SUPPORT THE WORK

# GetWiki

### hydropower

ARTICLE SUBJECTS
news  →
unix  →
wiki  →
ARTICLE TYPES
feed  →
help  →
wiki  →
ARTICLE ORIGINS
hydropower
[ temporary import ]
- the content below is remote from Wikipedia
- it has been imported raw for GetWiki

## Calculating the amount of available power

A hydropower resource can be evaluated by its available power. Power is a function of the hydraulic head and volumetric flow rate. The head is the energy per unit weight (or unit mass) of water.{{Citation needed|date= February 2019}} The static head is proportional to the difference in height through which the water falls. Dynamic head is related to the velocity of moving water. Each unit of water can do an amount of work equal to its weight times the head.The power available from falling water can be calculated from the flow rate and density of water, the height of fall, and the local acceleration due to gravity:
dot{W}_{out} =-eta (dot{m} g Delta h) =-eta ((rho dot{V}) g Delta h)
where
* dot{W}_{out} (work flow rate out) is the useful power output (in watts) * eta ("eta") is the efficiency of the turbine (dimensionless) * dot{m} is the mass flow rate (in kilograms per second) * rho ("rho") is the density of water (in kilograms per cubic metre) * dot{V} is the volumetric flow rate (in cubic metres per second) * g is the acceleration due to gravity (in metres per second per second) * Delta h ("Delta h") is the difference in height between the outlet and inlet (in metres)
To illustrate, the power output of a turbine that is 85% efficient, with a flow rate of 80 cubic metres per second (2800 cubic feet per second) and a head of 145 metres (480 feet), is 97 Megawatts:{{Refn|group="note"|Taking the density of water to be 1000 kilograms per cubic metre (62.5 pounds per cubic foot) and the acceleration due to gravity to be 9.81 metres per second per second.}}
dot{W}_{out} = 0.85times 1000 (text{kg}/text{m}^3) times 80 (text{m}^3/text{s}) times 9.81 (text{m}/text{s}^2) times 145 text{m} = 97 times 10^6 (text{kg} text{m}^2/text{s}^3) = 97 text{MW}
Operators of hydroelectric stations will compare the total electrical energy produced with the theoretical potential energy of the water passing through the turbine to calculate efficiency. Procedures and definitions for calculation of efficiency are given in test codes such as ASME PTC 18 and IEC 60041. Field testing of turbines is used to validate the manufacturer's guaranteed efficiency. Detailed calculation of the efficiency of a hydropower turbine will account for the head lost due to flow friction in the power canal or penstock, rise in tail water level due to flow, the location of the station and effect of varying gravity, the temperature and barometric pressure of the air, the density of the water at ambient temperature, and the altitudes above sea level of the forebay and tailbay. For precise calculations, errors due to rounding and the number of significant digits of constants must be considered.{{citation needed|date=July 2014}}Some hydropower systems such as water wheels can draw power from the flow of a body of water without necessarily changing its height. In this case, the available power is the kinetic energy of the flowing water. Over-shot water wheels can efficiently capture both types of energy.BOOK, S. K., Sahdev, Basic Electrical Engineering, Pearson Education India, 978-93-325-7679-7, 418, The water flow in a stream can vary widely from season to season. Development of a hydropower site requires analysis of flow records, sometimes spanning decades, to assess the reliable annual energy supply. Dams and reservoirs provide a more dependable source of power by smoothing seasonal changes in water flow. However reservoirs have significant environmental impact, as does alteration of naturally occurring stream flow. The design of dams must also account for the worst-case, "probable maximum flood" that can be expected at the site; a spillway is often included to bypass flood flows around the dam. A computer model of the hydraulic basin and rainfall and snowfall records are used to predict the maximum flood.{{citation needed|date=July 2014}}

## Use of hydropower

File:Garwnant Hydropower Scheme, Breckon Beacons, Cymru, (Wales).webm|thumb|A hydropower scheme which harnesses the power of the water which pours down from the Brecon Beacons mountains, WalesWalesFile:Higashiyama Botanical Garden Shishiodoshi 20170617.gif|thumb|A shishi-odoshishishi-odoshi

### Mechanical power

#### Compressed air hydro

{{See also|Trompe}}Where there is a plentiful head of water it can be made to generate compressed air directly without moving parts. In these designs, a falling column of water is purposely mixed with air bubbles generated through turbulence or a venturi pressure reducer at the high-level intake. This is allowed to fall down a shaft into a subterranean, high-roofed chamber where the now-compressed air separates from the water and becomes trapped. The height of the falling water column maintains compression of the air in the top of the chamber, while an outlet, submerged below the water level in the chamber allows water to flow back to the surface at a lower level than the intake. A separate outlet in the roof of the chamber supplies the compressed air. A facility on this principle was built on the Montreal River at Ragged Shutes near Cobalt, Ontario in 1910 and supplied 5,000 horsepower to nearby mines.JOURNAL, Maynard, Frank, November 1910, Five thousand horsepower from air bubbles, Popular Mechanics, 633,weblink

### Hydroelectricity

Hydroelectricity is the application of hydropower to generate electricity. It is the primary use of hydropower today.Hydroelectric power plants can include a reservoir (generally created by a dam) to exploit the energy of falling water, or can use the kinetic energy of water as in run-of-the-river hydroelectricity.Hydroelectric plants can vary in size from small community sized plants (micro hydro) to very large plants supplying power to a whole country. As of 2019, the five largest power stations in the world are conventional hydroelectric power stations with dams.Hydroelectricity can also be used to store energy in the form of potential energy between two reservoirs at different heights with pumped-storage hydroelectricity. Water is pumped uphill into reservoirs during periods of low demand to be released for generation when demand is high or system generation is low.Other forms of electricity generation with hydropower include tidal stream generators using energy from tidal power generated from oceans, rivers, and human-made canal systems to generating electricity.WEB,weblink Tidal Range & off Shore, File:Hydroelectric dam.svg|A conventional dammed-hydro facility (hydroelectric dam) is the most common type of hydroelectric power generation.File:Chief Joseph Dam.jpg|Chief Joseph Dam near Bridgeport, Washington, is a major run-of-the-river station without a sizeable reservoir.File:Nw vietnam hydro.jpg|Micro hydro in Northwest VietnamFile:Stwlan.dam.jpg|The upper reservoir and dam of the Ffestiniog Pumped Storage Scheme in Wales. The lower power station can generate 360 MW of electricity.

{{div col|colwidth=30em}} {{div col end}}

## Notes

{{Reflist |group="note"}}

## References

{{Reflist}}

{{Commons category}}
{{Footer energy}}{{Hydropower}}{{Natural resources}}

- content above as imported from Wikipedia
- "hydropower" does not exist on GetWiki (yet)
- time: 8:41pm EDT - Sat, Oct 19 2019
[ this remote article is provided by Wikipedia ]
LATEST EDITS [ see all ]
GETWIKI 09 JUL 2019
Eastern Philosophy
History of Philosophy
GETWIKI 09 MAY 2016
GETWIKI 18 OCT 2015
M.R.M. Parrott
Biographies
GETWIKI 20 AUG 2014
GETWIKI 19 AUG 2014
CONNECT