Clean Power

Published on August 30th, 2011 | by Guest Contributor


Innovative, New Approach to Low-Head, Low-Flow Water Power

August 30th, 2011 by  

by John Saavedra of Look for the Power

Interest and investment in low-head (vertical drop), low-flow hydro power peaked a century ago.  This corresponds to the rise of interest in hydro turbines.  The improved power output of the larger units dictated their priority over traditional stream and water wheels.

There were 25,000 – 30,000 water wheels in use in England in the 1850’s, and 33,500 water wheels in use in Germany in 1925.  Most are now rusted and broken, quaint relics of the Industrial Revolution, in both Europe and the USA.

With our current energy needs, this should be revisited.

Consider that the geographic features (high vertical drop and high flow rate) necessary for conventional hydro turbines are all well-known and surveyed in developed countries, and the number of potential new sites is small.  There is a current revival of interest in getting the old wheels back into service, spurred by record-level demand for energy and ever-increasing prices of fossil fuels.

A survey conducted by the Sustainable Energy Research Group at the University of Southampton, England in Feb. 2006 contains these prescient statements:

“Today, the requirement for the utilisation of low head hydro power sources for electricity generation is greater than ever. In developing countries, the rising demand for electricity in combination with large distances means that decentralised electricity generation has a high priority.

Most low head, low flow hydro power sources however are today not exploited since standard turbines can not be employed economically in such conditions.

“Consequently, there exists a demand for a cost-effective low head hydraulic energy converter, which still could not be met.

“Although stream wheels could be potentially quite interesting since e.g. their application would not constitute a major change of the river, no such wheel has been built for more than 100 years and very little is known about the performance characteristics and design requirements for such wheels.

This is a clear statement made five years ago by a research university that there is an urgent demand which has not been met.  This is an open invitation to both innovation and investment. “Ideas Wanted.”

Is there a way, other than traditional stream and water wheels, to harvest and harness the energy in low-head, low-flow streams?

What if a “reverse oar,” or “fixed oar,” had a length of 100 – 200 ft,

with the oarlock securely mounted on the bank of a low-head, low-flow stream,

with the ‘blade’ of the oar made of metal, weighing 200 lbs, giving the “oar” a weight of 300 lbs,

with the blade of the oar carried downstream by the forces of the hydro current, while compressing a return spring,

with the return spring lifting and carrying the “fixed oar” back upstream through the air, ready for another “power stroke”,

with a shaft at the oarlock mated to a large (8 ft. diameter) pulley,

with this large diameter pulley linked by V-belts to numerous smaller pulleys,

thereby converting the high-torque, low-speed large pulley motion to lower-torque, higher-speed RPM’s for the smaller pulleys,

each smaller pulley secured to a permanent-magnet alternator,

producing constant, clean, green, renewable, sustainable electrical power?

Stated differently, if an oar, 200 feet long, weighing 300 lbs, were mounted with its oarlock on the bank of a stream, would you want to be the guy bolting it to an 8-ft diameter pulley?  Wouldn’t the low-speed, high-torque rotational force of the oar be more than enough to cause serious bodily harm if my arm got in the way?

Consider this logical progression:

In the 4th and 5th centuries BC, Athenian triremes like the one below gave Greece naval superiority.  They were rowed by human power:

Today, such a boat would be powered by a diesel engine.

A diesel engine can power an electrical generator.

Therefore, could oars also be used to power an electrical generator?

Question — What is missing in these logical progressions?

Answer — basic research into the design, materials, sizes and sites for the concept.

One in four people now living on Earth lives off of any electrical grid.   This idea may be of particular interest to those who may also live near a low-head, low-flow stream of water. Living off the grid closely correlates to poverty, illiteracy, disease, hunger, unsafe drinking water, infant mortality, and other problems.

There is a website — — that describes this and several other projects.

Your comments, feedback, reactions, and suggestion are all welcome.


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About the Author

  • Engineer

    Interesting concept. Though resurrecting the floating undershot water wheel would be easier, and would also provide power, with very little infrastructure required, except for anchor points on the bank. A lot simpler and probably much more efficient.

  • Pingback: Water Power: Out with the New, In with the Old | CleanTechnica()

  • Anumakonda Jagadeesh

    Excellent post on low-head, low- flow water power. Infact water power is efficient compared to other farms like solar, wind so long as the flow is there.

    I designed a simple but innovative microhydro device for low heads. In Southern India in Agricultural fields water is pumped by irrigation pumpsets in to storage tank (about 1 m height) and released at the bottom to the fields through small canal. After release from the tank the water flows by natural gravitation.

    I devised a Microhydro device with Pelton wheel made from buckets used in rice mills for elevating rice. The Pelton wheel is attached to a bigger aluminium wheel (1 ft diameter through shaft and to a smaller diameter wheel attached to a low RPM Generator through V-belt). There is a diode to arrest the reverse flow of current. The buckets are made of hard plastic so that they won’t get rusted.

    The whole set up is fixed on a frame. The system is placed at the outlet of the water tank so that the flow falls on the pelton wheel which in turn rotates the generator to give power. This power can be utilised to charge the batteries in parallel. Three 12 V batteries can be charged. The whole system costs about Rs 10,000(about US $ 210) in South India. The Unit can be fabricated at local workshops and mobile. It provides livelihood for people in rural areas in developing countries. Also the unit can be placed directly under Electric/Diesel pump sets so that the water (with force) from delivery pipe falls on the pelton wheel.

    Dr.A.Jagadeesh Nellore (AP), India
    Renewable Energy Expert

  • Origo1

    Within the past two years, either on Clean Technica or Gizmag, it was reported in the UK that a method of utilising [to use the British spelling] flowing water with a head as little as 8 inches to generate electricity. Whatever happened to that technology?
    Also, I can’t find a third level of oars on that boat, so it looks like a bireme to me.

    • Anonymous

      Doesn’t ring a bell to me, and been writing on CleanTechnica for 2+ years now. BUt perhaps someone else wrote on it & i just forgot about it

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