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TECHNICAL PAPER #18
Christopher S. Weaver, P.E.
Theodore Alt, P.E.
Paul N. Garay
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
Tel: 703/276-1800 . Fax:703/243-1865
Understanding Micro-Hydroelectric Generation
[C]1985, Volunteers in Technical Assistance
This paper is one of a series published by Volunteers in
Assistance to provide an introduction to specific
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
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
almost entirely by VITA Volunteer technical experts on a
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
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
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
control as well as in small hydroelectric systems as a
is the author of another VITA technical paper,
Understanding Mini-Hydroelectric Generation.
The reviewers of
this paper are also technical experts in
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
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
VITA is a private, nonprofit organization that supports
working on technical problems in developing countries.
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to
maintains an international Inquiry Service, a
specialized documentation center, and a computerized roster
volunteer technical consultants; manages long-term field
and publishes a variety of technical manuals and papers.
UNDERSTANDING MICRO-HYDROELECTRIC GENERATION
by VITA Volunteer Christopher weaver
The power of flowing water can be used to generate
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
down, such as a drop in an irrigation canal, a place where a
river runs through rapids or over a waterfall, or where a
backed up water above the level of the river, to name just a
Hydroelectric generating plants come in all sizes--from
huge plants that produce more electricity than most nations
use to very small plants that supply electricity for a
house. The smallest
hydroelectric plants are often called micro-hydroelectric
plants, or micro-hydro for short.
are usually called mini-hydro plants.
Other names for this size
of plant are "small-scale hydro" and "small
This report deals only with micro-hydroelectric plants.
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
and other services to a village of 50 to 80 houses.
generation is best suited to providing small amounts of
individual houses, farms, or small villages in isolated
Mini-hydro systems are larger.
They can range from about 15 KW up
to 15,000 KW, which is enough electric power for a
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
technology than mini-hydro plants.
For this reason, micro-hydro
plants are usually well suited to village level development
local self-help projects.
With their simpler technologies, they
can usually be built by people without much special
using mostly local materials and skills.
They are usually lower
in cost than mini-hydro and conventional hydro plants, but
are also less efficient, and the quality of the electricity
not as good.
Mini-hydro plants, on the other hand, cost more, but
they produce the same constant-frequency alternating current
electricity as large electric power systems, so that they
even be interconnected with a larger system.
Micro-hydro plants generally produce low-voltage direct
(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
large motors, many appliances, or most industrial machinery.
Perhaps most importantly, micro-hydro plants cannot be
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
If you expect to need a fairly large amount of power, if
you need to interconnect with a power line, or if you
high reliability, you should probably consider mini-hydro
Another VITA technical paper, Understanding
Generation talks about mini-hydro.
HISTORY OF HYDROELECTRIC GENERATION
Water wheels have been used since ancient times to supply
for grinding grain and other laborious tasks.
The first modern
hydraulic turbines were developed in the first part of the
century by Fourneyron in France.
These were further developed by
a number of researchers during the middle of the century, so
by 1890 most of the types of turbines now in use had been
Thomas Edison's invention of the electric light and of
ways to distribute electricity occurred at about the same
leading to a great boom in hydroelectric development in
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
and the small electric transmission systems of the time made
difficult to sell large amounts of electricity.
systems would be used to power a town and its surrounding
area, while micro-hydro systems were used on isolated farms
ranches to provide power.
During the era of the 1950s and 1960s, advancing technology
cheap oil, combined with improved long-distance electric
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
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
being planned. Small
hydro is also well suited for developing
countries, and is being actively encouraged by many
and development organizations in order to reduce oil imports
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
even in areas far from the main electric power systems.
Micro-hydro can thus play an important role in promoting
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
or a bad hydroelectric site.
It will also help you to understand
the more detailed technical material that you will need to
if you decide to build a micro-hydro plant.
Power is defined as an amount of energy divided by the time
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
One kilowatt is equal to 1,000 watts.
Power is also measured in
horsepower equals 746 watts.
Two other quantities that are important in talking about
power are the electric current and the voltage.
can be thought of as the amount of electricity flowing
wire (like the amount of water flowing through a pipe),
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.
power (in watts) is equal to the product of the current and
voltage, so that a current of 1 amp with a voltage of 100
would give a power of (1 x 100) = 100 watts.
Two types of electricity are commonly used.
(AC) electricity is generated in a way that makes it change
(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
Large electric power systems and many small ones use
current, in order to be able to use transformers to change
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
AC can be converted into DC using a device called a
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
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
systems) the frequency to drop.
Conversely, shutting off lights
will reduce the load, permitting the generator to run
These systems must have some kind of an automatic control
detects when the speed changes, and takes action (such as
more water into a turbine) to bring the generators back up
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
on and off, so it is a good idea to keep this to a minimum.
Batteries can help this situation by providing extra power
the system is heavily loaded, and absorbing extra power when
is lightly loaded.
Electrical equipment is rated in terms of the voltage and
type of current it is designed for, and the maximum amount
power it can produce (for a generator) or use (for things
consume electricity, such as motors and light bulbs).
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
The same generator could also produce smaller amounts of
The amount of power put out by the generator must be equal
amount of power being used by the electrical equipment
to it (unless you are using batteries to store some
voltage ratings and type of electricity (DC or AC) used for
electrical equipment should always be the same as the
type of electricity being supplied.
If you connect a device rated
for one voltage to a wire at another voltage, it almost
will not work, and the device is very likely to be
same is true of connecting AC devices to DC.
However, many DC
devices such as light bulbs and motors can also be used with
if the voltage ratings are the same.
The amount of energy produced in a generator or used by an
machine can be calculated by multiplying the amount of
power used by the length of time that it is used.
measured in units of joules--one joule is equal to one watt
one second. One
joule is a very small amount of energy, So we
commonly use units like megajoules (one megajoule is one
joules) or kilowatt-hours (abbreviated KWH).
A kilowatt hour is
equal to one kilowatt provided for one hour, which is 3.6
joules. As an
example, a 5-KW generator, if it ran at full load
for one hour, would produce produce five KWH of electric
If it ran for two hours, it would produce 10 KWH.
Mechanical power is the force that causes machinery and
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
and electrical power can be converted back to mechanical
(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
energy, because of where it is.
This potential energy is measured
in terms of the "head," which is the vertical
the water level at the top of the drop to the water level at
bottom. Figure 1
shows how head is measured.
In natural streams, the potential energy or head of the
dissipated by friction against the stream bed as the water
downhill, or by turbulence at the bottom.
However, if we put in
a smooth pipe from the top to the bottom to reduce friction,
then put in a water turbine at the bottom, we can use the
the water to turn the turbine and produce mechanical
amount of power we can theoretically get is given by:
[P.sub.th] = F x H x 9.807
where [P.sub.th] is the theoretical power output in watts,
F is the rate
of flow of water through the pipe in liters
H is the head
in meters, and
9.807 is the
conversion factor that accounts for the force of
on the water.
However, turbines and generators are not perfectly
the amount of electric power we can actually get from a
plant with a given head and flow rate is less than
This amount is given by:
[P.sub.act] = [P.sub.th] x [E.sub.t] x [E.sub.g] x [E.sub.s]
where [P.sub.act] is the actual useful power output from the
the efficiency of the turbine,
the efficiency of the generator, and
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
pumps used as turbines, and 0.5 to 0.7 for locally-built
is usually 0.9 or more, for most kinds of generators.
[E.sub.s] will be about 0.9, unless you are transmitting
a great distance, or you are using an inverter, in which
may be less.
Thus, a flow of 100 liters per second, with a head of 10
could theoretically produce 100 x 10 x 9.807 = 9,807 watts,
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
rest would be lost due to inefficiencies in the system.
MICRO-HYDROELECTRIC SYSTEMS AND COMPONENTS
There are many variations of micro-hydro systems.
Some of the
factors that will affect the kind of system you decide to
are: the amount of power you need; the amount of flowing
available; the available head; the source of the water (from
irrigation canal, a pipeline, behind a dam, or from a
river or stream); how much money you can afford to spend;
the manual skills and local materials available to you.
describes the major components of a micro-hydro system, and
explains some of the different choices.
BASIC SYSTEM LAYOUT
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All micro-hydro systems, whatever their other differences,
number of features in common.
Each must have a source of water,
and a place to put the water afterwards (the discharge).
source must be higher than the discharge; the greater the
in height, the greater the available head will be.
addition, there must be some means of getting the water from
source to the power-plant, and then from the power plant to the
there must be the power plant itself, which
will contain one or more turbines driven by the flowing
and one or more generators driven by the turbines.
the turbines can supply mechanical power to drive some other
machinery, such as a mill or saw, directly, without
the mechanical power into electrical power and back.
systems are arranged to supply mechanical-power-during the
and then supply electricity for lighting at night.
Figure 2 is a sketch of a typical micro-hydroelectric
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
collected and channelled to the turbine.
Water may be backed up
behind a dam (as shown in Figure 2), or diverted out of a
stream by some kind of diversion structure.
After it is diverted,
it flows into a canal, called the headrace until it is
uphill from the power plant.
Once there, the water enters
the penstock, which is the pipe leading to the turbine.
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
flow straight into the turbine.
After leaving the turbine, the
water passes out through the draft tube into the tailrace,
is a canal leading to the discharge point.
The powerhouse is
usually built near the discharge, so the tailrace can be
short, and may be absent completely.
The water flows through the turbine, forcing it to
the flow through the turbine is controlled by one or more
valves or gates, which allow the flow to be reduced or shut
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
generator, the electric wires, and the other devices
with them are referred to as the electrical gear.
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
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.
The extent and the cost of the civil works needed for a
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
many low-head plants can be built to take
advantage of existing irrigation and water-supply works,
dams and canals.
Combining micro-hydro with a water supply or
irrigation project can also help to make that project more
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,
local construction techniques and labor, along with a few
materials such as cement.
The exception to this may be the
penstock, which must be able to withstand the pressure of
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
In building the civil works, it is important to have advice
someone who is knowledgeable about dams and canals and other
hydraulic structures, since building something to carry
water is not the same as building a house or a wall.
especially true of dams.
You should never build a dam across any
stream without checking to make sure what is legal in your
and you should never build a dam more an about 1.5 meters
flat country, or, in hilly country, and dam that will back
significant amount of water without advice and supervision
If a dam should break, it can release water
with great violence, and even a seemingly small amount of
can cause enormous destruction and loss of life.
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
are a number of different kinds of hydraulic turbines.
kinds of turbines that are most useful for micro-hydro
the Michell or Banki turbine (also called the crossflow turbine)
and the Pelton turbine (also called the Pelton wheel).
turbines are used for low and moderate heads, up to about 40
meters, while Pelton turbines can be used at any head above
Some other types of turbines that are commonly used are
or Kaplan turbines for low heads, and Francis turbines for
heads. Except for
the crossflow turbine, all hydraulic turbines
are high-technology items which must be built by a
manufacturer. A list
of manufacturers of small-turbines-is
given in the appendix.
Crossflow turbines can be built by a local machine shop, but
specialized manufacturer may be able to make a more
Development of Small Water Power Sites (listed in
the appendix) gives instructions for building a crossflow
In response to the increasing interest in small hydro, a
of manufacturers have recently begun to come out with
turbines for small hydroelectric plants.
Since each turbine
does not need to be individually designed and built, this
the turbine's cost significantly.
These turbines are normally
sold as part of a package, which includes a generator and
packages usually produce high-quality AC power,
the same as is available from electric utilities, but they
fairly expensive, especially in micro-hydro sizes.
It is also possible to use ordinary rotating water pumps as
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.
pumps are mass-produced in great quantities, their cost can
less than a third of a specially-made turbine.
lower cost must be balanced against a generally lower
which reduces the amount of power you can get from a given
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
head they were designed to produce as pumps.
A local pump dealer
or serviceman can provide more information.
The electrical gear or electrical system for a micro-hydro
consists of the electric generator, other electrical devices
the powerhouse, and electric wires that take the electricity
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
DC system, similar to an automobile's electrical
arrangement can also be used to produce moderate-voltage AC
(like that which is available from an electric utility) by
of an inverter.
Another arrangement, which is commonly used in
mini-hydro, is to generate moderate-voltage or high-voltage
directly, using a synchronous generator.
A sketch of a low-voltage DC system is presented in Figure
This system uses a generator called an alternator, which
low-voltage AC. This
power goes through a rectifier and voltage
regulator which convert it to DC, which is then either used
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
The final link in the system consists of one or more wires
from the batteries to the lights and other items that are to
Alternatively, the system may be connected to an inverter,
which converts the low-voltage DC power from the batteries
AC, for use with appliances requiring AC power.
In either case,
the wires usually go through a fuse or a circuit breaker in
to protect the system from being damaged by a short circuit
overloaded by too much demand.
The low-voltage DC system has many advantages--it is simple
cheap, and can even be made of parts salvaged from an
electrical system. However, it requires special low-voltage
bulbs, and motors which are capable of being run with DC.
problem can be eliminated by using an inverter, but this
the cost. Low voltage systems also require heavy wire, and
difficult to transmit low-voltage power for more than a
distance, since the lower the voltage, the higher the losses
the wire will be. If the hydro site is not within about 50
100 meters of the place you will use the electricity, you
either use an inverter to produce AC, or generate it
with a synchronous generator.
Synchronous generators can produce moderate-voltage AC
or can produce high-voltage AC which is then converted to
voltages with a transformer. The latter is best if you need
to transmit power any distance. However, unlike DC systems,
systems have no place to store electricity, so they must
adjust the amount of power they produce to match the amount
used. This requires a control system, which can add a great
to the cost of a micro-hydro plant, and which also requires
specialized maintenance. It is usually best to buy
generators as part of a "package," which includes
turbine, and control system. These packages are available
some of the hydro turbine manufacturers listed in the
Any electrical system requires special knowledge and
This is especially true of high and moderate voltage
since these can be very dangerous--causing shocks and
electrical fires if they are set up wrong. Low-voltage DC
are much safer, since it is nearly impossible to be
by them, but they can still cause fires. You should not work
even a low-voltage system unless you are sure you know what
are doing, and you should not work on a moderate or
system at all without help from a professional electrician
other knowledgeable person. You should also be very careful
arrange the powerhouse, electric wires, and other parts of
system so that children and animals cannot come into contact
them and be injured.
SYSTEM COSTS, OPERATION, MAINTENANCE, AND OTHER CONCERNS
The cost of a micro-hydro plant will vary, depending on what
of equipment you use, how much material and equipment you
buy, how much it costs for the civil works, and other
For instance, if you were able to use salvaged pipe to carry
water down a steep hill, building the diversion structure,
and tailrace yourself from local stones, and using a
irrigation pump connected to an alternator and battery
salvaged from an automobile, your system would cost very
On the other hand, if you had to hire a contractor to build
dam, a long headrace canal, powerhouse, and tailrace; then
a new hydro-turbine and generator from overseas, you might
wind up spending more than $30,000 for a 5-KW generating
Of course, any figure between these two extremes would also
The best sources of price information for hydro turbines and
are manufacturers. You will need to estimate the cost of
the civil works yourself, or talk to a qualified contractor
the job is too complex for you. For the costs of other
such as pipe, electric wires, and so forth, it is best to
local suppliers. Equipment such as alternators, batteries,
rectifiers can be gotten from auto or marine supply stores
places that sell wind generators. The costs for alternators
about $80 for a 500- to 1,000-watt car alternator (including
rectifier and voltage limiter); costs for larger sizes will
more. Batteries cost about $50.00 for a size that holds
1/2-KWH. Inverters cost about $500 for one with 1-KW
Maintenance and operation of micro-hydro plants generally
very little time. It is necessary to check the plant daily
make sure the intake is not getting clogged, and that the
is in good working order. Depending on the design of the
you may also need to adjust the intake valve occasionally to
match the water flow into the turbine with the amount of
you are using. More extensive maintenance, such as oiling
machinery, tightening any belts, and checking the water
the batteries should be done every month. It may also be
to clean out silt, weeds, and so forth in the civil works,
and to repair any leaks or deterioration. This is usually
about once a year or more often if needed.
APPLICATIONS OF MICRO-HYDROELECTRIC GENERATION
Micro-hydropower can be used anywhere that there is flowing
and a difference in elevation for it to run down. However,
usually not worthwhile building a micro-hydro plant if there
another source of electricity nearby. Thus, micro-hydro is
useful in providing electricity for basic services such as
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
can also be used directly to provide mechanical power to
machine such as a saw, a mill, a grain huller, or any other
machine. In one reported project in Colombia, a village
uses a small Pelton turbine to run a sawmill during the day.
night, the same turbine is connected to a generator,
power for lighting and other uses.
In another set of projects in Pakistan, the government has
villages in setting up micro-hydro units, which provide
electricity for three or four light bulbs per house. This
is also used for small industrial equipment such as arc
welders, electric maize shellers, and electric wheat
A number of industries have also been established to use
power from the turbine directly to run equipment such as
flour mills, rice hullers, band saws, wood lathes, cotton
corn shellers, and grinders.
IV. COMPARISON WITH ALTERNATIVE TECHNOLOGIES
The major use for micro-hydro generation is to provide small
amounts of electric power in isolated areas, where other
of electricity, such as an electric utility, are not
If an electric utility or some other large electricity
available, it is almost always cheaper and easier to buy
from that source. Where a large source is not available,
however, there are still a number of other possibilities.
most important of these are: diesel and gasoline-engine
wind-electric generation, photovoltaic cells, and human- or
animal-powered generators. These are each discussed below.
DIESEL AND GASOLINE-ENGINE GENERATORS
Diesel and gasoline generators are convenient and cost less
buy than most other means of producing electricity, but they
require fuel, which is becoming increasingly expensive. The
of a diesel generating system is typically $1,000 to $3,000
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
least $0.20 per KWH (for diesel fuel at $0.50 per liter),
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
Wind-electric generation can be a very advantageous form of
production where the wind is strong and reliable. In some
wind-electric generators have even been able to compete with
conventional large utilities in cost. Generally, a small
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
turn a generator (usually an alternator) that charges
and provides electric power directly. These systems are very
similar to the kinds of micro-hydro systems using batteries
were described earlier. wind-electric systems can be
cost about $2,000 to $4,000 per kilowatt of generating
The cost per kilowatt-hour will vary, depending on the
wind. Usually, only about 20 to 30 percent of the total
KWH per year are actually generated, even in fairly windy
Thus a 1-KW unit could conceivably produce 8,760 KWH per
year, but would actually produce only about 1,800 to 2,600
Photovoltaic cells, or solar cells, can change sunlight
into electricity. This electricity can then be used to
batteries for nighttime lighting, or it can be used directly
run motors and other small devices during the day. Solar
are presently an area of great interest in both developed
less-developed countries, and it seems likely that they will
eventually make a significant contribution to rural
However, solar cells are still three to four times too
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
days, however, the actual number of kilowatt-hours generated
year is only about 20 to 30 percent of the maximum--about
same as for wind generators.
Solar cells are most advantageous where very small amounts
power are needed, since their cost per watt does not
even in very small sizes. A 100-watt hydro plant might not
much less than a 1,000-watt plant, but a set of solar cells
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
charge batteries for a television, for example) solar cells
be the best choice.
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HUMAN AND ANIMAL POWER
Humans can generate power by pedaling a bicycle-like
connected to a generator. Animals such as horses and
can also be used to produce power, by having them turn a-
connected to the generator through speed-increasing gears or
pulleys. The original English unit of power, in fact, was
horsepower, which was defined to be roughly the power that a
draft horse could supply. One English horsepower is about
watts, but this is actually more work than can be expected
most horses. After allowing for the inefficiency of the
and the gears, it seems likely that only 200 to 300 watts
of electricity could be generated per animal. For humans,
amount that can be produced comfortably is even
around 50 watts. This would be enough to charge batteries
radio or television, or to provide a few hours of light, but
for much else. The cost of such a system would be fairly
nothing at all (using salvaged parts) to U.S. $100 or $200
for a new alternator and batteries. However, don't forget
both humans and animals require fuel in the form of food.
V. BUILDING A MICRO-HYDRO PLANT
Building a micro-hydro plant is a complex process that
great deal of planning and preparation. The major steps in
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
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
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
o Check for legal
and institutional problems with the site you
Find out what laws you must obey and what
will need to build and run the plant.
o Check for environmental
effects of the plant. Some of the
are the effect of the dam on fish, possible
cropland or other valuable land, and the possibility
of creating a
breeding ground for disease-causing
as water snails if bilharzia or schistomiasis
is a problem in
your area. Also check for the effects of
(e.g., flooding) on the plant.
o Check for bad
social effects--people whose use of the stream
disrupted, women unable to wash clothes on the bank,
and so forth.
These must be balanced against the positive
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
year. Calculate the annual cost of the plant
payments, annual maintenance, and all other
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
problems they might have.
o Consider all of
the costs, the social and environmental
effects, and the
different characteristics of the possible
and decide whether to go ahead with a micro-hydro
investigate some other kind of generator, or
to do nothing at
DESIGNING THE PLANT AND PLANNING ITS CONSTRUCTION
Assuming you have decided to go ahead with a micro-hydro
the next step is to design it. This does not need to be a
lengthy project--just make sure you know everything that
needed, how much it will cost, where you will get it, and
you will need to order it in order for it to arrive on time.
Unless you are very confident of your knowledge, you will
want to get additional help at this point. Some of the
books listed in the appendix (especially Low-Cost
Small Water Power Sites, may be useful to you. If your
will be at all elaborate, and especially if it will involve
constructing any dams or canals, it is a good idea to show
plans to a qualified engineer before proceeding.
BUILDING THE PLANT
This phase includes all the things involved in going from
design to the operating plant.
o Prepare a budget
and facilities schedule.
financing, if you are planning to borrow the money
to build the plant.
o Order the
turbine, generator, batteries, pipe for the penstock,
and any other items that you plan to
enough time for delivery--it can take several
months to get a
hydro turbine. It may be well to use a
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 make sure that all planning for the civil
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
everything thoroughly, first component by component,
then the system
as a whole.
OPERATING THE PLANT
Make arrangements for regular inspection and maintenance of
plant and the rest of the system, cleaning out the water
oiling the machinery, tightening the belts, etc. Depending
the system, you may also need to check on the water supply,
adjust the intake valves if too much or too little water is
used. This usually takes very little time--a few minutes a
You can carry out most of the preparatory steps of this
using this paper. Once you begin designing and building the
plant, however, you will need much more help. Some of the
listed in the bibliography may be useful to you. You may
want to talk to local experts, consultants, or VITA for
VI. FOR MORE INFORMATION
The bibliography at the back of this paper lists a number of
useful books and magazines which can provide general
as well as some which give specific directions for
potential hydro site. This reference list is followed by a
of manufacturers of small hydroelectric equipment, who may
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
last longer and work better than homemade systems.
can also be very helpful in telling you how to go about
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
the head and either the minimum and maximum flow
rates or the amount of power you want to generate. For
on using pumps as turbines, you should contact a local pump
supplier, who will be able to get information from the
The best source of information about things like building
canals, and other civil works is probably a local builder.
to find someone who has experience in building irrigation
or other water systems. The best source of information on
and electrical equipment is probably a local electric-motor
seller or repairman. This person will know how to contact
manufacturers for your specific requirements, and will also
great help in setting up the electrical system. You can also
to contact electric motor and generator manufacturers
Boating supply stores and auto supply stores are some of the
sources for lights and appliances used with low-voltage DC
Many organizations may be able to provide information or
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
probably employ engineers knowledgeable in the area, and may
able to refer you to consultants, government agencies, or
who may be able to help. If there is a government agency
with rivers, dams, navigation, or similar areas, it will
probably be a good source of information. You will need to
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
mechanical engineering, or agricultural engineering at a
university or technical institute. Finally, VITA and other
organizations may be able to provide information, technical
assistance, or both, in some cases.
SUGGESTED READING LIST
International Water Power and Dam Construction, Business
Ltd. Oakfield House, Perrymount Road, Haywards
RH16-3DH, Great Britain.
This magazine is an excellent source of information on all
of hydropower. It frequently carries articles on aspects of
mini-hydro, and has devoted several special issues to the
It also advertises engineers, manufacturers, and consultants
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
BOOKS AND REPORTS
Low-Cost Development of Small Water Power Sites by Hans
VITA, c/o VITA Publications Sales, 80 S.
Alexandria, Virginia 22304 USA.
This book was written in 1967, so it is somewhat out of
Nonetheless, it is an excellent, understandable guide to
assessing a hydro site, determining head and flow, and so
includes a good discussion of low-technology hydro schemes.
is a good book for beginners. It also contains a good set of
instructions for building a Banki turbine, which is the only
of turbine that can be built with village-level
Micro-Hydro: A Bibliography, Beth Moore and John S.
Resources Research Institute, University of
Idaho, USA, 1979.
This bibliography is somewhat old, but contains a very
set of references to the literature on micro-hydro, from
introductory material to how-to-do-it manuals and
Simplified Methodology for Economic Screening of Potential
Hydroelectric Sites, Electric Power Research Institute,
EPRI EM 3213,
Project 1745-8, P.O. Box 50490, Palo
Small Michell (Banki) Turbine: A Construction Manual. VITA.
VITA, c/o VITA Publications Sales, 80 S.
Alexandria, Virginia 22304 USA.
This book describes a low-cost water turbine that can
AC/DC electricity for your home. It includes complete
instructions for making parts and assembly, and is
MANUFACTURERS AND DISTRIBUTORS
Allis-Chalmers Fluid Products Co.
Hydro Turbine Division
York, Pennsylvania 17405
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
5346 Moquito Lake Rd.
Deming, Washington 98224
C-E/Neyrpic Hydro Power, Inc.
969 High Ridget Rd.
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
129 Glover Ave.
Norwalk, Connecticut 06856
General Electric Co.
Small Hydroelectric Operation
One River Rd.
Bldg. 4, Rm. 305
Schenectady, New York 12345
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
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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
organization also sells wind generators and photovoltaic
systems, and many low-voltage DC appliances. Their catalog
is an excellent introduction to low-voltage power
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
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
Barber Hydraulic Turbine Division of Marsh Engineering
P.O. Box 340
Port Colborne, Ontario L3K 5W1 Canada
Canbar Products Ltd.
P.O. Box 280
China National Machinery Company
People's Republic of China
(Contact the Chinese embassy in your country for
Dependable Turbines Inc.
#7, 3005 Murray St.
Rue General Mangin, BP 75
38041, Grenoble Cedex
P.O. Box 425
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