Water Turbines

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The Egyptians were using mechanical energy to lift water with a wheel in the 3rd century BC.   Four hundred years later in the 1st century AD Greek, Roman and Chinese civilizations were using waterwheels to convert the power of flowing water into useful mechanical energy.   The word “turbine” was coined from a Latin word for “whirling” or “vortex”.  The main difference between a water wheel and a water turbine is usually the swirl component of the water as it passes energy to a spinning rotor.  Although the Romans might have been using a simple form of turbine in the 3rd century AD, the first proper industrial turbines began to appear about 200 years ago.  Turbines can be smaller diameter for the same power produced, spin faster and can handle greater heads (water pressure) than waterwheels.  Windmills and wind turbines are generally differentiated by the reasoning that windmills turn wind-power into mechanical energy whereas ‘wind turbines’ convert wind-power into electricity.  This post attempts to reveal to those individuals with an exploitable water source that – modest advancements in ‘micro’ hydro technology have made it feasible for them to potentially create useful power from low water heads or from very modest water sources.

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Above the horizontal undershot waterwheel requires the least engineering and landscaping labor to install; the width of the runner can be tailored to match the flow rate and only a small water ‘head’ is required.  The ‘breastshot’, ‘overshot’ and ‘backshot’ styled waterwheels get progressively more efficient.

Water head can be thought of as the weight of water in a static column.  Since fluids don’t compress, the weight of water in a pipe is directly related to its pressure at the bottom (measured as psi or pounds per square inch).  As a stream drops in elevation its head is a measurement of that drop.  Water weighs 62.427 lbs per cubic foot.  There are 1,728 cubic inches in a cubic foot.  A cube of water 12” high, 12” wide and 12”deep would have a psi of ((62.427 / 12) /12)  or 0.433 lbs. per square inch.   Any column of water 1 ft. high, regardless of width, still has a water head of 1 ft. and a psi of 0.433 lbs/in².   Water drop is simply multiplied by the constant 0.433 to determine the potential psi. 

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Boyden turbine

A Frenchman named Fourneyron invented the first industrial turbine in 1827.  The idea was brought to America and improved upon in the form of the Kilburn turbine in 1842.  By 1844 a conical draft tube addition resulted in the Boyden turbine.  There were dozens of Boyden turbines in operation in northeast America by the time radical abolitionist John Brown raided Harper’s Ferry in 1859.   Located at the confluence of the Shenandoah and Potomac rivers, Harper’s Ferry was a national armory and a beehive of activity where gunsmiths made small arms.   In 1859 at least 2 Kilburn and 5 Boyden turbines were driving the  jack-shafts and belts needed to the power lathes, sawmills and other equipment necessary to keep 400 employes busy at the armory.

Fourneyron’s turbine and subsequent Kilburn and Boyden types were further followed themselves by increasingly efficient  turbines including:  the Leffel double turbine, John B. McCormick’s mixed-flow turbine, the New American and Special New American turbinesAll of these are known as outward flow reaction turbines (which are reminiscent of cinder, sand or fertilizer spreaders – but with water spraying out at the bottom).

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A different type of turbine called an inward flow (or radial flow) reaction turbine was developed by James b. Francis in 1849.  In the snail shaped Francis turbine water is sucked into a spiraling funnel that decreases in diameter.  Used at the beginning of the 20th century mainly to drive jack-shafts and belts for machinery in textile mills, Francis type turbines soon became the type favored for hydroelectric plants and are the type most frequently used for that purpose today.  This <link to an image> apparently taken in Budapest before 1886 shows what looks to be a Francis turbine being installed in the vertical axis rather than the horizontal axis.

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A “runner” is that part of a turbine with blades or vanes that spins.   As with any other turbine the scale of dimensions can be adjusted up or down to suit individual needs.   Although small Francis turbines are produced the ones used in large hydroelectric power stations are impressively huge – some producing more than a million horsepower each (1,341 hp = 1 Megawatt).   The largest and most powerful Francis type turbines in the world are in the Grand Coulee Dam (Washington USA).  The runners of the turbines there have diameters of 9.7 meters and are attached to generators producing as much as 820 Mw each.   China’s “Three Gorges Dam” is capable of the world’s largest electrical output however with 32 main generators producing an average 700Mw each for a total 22,500 MW optimum output.   Located between Brazil and Paraguay the world’s second largest dam (in terms of generating capacity) is the Itaipu dam with 20 Francis  turbines powering 700 MW generators.   In 2012 and 2013 Itaipu’s annual electrical output actually surpassed that of Three Gorges due to the amount of  rainfall and available water.

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Another type of reaction turbine was developed by an Austrian in 1913 looks like a boat propeller.  Some windmills are called Kaplan turbines.  The blades or vanes on a Kaplan designed hydro turbine are adjustable, allowing the turbine to be efficient at different workloads or with varying water pressures.  Although complicated and expensive to manufacture, the Kaplan design is showing up more frequently around the world, especially in projects with low-head, high flow watersheds.  They can be found working in the vertical or the horizontal planes.  Large Kaplan turbines have been working continuously for more than 60 years at the Bonneville dam.  The Bonneville dam is on the Columbia River between Washington and Oregon, several hundred miles downstream from the Grand Coulee dam.  Both dams were started at the same time during the depression and were initiated by Roosevelt’s (FDR’s) “New Deal”.  Small inexpensive Kaplan turbines (without adjustable vanes) can be made to work in streams with as little as 2 feet of head.

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The so called “Tysonturbine looks like it could qualify as a Kaplan turbine but  this modern example of micro hydroelectric technology encases its own generator in a waterproof housing.  The unit is submerged into a stream and usually suspended from a small tethered raft.  The stream can be shallow but obviously a high flow rate will encourage the best electrical generation.

Yet another type of water turbine is tenuously referred to as a “crossflow turbine.   In the early 1900’s two individuals on opposite sides of the world independently contrived about the same turbine design.  A Hungarian professor named Banki and an Australian engineer named Mitchell invented turbines that combine aspects of both a reaction (or constant-pressure) turbine and an impulse (or free jet) turbine.  The runner of a Banki -Mitchell (or Ossberger)  crossflow turbine is cylindrical and resembles a barrel fan that one might find in a forced air furnace or evaporative swamp cooler.  The design uses a broad rectangular water jet that travels through the turbine only once but travels past each runner blade twice.  The moving water has two velocity stages and very little back pressure.

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Most suited to locations with low head but high flow, low-speed cross flow turbines like this have a flat efficiency curve (the annual output is fairly constant and not as much affected by fluctuating water supply as are some other designs).  Large commercial crossflow turbines are manufactured that can handle 600 ft. of head and produce 2,500 hp.  Small homemade Banki – Mitchell units have been constructed that are capable of producing about 400 watts using a car alternator with 5.5 CFS (cubic feet/sec) of water from a stream with a head of only 33 inches.  These units can make considerable noise, so to keep vibrations minimized these turbines should be well balanced and spun at moderate revolutions per minute.

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Two rising celebrities in the world of mini or micro hydroelectric technology are both impulse turbines.  The Pelton wheel or runner works in the vertical plane usually, and the somewhat similar Turgo in the horizontal.  Water pressure is concentrated into a jet that impacts spoon shaped cups of the Pelton or curved vanes of the Turgo.  These systems capitalize on high head, low flow water sources.  Turgo runners are sometimes quite small (like 3 or 4″ in diameter) and are designed to run at high speeds.   A small uphill water source and enough penstock (piping) to reach it are the main requirements necessary to make one of these small impact turbines useful.   Under the right circumstances a small Pelton or Turgo wheel of just a few inches in diameter is capable of producing perhaps 500 watts.   In the absence of running streams, snow pack or plentiful rainfall an individual living in a mountainous area might still be able to collect up-slope groundwater from perforated pipes buried in boggy areas, springs or the drainage ditches alongside roads.  A long run of water hose, polyethylene or polyvinyl chloride (PVC) pipe could conduct the water down slope, which would gain another pound per square inch of pressure for every 2.31 feet of drop.  Water catchment from barn and house roofs could be redirected to holding cisterns and used by these little turbines when appropriate to augment other alternative off-GRID power systems.

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Built 1901 – used to power the mining town of Victor, CO. Courtesy of Gomez.

The Pelton wheel was patented in 1880 but Lester Allan Pelton actually got the idea from using and examining similar Knight water wheels in the placer mining gold fields of 1870’s California.  Employing fluid often diverted by sluices to a holding pond before being collected into a penstock and dropping further, miners washed entire hillsides away with jets of high pressure water.  The tip end of this water cannon was a nozzle called a “monitor” and there was no ‘off button’.  Most of these hydraulic mining monitors spewed water around the clock so it was probably just a matter of time before some enterprising miner attempted to convert that wasted energy into a useful mechanical energy by spinning a wagon wheel with pots and pans attached to its rim.  While ‘Knight wheels’ (the 1st impact water turbines) were originally constructed to power saws, lathes, planers and other shop tools some were actually used in the first hydroelectric plants built in California, Oregon and Utah.  Lester Pelton’s innovation was to extract energy more efficiently from a water jet by splitting the cup and deflecting the splash out of the way.

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Between the 1870’s and the 1890’s innovations for both hydroelectric turbine and alternating current development were occurring at breakneck pace.  The first hydroelectric power schemes began to appear after 1878 onward and for several years created only DC current.  In three years between 1886 and 1889, the number of hydroelectric power stations in the U.S. and Canada alone quadrupled from 45 to over 200.  AC development milestones during this period include: step up and step down transformers, single phase, polyphase or triple phase AC, and great improvements in the distance of power transmission.   <This site> provides an interesting history and timeline on the maturation of AC power.

The Ames hydro electric power plant in Colorado claims to “be the world’s first generating station to produce and transmit alternating current”.   Perhaps that claim should be amended to specify only “AC for industrial use”.  Originally the Ames plant attached a 6 foot tall Pelton wheel to a Westinghouse generator.  The largest generator ever built up to that time, it made 3,000 volts, single phase AC @ 133Hz.  The Pelton wheel was driven by water from a penstock with a head of 320 feet.  The power was transmitted 2.6 miles to an identical alternator/motor, driving a stamp mill at the Gold King Mine.  The mine owners chose this newfangled electricity over steam powered machinery because of the prohibitive cost of shipping coal by railway.  In 1905 the Ames power plant was rebuilt with a new building, two Pelton wheels with separate penstocks from two water sources and a General Electric generator of slightly less output capacity.  After 123 years this facility’s impact turbines are still producing electricity.

The success of the Ames power plant along with a well done 1893 World’s Fair exhibit by Tesla and Westinghouse helped determine a victor in the famous “War of the Currents” and more immediately, who would win the prestigious Adam’s power station contract soon to be constructed at Niagara Falls.

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The main characters in the ‘War of the Currents’ were (from left to right above) the DC proponents Thomas Edison and J.P. Morgan and their AC rivals Nikola Tesla and George Westinghouse.  Pride, patents, reputations and big money were at risk in this somewhat ridiculous conflict.  At its peak the quarrel was exemplified by Edison going about the country and staging demonstrations wherein he electrocuted old or sick farm & circus animals with ‘dangerous’ AC current.  It is rumored that the electric-chair used for executions was itself created due to a secret bribe from Edison.  In response Tesla staged some carefully controlled demonstrations where he shocked himself with AC to prove its safety.  In truth both DC and AC currents are potentially deadly at higher voltages, but AC may ‘win out’ slightly because its alternating fluctuation might induce ventricular fibrillation (where the heart looses coordination and rhythm).

* For those that may not know: Edison was a prominent inventor who formed 14 companies and held 1,093 patents under ‘his’ name although his formal education consisted of only 3 months schooling.  The largest publicly traded company in the world (General Electric) was formed by a merger with one of Edison’s companies.   JP Morgan was one of the most powerful banker/ financier/ robber barons in the world in the 1890’s.   JP reorganized several railroads, created the U.S. Steel Corporation, and bailed the government and U.S. economy out of two near financial crashes – once in 1875 and again in 1907.  He was also self conscious about his big nose and did not like to have his picture taken.   Recognized as a brilliant electrical and mechanical engineer Tesla never actually graduated from his university.  Immigrating to the U.S. in 1884, Tesla even worked for Edison before the two had a falling out.   Westinghouse attended college for 3 months before receiving the first of his 100 patents and dropping out.  He went on to found 60 companies.  

Although AC has been the favored method of current transmission for the last century, in the War of the Currents, DC power never fully capitulated.  Considering storage benefits, DC may someday stage a spectacular comeback.  In Cities like Chicago and San Francisco an old DC grid may run parallel to its AC complement.  Most consumer electronics convert AC into DC anyway.  DC offers some advantages over AC, including battery storage which provides load leveling and backup power in the event of a generator failure.  There is no convenient way to store excess AC power on the GRID so it is shuffled around for as long as possible.

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Alternating current originally offered advantages over direct current in its ease of transmission.  High voltage / low current travels more efficiently in a wire than low voltage / high current will.  The introduction of the transformer (which works with AC but not DC) allowed AC to be “stepped up” to a higher voltage, transmitted and then stepped back down to usable power at the destination.  DC current (under the Edison scheme) had to be generated very close to its finial destination or otherwise use expensive and ungainly methods to achieve transmission over longer distances.  Voltage drop (the reduction of voltage due to resistance in the conducting wire) affects both currents equally.  Due to resistance, some power will be lost as heat during transmission.  AC suffers from a resistance loss during transmission that does not affect DC.  “Skin effect” is the tendency of AC to conduct itself predominately along the outside surface of a conductor rather than in the conductor’s core.  The whole wire is not being used – just the skin.  This skin effect resistance increases with the frequency of the current.  This phenomenon along with new technology for manipulating DC voltages has recently encouraged several companies to construct new High Voltage Direct Current (HVDC) power lines for long distance transmission.  The Itaipu Dam mentioned earlier for example transmits HVDC over 600 kV lines to the São Paulo and Rio de Janeiro – some 800 km away.

The huge dams built in the U.S. were not created to provide electrical power to customers but to control and redirect water for the purpose of agriculture.  Even today the bulk of power created by those dams is used to pump water back uphill so that it can be broadly distributed by irrigation.  In 2008 the U.S. Energy Information Agency (EIA) estimated that only 6% of the nation’s power was generated hydroelectrically and that amount has changed little in the last 5 years.  The EIA  does predict a growth in the future for photovoltaic and wind generated power.  Canada with a much smaller population supplies itself with a greater percentage of hydroelectric power than the U.S. and also has more kinetic energy available in terms of exploitable water resources.

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– Wind turbines, water turbines, Archimedes screws and centrifugal pumps in reverse can be mounted to the same types of alternators or generators.  Small or miniature turbines can be affixed to a wide range of DC motors from tools, toys, treadmills, electric scooters, old printers, stepper motors and servos.  Commonplace AC induction motors from laundry machines, blowers, furnaces, ceiling fans, tools and other sources can be converted into brush-less low rpm alternators by rewiring or installing permanent magnets in the armature.  Usually but not always in a modest off-grid power scheme AC current from an alternator or magneto needs to be rectified into DC so that the energy can be stored in a deep cycle ‘battery sink’.  Automotive alternators contain their own rectification but these are less than ideal for turbines for a couple of reasons.  Charge controllers and inverters are also pertinent subjects in the discussion of alternate energy.  These topics may be addressed in some future post.  For now a final image (of a rectifying ‘full wave bridge’) and some miscellaneous video links are offered.

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CIVIL 202 – Pelton wheel project –  3 minute video – school science project

Micro Hydro Electric Power- off grid energy alternatives – 7.5 minute video – something of an advertisement

Home Made Pelton Wheel – rather long 12 minute video

Turning Green In Oxford – 9 minute video / power by Archimedes screw

Algonquin Eco-Lodge – 8 minute video – generating by reversing water flow through centrifugal pump

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