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                              TECHNICAL PAPER #18
                          Christopher S. Weaver, P.E.
                             Technical Reviewers
                              Theodore Alt, P.E.
                                 Paul N. Garay
                                 Published By
                       1600 Wilson Boulevard, Suite 500
                         Arlington, Virginia 22209 USA
                     Tel: 703/276-1800 . Fax:703/243-1865
                 Understanding Micro-Hydroelectric Generation
                             ISBN: 0-86619-218-2
                  [C]1985, Volunteers in Technical Assistance
This paper is one of a series published by Volunteers in Technical
Assistance to provide an introduction to specific state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their situations.
They are not intended to provide construction or implementation
details.  People are urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and illustrated
almost entirely by VITA Volunteer technical experts on a purely
voluntary basis.  Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.  VITA staff included Maria Giannuzzi
and Leslie Gottschalk as editors, Julie Berman handling typesetting
and layout, and Margaret Crouch as project manager.
The author of this paper, Christopher S. Weaver, P.E., is a
senior engineer with Energy and Resource Consultants, an interdisciplinary
consulting firm in Boulder, Colorado.   He is a registered
Professional Engineer, and has worked in the areas of
electric-utility planning, solar energy, cogeneration, and air-pollution
control as well as in small hydroelectric systems as a
consultant.  Weaver is the author of another VITA technical paper,
Understanding Mini-Hydroelectric Generation.   The reviewers of
this paper are also technical experts in hydroelectricity.  Theodore
Alt, P.E., is a mechanical engineer who has been in the
energy field since 1942.  Be has worked with the energy research
and development group of the Arizona Public Service Company and
the Government of Mexico's electric commission.   Paul N. Garay, an
associate engineer with F.M.C.   Associates, has written many
papers on various aspects of water transportation and energy uses
of water.
VITA is a private, nonprofit organization that supports people
working on technical problems in developing countries.   VITA offers
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to their
situations.  VITA maintains an international Inquiry Service, a
specialized documentation center, and a computerized roster of
volunteer technical consultants; manages long-term field projects;
and publishes a variety of technical manuals and papers.
                     by VITA Volunteer Christopher weaver
The power of flowing water can be used to generate electricity,
or to do other kinds of useful work.   Generating electricity in
this way is called hydroelectric generation.   It can be done
anywhere that there is water and a hill or drop for it to run
down, such as a drop in an irrigation canal, a place where a
river runs through rapids or over a waterfall, or where a dam has
backed up water above the level of the river, to name just a few
examples.  Hydroelectric generating plants come in all sizes--from
huge plants that produce more electricity than most nations can
use to very small plants that supply electricity for a single
house.  The smallest hydroelectric plants are often called micro-hydroelectric
plants, or micro-hydro for short.   Larger plants
are usually called mini-hydro plants.   Other names for this size
of plant are "small-scale hydro" and "small hydro."
This report deals only with micro-hydroelectric plants.   Microhydro
is usually defined as having a generating capacity of up to
about 15 kilowatts (KW).  This is about enough power for 6 or 8
houses in a developed country, or it can provide basic lighting
and other services to a village of 50 to 80 houses.   Micro-hydro
generation is best suited to providing small amounts of power to
individual houses, farms, or small villages in isolated areas.
Mini-hydro systems are larger.   They can range from about 15 KW up
to 15,000 KW, which is enough electric power for a medium-sized
town, or for a whole rural region.   However, the difference
between mini-hydro and micro-hydro plants is not just size.
In general, micro-hydro plants use much simpler and lower cost
technology than mini-hydro plants.   For this reason, micro-hydro
plants are usually well suited to village level development and
local self-help projects.  With their simpler technologies, they
can usually be built by people without much special training,
using mostly local materials and skills.   They are usually lower
in cost than mini-hydro and conventional hydro plants, but they
are also less efficient, and the quality of the electricity is
not as good.  Mini-hydro plants, on the other hand, cost more, but
they produce the same constant-frequency alternating current (AC)
electricity as large electric power systems, so that they can
even be interconnected with a larger system.
Micro-hydro plants generally produce low-voltage direct current
(DC) electricity, or else low-voltage variable-frequency AC
(these technical terms are defined in the section on electric
power below).  These kinds of electricity are suited to running
lights, small motors, and electric cookers, but not to running
large motors, many appliances, or most industrial machinery.
Perhaps most importantly, micro-hydro plants cannot be interconnected
with other generating plants in an electric system the way
mini-hydro and large hydro plants can.   Special machines called
inverters can convert DC power to the AC power used in large
electric systems, but these are expensive and have limited capacity.
If you expect to need a fairly large amount of power, if
you need to interconnect with a power line, or if you require
high reliability, you should probably consider mini-hydro instead.
Another VITA technical paper, Understanding Mini-Hydroelectric
Generation talks about mini-hydro.
Water wheels have been used since ancient times to supply power
for grinding grain and other laborious tasks.   The first modern
hydraulic turbines were developed in the first part of the 19th
century by Fourneyron in France.   These were further developed by
a number of researchers during the middle of the century, so that
by 1890 most of the types of turbines now in use had been invented.
Thomas Edison's invention of the electric light and of
ways to distribute electricity occurred at about the same time,
leading to a great boom in hydroelectric development in Europe
and North America.  Until about the 1920s, most hydroelectric
developments were quite small--in the size range which is now
called mini-hydro or even micro-hydro.   This was for two reasons:
people didn't know how to build really large dams and turbines,
and the small electric transmission systems of the time made it
difficult to sell large amounts of electricity.   Generally, mini-hydro
systems would be used to power a town and its surrounding
area, while micro-hydro systems were used on isolated farms and
ranches to provide power.
During the era of the 1950s and 1960s, advancing technology and
cheap oil, combined with improved long-distance electric transmission,
made it possible to sell electricity cheaper than the
earlier small hydro plants could make it.   Many hundreds of small
hydroelectric facilities were abandoned or dismantled during this
period.  With the oil embargo of 1973, which has led to enormous
increases in the cost of oil, small hydro once again appears
competitive.  Many of the early plants which were abandoned in the
1950s and 1960s are now being refurbished, and many new ones are
being planned.  Small hydro is also well suited for developing
countries, and is being actively encouraged by many governments
and development organizations in order to reduce oil imports and
encourage development.  Micro-hydro has a special role to play in
developing countries, since it makes it possible to provide
lighting, power, and communications (such as television and radio)
even in areas far from the main electric power systems.
Micro-hydro can thus play an important role in promoting rural
development in remote areas.
This section presents a few basic facts and principles about
electric power and hydroelectric generation.   Reading it will not
make you into a hydroelectric engineer, but it will help you
understand how hydroelectric systems work, and what makes a good
or a bad hydroelectric site.   It will also help you to understand
the more detailed technical material that you will need to read
if you decide to build a micro-hydro plant.
Electric Power
Power is defined as an amount of energy divided by the time it
takes to supply the energy, or in other words as the rate at
which energy is delivered.  Power is measured in units called
watts, or (for large amounts of power) in units of kilowatts.
One kilowatt is equal to 1,000 watts.   Power is also measured in
horsepower.  One horsepower equals 746 watts.
Two other quantities that are important in talking about electric
power are the electric current and the voltage.   Electric current
can be thought of as the amount of electricity flowing through a
wire (like the amount of water flowing through a pipe), while
voltage can be thought of as a measure of how much force is
needed to push the current.  Current is measured in amperes, or
amps for short, while voltage is measured in volts.   The electric
power (in watts) is equal to the product of the current and the
voltage, so that a current of 1 amp with a voltage of 100 volts
would give a power of (1 x 100) = 100 watts.
Two types of electricity are commonly used.   Alternating current
(AC) electricity is generated in a way that makes it change directions
(alternate) many times each second.   The number of times
it changes direction is called the frequency. Direct current
(DC) electricity does not change directions; it always flows the
same way.
Large electric power systems and many small ones use alternating
current, in order to be able to use transformers to change voltages
up and down.  Transformers will not work with direct current.
On the other hand, batteries can produce only DC, so small
electric systems which use batteries generally use DC current.
AC can be converted into DC using a device called a rectifier,
while DC can be changed into AC using an inverter.
Mini-hydro systems, and large electric power systems such as
those in cities use alternating current.   In these systems, the
voltage and frequency of the electricity produced are carefully
controlled to keep them constant.   Adding more load to an operating
power system (such as by turning on more lights) tends to
slow the generators down, which causes the voltage and (for AC
systems) the frequency to drop.   Conversely, shutting off lights
will reduce the load, permitting the generator to run faster.
These systems must have some kind of an automatic control which
detects when the speed changes, and takes action (such as letting
more water into a turbine) to bring the generators back up to the
right speed.  These controls are expensive, and most micro-hydro
systems don't have them.  As a result, the generator speed and
voltage in micro-hydro systems will change as people turn lights
on and off, so it is a good idea to keep this to a minimum.
Batteries can help this situation by providing extra power when
the system is heavily loaded, and absorbing extra power when it
is lightly loaded.
Electrical equipment is rated in terms of the voltage and the
type of current it is designed for, and the maximum amount of
power it can produce (for a generator) or use (for things that
consume electricity, such as motors and light bulbs).   A generator
with a rating of 5 KW at 100 volts is designed to produce 50
amperes at 100 volts at full load, which is 5,000 watts or 5 KW.
The same generator could also produce smaller amounts of power.
The amount of power put out by the generator must be equal to the
amount of power being used by the electrical equipment connected
to it (unless you are using batteries to store some power).  The
voltage ratings and type of electricity (DC or AC) used for the
electrical equipment should always be the same as the voltage and
type of electricity being supplied.   If you connect a device rated
for one voltage to a wire at another voltage, it almost certainly
will not work, and the device is very likely to be damaged.  The
same is true of connecting AC devices to DC.   However, many DC
devices such as light bulbs and motors can also be used with AC,
if the voltage ratings are the same.
The amount of energy produced in a generator or used by an electrical
machine can be calculated by multiplying the amount of
power used by the length of time that it is used.   Energy is
measured in units of joules--one joule is equal to one watt times
one second.  One joule is a very small amount of energy, So we
commonly use units like megajoules (one megajoule is one million
joules) or kilowatt-hours (abbreviated KWH).   A kilowatt hour is
equal to one kilowatt provided for one hour, which is 3.6 million
joules.  As an example, a 5-KW generator, if it ran at full load
for one hour, would produce produce five KWH of electric energy.
If it ran for two hours, it would produce 10 KWH.
Mechanical Power
Mechanical power is the force that causes machinery and other
things to move.  The engine of a car produces mechanical power,
and so does an electric motor.   Mechanical power can easily be
converted into electrical power (this is what a generator does),
and electrical power can be converted back to mechanical power
(this is done by an electric motor).   Mechanical and electrical
power are measured in the same units--watts and kilowatts.
Head, Flow Rate, and Power Output
Water at the top of a hill or drop has energy, called potential
energy, because of where it is.   This potential energy is measured
in terms of the "head," which is the vertical distance from
the water level at the top of the drop to the water level at the
bottom.  Figure 1 shows how head is measured.

ume1x6.gif (600x600)

In natural streams, the potential energy or head of the water is
dissipated by friction against the stream bed as the water flows
downhill, or by turbulence at the bottom.   However, if we put in
a smooth pipe from the top to the bottom to reduce friction, and
then put in a water turbine at the bottom, we can use the head in
the water to turn the turbine and produce mechanical power.  The
amount of power we can theoretically get is given by:
                   [] = F x H x 9.807    (Equation 1)
where [] is the theoretical power output in watts,
        F is the rate of flow of water through the pipe in liters
            per second,
        H is the head in meters, and
    9.807 is the conversion factor that accounts for the force of
            gravity on the water.
However, turbines and generators are not perfectly efficient, so
the amount of electric power we can actually get from a microhydro
plant with a given head and flow rate is less than [].
This amount is given by:
                 [P.sub.act] = [] x [E.sub.t] x [E.sub.g] x [E.sub.s]     (Equation 2)
where [P.sub.act] is the actual useful power output from the plant,
        [E.sub.t] is the efficiency of the turbine,
        [E.sub.g] is the efficiency of the generator, and
        [E.sub.s] is the efficiency of the rest of the electrical system.
Efficiencies are always less than 1.0.   Typically, [E.sub.t] is about
0.85 for turbines from a specialized manufacturer, 0.6 to 0.8 for
pumps used as turbines, and 0.5 to 0.7 for locally-built cross-flow
turbines.  [E.sub.g] is usually 0.9 or more, for most kinds of generators.
[E.sub.s] will be about 0.9, unless you are transmitting power
a great distance, or you are using an inverter, in which case it
may be less.
Thus, a flow of 100 liters per second, with a head of 10 meters,
could theoretically produce 100 x 10 x 9.807 = 9,807 watts, or
9.807 KW.  With a turbine efficiency of 0.75, a generator efficiency
of 0.9, and a system efficiency of 0.9, we would actually
get 9,807 x 0.75 x 0.9 x 0.9 = 5,958 watts of useful power.  The
rest would be lost due to inefficiencies in the system.
There are many variations of micro-hydro systems.   Some of the
factors that will affect the kind of system you decide to build
are: the amount of power you need; the amount of flowing water
available; the available head; the source of the water (from an
irrigation canal, a pipeline, behind a dam, or from a free-flowing
river or stream); how much money you can afford to spend; and
the manual skills and local materials available to you.   This section
describes the major components of a micro-hydro system, and
explains some of the different choices.
All micro-hydro systems, whatever their other differences, have a
number of features in common.   Each must have a source of water,
and a place to put the water afterwards (the discharge).   The
source must be higher than the discharge; the greater the difference
in height, the greater the available head will be.   In
addition, there must be some means of getting the water from the
source to the power-plant, and then from the power plant to the
discharge.  Finally, there must be the power plant itself, which
will contain one or more turbines driven by the flowing water,
and one or more generators driven by the turbines.   Alternatively,
the turbines can supply mechanical power to drive some other
machinery, such as a mill or saw, directly, without converting
the mechanical power into electrical power and back.   Sometimes,
systems are arranged to supply mechanical-power-during the day,
and then supply electricity for lighting at night.
Figure 2 is a sketch of a typical micro-hydroelectric system,

ume2x8.gif (600x600)

showing the major components.   Not all systems will have all of
these components, however.
Beginning at the source of the water, the water must first be
collected and channelled to the turbine.   Water may be backed up
behind a dam (as shown in Figure 2), or diverted out of a flowing
stream by some kind of diversion structure.   After it is diverted,
it flows into a canal, called the headrace until it is directly
uphill from the power plant.   Once there, the water enters
the penstock, which is the pipe leading to the turbine.   Alternatively,
the penstock may go all the way to the source, eliminating
the need for the headrace.  In some systems with low head,
there may not be a penstock--water from behind a dam may simply
flow straight into the turbine.   After leaving the turbine, the
water passes out through the draft tube into the tailrace, which
is a canal leading to the discharge point.   The powerhouse is
usually built near the discharge, so the tailrace can be very
short, and may be absent completely.
The water flows through the turbine, forcing it to turn.  Usually,
the flow through the turbine is controlled by one or more
valves or gates, which allow the flow to be reduced or shut off
completely.  The turbine is either connected directly to a generator,
or it may be connected by means of gears or belts and
pulleys to the generator or other machinery to be driven.  The
generator, the electric wires, and the other devices associated
with them are referred to as the electrical gear.   The different
kinds of turbines and electrical gear are discussed in more
detail below.  The structural parts of the hydro plant--the dam,
headrace, penstock, draft tube, tailrace, and power house are
called the civil works, although this term is more common in
larger plants than in micro-hydro plants.   These are also discussed
in more detail below.
Civil works
The extent and the cost of the civil works needed for a microhydro
plant vary a great deal, depending on the nature of the
site where the plant is located.   Generally, the more water-hydropower
plants must handle, and the further they must carry it, the
more expensive the civil works will be.   For this reason, microhydro
plants with a lot of head are usually cheaper than low-head
plants, since the lower head means a greater amount of water is
required.  However, many low-head plants can be built to take
advantage of existing irrigation and water-supply works, such as
dams and canals.  Combining micro-hydro with a water supply or
irrigation project can also help to make that project more practical,
since the power from the hydro plant can help to pay for
some of the cost of the total project.
The civil works can usually be built from local materials, using
local construction techniques and labor, along with a few imported
materials such as cement.  The exception to this may be the
penstock, which must be able to withstand the pressure of the
water.  If the head is more than 5 meters, this will require
metal pipe.  This can be expensive, since a fairly large diameter
pipe is required in order to reduce the amount of head lost from
In building the civil works, it is important to have advice from
someone who is knowledgeable about dams and canals and other
hydraulic structures, since building something to carry flowing
water is not the same as building a house or a wall.   This is
especially true of dams.  You should never build a dam across any
stream without checking to make sure what is legal in your area,
and you should never build a dam more an about 1.5 meters high in
flat country, or, in hilly country, and dam that will back up a
significant amount of water without advice and supervision from a
competent engineer.  If a dam should break, it can release water
with great violence, and even a seemingly small amount of water
can cause enormous destruction and loss of life.
Hydraulic Turbines
A hydraulic turbine is a machine which converts the head or
potential energy in water flowing through it into mechanical
energy (also called work) which is used to turn a shaft.  There
are a number of different kinds of hydraulic turbines.   The two
kinds of turbines that are most useful for micro-hydro plants are
the Michell or Banki turbine (also called the crossflow turbine)
and the Pelton turbine (also called the Pelton wheel).   Crossflow
turbines are used for low and moderate heads, up to about 40
meters, while Pelton turbines can be used at any head above 20
Some other types of turbines that are commonly used are propeller
or Kaplan turbines for low heads, and Francis turbines for moderate
heads.  Except for the crossflow turbine, all hydraulic turbines
are high-technology items which must be built by a specialized
manufacturer.  A list of manufacturers of small-turbines-is
given in the appendix.
Crossflow turbines can be built by a local machine shop, but a
specialized manufacturer may be able to make a more efficient
unit.  Low-Cost Development of Small Water Power Sites (listed in
the appendix) gives instructions for building a crossflow turbine.
In response to the increasing interest in small hydro, a number
of manufacturers have recently begun to come out with standardized
turbines for small hydroelectric plants.   Since each turbine
does not need to be individually designed and built, this reduces
the turbine's cost significantly.   These turbines are normally
sold as part of a package, which includes a generator and control
system.  These packages usually produce high-quality AC power,
the same as is available from electric utilities, but they are
fairly expensive, especially in micro-hydro sizes.
It is also possible to use ordinary rotating water pumps as
hydraulic turbines.  Typically, a pump uses mechanical power to
increase the head of the water being pumped.   By reversing this
process, a pump can convert head into mechanical power.   Since
pumps are mass-produced in great quantities, their cost can be
less than a third of a specially-made turbine.   However, this
lower cost must be balanced against a generally lower efficiency,
which reduces the amount of power you can get from a given amount
of water.  Nevertheless, if you have plenty of water a pump can be
a very low-cost choice, especially if you can get one second
hand.  Most pumps work best as turbines when the head of the water
going through them is about 30 to 60 percent greater than the
head they were designed to produce as pumps.   A local pump dealer
or serviceman can provide more information.
Electrical Gear
The electrical gear or electrical system for a micro-hydro system
consists of the electric generator, other electrical devices in
the powerhouse, and electric wires that take the electricity from
the powerhouse to the place where it is to be used.   There are a
number of different possible arrangements for this.   One of the
most common arrangements for micro-hydro systems is a low-voltage
DC system, similar to an automobile's electrical system.  This
arrangement can also be used to produce moderate-voltage AC power
(like that which is available from an electric utility) by means
of an inverter.  Another arrangement, which is commonly used in
mini-hydro, is to generate moderate-voltage or high-voltage AC
directly, using a synchronous generator.
A sketch of a low-voltage DC system is presented in Figure 3.

ume3x12.gif (600x600)

This system uses a generator called an alternator, which produces
low-voltage AC.  This power goes through a rectifier and voltage
regulator which convert it to DC, which is then either used directly,
or used to charge batteries if more power is being produced
than is needed.  In many modern alternators, the rectifier
and voltage regulator are built in.   The batteries then return
this power later, when more power is being used than produced.
The final link in the system consists of one or more wires going
from the batteries to the lights and other items that are to be
powered.  Alternatively, the system may be connected to an inverter,
which converts the low-voltage DC power from the batteries to
AC, for use with appliances requiring AC power.   In either case,
the wires usually go through a fuse or a circuit breaker in order
to protect the system from being damaged by a short circuit or
overloaded by too much demand.
The low-voltage DC system has many advantages--it is simple and
cheap, and can even be made of parts salvaged from an automobile
electrical system. However, it requires special low-voltage light
bulbs, and motors which are capable of being run with DC. This
problem can be eliminated by using an inverter, but this adds to
the cost. Low voltage systems also require heavy wire, and it is
difficult to transmit low-voltage power for more than a short
distance, since the lower the voltage, the higher the losses in
the wire will be. If the hydro site is not within about 50 to
100 meters of the place you will use the electricity, you should
either use an inverter to produce AC, or generate it directly
with a synchronous generator.
Synchronous generators can produce moderate-voltage AC directly,
or can produce high-voltage AC which is then converted to moderate
voltages with a transformer. The latter is best if you need
to transmit power any distance. However, unlike DC systems, AC
systems have no place to store electricity, so they must always
adjust the amount of power they produce to match the amount being
used. This requires a control system, which can add a great deal
to the cost of a micro-hydro plant, and which also requires
specialized maintenance. It is usually best to buy synchronous
generators as part of a "package," which includes the generator,
turbine, and control system. These packages are available from
some of the hydro turbine manufacturers listed in the appendix.
Any electrical system requires special knowledge and understanding.
This is especially true of high and moderate voltage systems,
since these can be very dangerous--causing shocks and
electrical fires if they are set up wrong. Low-voltage DC systems
are much safer, since it is nearly impossible to be electrocuted
by them, but they can still cause fires. You should not work on
even a low-voltage system unless you are sure you know what you
are doing, and you should not work on a moderate or high-voltage
system at all without help from a professional electrician or
other knowledgeable person. You should also be very careful to
arrange the powerhouse, electric wires, and other parts of the
system so that children and animals cannot come into contact with
them and be injured.
The cost of a micro-hydro plant will vary, depending on what kind
of equipment you use, how much material and equipment you need to
buy, how much it costs for the civil works, and other factors.
For instance, if you were able to use salvaged pipe to carry
water down a steep hill, building the diversion structure, headrace,
and tailrace yourself from local stones, and using a second-hand
irrigation pump connected to an alternator and battery
salvaged from an automobile, your system would cost very little.
On the other hand, if you had to hire a contractor to build a
dam, a long headrace canal, powerhouse, and tailrace; then purchased
a new hydro-turbine and generator from overseas, you might
wind up spending more than $30,000 for a 5-KW generating plant.
Of course, any figure between these two extremes would also be
The best sources of price information for hydro turbines and generators
are manufacturers. You will need to estimate the cost of
the civil works yourself, or talk to a qualified contractor if
the job is too complex for you. For the costs of other materials,
such as pipe, electric wires, and so forth, it is best to consult
local suppliers. Equipment such as alternators, batteries, and
rectifiers can be gotten from auto or marine supply stores and
places that sell wind generators. The costs for alternators are
about $80 for a 500- to 1,000-watt car alternator (including the
rectifier and voltage limiter); costs for larger sizes will be
more. Batteries cost about $50.00 for a size that holds about
1/2-KWH. Inverters cost about $500 for one with 1-KW capacity.
Maintenance and operation of micro-hydro plants generally takes
very little time. It is necessary to check the plant daily to
make sure the intake is not getting clogged, and that the system
is in good working order. Depending on the design of the plant,
you may also need to adjust the intake valve occasionally to
match the water flow into the turbine with the amount of power
you are using. More extensive maintenance, such as oiling the
machinery, tightening any belts, and checking the water level in
the batteries should be done every month. It may also be necessary
to clean out silt, weeds, and so forth in the civil works,
and to repair any leaks or deterioration. This is usually done
about once a year or more often if needed.
Micro-hydropower can be used anywhere that there is flowing water
and a difference in elevation for it to run down. However, it is
usually not worthwhile building a micro-hydro plant if there is
another source of electricity nearby. Thus, micro-hydro is most
useful in providing electricity for basic services such as lighting,
electric cooking, running small motors like those of sewing
machines and electric fans, and running televisions and radios
(with special adapters) in isolated rural areas. A hydro turbine
can also be used directly to provide mechanical power to drive a
machine such as a saw, a mill, a grain huller, or any other low-power
machine. In one reported project in Colombia, a village
uses a small Pelton turbine to run a sawmill during the day. At
night, the same turbine is connected to a generator, providing
power for lighting and other uses.
In another set of projects in Pakistan, the government has assisted
villages in setting up micro-hydro units, which provide
electricity for three or four light bulbs per house. This electricity
is also used for small industrial equipment such as arc
welders, electric maize shellers, and electric wheat threshers.
A number of industries have also been established to use mechanical
power from the turbine directly to run equipment such as
flour mills, rice hullers, band saws, wood lathes, cotton gins,
corn shellers, and grinders.
The major use for micro-hydro generation is to provide small
amounts of electric power in isolated areas, where other sources
of electricity, such as an electric utility, are not available.
If an electric utility or some other large electricity source is
available, it is almost always cheaper and easier to buy electricity
from that source. Where a large source is not available,
however, there are still a number of other possibilities. The
most important of these are: diesel and gasoline-engine generators,
wind-electric generation, photovoltaic cells, and human- or
animal-powered generators. These are each discussed below.
Diesel and gasoline generators are convenient and cost less to
buy than most other means of producing electricity, but they
require fuel, which is becoming increasingly expensive. The cost
of a diesel generating system is typically $1,000 to $3,000 per
kilowatt, depending on the size (small systems cost more per
kilowatt), and gasoline generators are even cheaper. However,
the cost of supplying diesel fuel for the generator will be at
least $0.20 per KWH (for diesel fuel at $0.50 per liter), which
amounts to $1,750 for a 1-KW unit running continuously for a
year. Gasoline engines are lighter in weight and cheaper than
diesels, but also less efficient. The cost would be even greater
for them.
Wind-electric generation can be a very advantageous form of power
production where the wind is strong and reliable. In some cases,
wind-electric generators have even been able to compete with
conventional large utilities in cost. Generally, a small wind-electric
system consists of a wind turbine, which usually looks
like an airplane propeller mounted on a pole. These must be
purchased. Some other designs of wind turbines use sails and
operate at lower speeds; VITA can provide information about
building these. In either type of system, the turbine is used to
turn a generator (usually an alternator) that charges batteries
and provides electric power directly. These systems are very
similar to the kinds of micro-hydro systems using batteries that
were described earlier. wind-electric systems can be expected to
cost about $2,000 to $4,000 per kilowatt of generating capacity.
The cost per kilowatt-hour will vary, depending on the amount of
wind. Usually, only about 20 to 30 percent of the total possible
KWH per year are actually generated, even in fairly windy locations.
Thus a 1-KW unit could conceivably produce 8,760 KWH per
year, but would actually produce only about 1,800 to 2,600 KWH.
Photovoltaic cells, or solar cells, can change sunlight directly
into electricity. This electricity can then be used to charge
batteries for nighttime lighting, or it can be used directly to
run motors and other small devices during the day. Solar cells
are presently an area of great interest in both developed and
less-developed countries, and it seems likely that they will
eventually make a significant contribution to rural development.
However, solar cells are still three to four times too expensive
to be practical for most uses. A solar-cell system now costs
about $12,000 to $17,000 per peak kilowatt of generating
capacity. Since sunlight is not available at night or on cloudy
days, however, the actual number of kilowatt-hours generated per
year is only about 20 to 30 percent of the maximum--about the
same as for wind generators.
Solar cells are most advantageous where very small amounts of
power are needed, since their cost per watt does not increase
even in very small sizes. A 100-watt hydro plant might not cost
much less than a 1,000-watt plant, but a set of solar cells to
produce 100 watts costs about one tenth as much as a set to
produce 1,000 watts. Thus, if you only need a little power (to
charge batteries for a television, for example) solar cells may
be the best choice.
Humans can generate power by pedaling a bicycle-like apparatus
connected to a generator. Animals such as horses and bullocks
can also be used to produce power, by having them turn a- crank
connected to the generator through speed-increasing gears or
pulleys. The original English unit of power, in fact, was the
horsepower, which was defined to be roughly the power that a
draft horse could supply. One English horsepower is about 750
watts, but this is actually more work than can be expected from
most horses. After allowing for the inefficiency of the generator
and the gears, it seems likely that only 200 to 300 watts
of electricity could be generated per animal. For humans, the
amount that can be produced comfortably is even less--probably
around 50 watts. This would be enough to charge batteries for a
radio or television, or to provide a few hours of light, but not
for much else. The cost of such a system would be fairly small--from
nothing at all (using salvaged parts) to U.S. $100 or $200
for a new alternator and batteries. However, don't forget that
both humans and animals require fuel in the form of food.
Building a micro-hydro plant is a complex process that requires a
great deal of planning and preparation. The major steps in this
process are described below.
Not all of the steps listed below will be necessary in every
case. You should use your own judgment, but generally, the
larger and more complex your plant will be, the more time you
should spend in the preparatory stage.
o    Decide how much electric power you will need, and whether
     you need AC power or low-voltage DC power.
o    Find a promising site for your hydro plant. The best sites
     have a reliable water supply year-round and a large vertical
     drop in a short distance (the more drop, the less water is
o    Calculate the amount of power available at the site, using
     Equations 1 and 2 (page 5). Decide whether that will be
     adequate for your needs. Be sure to consider the efficiency
     of the equipment in making this decision.
o    Make sure that you can install electric wires from the site
      to the place you want to use the electricity.
o    Check for legal and institutional problems with the site you
     have chosen. Find out what laws you must obey and what
     licenses you will need to build and run the plant.
o    Check for environmental effects of the plant. Some of the
     concerns here are the effect of the dam on fish, possible
     flooding of cropland or other valuable land, and the possibility
     of creating a breeding ground for disease-causing
     organisms such as water snails if bilharzia or schistomiasis
     is a problem in your area. Also check for the effects of
     the environment (e.g., flooding) on the plant.
o    Check for bad social effects--people whose use of the stream
     will be disrupted, women unable to wash clothes on the bank,
     and so forth. These must be balanced against the positive
     social effects of electric light, machines, and so forth.
o    Estimate the cost of building a hydro plant at the site, and
     the total amount of energy (in KWH) that the plant will
     produce per year. Calculate the annual cost of the plant
     (including loan payments, annual maintenance, and all other
     costs) and divide by the number of KWH per year to get the
     cost per KWH.
o    Estimate the cost per KWH of other sources of electricty,
     such as wind or a diesel generator. Also try to estimate
     the social and environmental effects, and any legal or
     institutional problems they might have.
o    Consider all of the costs, the social and environmental
     effects, and the different characteristics of the possible
     alternatives, and decide whether to go ahead with a micro-hydro
     plant, to investigate some other kind of generator, or
     to do nothing at all.
Assuming you have decided to go ahead with a micro-hydro plant,
the next step is to design it. This does not need to be a
lengthy project--just make sure you know everything that will be
needed, how much it will cost, where you will get it, and when
you will need to order it in order for it to arrive on time.
Unless you are very confident of your knowledge, you will probably
want to get additional help at this point. Some of the
books listed in the appendix (especially Low-Cost Development
Small Water Power Sites, may be useful to you. If your system
will be at all elaborate, and especially if it will involve
constructing any dams or canals, it is a good idea to show your
plans to a qualified engineer before proceeding.
This phase includes all the things involved in going from the
design to the operating plant.
o    Prepare a budget and facilities schedule.
o    Arrange financing, if you are planning to borrow the money
     to build the plant.
o    Order the turbine, generator, batteries, pipe for the penstock,
     the inverter, and any other items that you plan to
     purchase. Allow enough time for delivery--it can take several
     months to get a hydro turbine. It may be well to use a
     reverse-operated commercial pump. Commercial pumps, which
     can also be used as turbines, have much shorter delivery
o    Take delivery on important components such as the turbine
     and generator, and make sure that all planning for the civil
     works is complete.
o    Build the dam, powerhouse, headrace, tailrace, and other
     civil works, and install the penstock and valves.
o    Install the turbine, the generator, and the other electrical
     gear. Test everything thoroughly, first component by component,
     then the system as a whole.
Make arrangements for regular inspection and maintenance of the
plant and the rest of the system, cleaning out the water intakes,
oiling the machinery, tightening the belts, etc. Depending on
the system, you may also need to check on the water supply, and
adjust the intake valves if too much or too little water is being
used. This usually takes very little time--a few minutes a day
are enough.
You can carry out most of the preparatory steps of this process
using this paper. Once you begin designing and building the
plant, however, you will need much more help. Some of the books
listed in the bibliography may be useful to you. You may also
want to talk to local experts, consultants, or VITA for further
The bibliography at the back of this paper lists a number of
useful books and magazines which can provide general information,
as well as some which give specific directions for evaluating a
potential hydro site. This reference list is followed by a list
of manufacturers of small hydroelectric equipment, who may be
able to provide further information and references.
Hydroelectric equipment in the 0- to 5-RW range tends to be
rather expensive if bought from a manufacturer, but is likely to
last longer and work better than homemade systems. Manufacturers
can also be very helpful in telling you how to go about evaluating
a site, setting up and installing their systems, and making
sure they work properly. If you are contacting manufacturers
about a specific site, you should first find out (at least approximately)
the head and either the minimum and maximum flow
rates or the amount of power you want to generate. For information
on using pumps as turbines, you should contact a local pump
supplier, who will be able to get information from the manufacturers.
The best source of information about things like building dams,
canals, and other civil works is probably a local builder. Try
to find someone who has experience in building irrigation systems
or other water systems. The best source of information on generators
and electrical equipment is probably a local electric-motor
seller or repairman. This person will know how to contact the
manufacturers for your specific requirements, and will also be a
great help in setting up the electrical system. You can also try
to contact electric motor and generator manufacturers yourself.
Boating supply stores and auto supply stores are some of the best
sources for lights and appliances used with low-voltage DC systems.
Many organizations may be able to provide information or assistance
to you in developing a small hydroelectric site. The first
place you ask should be a local authority or other organization
which is concerned with dams and canals. These organizations will
probably employ engineers knowledgeable in the area, and may be
able to refer you to consultants, government agencies, or others
who may be able to help. If there is a government agency concerned
with rivers, dams, navigation, or similar areas, it will
probably be a good source of information. You will need to contact
such an agency anyway to find out whether there are any laws
or regulations that may prevent you from developing a hydroplant.
Another good source may be the departments of civil engineering,
mechanical engineering, or agricultural engineering at a nearby
university or technical institute. Finally, VITA and other international
organizations may be able to provide information, technical
assistance, or both, in some cases.
                            SUGGESTED READING LIST
International Water Power and Dam Construction, Business Press
     International, Ltd. Oakfield House, Perrymount Road, Haywards
     Heath, Sussex RH16-3DH, Great Britain.
This magazine is an excellent source of information on all forms
of hydropower. It frequently carries articles on aspects of
mini-hydro, and has devoted several special issues to the topic.
It also advertises engineers, manufacturers, and consultants in
the hydropower field.
Alternative Sources of Energy, Alternative Sources of Energy
     Inc., 107 S. Central Ave., Milaca, Minnesota 56353 USA.
Issue No. 68, July/August 1984, is a special issue on hydropower.
Low-Cost Development of Small Water Power Sites by Hans Hamm.
     Available from VITA, c/o VITA Publications Sales, 80 S.
     Early St., Alexandria, Virginia 22304 USA.
This book was written in 1967, so it is somewhat out of date.
Nonetheless, it is an excellent, understandable guide to
assessing a hydro site, determining head and flow, and so on, and
includes a good discussion of low-technology hydro schemes. It
is a good book for beginners. It also contains a good set of
instructions for building a Banki turbine, which is the only kind
of turbine that can be built with village-level technologies.
Micro-Hydro: A Bibliography, Beth Moore and John S. Gladwell,
     Idaho Water Resources Research Institute, University of
     Idaho, Moscow, Idaho, USA, 1979.
This bibliography is somewhat old, but contains a very complete
set of references to the literature on micro-hydro, from
introductory material to how-to-do-it manuals and engineering
Simplified Methodology for Economic Screening of Potential Small
     Capacity Hydroelectric Sites, Electric Power Research Institute,
     EPRI EM 3213, Project 1745-8, P.O. Box 50490, Palo
     Alto, California, 1983.
Small Michell (Banki) Turbine: A Construction Manual. VITA.
     Available from VITA, c/o VITA Publications Sales, 80 S.
     Early St., Alexandria, Virginia 22304 USA.
This book describes a low-cost water turbine that can provide
AC/DC electricity for your home. It includes complete step-by-step
instructions for making parts and assembly, and is illustrated.
Allis-Chalmers Fluid Products Co.
Hydro Turbine Division
Box 712
York, Pennsylvania 17405
Arbanas Industries
24 Hill St.
Xenia, Ohio 45385
Axel Johnson Engineering
666 Howard Street
San Francisco, California 94105
Bouvier Hydropower Inc.
12 Bayard Lane
Suffern New York 10901
BBC Brown Boveri Corp.
1460 Livingston Ave.
North Brunswick, New Jersey 08902
Canyon Industries
5346 Moquito Lake Rd.
Deming, Washington 98224
C-E/Neyrpic Hydro Power, Inc.
969 High Ridget Rd.
Box 3834
Stamford, Connecticut 06905
Elektra Power Corp.
744 San Antonio Rd.
Palo Alto, California 94303
Essex Development Associates
110 Tremont St.
Boston, Massachusetts 02108
Fairbanks Mill Contracting
North Danville Village
St. Johnsbury, Vermont 05819
Flygt Corporation
129 Glover Ave.
Norwalk, Connecticut 06856
General Electric Co.
Small Hydroelectric Operation
One River Rd.
Bldg. 4, Rm. 305
Schenectady, New York 12345
Generation Unlimited
701 Placentia Ave.
Costa Mesa, California 92627
Hayward Tyler Pump Co.
P.O. Box 492
80 Industrial Pkwy
Burlington, Vermont 05402
Hydro-Tech Systems, Inc.
P.O. Box 82
Chattaroy, Washington 99003
Hydro Watt Systems, Inc.
146 Siglun Rd.
Coos Bay, Oregon 97420
International Power Machinery Co.
833-835 Terminal Tower
Cleveland, Ohio 44113
The James Leffel Company
426 East Street
Springfield, Ohio 45501
Layne & Bowler, Inc.
P 0. Box 8097
Memphis, Tennessee 38108
Mini Hydro Co.
110 East 9th St.
Los Angeles, California 90079
Micro Hydro, Inc.
P.O. Box 1016
Idaho Falls, Idaho 83401
New Found Power Co., Inc.
P.O. Box 576
Hope Valley, Rhode Island 02832
Northwest Energy Systems
P.O. Box 925
Malone, Washington 98559
Oriental Engineering and supply Co.
251 High St.
Palo Alto, California 94301
Philip C. Ellis
RD 7, Box 125
Reading, Pennsylvania 19606
Real Goods Trading Company, Inc.
308 East Perkins Street
Ukiah, California 95482
    (This organization also sells wind generators and photovoltaic
systems, and many low-voltage DC appliances. Their catalog
is an excellent introduction to low-voltage power generation.)
162 Battery St.
Burlington, Vermont 05401
Small Hydro East
Star Route 240
Bethel, ME 04217
Sunny Brook Hydro
P.O. Box 424
Lost Nation Rd.
Lancaster, New Hampshire 03584
Ted Miller Associates
2140 S. Ivanhoe
Denver, Colorado 80222
Worthington Group, McGraw-Edison Company
Box 91
Tarrytown, Maryland 21787
    (Worthington is a pump company that has done a lot of work on
using its pumps as turbines.)
Atlas Polar Company, Ltd.
Hercules Hydrorake Division
P.C. Box 160, Station O
Toronto, Ontario
Barber Hydraulic Turbine Division of Marsh Engineering Limited
P.O. Box 340
Port Colborne, Ontario L3K 5W1 Canada
Canbar Products Ltd.
P.O. Box 280
Waterloo, Ontario
China National Machinery Company
People's Republic of China
(Contact the Chinese embassy in your country for information.)
Dependable Turbines Inc.
#7, 3005 Murray St.
Port Moody
British Columbia
Rue General Mangin, BP 75
38041, Grenoble Cedex
P.O. Box 425
D-8832 Weissenberg/Bavaria
West Germany