The Prospect of Hybrid Wind System in Bangladesh
Abstract – In future, renewable energy like solar, wind, wave and tidal could be utilized in some areas of Bangladesh. The geographical location of Bangladesh is ideal for tapping solar energy effectively. There is also enormous potential for harnessing electrical power from wind in some selected areas of the country and in the coastal region. In this paper possibility of wind-solar hybrid system has been studied. There is a possibility of a total of 100 MW hybrid power generation in coastal areas. After a preliminary survey supported by measured ield data of wind velocities and solar radiation all over the country, two specific sites Patenga and Thakurgaon have been primarily identified where more than 100 kW wind-solar hybrid power generations is possible. Keywords: Wind energy, hybrid system 1. INTRODUCTION Bangladesh is a developing country lying in the areas where the expansion of national grid is very bleak. This study finds that Patenga and Thakurgaon are the two most promising sites of wind-solar hybrid system. Patenga is a rural area near Anowara thana in the district of Chittagong, the gateway of Bangladesh.
The western side of Patenga is surrounded by the Bay of Bengal. The site consists of five villages. The total population  is around 5,000. Thakurgaon is a district situated near the northern boundary of Bangladesh with a population 1,010,948 of which 916,442 (i. e. 90. 65%) are rural inhabitants. Only 8. 26% of the total households have access to electricity, which is principally generated by the 10. 5 MW diesel generator . 2. THEORY Wind energy is the kinetic energy of the moving air mass. The power, P, in watts, possessed by wind lowing with a velocity of V, in meters per second, is northeastern part of South Asia and is situated between 20 30? to 26 38? north latitude and 88 04? to 92 44? east longitude. The vast Bay of Bengal on the south of the country along with the V -shaped coastal belt is the main source of the southwesterly wind blowing over the terrain. The geographical location of the country has become an ideal place for utilization of solar energy. It has also a bright prospect of electricity generation from wind, especially in some northwestern districts and in the southern coastal areas.
In some parts of the country electricity demand is met by the existing power generating plants primarily run by imported furnace oil and high-speed diesel. Considering diurnal variation of wind velocities and available wind speed pattern , the existing diesel generation can be partially replaced by Wind Energy Conversion Systems (WECS) and also new wind-solar hybrids can be set up. According to the Bangladesh Power Development Board (BPDB) and Local Government Engineering Department (LGED), there is huge potential of wind-solar-diesel and wind-diesel hybrid ystems in Bangladesh and they could be future energy option of rural electrification  purpose in directly proportional to the rotor swept area and to the cube of the wind speed, and is given by; P = (? ). ? . A. V (in Watts) 3 (1) where, A is the area perpendicular to the direction of 2 -3 flow, meter , ? , density of air, kgm , is approximately 3 1. 2 kg/m , V, wind velocity, meters per second. Only a part of the total available power calculated by equation 1 can be extracted and is given by; P = (? ). ? . A. V . Cp (in Watts) 3 (2) Cp, the power coefficient  is the ratio of power xtracted by a wind turbine to power available in wind at that location. A theoretical maximum of 59. 3% of available power can be extracted; i. e. Cp is 0. 593. Practically a typical maximum of 40% is achievable. Solar cells represent the fundamental power conversion unit of photovoltaic system. They are basically p-n junctions made of semiconductor. Incident sunrays are converted directly into electricity by solar cells. ISBN 984-32-0328-3 212 little bit lower than that of the monsoon. During rainy season (May-July) wind electricity can predominate the solar electricity.
So 100 kW hybrid wind-solar power can be available throughout the year. The only problem is that, there is probability of cyclone in every 10 years or so. Sufficient control techniques can be provided to prevent overstressing of the turbine in high-speed wind during cyclone. Tilting the wind wheel and changing the blade angles to lower their loads during the high-speed wind period may protect wind turbines. An average yearly wind speed of at least 4 m/s is necessary to justify the use of a wind generator in a hybrid system . The annual average wind velocities -1 -1 f Patenga and Thakurgaon are 7. 48 ms and 6. 59ms  S. Ahmmed, “Investigation and Analysis of Wind Pumping System for Irrigation in Bangladesh”; February 2002, Ph. D. Thesis, Department of Mechanical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh. M. U. Mahfuz, “Wind Energy Status in Bangladesh” in Wind Engineering – International Journal of Wind Power, Vol. 25 No. 3, Multi-Science Publishing, Leicestershire, UK Primary Grid System of Bangladesh Power Development Board (BPDB), as of January 2001, prepared by Direct