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Small-Scale Water Power

Directly power machinery with a water turbine.

I have long been fascinated by the variety of mechanical power needs and sources on the village scale in the developing world, and how different it is from the power needs on farm or in a home in the developed world. In this post, I'll share some ways farming villages in the developing world use a local renewable source of mechanical power that we rarely think about - water power.

We are familiar with the developed world's power sources: thick high-capacity electrical cables running to a barn, the propane tank in the countryside, the natural gas line in town, the elevated diesel storage tank on the farm, the corner gas station. But the remote village in the developing world will have few of these power sources, and the ones they do have will be very expensive in relation to their meager yearly incomes. Their small tanks of butane or propane for cooking are a huge improvement over firewood or charcoal, but they do require scarce cash and frequent transportation to a refilling station. They will have access to diesel or gasoline, but the engine to run it through may cost more than any single family can afford.

One way they deal with some of these issues is by combining their resources on a village scale. This lets all the village farmers share a piece of processing equipment, or all the village households share a generator that fires up each evening for lights and radio access. The other way they deal with this is by using unique sources of local renewable mechanical power.

Mechanical power is often simple and easily visible; it rotates, or strokes, or oscillates something. It is used for a variety of tasks ranging from pumping to grinding to crushing to cutting. Taking a mental trip back to pre- or early-industrial times will help you get the idea. Think of the water wheels used for grinding grain, the windmills for pumping water, and the steam engines for powering machinery.

These remote farming villages have the same basic collection of local mechanical power source to work with. We are going to talk about small-scale water power, also called hydro power.

New developments in small-scale water power

It used to be that the only two options for using water power (hydropower) were the big wooden waterwheels of olden times, or the complex turbines used for generating electricity. But now there are micro-turbines for providing direct manual power. It may be hard to believe, but using the mechanical power directly is immensely better than generating electricity to run a motor for mechanical power. That's because every time you convert power from one form to another you loose some of it.

Let's imagine a village in a valley that has a stream on a nearby hill high enough to provide a consistent 10 horsepower. They have three options for using this power: an old-fashion waterwheel, a small turbine for electricity, or microturbine(s) for direct mechanical power. Let's look at all three...

 

Old-fashion waterwheel:
This option produces low-speed but high-torque mechanical power with an efficiency of 60%. So the village could convert their 10 horsepower stream into a steady 6 horsepower. This method has some pros and cons.

Pros

  1. method is tried-and-true for tasks like grinding grain or running pumps
  2. a wooden waterwheel can be built using local materials and skills
  3. it can be maintained and repaired with local skills

Cons

  1. the waterwheel is stationary and all work must be brought to it
  2. extensive chutes or pipes may be needed to carry ample water to the mill location
  3. limited variety of ways the low RPM power can be used
old-fashion wooden waterwheel

 

Small turbine for electricity:
This option would produce AC power using a modern small hydro turbine with an efficiency of 65%. So the village could convert their 10 hp stream into 6.5 hp of electrical power. But when this electricity is needed for mechanical tasks it must be run through an electric motor that is 70% efficient and that will reduce their 6.5 hp capacity down to 4.5 horsepower of mechanical power. This method results in the lowest final mechanical power.

Pros

  1. wide variety of uses includes lighting, communication, and running motors
  2. easy to distribute the power to the locations that are more handy for tasks
  3. power can be turned off and on with a simple switch

Cons

  1. the equipment is very expensive and complex
  2. local skills may not be able to handle maintenance and repair
  3. extensive chutes or pipes may be needed to carry ample water to the generator location
picture of a small hydroelectric generator

 

Micro-turbine for direct mechanical power:
This option would produce high-speed low-torque mechanical power with an efficiency of 80%. So the village could convert their 10 hp stream into 8 horsepower. Due to the design and piping requirements of these units it may possible locate two or more units in different parts of the village.

Pros

  1. less expensive and less complex than the electrical option.
  2. possible to match the size of the turbines to special tasks in different locations
  3. it can be maintained and repaired with local skills
  4. simpler piping possible if splitting the flow to two location through smaller pipes

Cons

  1. more expensive than the old-fashioned waterwheel
  2. added expense of small generator if electricity for evening lights is desired
tablesaw being run by small water turbine

 

An ideal arrangement for using mechanical microturbines in a village might have two units. One unit would be near the fields where it can be hooked up to various pieces of crop processing equipment and turned off and on as needed during different times of the year. The second unit could be in the village itself where it powers a rotating shaft used occasionally for tasks like grinding flour, woodworking, an air compressor, cloth fiber processing, and running a small generator for evening lights.

piping for a microturbine for water power

Image credit: Brian W. Raichle

interior mechanical parts of a small water turbine

Image credit: Watermotor

table saw and alternator hooked to a Watermotor

Image credit: Watermotor

 

Micro-turbines like this are currently being produced and promoted by Watermotor in Bolivia. You can find more info at watermotor.net and at their Facebook page. Their videos below give good descriptions of how these water motors are installed and connected. The quality of the videos is a bit weak, but the information is great.

 

 

 

And don't forget the fringe benefit of such a system: water. The water leaving the micro-turbine has to go somewhere, and it is still as clean as the stream was. By locating the turbine properly the water could be used for drinking, washing, watering animals, or irrigating crops. Since the piping used for these microturbines is the same as that used for plumbing, it is even possible to provide pressurized water to taps scattered around the village.

A special THANK YOU to Low-tech Magazine for making me aware of this technology!

 

I hope you found this interesting. Be sure to see our other posts at our Blog Index