Micro-hydro

Hydropower is an eco-friendly clean power generation method. The scope of hydropower generation is very limited in Bangladesh because of its plain terrains except in some hilly region in the northeast and southeast parts of the country. However there are lot of canals, tributaries of main river  Karnafuli, Shangu, Matamuhuri as well as tiny waterfalls having good potentials for setting up mini/micro hydropower unit in Chittagong Hill Tracts(CHT) region.

Micro-hydro power is a simple technology to convert hydropower primarily to mechanical power. They are generally 5-300 kW range. It is not feasible to supply electricity to the National grid from a micro-hydro power unit. Typically they provide captive power to just one rural community. In many cases micro hydro power units do not generate electricity. They are used for grinding cereals in mills and often driven directly from the turbine shaft. Classifications of hydro power based on generated power are as follows:

Pico Hydro up to 5 kW
Micro-hydro         >5<300 kW
Mini-hydro           >300kW<3MW
Small hydro         > 3MW<10MW

A hydro power scheme requires both water flow and a drop in height (referred to as a head) to produce useful power. It is a power conservation system, absorbing power in the form of head and flow, and delivering power in the form of electricity or mechanical shaft power. Indeed no power conservation system can deliver as much useful power as it absorbs. Some power is lost by the system itself in the form of friction, heating, noise etc.

Net power generation from a hydro power unit could be obtained from the following equation:
Pnet = hgross * Q *  g  * eo
Where
Pnet   = Net power generated from the unit in kW
hgross = Gross water head in meter
Q      = Discharge in m3/sec
eo     = System efficiency
g      = gravitation force in m/sec2

A typical hydro power has about 50% power loss, out of which about  5% losses in Channel, 10% loss in Penstock, 20% loss in turbine, 15% loss in Generator, 4% losses in step-up/down transformers loss and 10% Transmission losses.

‘Bamerchara’ is basically a water storage reservoir. To facilitate irrigation in dry period earthen dam with a sluice gate was constructed by the Local Government Engineering Department in 1994. Only rainwater is stored in the reservoir during the monsoon and there is no perennial source of stream. ‘Danerchara’; another storage reservoir was also connected with ‘Bamerchara’ to provide more water storage facility. At present maximum water storage area has been increased to about three sq. km. A spill way was constructed at ‘Danerchara’ in 2000 to release extra water. In 2002 a feasibility study was conducted by an International Expert to install a micro-hydro power unit at Bamerchra. However, irrigation is the main purpose of Bamerchara project therefore only supplementary power generation is possible during monsoon and irrigation period when the sluice gate is normally kept open.

Objective of the project:

• To demonstrate micro-hydro power unit
• To integrate hydropower with the irrigation infrastructure
• To explore possible replication of the model in the CHT region

Potentials of Micro Hydro power unit in Bangladesh:  To explore potential sites of micro-hydro, several studies have been conducted by Bangladesh Water Development Board (BWDB) and BPDB in 1981. List of prospective site is shown in table 1.1

Table 1.1 : Potential Small Hydro Sites identified by BPDB and BWDB

In 2004 Sustainable Rural Energy has explored some potential micro-hydro sites in CHT region which is listed in table 1.2  

Table1.2:  Micro-Hydropower sites identified by SRE study  in 2004

 LGED has implemented first micro-hydro power unit at Bashkhali in Chittagong district. Feasibility study report on micro-hydro power unit is also available on the web.