Wind power development in Bangladesh
Bangladesh has been struggling to take the advantage of the entirely clean and endless source of wind energy by using windmill technologies for decades. Recently the government of Bangladesh has stepped up its efforts by approving the maiden private wind power project to set up a 55 MW wind power plant on build-own-operate basis at Mongla in Bagerhat. A Chinese-Bangladeshi consortium consists of three companies: Consortium of Envision Energy, (Jiangsu) Co Ltd, China, SQ Trading and Engineering, Bangladesh and Envision Renewable Energy Limited, Hong Kong, will set up the plant under a 20- year contract with Bangladesh Power Development Board (BPDB).
State-owned BPDB will purchase the electricity from the plant at a levelised tariff of US$ 13.20 Cents, equivalent to Tk 10.56 per kilowatt hour over the period of 20 years. The government will pay a total of Tk 2035.12 crore for the entire contract period against its purchase of electricity from this project.
Nowadays the windmill is being considered as the most environment friendly, clean, renewable and pollution free sources of energy used for many purposes such as grinding grains, water pumping, generating electricity etc. According to the World Wind Energy Association (WWEA) about 100 countries around the world have been using electricity generated by wind turbines. The installed wind energy capacity of world's top ten countries includes: China (221 GW), USA (96.4 GW), Germany (59.3 GW), India (35 GW), Spain (23 GW), UK (20.7 GW), France (15.3GW), Brazil (14.5 GW), Canada (12.8 GW) and Italy (10GW).
In Bangladesh, wind power project began in 2005. According to the Sustainable and Renewable Energy Development Authority (SREDA), only three small wind energy plants, having a total capacity of 2.9 MW, have been installed by the Bangladesh Power Development Board (BPDB) so far against its target of setting up wind power projects having total capacity of 1152 MW by 2020. Besides these, some other organisations have installed wind power plants such as Grameen Shakti installed 4 hybrid power stations (combination of wind turbine and diesel generator) in four cyclone shelters of Grameen Bank. Power generated from the wind turbines is connected to four cyclone shelters for lighting.
BRAC under REP installed 11 small Wind Turbine at a capacity of 0.3 KW in various coastal area of Bangladesh. Local Government Engineering Department (LGED) has set up a number of 27ft high wind pumps having a power of 0.5hp (385W) at a wind speed of 4m/s in Tangail, Kushtia, Cox's Bazar and other places. LGED also installed 10Kwp in Wind-Solar hybrid system at St. Martins Island and another 400Wp at Kuakata LGED guest house. According to SREDA, the state-run Rural Power Company is working to set up a 10MW plant in Kalapara of Patuakhali which is scheduled to begin electricity generation on December 31, 2022.
For the last few decades numerous studies and researches have been carried out by various public and private sector agencies, departments, academic institutions, national and international organisations including BPDB, LGED, Meteorological department, BUET, CUET, KUET, Dhaka University, Free University of Brussels (FUB) Belgium, GTZ, Energy Technology and Services Unit (ETSU)UK, Netherlands Enterprise Agency, RISOE National Laboratory, Denmark, American National Renewable Energy Laboratory (ANREL), Centre for Wind Energy Technology (CWET) India, Bangladesh Centre for Advanced Studies (BCAS), BCSIR, BAEC and SREDA. It gives us huge information and knowledge to understand wind energy, windmills, wind turbines, to identify our potential wind resources, specific locations, wind-power development options, opportunities and challenges to harness the nature's great gift to mankind.
Wind is a form of solar energy produced by a combination of three concurrent events, namely: a) The sun unevenly heating the atmosphere; b) the Irregularities of the earth's surface and c) the rotation of the earth. 'The uneven heating of the earth creates areas of warm air that rises up and cold air that sinks and moves into its place. This movement of air and change in air pressure causes wind to form.'
The power of wind was first harnessed by the sailors, who were able to understand lift and harness the wind's power through sails. This knowledge led to the development of the first vertical axis sail-type windmill used by the ancient Persians in 500-900 AD and by the Chinese in 1200 AD for grinding grains and pumping water. The concept of harnessing wind energy via windmills reached Great Britain and Europe by 1137. In USA, advanced windmill was first designed and invented by Daniel Halladay in 1854.
The first windmill to generate electricity was invented in 1888 by an Ohio-based engineer named Charles Brush. In today's society the windmillused to generate electricity is referred to as wind turbine. In USA wind turbines first evolved from the four bladed systems, then to two bladed systems, and finally to the three-bladed system, which is considered as the most efficient and least troublesome way to harvest the wind and commonly seen in the wind farms today.
A wind mill is defined as a device that makes the use of wind as its power to convert wind energy into rotational energy by means of blades or vanes or sails commonly used for grinding grains, pumping water or generating electricity. There are mainly two types of windmills:
a) Horizontal axis windmill or turbine: A turbine with a shaft mounted horizontally parallel to the ground is known as a horizontal axis wind turbine; and b) Vertical axis windmill or turbine: A vertical axis wind turbine has its shaft normal to the ground. For higher efficiency, control, noise, aesthetics and its ability to survive and operate under varying wind conditions the horizontally mounted three bladed wind turbines have been in use widely around the world. A typical horizontal-axis wind turbine mainly consists of: 1) foundation, 2) tower, 3) shafts, 4) gears and axles,5) generator, 6) control, 7) nacelle, and 8) blades.
Working principles: 'Typically standing at least 80 meters (262 feet) tall, tubular steel towers support a hub with three attached blades and a "nacelle," which houses the shaft, gearbox, generator, and controls. An anemometer measures the wind speed and transmits the data to the controller. The controller senses the wind direction, wind speed, generator output and temperature, and initiates control signals to take appropriate action. Wind measurements are collected, which direct the turbine to rotate and face the strongest wind, and the angle or "pitch" of its blades is optimized to capture energy. Wind turbine converts the kinetic energy of wind to generate electric or mechanical energy. Wind passes over the blades exerting a turning force.
The rotating blades turn a shaft inside the nacelle, which goes into a gearbox. The gearbox increases the rotation speed for the generator, which uses magnetic field to convert the rotational energy into electrical energy. The power output goes to a transformer, which converts the electricity from the generator to the right voltage for the distribution system. A typical modern turbine will start to generate electricity when wind speeds reach six to nine miles per hour (mph), known as the cut-in speed. Turbines will shut down if the wind is blowing too hard (roughly 55 miles an hour) to prevent equipment damage.'
The writer is former editor, Journal of the Institution of Engineers, Bangladesh