Uses of Hydropower





Hydropower is the harnessing of energy from flowing water and its use dates back thousands of years. Most flowing water is caused by the cycle of evaporation and condensation driven by the Sun. While hydroelectricity is what most often comes to mind when people think about hydropower there are many other uses of this energy source.

Irrigation

Level basin flood irrigation of wheat in Yuma, AZ, USA. Image by USDA.

Level basin flood irrigation of wheat in Yuma, AZ, USA. Image by USDA. License: US PD

Ancient Egypt was one of the first civilizations to use hydropower in the form of irrigation. Large flat basins were constructed next to the Nile river with simple sluices that could divert some water into the basins at the peak of the floods.[1] This had the benefit of allowing storage of water year round to grow crops in the dry season. Water was also circulated every 40-60 days when the sediment had settled bringing fresh nutrients to the soil. Today irrigation is still of great importance to agriculture worldwide. Often pumps are used which are powered by electricity, gasoline, or diesel but many areas still use drip irrigation from suspended water sources, basins or flood plains, and even condensation.

Water Clocks

Elephant water clock from Al-Jazari's manuscript. Image by Al-Jazari.

Elephant water clock from Al-Jazari's manuscript. Image by Al-Jazari. License: US PD

One interesting use of hydropower is in telling the time by powering clocks. Water clocks use the flow of water through a precise opening to calculate the passage of hours. These ranged from simple cups for households to large mechanical devices mounted on buildings or carried by royal processions. Elaborate gearing systems allowed for more intricate features like sounding on the hour and displaying the time using other gadgets to hide the inner working of the clock. One of the most sophisticated early clocks was Al-Jazari’s castle clock built in the 12th century. This water clock could be adjusted daily to account for the hours of specific days, showed the passage of lunar and solar cycles, and displayed a show involving mannequins at every passing hour.[2]

Water Hydraulic Power Network

Out of service Waping Hydraulic Power Station pumps. Image by Fin Fahey.

Out of service Waping Hydraulic Power Station pumps. Image by Fin Fahey. License: CC BY-SA 2.5

Similar to our current electrical infrastructure water was once used in hydraulic power networks. Pumping stations pumped water through pipes to machinery operated by this pressurized water. One of the largest adopters of this technology was Britain starting in 1840 through the early 1900s. Britain’s hydraulic power network was shut down by 1970 with only a single station kept running for historical purposes. Machinery powered by this hydraulic power grid included cranes, dock gates, elevators, industrial machinery, and even electrical generators for lighting. Some of the last constructed pumping stations generated 1,120 pounds per square inch of pressure driven by six 200 horsepower (150 kW) steam engines.

Compressed Air Hydropower

Diagram of compressed air hydropower. Image by Renewable Energy Resource.

Diagram of compressed air hydropower. Image by Renewable Energy Resource.

Falling water can be harnessed to produce compressed air. Water diverted into a shaft falls deep underground mixing with air and creates a seal in the shaft to prevent air from escaping. Air and water separate out in a large reservoir. Two shafts lead back to the surface with one positioned at the top of the reservoir for air and the other submerged below the water. Pressure created forces the water to flow up and out of the system back into the river or other source of water at a lower elevation. Compressed air fills the other shaft and pipes connected to factories where machinery converts it into useful work. One such system generated 5,000 horsepower located in the mining area of Cobalt in Canada.[3] Known as Rugged Chutes it remains the largest use of compressed air hydropower to date.

Water Wheels

Persian water wheel used for irrigation in Nubia, 1864. Image by David Roberts.

Persian water wheel used for irrigation in Nubia, 1864. Image by David Roberts. License: US PD

Water wheels are typically a series of paddles arranged on a wheel that is placed in flowering or falling water. This produces mechanical energy harnessed by an attached shaft. Turning this shaft could also raise water using buckets instead of paddles. Ancient Greeks and Romans were the first to use water wheels and are credited as being the inventors.[4] Historically water wheels were used to either mill grain or lift water for irrigation. This technology was also used for draining dry docks, measuring distance traveled by ships, in siege warfare for submerging mines, and as a way to lower enemy morale. This method of harnessing hydropower was the precursor of modern hydroelectricity.

Hydroelectricity

Hoover Dam located in Nevada, USA. Image by Mikano.

Hoover Dam located in Nevada, USA. Image by Mikano. License: GNU FDL

When most people think of hydropower what comes to mind is likely hydroelectric dams. Hydroelectric power plants using dams block waterways such as rivers and use the large reservoirs created to power turbines that generate electricity. Hoover Dam in Nevada, USA has a significant impact on Lake Mead which is flooded by blocking the Colorado river. Other hydroelectric systems are pumped storage plants which use excess electricity during low demand periods to pump water into a higher elevation reservoir, run of the river hydroelectricity uses no reservoir and simply generates as much electricity as the flow of the water provides, underground generators are used at waterfalls both man-made or natural, and microhydroelectric is used for residential/small commercial scale.[5]

Wave Power

Pelamis wave generator rising out of a wave. Image by P123.

Pelamis wave generator rising out of a wave. Image by P123. License: US PD

Wave power harnesses the energy of ocean waves to generate electricity. Surface based generators produce electricity from hydraulic pressure created as the system bends in waves. Power buoys float on the surface and are tethered to the ocean ground by a cable. Waves lift the buoy up until the tether stops it while an outer floating case continues to rise. Magnets are mounted on the floating outer case and a coiled copper wire circuit is around the inner “core” of the buoy. Another cable transmits these generated electricity to a central distribution hub. Other uses of wave energy are surfing and wave powered boats.

Tidal Power

SeaGen, world's first commercial tidal generator. Image by Fundy.

SeaGen, world's first commercial tidal generator. Image by Fundy. License: CC BY-SA 3.0

Tidal power is a source of energy that is fueled by tidal changes caused by the changing position of the Moon. Locations for optimal tidal power depend on the height between low and high tides and if there are multiple tides in a day.[6] This energy sources is taped using a variety of technologies. Tidal stream generators are simply vertical columns equipped with generators powered by the tides. Tidal barrages are built across rivers or other ocean inlets and act similarly to hydroelectric dams. Many theoretical tidal energy power plant designs exist that haven’t been constructed due to the high initial construction costs. One such concept would use ocean currents anchoring turbines to the seabed in areas like the Gulf stream.

Osmotic Power

Osmotic power is energy generated from pressure created between bodies of water with different salinity. Three methods are used to harness energy from this pressure difference. Pressure retarded osmosis uses multiple tanks holding water of different salinity to create pressure differences that drive a turbine. There is only one osmotic power plant which is located on the Oslo fjord in Norway and it uses pressure retarded osmosis technology.[7] Reversed electrodialysis is another method that uses alternating anion and cation membranes to generate electricity by acting as a battery. Capacitive method generates electricity due to a gain in energy from charging electrodes in saline water and discharging in fresh water. This method has only been used in a laboratory setting for now but holds a lot of promise.

Sources:

1. Ancient Irrigation
2. Al-Jazari and the Castle Clock
3. Popular Mechanics, Nov. 1910
4. The Physics of a Water Wheel
5. Hydroelectric Brochure
6. Diurnal and Semi-dirunal internal tide energy flux
7. World’s First Osmotic Power Plant

Sponsors:

Leave a Comment

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>