BESC 320 – Water and Bioenvironmental Science(22 Feb 2019)

Hydropower19% of Global electricity is from hydropower!(Atlas of Water, Vignette 21: Water for Energy)

Only 10% in US, accounting for 73% of renewable energy (http://powerscorecard.org)

HistoryHistoric uses of waterpower were to elevate water into aqueducts (by noria), and entering the industrial revolution to turn millstones or sawblades, for production of milled grains and lumber. Use of hydropower to make electricity goes back to the 1880s, but became huge with the Hoover Dam in 1931.

Global perspective—Installed megawatts:

WRI

Percent of power through hydro (see vignette 21 in your Atlas of Water):

Note major patterns—near mountain ranges, major rivers, others?

So water infrastructure is vast. Find a lake or river—stop it up—spin turbines with released water. How easy is it to find a lake in Texas? Interestingly, there are no natural lakes in Texas, except arguably Lake Caddo.

Here is a look at how dams work…

Here is a worthy video on dam mechanics: http://www.youtube.com/watch?v=Hu60nn-GFzQ (43s, in class)

The fundamental physics are:Q α Ah, where A=catchment area, h=head, Q=outflow. See example:

A – catchment area determines sustainable level of Q (output from penstock/pipe)H – head determines pressure (a function of depth, not volume) and with penstock diameter influences how pressure converts to flow (Q). More flow, more energy.Reflection: What other factors may influence energy production?...

Q=(70,000 km2 )(106m2

km2 )(0 .6myear

)(1 year3.15x107 s

)

¿1300 m3 /s

Advantages of dams: Tremendous power output Arguably, flood control Provide water reserves Provide recreation

opportunities

Problems with dams: Interfere with nature

o migratory species, upstream colonizations

o habitat loss (e.g. floodplain)

o alters temperature regime

potential amelioration by hypolimnetic releaseo altered flow dynamics (many species have particular requirements)

operators release water according to electricity needso alters sediment structureo alters floodplain dynamics

Interferes with peopleo displaces indigenous peopleso displaces landowners

sedimentation (dams fill with sediment over time—nontrivial) increased evaporative loss

Reflection: What secondary fixes may there be for some of the problems?Try the migratory species one...

Reminder—do not forget to examine links posted on course page regarding dams. Go to... link

Case study: Three Gorges Dam

The Three Gorges Dam in China is the largest dam in the world. Proposed in 1919, it has a long history. It was completed in 2003ish. It harnesses the power of the Yangze River and produces the energy of 18 nuclear power plants. However, the 395 square mile reservoir displaced 1.3 million people and changed forever the waterway’s ecosystem. The reservoir obliterates many sites of cultural and archaelogical interest. Reservoirs created by dams also increase evaporation, resulting in a loss of fresh, usable water. The weight of impounded water is being blamed for settling in the broader landscape, involving many unusual occurrences of landslides, etc.

Basic Statistics of the Three Gorges Dam ProjectDam Height: 185 ms (head of 175 m)Dam Length: 2.335 km Installed Power Generation Capacity: 22,500 MW (84.7 billion kWh) annuallyProject Investment: $ 24.65 billion (reported)1994.12.14 Official commencement of the Three Gorges Dam project2003.06.16 Permanent ship lock opened to navigation

2003.07.10 Power generating began with Generator No. 22006.05.20 Completion of concreting to the entire dam to 185m level2010.10.26 Water level reached 175m for the first timehttp://en.wikipedia.org/wiki/File:Yangtze_longitudinal_profile_upstream.JPG

Lest I fail to mention, the dam is built in a seismically active area.Visualize…

Water and human populationsMini Case Study—snail genetics across flow control device

Rob Dillon, College of Charleston, SC Assessed genetic diversity of snails in a river previous to road construction. Road constructed with concrete culvert interrupting river. Re-assessed genetics a few years later. Found marked structure above and below the culvert; essentially two

different populations. Unusual occurrence – a storm washed out the culvert. Reassessment showed genetics homogenized.

Note that major scale Hydro may remain de rigeur but small scale hydro may be an important part of energy security going into the future at all economic scales (developed and developing countries): e.g. …

http://www.internationalrivers.org/resources/tide-turns-on-unconventional-hydropower-1893

That article by Carrie Dolwick talked about tidal and other “alternative” hydropower. Below is a look at two designs for tidal generators (LUNAR energy—I should copyright this phrase!!!)

The lunar connection is explained well here: http://oceanservice.noaa.gov/education/kits/tides/tides02_cause.html A pared down version:

● The moon creates a gravitational “pull” on the Earth, including its massive seas. ● This pull from the view of a fixed spot on Earth rotates around the planet slowly in the direction opposite Earth’s spin.● If the moon were stationary, it would seem to have a 24 hour rotation schedule. Since it is moving in the same direction as spin, the realized lunar cycle is 25 hours long. (link, 1.5 min in class)● The sun also creates a gravitational “pull” on the Earth, including its massive seas. This pull is experienced on a 24 hour cycle due to Earth’s rotation relative to the sun.● From NOAA: “Although the sun is 27 million times more massive than the moon, it is 390 times further away from the Earth than the moon. Tidal generating forces vary inversely as the cube of the distance from the tide-generating object. This means that the sun’s tidal generating force is reduced by 3903 (about 59 million times) compared to the tide-generating force of the moon. Therefore, the sun’s tide-generating force is about half that of the moon, and the moon is the dominant force affecting the Earth’s tides.“

Inventions questions? Invention brainstorm... _____. –––––|