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Mist Showers: Sustainable Decadence?

Thu, 17 Oct 2019 00:00:00 +0000

Image: Mist Shower Hack Kit. Jonas Görgen.

The daily shower would be hard to sustain in a world without fossil fuels. The mist shower, a satisfying but forgotten technology which uses very little water and energy, could be a solution. Designer Jonas Görgen developed a a-do-it-ourselves-guide kit to convert almost any shower into a mist shower and sent me one to try out.

The Carbon Footprint of the Daily Shower

The shower doesn’t get much attention in the context of climate change. However, like airplanes, cars, and heating systems, it has become a very wasteful and carbon-intensive way to provide for a basic need: washing the body. Each day, many of us pour roughly 70 litres of hot water over our bodies in order to be “clean”.

This practice requires two scarce resources: water and energy. More attention is given to the showers’ high water consumption, but energy use is just as problematic. Hot water production accounts for the second most significant use of energy in many homes (after heating), and much of it is used for showering. Water treatment and distribution also use lots of energy.

In contrast to the energy used for space heating, which has decreased during the last decades, the energy used for hot water in households has been steadily growing. One of the reasons is that people are showering longer and more frequently, and using increasingly powerful shower heads. For example, in the Netherlands from 1992 to 2016, shower frequency increased from 0.69 to 0.72 showers per day, shower duration increased from 8.2 to 8.9 minutes, and the average water flow increased from 7.5 to 8.6 litres per minute. ¹

In many industrial societies it’s now common to shower at least once per day

Altogether, the average Dutch person used 50.2 liter of water per day for showering in 2016, compared to “only” 39.5 litres of water per day in 1992. This is a conservative calculation: these data do not include the showers taken outside the home, for example in the gym. Research shows that in many industrial societies, and especially among younger people, it is now common to shower at least once per day. ²³⁴

The original man-made shower. Pouring a bucket of water over one's (or another person's) body. Image: Daniel Julie (CC-BY-2.0).

Taking the Dutch as an example, let’s look at the energy use and carbon emissions of a daily hot shower. Heating 76.5 litres of water (8.9 minutes x 8.6 litres per minute) from 18 to 38 degrees Celsius requires 2.1 kilowatt-hours (kWh) of energy. Depending on the energy source (gas, electricity), the carbon intensity of the power grid (US/EU), or the efficiency of the gas boiler (new/old), the resulting CO2-emissions of an average shower amount to 0.462 – 0.921 kg. ⁵ If we compare this to the carbon emissions of a relatively fuel efficient car (130 gCO2/km), the emissions of a typical shower equal 3.5 – 7 km of driving, and this result ignores the energy cost demanded by water treatment and distribution.

The emissions of a typical shower equal 3.5 – 7 km of driving

In principle, the energy for a shower could be generated by renewable energy sources. However, if eight billion people were to shower daily, total energy use per year would be 6,132 terawatt-hours (TWh). This is eight times the energy produced by wind turbines worldwide in 2017 (745 TWh). All (current) wind turbines in the world could provide only 1 billion people with a “sustainable” daily shower. Furthermore, the use of renewable energy sources doesn’t lower the water use of the daily shower. To be clear, renewable energy is part of the solution – solar boilers, biomass, heat generating windmills – but we also need to look at the demand side of washing in a post-carbon world.

More Powerful Showers

Since the early 1990s, low flow shower heads have provided a more water and energy efficient way of showering. These shower heads use between four and nine litres of water per minute, roughly half the flow rate of a normal shower (ten to fifteen litres per minute). Almost half of all Dutch households had a low flow shower head installed in 2016, but as we have seen, the flow rate of the average shower since the 1990s has been increasing, not decreasing. ¹

A rain shower. Image: soak.com.

That’s because other Dutch people have upgraded to rain showers, which have a water flow of about 25 litres per minute – double that of a normal shower head, and three times more than what a low flow shower head uses. A 8.9 minute rain shower requires 222 litres of water and 6.3 kilowatt-hour of energy to heat it. The carbon footprint corresponds to 14.3 – 21.3 km of driving.

Life Before Showers

It may shock some younger readers, but only fifty years ago most people in industrial societies didn’t shower at all. Wall-mounted shower units, installed over the bathtub, became widespread only in the 1970s, and dedicated shower cubicles became a regular fixture in new homes only since the 1980s and 1990s. ²³⁴ Before the arrival of the shower, people took one (or a few) bath(s) per week, and in between they washed themselves at the sink using a washcloth (the so-called sink wash, bird bath or sponge bath).

The weekly water and energy use of a daily shower quickly surpasses the water and energy use of a once, twice or even thrice weekly bath

The shower is often presented as a more sustainable option than the bath, because the latter is said to use more water. However, the weekly water and energy use of a daily shower quickly surpasses the water and energy use of a once, twice or even thrice weekly bath. ² The sponge bath is even more water and energy efficient: roughly two litres of water is sufficient to get clean, and the water could even be cold because not the whole body gets wet at the same time.

Taking a sponge bath. Summer Morning, a painting by Carl Larsson, 1908

Environmental organisations, water companies, and municipalities encourage people in industrial societies to take shorter showers, use low flow shower heads, and install energy efficient water boilers. There’s also factors influencing energy and/or water use that these institutions don’t dare to question: shower frequency, water temperature (“take cold showers”), or the act of showering itself – it is never suggested that a sponge bath would actually suffice. Clearly, the daily hot shower is today regarded not as a luxury but as a basic necessity.

Why Do We Shower?

However, showering does not only wash the body. A shower that’s entirely focused on cleaning the body – a so-called Navy shower or Sea shower– takes very little time, energy and water. A Navy shower consists of a 30 seconds shower to get wet, soaping the body while the water is off, and is completed by another 30 second shower to rinse the soapy water.

Until the 1970s, showers were only used in barracks or prisons to wash many people in a short time. [^2] Image: La douche au Régiment, a painting by Eugène Chaperon, 1887.

Assuming an average water flow, a (hot) Navy shower uses only 8.3 litres of water and 0.2 kilowatt-hour of energy. A daily sponge bath would have even lower water and energy use. A nine minute hot shower per day is by no means a basic necessity: it’s a treat. Since the 1990s, the daily shower has been portrayed in advertisements as a means of relaxation, stress relief, and sensual pleasure. ²⁴

Mist Showers

The use of the shower to treat oneself seems to be incompatible with a drastic reduction of its water and energy use. However, there is a technology that might just do that: the mist shower. A mist shower atomizes water to very fine drops (less than 10 microns), which greatly reduces the water flow. Buckminster Fuller invented the first one in 1936 as part of his Dymaxion bathroom (he called it a “fog gun”). The idea was taken up again in the 1970s, when several trials and experiments were conducted with both atomised hand washing and showering.

Left: Mist shower developed by NASA. Right: Mist shower developed by the Canadian Minimum Housing Group. Both are from the 1970s. [^7]

NASA developed a mist shower with a hand-held, movable nozzle that incorporated an on-off thumb controlled water valve attached to a flexible hose. The average water use for a nine-minute shower was measured to be 2.2 litres, which corresponds to a water flow of only 0.24 litres per minute. ⁶ The Canadian Minimum Housing Group developed and tested several mist showers and obtained a flow rate of 0.33 liters of water per minute. ⁷. In both cases, swab tests of bacteria on the skin showed that mist showers clean the body just as well as a “normal” shower of the same duration – using 30 to 40 times less water.

Jonas Görgen developed a kit that converts almost any shower into a mist shower.

Jonas Görgen, a young designer who graduated from the Design Academy Eindhoven in 2019, became fascinated by the history of the mist shower and decided to build one himself. Compared to earlier mist showers, Görgen has improved the concept in two important ways. First, he developed a kit that can turn almost any shower into a mist shower with very little effort. Second, in contrast to earlier experiments, his mist shower uses not one but three to six nozzles. This turns a functional but very basic mist shower (using only one nozzle), into a pleasant experience that feels just as comfortable and invigorating as a “normal” shower.

A 6-nozzle mist shower in the bathroom of designer Jonas Görgen. Image: Jonas Görgen.

The kit that Jonas sent me contains six nozzles, some connectors and dividers, some flexible plastic tubes (“feel free to cut to any length”), and some pieces of copper wire (“to fix and attach the nozzles in the right positions”). I installed a five-nozzle mist shower in less than twenty minutes, and although the result won’t win a design award (in fact, Jonas built a more beautiful mist shower for his graduation project), as a a-do-it-ourselves-guide shower hack it is simply brilliant.

With five nozzles, I measured a water flow of two liters per minute, which is five times less than my now obsolete shower head

In my set-up, four of the nozzles are fixed (one aimed at the head, one aimed at the back, and two aimed at the hips), while one is flexible and can be aimed where it’s needed – as in the NASA experiments. Using more than one nozzle increases the water flow, but the water savings remain significant.

Image: Detail of a mist shower.

For five nozzles, I measured a water flow of two litres per minute, which is five times less than my now obsolete shower head (ten litres per minute) and 12.5 less than the water flow of a rain shower. It’s unusual to obtain such large savings with so little effort. Jonas writes about his shower that “it is not all a compromise in comfort, as it is sometimes suggested in the research papers of the 1970s” and I totally agree. The difference is clearly due to the fact that earlier mist showers only used one nozzle.

Energy Savings of a Mist Shower

The energy savings of a mist shower are smaller than its water savings. That’s because a mist shower requires a higher water temperature. The increased surface area of the water decreases water use but also causes the heat to dissolve more quickly in the air. Even if the water coming from the tap is at maximum temperature (usually 60 degrees Celsius and already slightly too hot to touch), when sprayed by a nozzle it quickly loses its temperature the further you place your body from the opening. The trick is to position the nozzles in such a way that they closely surround the body. I did this with the iron wires and some duct tape, but there are more elegant ways.

The energy savings of a mist shower are smaller than its water savings

I found a water temperature of about 50 degrees Celsius to be sufficient for thermal comfort, but a mist shower in winter may require a higher water temperature, so let’s assume a value of 60 degrees to calculate the energy use of my 5-nozzle mist shower. At a flow rate of two litres per minute, a 8.9 minute shower consumes 17.8 litres of water. Heating that volume of water from 18 degrees to 60 degrees requires 1.04 kWh. That’s half the energy use of the average shower in the Netherlands (2.1 kWh), and six times lower than the energy use of a rain shower (6.3 kWh).

Details of Jonas Görgen's a-do-it-ourselves-guide mist shower.

The energy use of a mist shower could be further reduced by showering in an enclosed cabin, which increases thermal comfort with lower water temperatures. Another trick to increase thermal comfort in winter is to open the nozzles a bit so that the surface area of the water decreases. This increases water use but decreases heat loss. It is down to the individual to find balance between saving energy or water, based on local circumstances.

An argument that is often made against water saving shower heads is that people compensate lower water flows by taking longer showers. A similar argument could be made against mist showers, because the use of mist increases the time needed to rinse the body of soapy water. However, a mist shower of 8.9 minutes offers plenty of time to get rid of soap and shampoo. The test subjects in the NASA experiments all managed to wash and rinse within 9 minutes, using only one nozzle on a flexible hose. Washing long hair is more problematic, but also in this case the problem can be addressed by opening the nozzles a bit more, increasing the water flow.

How Many Nozzles Can We Afford?

The five-nozzle mist shower offers significant water and energy savings compared to a “normal” shower and does so without sacrificing comfort. However, is it sustainable enough? If eight billion people used a five-nozzle mist shower, all wind turbines in the world could still only provide two billion people with a daily hot shower. And, compared to a one-minute Navy shower – which is entirely focused on efficiency, not on comfort – energy use is five times higher, and water use is twice as high. So, let’s see what happens when we decrease the number of nozzles, still assuming average shower frequency and duration.

Three nozzles – with a flow rate of roughly one liter of water per minute – are the minimum for providing the comfort of a hot shower

I found three nozzles – with a flow rate of roughly one liter of water per minute – to be the minimum for providing the comfort of a hot shower. This would bring the water use of a 8.9 minute mist shower down to 8.9 litres, which corresponds with the water use of a one-minute Navy Shower. The energy use would come down to 0.52 kWh, two to three times higher than that of a Navy shower. This would provide four billion people with a wind-powered daily hot shower, meaning that if we halved the shower duration (from 8.9 to 4.5 minutes) or showered less frequently (once every two days), the global population could be cleaned and pampered using only wind power.

A nozzle in my mist shower.

If we give up on comfort and simply get clean with as little energy and water as possible, we could take a mist shower using only one nozzle, just like in the seventies. Using just one nozzle I measured the water flow to be 0.3 litres per minute, meaning that a 8.9 minute mist shower would need only 2.67 litres of water and 0.156 kilowatt-hour of energy. The resource use of a mist shower then corresponds to that of a sponge bath, and is significantly lower than that of a one-minute Navy Shower. All wind turbines in the world could provide roughly 15 billion people with a daily 8.9 minute hot mist shower.

If more than fifteen nozzles are used, the energy use of a mist shower is higher than that of a conventional shower

Conversely, the water and – especially – energy use of a mist shower increases quickly as more nozzles are added. With twenty nozzles, the water use is still below that of the average shower (6-7 litres vs. 8.3 litres per minute), but the energy use is already higher: 3.1 kWh compared to 2.1 kWh. With ten nozzles – see for instance the commercially available Nebia Spa Shower – water use remains very low at only 3 liters per minute, but energy use is only 25% lower in comparison to a normal shower (1.45 vs. 2.1 kWh). Mist showers are not low energy products by definition. It depends how we use them.

Off-Pipe

There’s one problem with mist showers operating with only one to three nozzles: modern water boilers don’t get triggered by a flow rate below 1 litre of water per minute, meaning that only cold mist comes out. This is not a fundamental problem – it’s technically possible to make water boilers that heat small amounts of water – and it brings us to another potential advantage of the mist shower: its effect on the bathroom.

I got so fond of my mist shower that I'm travelling with it.

The modern shower is not a device that stands on its own. It is plugged into several infrastructure networks, like the water supply, the sewer network, and the power grid or gas infrastructure. In contrast, although a mist shower could be plugged into the same infrastructures, it could also operate without them, further reducing the use of resources.

Modern water boilers don’t get triggered by a flow rate below 1 liter of water per minute, meaning that only cold mist comes out

First of all, a switch to mist showers would make it possible to use much smaller and less powerful water boilers, which could be powered by local solar or wind powered systems that are smaller and cheaper than those required for conventional water boilers. With a minimal mist shower, one could even question the need for a water boiler at all. The quantity of water is so small (2.67 litres) that it could be heated on the fire – just like in the old days.

A portable mist shower from the 1970s, pressurized with a bicycle pump. [^7]

Secondly, because of its high water use, a conventional shower needs to be connected to the drain. The mist shower discharges much less water, which makes it possible to take the shower off-pipe and treat the water on site, for example to flush the toilet, water the plants, or clean the pavement. Third, a water supply in the bathroom is not strictly necessary either: a small container could be filled elsewhere and taken to the bathroom.

The Canadian experiments in the 1970s resulted in such a portable mist shower. The water was stored in a Volkswagen window washing reservoir connected to a bicycle pump to pressurize the water. The 2.5 litres of water were pressurized with about twenty strokes of the bicycle pump. ⁷ In short, if we switch to mist, the infrastructure that made the modern shower possible can be scaled down and simplified, to such an extent that the bathroom could be taken off-grid and off-pipe even in an urban context, bringing further reductions in the use of water and energy. The same approach could be applied to hand washing and dish washing.

Jonas Görgen’s mist shower is not for sale. A mist shower is on display at the Dutch Design Week Eindhoven, 19-27 Oct. 2019.

Please note that all showers carry a legionella risk. The smaller water droplets from a mist shower remain in the air for a longer time, which increases the risk of inhalation. Therefore, it is important to take elementary precautions.

van Thiel, Lisanne. “Watergebruik thuis 2013.” TNS NIPO, Amsterdam (2014). ↩︎ ↩︎
Shove, E. A. Comfort, Cleanliness and Convenience: the Social Organization of Normality. Berg, 2003. ↩︎ ↩︎ ↩︎ ↩︎
Hitchings, Russell, Alison Browne, and Tullia Jack. “Should there be more showers at the summer music festival? Studying the contextual dependence of resource consuming conventions and lessons for sustainable tourism.” Journal of Sustainable Tourism26.3 (2018): 496-514. ↩︎ ↩︎
Hand, Martin, Elizabeth Shove, and Dale Southerton. “Explaining showering: A discussion of the material, conventional, and temporal dimensions of practice.” Sociological Research Online10.2 (2005): 1-13. ↩︎ ↩︎ ↩︎
If electricity is used, the resulting CO2-emissions of a shower are 0.621 kg in Europe and 0.921 kg in the US. [Overview of electricity production and use in Europe. European Environmental Agency, created 2017, updated 2019] [Assessing the evolution of power sector carbon intensity in the United States, Greg Schivley et al, 2018.] If gas is used, the emissions of a shower amount to between 0.462 kg (for new gas boilers) and 0.714 kg (for older boilers). [Carbon footprint of heat generation, houses of parliament.] ↩︎
Space Shower Habitability Technology, Arthur Rosener, 1972. ↩︎
Water conservation and the mist experience, 1978. ↩︎ ↩︎

Power Water Networks

Wed, 30 Mar 2016 00:00:00 +0000

Image: A hydraulic accumulator. Picture: [Les Chatfield](https://www.flickr.com/photos/61132483@N00/7184633723)

During the second half of the nineteenth century, water motors were widely used in Europe and America. These small water turbines were connected to the tap and could power any machine that is now driven by electricity. As we have seen in a previous article, operating motors with tap water was not very sustainable. Because of the low and irregular water pressure of the town mains, these motors used unacceptably high amounts of drinking water.

While the use of water motors in the US came to an end early in the twentieth century, the Europeans found a solution for the high water use of water motors and took hydraulic power transmission one step further. They set up special “power water” networks, which distributed water under pressure for motive power purposes only, and switched to a much higher and more regular water pressure, made possible by the invention of the hydraulic accumulator.

Almost all these power water networks remained in service until the 1960s and 1970s. Hydraulic power transmission is very efficient compared to electricity when it is used to operate powerful but infrequently used machines, which can be distributed over a geographical area the size of a city.

“The use of water is a curiously neglected subject in the literature of engineering. As a romantic or popular facet of engineering, hydraulic power has never caught the public eye like the steam engine, the locomotive or even the internal combustion engine.” Ian McNeil, Hydraulic Power, 1972

The theoretical basis for hydraulic power transmission was laid in 1647 by French whizz-kid Blaise Pascal. By means of experiments, he discovered that water — unlike air — is virtually incompressible and transmits pressure equally in all directions.

The implications of the “hydrostatic paradox” were demonstrated in Pascal’s “machine for multiplying forces”, illustrated below. It consists of two upright cylinders, connected together by a pipe. The whole system is filled with water and sealed water-tight. One cylinder contains a small diameter plunger, while the other cylinder contains a plunger that has a cross-sectional area 100 times larger.

Machine for multiplying forces.

Pascal demonstrated that if a weight is placed on top of the small piston, it will be able to raise a weight placed on top of the larger piston that is 100 times heavier. Pascal’s machine thus allowed forces to be multiplied — in the example above, the ratio of force output to force input is 100 to 1. In other words, you can produce an output force of 100 kg for an input force of only 1 kg.

A Machine for Multiplying Forces

Force multiplication was anything but new in the 1600s. More simple devices such as pulleys, gear trains, capstans, winches and treadwheels — all variations on the 7,000 year old lever — could also derive a high output force output from a small input force. For example, the Romans built cranes with a mechanical advantage of up to 70 to one, meaning that one man exerting a force of only 25 kg could raise a weight of 1.75 tonnes.

However, the hydraulic version of the lever has one outstanding advantage over earlier mechanisms: the friction loss is very small and independent of the mechanical advantage. Therefore, the possible multiplication ratio is almost infintely greater and both pistons may be a considerable distance apart — up to about 25 km, as we shall see.

In hydraulics, friction loss is independent of the mechanical advantage, therefore the possibile force multiplication ratio is almost infinite

Increasing force multiplication could be done by either extending the proportion between the diameter of both plungers, or by applying greater power to the smaller piston. In common with the earlier mechanisms, what is gained in mechanical advantage is lost in velocity ratio.

If a small hydraulic force is converted into a larger force, its speed of operation will be reduced in exactly the inverse proportion, because the distance traversed increases in the same proportion as the force. For example, a person pressing down the small piston 10 centimetres would move the other piston up only 1/100th of that distance.

Illustration: Pascal's Barrel experiment. Source unknown.

Consequently, in a closed system, the heavier weight could be lifted only over a very limited distance, depending on the length of the plunger. However, this limit is removed when more water is added to the system and the smaller piston, instead of coming down just once, makes a number of strokes — in other words, when it functions as a pump. In this case, the larger piston will keep rising.

The Hydraulic Press

Pascal could only prove his point indirectly, as the available materials at the time were not strong enough to withstand the pressure. It would take another century and a half before hydraulic force multiplication was put into practice. Its first use was not a lifting device, but rather the opposite: the hydraulic press, which generates a compressive force.

The conventional screw press of the time, little developed since the Romans had used it for pressing olives and grapes, required a great effort to operate, had large frictional energy loss (+80%), and could not have exerted more than 25 tonnes load. (The screw, which converts rotational motion into linear motion, is basically an inclined plane wrapped around a cylinder).

Left: The screw press. Picture credit: [Bruce K. Satterfield](http://emp.byui.edu/SATTERFIELDB/Olive%20Tree/olive%20tree%20horticulture.htm) Right: The hydraulic press.

The hydraulic press was invented in 1796 by English locksmith and carpenter Joseph Bramah. It was entirely based on the theoretical work of Pascal. Bramah’s hydraulic press, which was driven by a hand-operated pump, brought a large increase in the load that could be exerted by a human.

With the available materials at the time, Bramah achieved an overall ratio of 1,000 to 1, which means that an effective load of 60 tonnes on the lifting piston could be balanced by a mere 60 kg on the pump handle. The efficiency of the hydraulic press was over 90%.

Harbours and Dockyards

In spite of its eminent suitability for crane operation, hydraulics made little progress in this field during the first half of the nineteenth century. This was largely due to the problem of reliably and efficiently translating the linear motion of a ram to rotary motion of the crane barrel or drum. During the first half of the nineteenth century, cargo handling in harbours, dockyards and railway yards was still done by means of human powered cranes, but the need for taller and stronger cranes was great.

Starting in the 1830s, iron began to be used as a material for ship building, with a parallel growth in the dimensions of ships. Conventional lifting systems were no longer adequate. In most countries, the solution was found in the steam powered crane, which appeared in the 1850s. However, in harbours and dockyards in Britain, a worthy alternative appeared: the water powered crane.

During the first half of the nineteenth century, cargo handling in harbours, dockyards and railway yards was still done by means of human powered cranes

British engineer William Armstrong started designing and operating powerful hydraulic cranes in the 1840s. Being fully aware that hydraulics was best adapted for giving a slow, steady motion, Armstrong deviced a method of lifting the load at one stroke of a ram or piston, multiplying the motion sufficiently by means of pulleys.

Image: hydraulic crane

However, his efforts were complicated by the low and irregular pressure of the town mains, which was the power source for these machines. The maximum power output of a water powered machine is determined by water pressure and water flow. In the town mains, water pressure was (and often still is) supplied by a water tower. Because the practical height of a water tower is limited, so is the water pressure. A 50 m (165 ft.) tall water tower can produce a water pressure of 70 pound-per-square-inch (psi).

Consequently, the only way to further increase the power output of a crane running on water from the town mains is to increase the water flow. However, this raises potable water consumption and increases the size and costs of pipes, valves, cylinders, and other parts of the system. Moreover, if there is a higher than average demand for potable water from other users, the water level in a water tower will fall, and so will the water pressure and the power output of the machine.

The Hydraulic Accumulator

In 1851, Armstrong came up with an alternative solution that solved these issues: the hydraulic accumulator. Although much more compact than a water tower, it could produce a regular water pressure of 700 psi or higher — at least 10 times the water pressure in the town mains. This allowed to produce an order of magnitude more power without raising water consumption or increasing the size of system components.

Armstrong’s hydraulic accumulator was a contraption in which a ram or piston exerted pressure on the water in a vertical cylinder. The piston was loaded by dead weight ballast, which generally took on the form of a cylindrical ballast container surrounding the central cylinder (image below, on the left). The container was filled with crushed rock, scrap iron or other ballast material.

Left: Hydarulic Accumulator in Bristol Harbour. Wikipedia Commons. Right: Hydraulic Accumulator, Walsh Bay, Sydney. Source: [NSW HSC Online](http://hsc.csu.edu.au/engineering_studies/application/lift/3377/hydraulics.htm)

For a water pressure of 700 psi the ballast was about 100 tonnes, acting on a ram of about 45 cm in diameter with a vertical stroke of 6 to 7 meters. Another type of accumulator utilised a rectangular platen to support a brickwork ballast (image above, on the right) or steel slabs. Hydraulic accumulators could be set up outdoors, or housed in a purpose designed building.

In comparison with a water tower, a hydraulic accumulator could deliver ten times more power, and maintain an even pressure all over the network

The workings of the hydraulic accumulator are somewhat similar to those of a water tower. The central cylinder has a water inlet and outlet at the bottom. Water from the docks could be pumped in through the inlet by a steam powered pump, raising the piston, while it could be pushed out through the outlet into the mains for distribution, lowering the piston.

Energy was stored by upward movement of the ram and recovered upon its descent. The pumping rate of the steam engine was regulated in function of the water level in the accumulator, either automatically via mechanical linkages or via the aid of a human being.

Fielding and Platt hydraulic accumulator

Contrary to a water tower, however, the accumulator could maintain an even pressure all over the system regardless of the volume of water in the cylinder, because it’s the weight of the ballast and not the weight of the water that creates the pressure — in other words, the hydraulic accumulator gives pressure by load instead of by elevation.

With a charging/discharging efficiency above 98%, and no self-discharge, the hydraulic accumulator was an extremely energy efficient device.

Water Powered Factory Machinery

The introduction of the hydraulic accumulator had two important effects. First, it greatly expanded the range of hydraulically operated machines. The water motors connected to the town mains were household devices and workshop tools. But Armstrong and other engineers adapted high pressure water to a variety of industrial applications that required great power such as forging, punching, stamping, flanging, shearing and riveting (the predecessor of welding).

Hydraulically powered riveting machine.

In harbours, high pressure water not only operated cranes and hoisting machines handling cargo on docks and in warehouses, but also lock gates, swing bridges, boat lifts, and graving docks. At railway yards, hydraulic power transmission was used for freight handling and for moving railway cars (using hydraulic capstans), as well as for operating turntables, elevators and traversing mechanisms. All these applications of hydraulic power would have been impossible with the low and irregular pressure prevailing on the town mains.

To give an idea of the importance of hydraulic power, it suffices to look once more at the evolution of lifting devices. In 1586, a 344 ton obelisk was moved between squares in Rome. Domenic Fontana, master builder of the Vatican, raised the obelisk with the help of 40 capstans worked by 400 men and 75 horses. In 1878, John Dixon raised another obelisk — Cleopatra’s needle, weighing 209 tons — using four hydraulic lifting jacks, worked by four men.

Power Water Networks

Secondly, the hydraulic accumulator made it possible to transmit power efficiently over large distances. For a 30 cm diameter pipeline, the pressure drop in water distribution amounts to about 10 psi per mile, a figure that is independent of water pressure. Thus, if you transmit water with a pressure of 70 psi over a distance of 7 miles (12 km), all energy is lost. But if you transmit water over the same distance with a pressure of 700 psi, a water pressure of 630 psi remains, which comes down to a transmission efficiency of 90%.

The high transmission efficiency of high-pressure water led to the construction of at least a dozen public power water networks with accumulator storage, half of them in Britain, in which centrally located steam engines pumped water into hydraulic accumulators that distributed high pressure water over a large geographical area. One or more accumulators would be installed at each hydraulic power station and others could be sited at strategic points along the supply main as sub-stations.

The idea of a truly hydraulic power network — analogous to the electric grid that came a bit later — was already outlined in a 1812 patent by Joseph Bramah, the inventor of the hydraulic press.

From the 1870s to the 1890s, hydraulic power networks were established in the leading industrial cities of Britain: Kingston upon Hull, London, Liverpool, Birmingham, Grimsby, Manchester and Glasgow. Dock and railway companies pioneered the technology, and remained the most important users for decades.

Illustrations of a hydraulic accumulator, a hydraulic crane, and a hydraulic lift.

However, power water was also running manufacturing processes in factories, operating elevators in public, private and commercial buildings, and activating household devices and workshop tools. Anybody who was lucky enough to have a mains running through the street could connect to the public network. Power water consumption was metered, as it happens today with potable water and electricity.

The idea of a truly hydraulic power network — analogous to the electric grid that came a bit later — was already outlined in a 1812 patent by Joseph Bramah, the inventor of the hydraulic press. But Bramah, who also conceived the hydraulic accumulator and the hydraulic crane, was ahead of his time. It took another sixty years before his ideas were brought into practice by Armstrong and his contemporaries.

London Hydraulic Power Company

The most extensive hydraulic power network was built in London, operated by the “London Hydraulic Company”. At the company’s peak in 1917, five interconnected central power stations pumped high pressure water in about a dozen hydraulic accumulators and almost 300 km of supply mains, powering more than 8,000 machines and serving most of the city. In London theatres and other cultural buildings, power water was moving floors, organ consoles, fire curtains and stages. Water under pressure worked water pumps and lifted the bascules of the Tower Bridge.

Illustration: layout of London Hydraulic Power Co. mains and pumping stations, 1895.

Fire hydrants were also advantageously served by the high pressure system and several hundreds of them were connected to the London Hydraulic Power Company’s mains. These fire-fighting systems increased the pressure of the domestic water mains by injecting a small amount of high pressure water in them, using a jet pump. By itself, water at high pressure from the hydraulic power mains could not be supplied in adequate quantity to have an effect on a large fire, while the domestic supply mains had enough quantity but not enough pressure to reach the top floors of buildings.

In London, five interconnected central power stations pumped high pressure water in a dozen hydraulic accumulators and almost 300 km of supply mains, powering more than 8,000 machines and serving most of the city.

Another remarkable application of high pressure water in London was the Silent Dustman, a water powered vacuum cleaning system that came on the market in 1910. Several large hotels were completely “wired” for this system: water from the town mains was used in a jet pump to produce a vacuum in a pipe to which the system was to be fitted. Along these pipes were a number of nozzles to which flexible hoses could be fixed. Thus the dirt from the sweepers was drawn into the hydraulic pipe and carried away into the drains. The system, which operated silently and efficiently, remained in operation until 1937.

One of the London power stations. Note the tower on the right, which houses the hydraulic accumulators.

In London, however, hydraulic power does not seem to have made a great impact on the domestic scene. In The Hydraulic Age (1980), B. Pugh notes that this was “possibly due to the fact that in its day domestic labour was cheap and in plentiful supply. Had present-day conditions operated then possibly the story would have been different since the potentialities of hydraulic power were not less than those of electricity today.”

Most public power water networks supplied water under a pressure of 700 to 800 psi (48 to 55 bar), with the exception of Manchester and Glasgow, where water was pressurized to 1120 psi. In these cities, there was a heavy demand for power for hydraulic presses used for baling, an application that required a higher pressure.

Power Networks Outside Britain

The British power systems inspired similar networks elsewhere: Antwerp in Belgium, Buenos Aires in Argentina, and Melbourne and Sydney in Australia. While the Australian systems were reminiscent of those in Britain (with 80 km of mains, the one in Melbourne was the second largest ever built), the Argentinian system was used to pump sewage, and the network in Antwerp was aimed at the combined production of mechanical power and electricity. The latter was an attempt to overcome the very high transmission losses of electricity at the time.

\"Zuiderpershuis\": a former hydraulic pumping plant in Antwerp. The towers housed the hydraulic accumulators.

In The Hydraulic Age, B. Pugh writes that:

“For power transmission, the early electric stations were faced with the same difficulties as the hydraulic power stations, their voltage being analogous to working pressure, and voltage drop due to mains resistance analogous to pressure drop due to pipe friction. The early electric public power stations were direct or continuous current stations, the voltage of generation essentially being only slightly higher (by the voltage drop in the cables) than at the consumer’s premises which for safety reasons had to be less than 250 volts. Due to voltage limitation, the area of supply as well as the amount of power that could be transmitted was limited.”

The network in Antwerp was aimed at the combined production of mechanical power and electricity.

Since 1865, Antwerp had been using a high pressure hydraulic network for powering cranes, bridges and sluices in the harbour. To this was added a second network in 1893, which distributed high pressure water to electric substations scattered across the city (twelve according to the plan, but only three were built). There, water turbines generated electricity which was distributed in a radius of 500 m via underground electric conduits — this was about the distance at which low voltage could be distributed efficiently.

Hydraulic cranes in Antwerp harbour. Picture by Low-tech Magazine.

The Antwerp system, which was used for operating street lighting, thus did on a large scale what water motors connected to dynamos did on a small scale with water from the town mains (see the previous article. About 66% of the hydraulic energy was converted to electricity. At its peak, the network reached a length of 23 km with an output of 1200 hp. There were also a number of places in London where consumers ran small electric generators from the hydraulic supply.

Power Water Versus Electricity

The breakthrough in high voltage electric transmission at the turn of the century made systems like those in Antwerp immediately obsolete. The electricity generating part of the network disappeared in 1900. Producing water under pressure in order to produce electricity involves a fourfold energy conversion, which is needlessly wasteful if you can just produce electricity and transport it efficiently.

The expansion of efficient electrical transmission also stopped the construction of other large-scale power water networks before the century was over. “Had these systems been started some years earlier, they might have become vastly more popular”, writes Ian McNeil in Hydraulic Power (1972). “A few years later, and they would probably never have been built at all.”

However, almost all public power water systems that were built between the 1870s and 1890s remained in service until the 1960s and 1970s, eventually using electric motors instead of steam engines for pumping. The power water network operated by the London Hydraulic Company, the last to survive, worked until 1977. Most of the public power water networks kept growing during the first decades of the twentieth century, reaching their heydays at the end of the 1920s. The fatal decline came only when factories started leaving the cities in the 1960s and 1970s.

If electricity is the most efficient and practical way of transmitting and distributing power, then why did almost all power water networks remain in service for almost a century?

This raises two questions. First, why didn’t power water become the universal method of power distribution that Joseph Bramah and William Armstrong had envisioned? And second, if electricity is the most efficient and practical way of transmitting and distributing power, then why did almost all power water networks remain in service for almost a century?

Advantages of Electric Power

As a power transmission technology, power water has three important disadvantages in comparison to electricity. First of all, electricity can be transported efficiently over much longer distances. Hydraulic power transmission was (and still is) at least as efficient as electric power transmission up to distances of 15 to 25 km. Beyond those distances, however, electric transmission is a clear winner.

Greenland dock hydraulic lock gates in London, built in the 1880s. Picture credit: [Chris Allen](http://www.geograph.org.uk/photo/2569524)

A second shortcoming of hydraulic transmission is that a complex distribution network introduces additional energy loss. Every curve or bend in the mains increases friction losses. The more intricate the network, the less efficient it becomes. Electric transmission doesn’t have this problem, at least not in a significant way. The friction losses in the water mains limit the amount of machines that can be attached to a power water network, while electricity can be subdivided almost infinitely.

The third limitation of power water is the limited capacity of a hydraulic transmission line. Water under pressure can only be moved through thin pipes at walking speeds in order to avoid excessive friction losses. At higher speeds, the loss of friction increases as the square of the velocity and efficiency goes down fast, even over relatively short distances. This limits the flow rate and thus the power that could be delivered by a hydraulic transmission line.

Using a 10 to 12 cm diameter pipe — a common size in most high pressure system at the time — a hydraulic transmission line could produce a maximum continuous power of 115 to 205 horse power (85 to 150 kW). High voltage electric transmission lines of similar size can carry an amount of power that was orders of magnitude greater than that.

Advantages of Power Water

However, none of these disadvantages mattered for the power water networks that we have discussed. These were all decentralized systems, with machines no more than 15-25 km away from the power source. Secondly, because the hydraulically operated machinery in harbours, railway yards, factories and buildings was characterized by slow motion and infrequent use, the slow transmission speed of power water presented no obstacle.

With the exception of the short-lived electricity generating system in Antwerp, none of the Armstrong-type power water networks supplied power to a large amount of continuously operating machines. (But note the medium pressure power water networks in Switzerland. Lastly, because a power water network operated relatively few (but very powerful) machines, friction loss through bends and curves in the network was limited.

Hydraulic pump, accumulator and press. Source: Portefeuille économique des machines, de l'outillage et du matériel, December 1864, [Bibliothèque nationale de France](http://gallica.bnf.fr/ark:/12148/bpt6k5539152w/f79.pleinepage.langFR)

The limitations of hydraulic transmission were very well understood at the end of the nineteenth century. However, engineers also grasped the unique benefits of the technology, which still hold today. For example, Robert Zahner, an advocate of yet another alternative to electricity, compressed air, wrote in The Transmission of Power by Compressed Air (1890) that:

“The practical incompressibility of water renders the hydraulic method unfit for transmitting regularly a constant amount of power. It can be used to advantage only where motive power is to be accumulated and applied at intervals, such as raising weights, operating punches, compressive forging and other work of intermittent character, requiring a great force through a small distance.”

Hydraulic transmission is “admirably adapted for use with heavy machinery and equipment in operations requiring marked concentration of power, reciprocating straight-line motion, and intermittent action”, wrote Louis Hunter in The Transmission of Power (1991). The main excellence of the hydraulic accumulator is that it allows to operate machines that require much more power than the energy source can supply — Pascal’s “force multiplication”.

The limitations of hydraulic transmission were very well understood at the end of the nineteenth century. However, engineers also grasped the unique benefits of the technology, which still hold today.

When high force or torque are needed, hydraulic power systems are a much more compact and energy efficient solution than mechanical or electric drives. Both electric motors and combustion engines often need mechanical power transmission (gears, chains, belts) to convert their high rotational speed to a slower speed with higher torque.

Likewise, hydraulic power systems easily produce linear motion using hydraulic cylinders, while electric power requires costly linear motors or mechanical power transmissions such as rack-and-pinion assemblies. Hydraulic and electric power are complementary in this sense: one of the limitations of power water transmission was the relative difficulty of converting linear motion to rotary motion.

Illustration: hydraulic lift

Pelton wheels were the most obvious choice, but their high rotational speed involved the use of gearing for the operation of slow speed machinery. A number of hydraulic engines of the ram type was available to supply rotative power involving variable or slow speed operation, but these engines had few advantages compared to electric or mechanical drives.

A third important advantage of hydraulics is that the power is always readily available in the pipes and in the accumulator, but when there is no demand there is no waste. When none of the machines in a power water network was in operation, the hydraulic accumulators kept the lines pressurized without using any energy. This advantage is especially relevant when machines are used intermittently.

Hydraulics Today

Hydraulic power is still in use today, especially in heavy industrial equipment that requires a slow but powerful linear motion, and in mobile construction machinery such as excavators. However, the raised-weight hydraulic accumulator and the power water networks have disappeared.

The pressurized fluid is no longer water but oil, mixed with additives. (Vegetable oil had been used as a hydraulic medium in the 19th century). Unlike water, oil doesn’t freeze and is not corrosive. However, it makes hydraulic power more expensive and it obviously doesn’t permit the exhaust fluid to end up in the sewer network, the docks or the sea.

Partly as a consequence of the use of oil, there evolved the self-contained hydraulic power pack consisting of pump, hydraulic accumulator, and return flow systems, ready to be coupled to an electric motor or a diesel engine. The hydraulic accumulators in these systems are much smaller, they use a gas to compress the fluid, and they do not maintain a steady pressure.

Today's hydraulic accumulators (usually compressed gas types) have little in common with the raised-weight accumulators in power water networks. Picture: [HYD](http://www.hyd.com/tejas/products/products_frame.htm).

While the practical benefits of hydraulics remain — a large amount of power can be transferred and controlled precisely using very compact components — the modern approach erases an important efficiency advantage specific to the more centralized power water networks of the nineteenth and twentieth century. In a city-wide power water network, a comparably small central power source — a handful of hydraulic accumulators — could operate a large number of very powerful machines. The pumping engines didn’t have to be dimensioned for peak loads.

A great advantage of power water networks was that comparatively little power capacity was required to operate a large number of powerful machines over a wide area.

B. Pugh laments this evolution in The Hydraulic Age (1980):

“One century ago, only a few very large machines — swing bridges and an occasional hydraulic press — had their own individual pumping equipment. More recently, this trend spread throughout hydraulically operated machinery of all types and sizes, and is accepted practice today. With unit hydraulic power packs each piece of equipment will be driven by its own motor and will have its own instrumentation, filters, etcetera, which will call for periodic inspection and maintenance.”

“The motor will run continuously while the unit is in use regardless of the load on the pump it drives. In the case of a number of such units not all will be working to capacity all the time. Appreciable economy could be effected by having a central pumping plant to supply a number of units and due to the diversification of the load the maximum load at any one time will be less than the sum of the individual maximum loads.”

“An advantage of a large station over a number of smaller ones lies in the ability to meet diversity of demand. A number of small, independent power stations must each have sufficient capacity to meet the peak demand of its own area of supply and the peaks will not occur at the same time. A large station, embracing the total area of a number of small stations, will need only to meet the maximum simultaneous demand and this will normally be less than the sum total of the local peaks.”

Alternatives to Electricity

Just like mechanical power transmission technologies — such as jerker line systems and endless rope drives — power water networks have disappeared largely because electric transmission has superior efficiency over long distances. However, in a more decentralized energy system based on renewable energy, all these forgotten alternatives for electricity deserve to be reconsidered for specific purposes. Raised-weight hydraulic accumulators could be solar, wind or even pedal powered.

Picture: J.W. Gibson

Around 1900, the superiority of electricity for transmitting power over very long distances was not disputed. For moderate distances, however, quite a few authors doubted its usefulness. For example, R. Kennedy wrote in Modern Engines and Power Generators (1905):

“Electricity offers paramount advantages for power transmission to a distance in most cases. Electrical engineers, however, claim far too much for it. They are apt to forget other means for transmitting power, which means have paramount advantages over electricity in a good many cases.”

W.C. Unwin, the author of the most complete nineteenth-century book on power transmission (On the Development and Transmission of Power from Central Stations), expressed a similar concern in 1894:

“Granting that electrical distribution will play an important part before long in the development of systems of power distribution, there is a popular tendency at the moment to regard too exclusively electrical methods, and to overlook other means of power distribution which have been usefully applied in the past, and will, in suitable conditions, be still employed in the future… For transmission to moderate distances there is a choice of several means of transmission, and electrical distribution has not in such cases and up to the present established any universal superiority.”

In the next installment of our power transmission series, we will discuss compressed air, which is probably the most usable alternative for electricity.

This article is dedicated to Charles Steele. RIP.

Sources (in order of importance):

The Hydraulic Age, B. Pugh, 1980

Hydraulic Power (Industrial Archaeology), Ian McNeil, 1972

On the Development and Transmission of Power from Central Stations, W.C. Unwin, 1894. Also here.

Hydraulic Machinery, with an introduction to hydraulics, R.G. Blaine, 1897

A History of Industrial Power in the U.S., 1780-1930: Vol 3: The Transmission of Power, Louis C. Hunter and Lynwood Bryant (1991)

Modern Engines and Power Generators; a Practical Work on Prime Movers and the Transmission of Power, Steam, Electric, Water and Hot Air — Volume One, R. Kennedy, 1905

Modern Engines and Power Generators; a Practical Work on Prime Movers and the Transmission of Power, Steam, Electric, Water and Hot Air — Volume Six, R. Kennedy, 1905

Power and Power Transmission, E.W. Kerr, 1908

Remnants of Early Hydraulic Power Systems (PDF), J.W. Gibson, 3rd Australasian Engineering Heritage Conference 2009

L’eau à Genève et dans la région Rhône-Alpes: XIXe-XXe siècles, Serge Paquier, 2007

L’eau des villes: Aux sources des empires municipaux, Géraldine Pflieger, 2009

Revue technique de l’Exposition universelle de 1889, Section II, récepteurs hydrauliques (PDF), 1893

Revue technique de l’Exposition universelle de 1889, Volume 9. Septième partie. Mécanique générale. Machins outils. Hydraulique générale. Travail du bois. Travail des métaux. Machineries industrielles, 1893

L’usine des forces motrices de la Coulouvrenière à 100 ans: 1886-1986, Services industriels, 1986

Waterdruk in Antwerpen. Een stroom van elektriciteit", Dirk De Vleesschauwer and Noël Kerckhaert, 1993

Kroniek van de stroomverdeling van Antwerpen-stad tot de Rupelstreek tot de Eerste Wereldoorlog, Geschiedkundige Studiegroep Ten Boome. (website)

Het Zuiderpershuis, een monument. Brochure bij de tentoonstelling n.a.v. Open Monumentendag 2010 (PDF), Steunpunt Industrieel en Wetenschappelijk Erfgoed, 2010.

The Centrifugal Pump, Turbines, and Water Motors, Including the Theory and Practice of Hydraulics, Charles Herbert Innes, 1898

Metropolitan Works: Collected Papers on London History, Ralph Turvey, date unknown.

Hydraulic Power Company, The Vauxhall Society, 2012 (website)

London Hydraulic Power Co, Grace’s Guide, date unknown (website)

Hydraulic Power, NSW HSC Online (website)

The Transmission of Power by Compressed Air, Robert Zahner, 1890

Water Engines, The Museum of Retrotechnology, 2011 (website)

The History of Cranes (The Classic Construction Series), Oliver Bachmann,1997.

On the employment of a column of water as a motive power for propelling machinery, William Armstrong, 1840

Power from the Tap: Water Motors

Mon, 09 Sep 2013 00:00:00 +0000

A late nineteenth-century water motor with one side of the casing removed. Image: [Old Pelton](http://www.oldpelton.net/).

Few people in the western world realize that they have an extra power source available in their household, workshop or factory: tap water.

Just before the arrival of electricity at the end of the nineteenth century, water motors were widely used in Europe and America.

These miniature water turbines were connected to the tap and could power any machine that is now driven by electricity.

Power from the tap

Water has been the main inanimate source of mechanical power from antiquity right up to the beginning of the twentieth century. Although most water wheels were located at the banks of the river (or in the river itself), some were set up at considerable distances from a water source. This was made possible by the introduction of hydraulic power transmission—the process by which water from a stream is led through artificial watercourses to water wheels built on the land.

To support hydraulic power transmission, man-made channels (“power canals” or “aqueducts”) could be dug into the earth or carved out of the rocks (“ditches”). They could also be elevated structures whose walls were raised above the surrounding terrain (“flumes”). Water reservoirs formed by dams could be integrated into these power transmission networks, regulating water flow, providing power storage for times when water was running low, and increasing the “head” or fall of water for a vertical overshot water wheel. The use of power canals increased throughout the medieval period and became widespread during the 1500s.

In the mid-nineteenth century, many European and American cities introduced a more sophisticated water distribution system: the public water supply. Although this introduction was an answer to health concerns (it had become clear that reoccurring epidemics were the consequence of drinking contaminated water), it became quickly obvious that the potable water sent through the pipelines of the public water supply could also provide motive power.

Waterwheels were still the most important source of mechanical power in the early days of public water mains. Most European and American cities had running water before they had electricity, so there was a market for a compact power source that could be used in the city, as an alternative to steam engines (which were too expensive, too dangerous and too unpractical to operate on a small-scale) or hand and foot powered machines.

Late nineteenth-century water motors. Images: [Smokstack](http://www.smokstak.com/forum/showthread.php?t=19878) and [Old Pelton](http://www.oldpelton.net/).

The town mains were no different from the hydraulic power transmission systems built in earlier times. In public water supply systems, traditional reliance on geological features as a head for the hydropower cycle is replaced by the use of a water tower. Water is pumped into an elevated reservoir, which could be on a hill or on top of a specially built water tower (a combination of both is also possible).

The height differential between the water level in the reservoir and the water level in the mains determines the pressure of the water. For every 10.20 cm of elevation, a water column produces 0.145 psi (pounds per square inch) of pressure. To produce 70 psi of pressure at street level, a water tower must be 50 m tall.

It became quickly obvious that the potable water sent through the pipelines of the public water supply could also provide motive power.

In the town mains, the role of the aqueducts or power canals is taken over by a much more intricate network of pipelines. This prevents debris from entering the water and makes uphill water transport easier. Water piping technology was used in some ancient civilizations, but the nineteenth-century systems introduced some lasting innovations.

First of all, thanks to the screw type tap (which was patented in 1845), the water supply could be easily regulated. Second, the water could be further distributed inside individual buildings, often reaching multiple rooms at several floors. At any of these spots, all you had to do to receive motive power from the town mains was to connect a small water turbine to the tap. This is exactly what happened.

Water Powered Household Devices

In Europe, small motors using the public water supply appeared in the 1840s. In the US, they came into extensive use in the 1870s and 1880s. A water motor consisted of a small water turbine that was suspended in a metal casing. The diameter of the turbine runner could be anywhere between from 20 to 90 cm.

A 1906 advertisement for a typical American water motor.

A hydraulic dynamo. Image: [The Museum of Retrotechnology](http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/watermotor/watermotor.htm).

The smallest water motors were used to run sewing machines, jigsaws, fans, and other similarly mechanized items. The somewhat larger water motors were recommended for operating coffee grinders, ice cream freezers, jeweler’s and locksmith’s lathes, grindstones, church organs, or drug and paint mills. The largest water motors were used to run elevators or circular saws. In water powered washing machines, the water that was needed to wash the clothes was capable of providing power to the machine simultaneously.

Water motors operated machinery by means of a mechanical power transmission, similar to old-fashioned wind, water, and pedal powered machines from that era. The shaft of the water turbine was either equipped with a belt pulley to which different machines could be attached, or it drove one machine directly.

At the end of the nineteenth century, water motors were also used to power electrical devices, especially radios and light bulbs. In this case, the water motor drove a dynamo that produced electricity on the spot. Compact units consisting of a small water turbine directly coupled to a dynamo were commercially available.

Output and Efficiency of a Water Motor

Most water turbines derived pressure by extracting energy from the impulse of moving water as opposed to generating energy via weight, as was the case with most water wheels and some other water turbines. A major innovation was the Pelton wheel, which was invented in 1878.

This water turbine consists of a series of cups fastened at equal intervals around the periphery of a circular disc (the “runner”). The water enters the casing through an inlet pipe, where it is forced through a nozzle which reduces its volume and increases its velocity, after which it is directed to the cups. By changing the nozzle which influences this fluxuation in pressure, the power obtained from a wheel could vary. The exhaust water is dropped out of the bottom of the casing, or led away by an outlet pipe.

The efficiency of a Pelton wheel is not dependent on its size, which makes it especially attractive for smaller powers.

The Pelton turbine is especially well suited for use in combination with the town mains, due to the fact that it requires a high head and a low water flow. A Pelton wheel is up to 90% efficient, which is comparable to the efficiency of a large, modern electric motor. Unlike steam engines, electric motors, and most other water turbines, which become less efficient as they become smaller, the efficiency of a Pelton wheel is not dependent on its size, which makes it especially attractive for smaller powers.

A water-powered sewing machine. Image: Knight's American Dictionary (1881).

Water turbines (such as the Pelton wheel) are much more compact than water wheels, which makes that a small motor can deliver more energy than one would suspect. The maximum power output of a water motor is determined by two factors. The first is the prevailing water pressure and the second is the water flow rate, which is defined by the pipe diameter and the velocity of the water. The latter factor is rather fixed for narrow pipes, because at velocities above 8 km/h friction becomes problematic.

Water pressure in the town mains is typically between 40 and 70 psi (2.75 to 4.8 bar), and was closer to 70 psi in the nineteenth century. With a water pressure of 70 psi and a pipe diameter of 1.25 cm (a typical size for individual branch lines running to the taps), the maximum power output of a water motor is 0.33 horse power (or 243 watts of mechanical power). Even after you take into account the efficiency loss in the motor, this is quite a lot of power: Two to three times as much as a human operating a pedal powered machine can sustain for an hour or longer.

Water Use

Water motors supplied a need almost entirely unmatched by other new motors from that time, and they exploited a source of energy readily available from centralized systems already built in most urban areas. However, at least in the United States, their succes was short-lived. When electric motors and gasoline engines became available, the water motor lost its attraction. In 1900, the amount of water motors in the US (an estimated 30,000 motors aggregating 26,000 horse power) was about one-fifth of the amount of gasoline engines and one-tenth of the amount of electric motors. Source: Hunter 1991.

At the end of the nineteenth century, water motors were also used to power electrical devices, especially radios and light bulbs

The main drawback of water motors was their very high use of potable water. Using a 1.25 cm diameter pipe and a pressure of 70 psi, a water motor consumed 30 litres of water per minute for a power output of 243 watts. This means that it took 7,440 litres of water to produce 1 kWh of mechanical energy. To give an idea: People today in the west consume less than 500 liters of potable water per day, and they consume at least 5 kWh of electric energy per day.

A water powered fan. Found at [Smokstak](http://www.smokstak.com/forum/showthread.php?t=27871).

If the water pressure dropped below 70 psi, a water motor’s power output decreased with it, while potable water consumption remained the same. The minimum pressure in the public water supply was (and still is) 20 psi (1.4 bar). Below that value, there is a risk of contamination because polluted water could enter the mains through leaks in the pipes.

If you were unlucky and you got a water pressure of just 20 psi, motor output would have been limited to a much less impressive 0.09 hp (67 watt). You could have chosen to restore the power output by increasing the pipe diameter, but that would have further increased the consumption of potable water.

There are many reasons why the water pressure in the town mains could be lower than 70 psi: adoption of a lower water pressure by a company, leaks in the pipelines, structural location of consumer residences in relation to the water tower, or use of a water motor on a higher floor. Water pressure drops by 10 psi per mile of pipeline. Water pressure is generally higher when it enters the house than when it comes out of the tap: It will decrease with every bend in the pipelines, and about 5 psi of pressure is lost each time you go up one floor.

Irregular Water Pressure

Water consumption was further increased by the irregularity of the water pressure. The use of a water tower is advantageous from an energy efficiency viewpoint, because you can create water pressure with low capacity pumps. The pumps only have to meet average demand. A higher than average demand (for instance, when everybody takes a shower in morning) can be dealt with by a decreasing water level in the tower. The reservoir will be filled again when demand is lower than average (mostly at night).

On the other hand, if you choose to create water pressure by pumping water directly into the mains (a modern approach that is gaining popularity), you need high capacity pumps that can meet peak demand, and they will be running inefficiently most of the time.

While the use of water motors in the US came to an end early in the twentieth century, the Europeans took hydraulic power transmission one step further

Irregular water pressure is not a problem for the distribution of potable water, but it is very disadvantageous for the use of water motors. If the water level in the tower decreases, so will the water pressure in the pipes. To insure enough motor output in the event of lower water pressures, water motors had to be larger and use larger diameter pipes than strictly necessary, further increasing the use of water, and wasting energy. Irregular water pressures lower the energetic efficiency of a water motor because it achieves its highest efficiency only when it is optimally adjusted to the prevailing water pressure.

A water-powered egg-beater. Images: [Smokstak](http://www.smokstak.com/forum/showthread.php?t=114931).

In Search of a Better Solution: the Hydraulic Accumulator

As we have mentioned before, the maximum power output by a water motor is determined by two factors: Water pressure and water flow. Increasing the pipe diameter (and thus the flow rate and water use) is only one way to increase the power capacity of a water motor. The other way is to increase the water pressure, which yields much more interesting results. For example, we could produce much more energy with much less water.

With a water pressure of 700 psi (48 bar), which equates to ten times the pressure in the public mains, a water motor connected to a 1.25 cm pipe could produce a power output of 3.3 horse power (or 2,500 watts of mechanical energy). That’s ten times more power for the same 30 litres of water per minute (or ten times less water use for the same power). To create a water pressure of 700 psi, it would be mandatory to build a water tower of almost 500 meters tall. Unfortunately, this is not practical to build.

While the use of water motors in the US came to an end early in the twentieth century, the Europeans found a solution for the high water use of water motors and took hydraulic power transmission one step further. Firstly, they set up special power networks which distributed water under pressure for motive power purposes only. This eliminated the need to use potable water. Secondly, Europe switched to a much higher (and regular) water pressure, which was made possible by the invention of the hydraulic accumulator.

Read part two: Power Water Networks.

Sources:

A History of Industrial Power in the U.S., 1780-1930: Vol 3: The Transmission of Power, Louis C. Hunter and Lynwood Bryant (1991)
“Water Motors”, The Museum of Retrotechnology
“Old Pelton”, website.
Efficiency Improvement of Pelton Wheel and Cross Flow Turbines in Micro Hydro Power Plants: Case Study.
Water Wheel Model: Water Motor.