Basics of Hydroelectric Power
Hoover Dam and Lake Mead
Columbia River Drainage System
Historical Growth of Hydroelectric power:
- Currently Hydro power is 7% of the total US
Energy Budget. This has been going decreasing
- This varies considerably with region
in the US due to the availability of freely
- Dam building really was initiated in the 1930's as part of
a public works program to combat the depression
- Low cost per KWH (see below) caused exponential increase of dam
building from 1950-1970 (lots of this on the Columbia)
- Since 1970 hydroproduction has leveled off and therefore becomes
an increasingly smaller percentage of the US energy budget.
The Politics of the Three Gorges
Does the world have the right to tell China how to deliver increased
energy to its population?
Hydropower is a natural renewable energy source as it makes use
Hydropower production is sensitive to secular evolution of
weather; seasonal snowpacks, etc, etc. Long term droughts
(10 years or so) seem to occur frequently in the West
About 30% of the hydropotential in the US has been tapped
Why is Hydro so attractive?
- BECAUSE ITS CHEAP! for the consumer --> average price
in the PNW is around 4 cents per KWH --> this is 3 times less than
the national average!
- Low cost to the consumer reflect relatively low operating costs
of the Hydro Facility. Most of the cost is in building the dam
Energy density in stored elevated water is high:
So one liter of water per second on a turbine generates 720 watts
of power. If this power can be continuously generated for 24 hours
per day for one month then the total number of KWH per month is
- Assume water falls a distance of 90 meters
- Efficiency of conversion from potential energy to
electrical energy is 80%
- PE of 1 kg of water at 90 meters is:
PE = mgh = (1)(10)(90) = 900 Joules
- At a flow rate of 1 kg/sec this is 900 Watts (1 Watt =
1 Joule per second).
- 1 kg of water = 1 liter so 1 kg/sec = 1 liter/sec of flow
- We convert at 80% efficiency so we get 720 Watts of Power
for a flow rate of 1 liter/sec over a drop of 90 meters
720 watts x 24 hours/day x 30 days/month = 518 Kwh/month.
For Just One Liter !!!
Scale of the turbines in big dams is very large:
Hoover Dam Turbine Room
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