Published on EGEE 401: Energy in a Changing World (https://www.e-education.psu.edu/egee401)

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Hydropower

Electricity Generation from Renewable Sources

Before beginning our closer look at individual renewable energy sources used for electricity generation, let's frame the discussion with current data about actual electricity generation from these sources. How much electricity do you think we currently generate from renewable energy sources such as wind? solar? biomass? (Hopefully you remember from last lesson!) Based on ads we see on television, you'd think it is a lot, right? Here are some numbers, from the U.S. Energy Information Administration [1]. (Chart generated by course instructor using most recent full-year data.)

Consumption of Electricity Generation by Energy Source: 2011. See link below for text version
Figure 7.1: Consumption for Electricity Generation by Energy Source: 2016 (The category "Other" includes petroleum and other non-renewable energy sources.)
Click to here to view the text version
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Consumption for Electricity Generation by Energy Source: 2016
Energy Source Percentage
Coal 30.4%
Nuclear 19.7%
Natural Gas 33.8%
Hydro 6.5%
Wind 5.6%
Biomass 1.5%
Geothermal 0.4%
Solar 0.9%
Other 1.0%
Energy Information Administration, FAQ

Hydropower

Hydropower, or hydroelectricity, uses the motion of water to turn a turbine and generate electricity. The water may be in a moving river (run-of-the-river hydro), moving from higher to lower elevations through a specially constructed dam, or in the motion of ocean tides or waves. Hydropower is the most widely used renewable energy source for generating electricity.

The U.S. Geological Survey's (USGS) Water Science for Schools [2] describes a typical hydroelectric plant:

So just how do we get electricity from water? Actually, hydroelectric and coal-fired power plants produce electricity in a similar way. In both cases a power source is used to turn a propeller-like piece called a turbine, which then turns a metal shaft in an electric generator, which is the motor that produces electricity. A coal-fired power plant uses steam to turn the turbine blades; whereas a hydroelectric plant uses falling water to turn the turbine. The results are the same.

[Referring to picture, Hydroelectric Dam]

The theory is to build a dam on a large river that has a large drop in elevation (there are not many hydroelectric plants in Kansas or Florida). The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carry electricity to your home and mine. The water continues past the propeller through the tailrace into the river past the dam. By the way, it is not a good idea to be playing in the water right below a dam when water is released!

drawing of a hydroelectric dam. See text alternative for details.
Figure 7.2: Hydroelectric Dam
Text Version [3]
Credit: Tennessee Valley Authority

Reading Assignments

Visit Department of Energy, Energy Explained [4].

  • Under “Renewable Sources", read "Hydropower" and all subpages.

Even though it is an established technology, hydropower is still very much in the news. During a White House forum in Pennsylvania that I attended in 2009, the then U.S. Energy Secretary Steven Chu said, "Hydropower capacity in the United States could double with minimal impact to the environment," clearly dismissing the notion that U.S. hydropower production has peaked. Chu said the industry could add 70,000 MW of capacity by installing more efficient turbines at existing hydroelectric projects or at dams without power components, increasing the use of pumped-storage projects, and encouraging the use of run-of-the-river turbines. "We will be pushing this," Chu said. "We're not talking about a lot of large, new reservoirs. Just work with what we have and it's a massive amount of power." (source Hydroworld [5]):

Shortly thereafter, funding for new hydroelectric projects was announced. Between 2009 and 2011, consumption of electricity generated by hydropower in the USA grew from 2,539 to 3,171 trillion BTUs. (EIA, Total Energy [6])

Reading Assignment

Read 3-Year DOE Study Assessed Potential Hydropower Upgrades in the US [7].

Read Troubling Interdependency of Water and Power [8]

 


Source URL: https://www.e-education.psu.edu/egee401/content/p7_p2.html

Links
[1] http://www.eia.gov/tools/faqs/faq.cfm?id=427&t=3
[2] http://water.usgs.gov/edu/hyhowworks.html
[3] https://www.e-education.psu.edu/egee401/sites/www.e-education.psu.edu.egee401/files/image/lesson07/Hydroelctric_LD.html
[4] http://tonto.eia.doe.gov/energyexplained/
[5] http://www.hydroworld.com/index/display/article-display/6337973254/articles/hydro-review/volume-28/issue-8/-departments/breaking-news__hydro.html
[6] http://www.eia.gov/totalenergy/data/annual/showtext.cfm?t=ptb0804a
[7] http://dailyfusion.net/2013/05/3-year-doe-study-assessed-potential-hydropower-upgrades-in-the-u-s-7296/#
[8] http://www.nytimes.com/2015/04/23/business/energy-environment/troubling-interdependency-of-water-and-power.html?ref=topics