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How it works
Hydropower is based on simple concepts. Moving water
turns a turbine, the turbine spins a generator, and electricity is produced.
Many other components may be in a system, but it all begins with the energy
already within the moving water.
power is the combination of head and flow. Both must be present to produce
electricity. In a typical hydro system water
is diverted from a stream into a pipeline, where it is directed downhill and
through the turbine (flow). The vertical drop (head) creates pressure at the
bottom end of the pipeline. The pressurized water emerging from the end of the
pipe creates the force that drives the turbine. More flow or more head produces
more electricity. Electrical power output will always be slightly less than
water power input due to turbine and system inefficiencies.
is water pressure, which is created by the difference in elevation between the
water intake and the turbine. Head can be expressed as vertical distance (
meters). Net head is the pressure available at the turbine when water is
flowing, which will always be less than the pressure when the water is turned
off (static head), due to the friction between the water and the pipe. Pipeline
diameter has an effect on net head.
is water quantity, and is expressed as "volume per time," such as
cubic feet per second (cfs), or liters per minute (lpm). Design flow is the
maximum flow for which your hydro system is designed. It will likely be less
than the maximum flow of your stream (especially during the rainy season), more
than your minimum flow, and a compromise between potential electrical output
and system cost.
When is hydropower micro?
The definition of micro hydropower varies in different countries and can even include systems with a capacity of a few megawatts. In some cases up to a rated capacity of 300 kW is considered as Microhydro because this is about the maximum size for most stand alone hydro systems not connected to the grid, and suitable for "run-of-the-river" installations.
But, In general Micro hydro is a
term used for hydroelectric power installations that typically produce 10 to 100 kW of power . They
are often used in water rich areas as a Remote Area Power Supply (RAPS).
Classification of Hydropower by size
More than 100 MW and usually feeding into a large
15 - 100 MW - usually feeding a grid
1 - 15 MW - usually feeding into a grid
Above 100 kW, but below 1 MW; either stand alone
schemes or more often feeding into the grid
From 5kW up to 100 kW; usually provided power for a small community or rural industry in
remote areas away from the grid.
From a few hundred watts up to 5kW
hydro is perhaps the most mature of the modern small-scale decentralized energy
supply technologies used in developing countries. There are thought to be tens of thousands of
plant in the “micro” range operating successfully in China, and significant numbers are operated in wide ranging countries such as
and Peru. This experience shows that in certain
circumstances micro hydro can be profitable in financial terms, while at
others, even unprofitable plant can exhibit such strong positive impacts on the
lives of poor people.
Components of a Micro Hydro system
Suitable conditions for micro-hydro power
The best geographical areas for
exploiting small-scale hydro power are those where there are steep rivers
flowing all year round, for example, the hill areas of countries with high
year-round rainfall, or the great mountain ranges and their foothills, like the
Andes and the Himalayas. Islands with moist marine climates, such as the
Caribbean Islands, the Philippines and Indonesia are also suitable. Low-head
turbines have been developed for small-scale exploitation of rivers where there
is a small head but sufficient flow to provide adequate power.
To assess the suitability of a potential site, the hydrology of the site
needs to be known and a site survey carried out, to determine actual flow and
head data. Hydrological information can be obtained from the meteorology or
irrigation department usually run by the national government. This data gives a
good overall picture of annual rain patterns and likely fluctuations in
precipitation and, therefore, flow patterns. The site survey gives more
detailed information of the site conditions to allow power calculation to be
done and design work to begin. Flow data should be gathered over a period of at
least one full year where possible, so as to ascertain the fluctuation in river
flow over the various seasons. There are many methods for carrying out flow and
head measurements and these can be found in the relevant texts