions f(v), and velocity duration functions S(v), are plotted from the observed and calculated values for each month and year. The cut-in speed (ve), rated speed (vr), furling speed (Vf), and availability factor (AF) can readily be determined from Weibull functions. The availability factor and capacity factor have been calculated for each month and year. The wind energy concentration (Wh/m2) has also been calculated. A model of WECS is designed to select an appropriate wind turbine and wind pump and to assess the wind potentiality for Chandona-Gazipur, Dhaka. Finally economic feasibility of the selected wind turbine has been shown. It is observed that the wind speeds of Chandona are low. The velocity frequency distributions follow very close to Raleigh distribution. The wind speeds remains very high during the monsoon period (June-July) and very lean from October to February. From the analysis of wind resource assessment it is found that 300-600 watt capacities Wind Electric Generators (WEGs) are preferable and windmills for water pumping are very much prospective for that site. The wind enerl,'Yof each month is not similar. It is very high during May to July and very low during October to December. A hybrid system is a must for Chandona, Gazipur.