Hydropower uses the Earth’s water cycle to generate electricity because movement of water as it flows downstream creates kinetic energy that can be then converted into electricity. Mechanical energy is created as the blades of the turbine begin to spin due to the force of the water on them. The motion of the turbine’s electro-magnets interacts with the coils of a generator to create electrical energy. Most installations in Nepal are without a reservoir, know as run-of-river installations, the water isn’t stored, but passes through the penstock at the flow-rate of the river to create electricity in the process. After the water has helped create electricity, it flows out to the river once more.
Hydropower is very efficient energy source because some turbines can achieve efficiency of 95% and more. Today hydro-power provides about 20 % of the world’s electricity and is the main energy source for more than 30 countries in the world. Its advantage over other renewable energy sources is the fact that average rainfall is highly predictable and therefore output is reliable and river flow doesn’t fluctuate from minute to minute like is the case with wind energy.
Hydropower could be a good clean energy choice for Nepal because Nepal has good hydropower potential and very little of installed hydropower capacity. Many energy experts agree that future looks bright for hydropower because of its good cost parity with fossil fuels and also because its climate benefits. Nepal is blessed with multiple source of water including glaciers, snowmelt from the Himalayas, rainfall, and ground water which could be used to generate hydro-electricity. Theoretically, hydropower potential for Nepal is about 83,000 MW out of which 40,000 MW is both technically and economically viable. Today only 40% of population has access to some form of electricity with the installed capacity of 600 MW.
Hydropower development is the only development activity that yields multiple benefits and, in many cases, can be an effective agent for poverty alleviation. Apart from being a source of renewable and clean energy, to stabilize the supply of electricity, it helps provide year round irrigation resulting in the increase in the cropping intensity and changing cropping pattern, and it reduces both deforestation and greenhouse gas (GHG) emissions. Nepal has adopted a policy of Integrated Water Resources Management (IWRM), by which hydropower projects are developed in conjunction with irrigation, flood control, water supply and navigation components whenever feasible. As an agriculture dependent country, Nepal should maximize the irrigation benefit, by providing year round irrigation through storage projects developed for peak energy generation. Nepal has planned to provide year round irrigation to 67% of the total irrigated area by 2027. Electricity from hydropower projects currently contributes only 1% of energy need, whereas fuel wood contributes 68%, and fossil fuels 8%. Development of hydropower not only helps reduce deforestation, reported at the rate of 0.7% per annum, but also helps reduce GHG emission by substitution of imported fossil fuels. The annual fossil fuel import cost for Nepal 2004/05 was about 310 million USD. Nepal could benefit substantially if consumption of petroleum products were replaced by hydropower (Electricity). Where, the Clean Development Mechanism (CDM) is effectively used to address the impact on climate change, hydropower gains significance by contributing positively to climate change.