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ELECTRONIC LOAD CONTROLLER
Water turbine, like petrol or diesel engine, will
vary in speed as load is applied or relieved.
This speed variation will seriously affect both frequency
and voltage output from a generator.
Traditionally, complex hydraulic or mechanical speed
governors altered flow as the load varied,
but we have developed an electric load controller(ELC)
which has increased the simplicity and
reliability. ELC is mounted directly on the generator.
The ELC prevents speed variations by
continually adding or subtracting an artificial load,
so that in effect, the turbine is working
permanently under full load. A further benefit is
that the ELC has no moving parts, is very
reliable and virtually maintenance free. The advent
of electronic load control has allowed the
introduction of simple and efficient, multi-jet turbine,
no longer burdened
Not everyone is lucky enough to have a source of
running water near their homes. But for those with
river-side homes or live-on boats, small water generators
(micro-hydro turbines) are the most reliable source
of renewable energy available. One relatively small
water turbine will produce power non-stop, as long
as running water is available, no matter what the
weather.
For people with a good source of year-round running
water, one or two water turbines may be all they need
to power their homes. However, for those with seasonal,
winter-only streams available, a small water generator
may be the perfect back up for a solar system's off-peak
season.
If you think a home water power system may work for
you, browse our site for more information, or contact
us for help putting together a microhydro system to
meet your needs.
If you have a creek or stream on your property that
drops along its course, a microhydro system could
be in your future. With the right circumstances, harnessing
microhydro electricity is cheaper and more constant
than either photovoltaic- or windpowered electricity,
partly because a source of flowing water is available
24/7, and not vulnerable to doldrums, clouds, or the
number of daylight hours. While a microhydro system
requires a more hands-on approach than PV, it is often
simpler for the system owner than harnessing wind.
It can also be a great do-it-yourself project—if
you have the appropriate knowledge and skills. Supplying
debris-free water to the hydro turbine is the first
critical step in developing a low-maintenance hydro
system. This article will introduce you to several
methods of constructing an intake to do just that.
Keep an eye out for additional articles
that will cover penstock (the pipeline to the turbine)
design, and system wiring and transmission voltage
considerations for high- and medium-head microhydro
systems.
What Makes Water Power
Water power is the combination of head and flow. Both
must be present to produce electricity. Consider a
typical hydro system. Water is diverted from a stream
into a pipeline, where it is directed downhill and
through the turbine (flow). The vertical drop (head)
creates pressure
at the bottom end of the pipeline. The pressurized
water emerging from the end of the pipe creates the
force that drives the turbine. More flow or more head
produces more electricity. Electrical power output
will always be slightly less than water power input
due to turbine and system
inefficiencies.
Head is water pressure, which is created by the difference
in elevation between the water intake and the turbine.
Head can be expressed as vertical distance (feet or
meters), or as pressure, such as pounds per square
inch (psi). Net head is the pressure available at
the turbine when water is flowing, which will always
be less than the pressure when the water is turned
off (static head), due to the friction between the
water and the pipe. Pipeline diameter has an effect
on net head.
Flow is water quantity, and is expressed as “volume
per time,” such as gallons per minute (gpm),
cubic feet per second (cfs), or liters per minute.
Design flow is the maximum flow for which your hydro
system is designed.
It will likely be less than the maximum flow of your
stream (especially during the rainy season), more
than your minimum flow, and a compromise between potential
electrical output and system cost.
Creating a Diversion
Water is diverted from a stream and channeledthrough
an open-top, elevated waterway that delivers water
to the turbine. Instead of the penstock, a pipe called
a drafttube is installed below the turbine. The draft
tube sucks water through the propeller, which in turn
spins the alternator. This particular turbine design
can generate electricity at sites with as little as
5 feet of head so long as a sufficient flow rate is
available.
The inexpensive turbine’s AC output is not designed
to be synchronized with the utility grid. While the
power quality regulation is pretty sloppy—probably
not something you’d want to subject your
home entertainment system to—it’s definitely
sufficient to power lighting and other simple appliances.
If you would like to run electromis, use the 110 volt
ac output to charge battery and then use appropriate
power inverter to supply 110 volts ac.
The simplest microhydro diversions are variations
of a screen-covered pipe stuck in a creek. However,
they require frequent cleaning. During the first rains
of the season in some locations, twice-daily cleanings
may be necessary to remove leaves and debris from
the screen.
If placed in the stream’s direct flow, the intake
should be situated at least 1 foot underwater for
pipe diameters up to 4 inches. This can create cleaning
issues, especially during high-water periods. Although
most folks aren’t interested in wading into icy
watersto clean their intakes, on small creeks these
diversions can be reasonably nuisance-free most of
the year,and the needed materials are inexpensive.
The simple screen can be used in many different situations.
A siphon intake over a diversion works by pulling
water up a short rise, using suction from the downhill-flowing
pipe below it. This kind of setup can work fine for
pumping water, but tends to lose the prime in a hydro
application. Because of this tendency, these intakes
require a foot valve and a priming process (usually
a hand-operated pump) to replace the trapped air with
water when suction is lost. They are used with a simple
screen-type filter as part of the foot valve. Use
this method if you must, but it is not advised—significant
attention will be required, and
you will eventually hate your microhydro system.
Useful HydroConversions Power
1 horsepower = 746 watts
1 kilowatt = 1.34 horsepower
* Efficiency not accounted for Static Head & Pressure
1 foot of head = 0.43 pounds per square inch (psi)
1 psi = 2.31 feet of head
Flow
1 gallon per minute (gpm) = 0.0022 cubic feet per
second (cfs)
1 gpm = 0.000063 cubic meters per second
1 gpm = 3.8 liters per minute
1 cfs = 449 gpm
1 cfs = 0.283 cubic meters per second
1 cfs = 1,700 liters per minute
Hydro Terms
Flow
Refers to the quantity of water supplied from a water
source or exiting a nozzle per unit of time. Commonly
measured in gallons per minute (gpm).
Francis Turbine
A type of reaction hydro-turbine used in low to medium
heads. It consists of fixed vanes on a
shaft. Water flows down through the vanes, driving
the shaft.
Friction Loss
Lost energy due to pipe friction. In hydro systems,
pipe sized too small can lead to serious friction
losses.
Head
The difference in elevation between a source of water
and the location at which the water from
that source may be used (synonym: vertical drop).
Expressed in vertical distance or pressure.
Headrace
A flume or channel that feeds water into a hydro turbine.
Hydroelectricity
Any electricity that is generated by the flow of water.
Intake
The structure that receives the water and feeds it
into the penstock (pipeline). Usually incorporates
screening or filtering to keep debris and aquatic
life out of the system.
Penstock
The pipe in a hydro system that carries the water
from the intake to the turbine.
Pipe Loss (Frictional Head Loss)
The amount of energy or pressure lost due to friction
between a flowing liquid and the inside surface of
a pipe.
Pressure
The “push” behind liquid or gas in a tank,
reservoir,or pipe. Water pressure is directly related
to
“head”—the height of the top of the
water over the bottom. Every 2.31 feet of vertical
head gives 1 psi (pound per square inch) of water
pressure.
Runner
The wheel that receives the water, changing the pressure
and flow of the water to circular motion
to drive an alternator, generator, or machine.
Tailrace
The pipe, flume, or channel in a hydroelectric system
that carries the water from the turbine
runner back to the stream or river.
Trash Rack
A strainer at the input to a hydro system. Used to
remove debris from the water before it enters the
pipe.
Before you can begin designing your hydro system
or estimating how much electricity it will produce,
you’ll need to make four essential measurements:
• Head (the vertical distance between the intake
and
turbine)
• Flow (how much water comes down the stream)
• Pipeline (penstock) length
• Electrical transmission line length (from turbine
to home
or battery bank)
We will discuss how to measure head and flow. Head
and flow are the two most important facts you need
to know about your hydro site. You simply cannot move
forward without these measurements. Your site’s
head and flow will determine everything about your
hydro system pipeline size, turbine type, rotational
speed, and generator size. Even rough cost estimates
will be impossible until you’ve measured head
and flow.
When measuring head and flow, keep in mind that accuracy
is important. Inaccurate measurements can result in
a hydro system designed to the wrong specs, and one
that produces less electricity at a greater expense.
Measuring Head
Head is water pressure, created by the difference
in elevation between the intake of your pipeline and
your water turbine. Head can be measured as vertical
distance (feet or meters) or as pressure (pounds per
square inch, newtons per square meter, etc.). Regardless
of the size of your stream, higher head will produce
greater pressure—and therefore higher output—at
the turbine.
An altimeter can be useful in estimating head for
preliminary site evaluation, but should not be used
for the final measurement. It is quite common for
low-cost barometric altimeters to reflect errors of
150 feet (46 m) or more, even when calibrated. GPS
altimeters are often even less accurate. Topographic
maps can also be used to give you a very rough idea
of the vertical drop along a section of a stream’s
course. But only two methods of head measurement are
accurate enough for hydro system design—direct
height measurement and water pressure.
Direct Height Measurement
To measure head, you can use a laser level, a surveyor’s
transit, a contractor’s level on a tripod, or
a sight level (“peashooter”). Direct measurement
requires an assistant.
One method is to work downhill using a tall pole with
graduated measurements. A measuring tape affixed to
a 20-foot (6 m) section of PVC pipe works well. After
each measurement, move the transit, or person with
the sight level, to where the pole was, and begin
again by moving the
pole further downhill toward the generator site. Keep
each transit or sight level setup exactly level, and
make sure that the measuring pole is vertical. Take
detailed notes of each measurement and the height
of the level. Then, add up the series of measurements
and subtract all of the level heights
to find total head.
Another method is to work uphill, with your assistant
walking up the slope as you site through the transit
or sight
level until the bottoms of the assistant’s feet
are level with the transit. At this point, the head
will be the same as the distance from your eye to
the ground where you are standing. Once you’ve
recorded this measurement, move to the spot where
your assistant was standing, and repeat the process.
Multiply the number of times you do this by the height
of the shooter’s eye from the ground for the
total head.
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