Article: Small Hydropower Brings Possibiity of Locally Generated Electricity for Local Consumption

As a source of renewable energy, hydropower has a history of over 100 years, and has played a key role in Japan's modernization and economic development as truly domestically produced energy. The most economically viable sites for hydropower generation in Japan, however, have already been completely developed. In addition, large hydropower development grows increasingly difficult these days, as people become more aware that large-scale development leads to issues such as environmental destruction and the loss of history and culture.

What is Small Hydropower?
Hydropower refers to a system in which electricity is generated by utilizing the vertical gradient over which water flows and its water volume to spin a turbine. Worldwide, small hydropower is classified as an installation capable of producing 10,000 kW or less. In Japan, the electrical power industry and the New Energy Development Organization guidelines agree with this classification.

For small to medium hydropower development projects subsidized by the Japanese Ministry of Economy, Trade and Industry, small to medium hydropower is defined as having a generation capacity of 30,000 kW or less. Meanwhile, both the Law Concerning Promotion of the Use of New Energy and the Renewables Portfolio Standard Law (Special Measures Law Concerning the Use of New Energy by Electric Utilities) define small hydropower as 1,000 kW or less.

Small hydropower refers not to the damming, storing and control of river water, but rather to the harnessing of energy from flowing water wherever it may be, whether is in a free-flowing river, an agricultural canal, a public water supply, a dam built for landslide prevention, or whatever. Rather than defining small hydropower by its generating capacity, the International Energy Agency's Hydropower Implementing Agreement defines small hydropower to be environment-friendly hydropower that does not involve large dams or other large-scale developments.

Advantages of small hydropower compared to other renewable energies include the ability to operate year-round and both day and night, the high utilization rate of total capacity (five to eight times as much as PV power generation), little fluctuation in generation capacity, as well as good economic potential and a large amount of technically and economically feasible hydropower energy. On the other hand, disadvantages include being limited to accessible sites that have sufficient elevation change and good water flow, fluctuation in power generation caused by changes in flow volume during wet and dry seasons, issues of stakeholders' interests concerning water use such as water rights, and complicated legal procedures.


—Excerpted from an article written by Kazumi Yagi, Japan for Sustainability Newsletter