Bangladesh has got 710 km long coastal belt along the Bay of Bengal. If the marine RETs become viable option in the future, then the country may harness energy from marine RETs. The main marine RETs are –
1. Tidal
2. Wave and
3. Oceanic Thermal Energy Conversion
Tidal
Tidal power utilizes the twice daily variation in sea level caused primarily by the gravitational effect of the Moon and, to a lesser extent the Sun on the world's oceans. The Earth's rotation is also a factor in the production of tides. The normal tidal head rise and fall in the coastal region of Bangladeshi is between 2 and 8 meters as shown in the following table. This tidal range can easily be converted to pollution free clean renewable energy busing the simple low-cost technology of a “tidal wheel” in the sluice gates.
Figure: One of many sluice gates in Sandwip that could be utilized for tidal power plant [Refocus 2001].
The real benefits of this technology however are that it can be applied in a way that simultaneously enables the development of local infrastructure and various resource producing activities such as agriculture and aquaculture along with improved living conditions for the local people [Salequzzaman et. al. 2001]. A demonstration tidal power project is being planned in Sandwip, one of the coastal island of Bangladesh, by ISTP of Murdoch University, Australia. ISTP has developed a feasibility plan for rebuilding a recently damaged sluice gate with a trial paddle wheel [REFOCUS March 2001]. If become successful, the tidal project of Sandwip can be replicated in the other coastal areas and which will usher new light in the region.
Explanation:
MLWS = Mean Low Water Spring, MHWS = Mean High Water Spring, MHWN = Mean High Water Neap, MLWN = Mean Low Water Neap, ML = Mean Level, AT = Astronomical Tide, LAT = Lowest Astronomical Tide, HAT = Highest Astronomical Tide, TR =Difference between lowest and highest tidal height in “m”.
Tidal Electric Inc. (TE) is one of the major global players in the field of tidal power projects around the world. TE is active in the two neighboring countries of Bangladesh – India and Myanmar in the Bay of Bengal. TE is carrying out feasibility study of a 1000 megawatt tidal power plant in Gujarat, India and target site in Myanmar. Wave Ocean waves represent a considerable renewable energy resource. Waves are generated by the wind as it blows across the ocean surface. They travel great distances without significant losses and so act as an efficient energy transport mechanism across thousands of kilometers. Energy can be taken from waves almost everywhere but if the waves are to small expenses will be to high. Wave energy is stronger around the poles and around the equator the water contains lesser potential.
Any site in the world with an average wave power level of over 15kW per meter has the potential to generate wave energy at competitive prices [OPD Ltd 2001]. From the atlas shown in Figure 7.2, it can be seen that for Bay of Bengal the value is 8 kW per meter of crest width. So, at present Wave power is not a viable option for Bangladesh.
Oceanic Thermal Energy Conversion (OTEC)
Ocean Thermal Energy Conversion (OTEC) utilizes the temperature difference between the warm surface sea water and cold deep ocean water to generate electricity. For OTEC to produce a net output of energy, the temperature difference between the surface water and water at a depth of 1000m needs to be about20°C [Australian RE Website]. From the atlas it can be seen that for Bay of Bengal the temperature difference between surface and subsurface (1000m) sea water is between 20 to 22°C.So, OTEC project is expected to be feasible in the Bay of Bengal in the future when the technology will be mature and cost of the system will go down.
