Hydroelectric Power: Risks and Rewards
Cheap Energy vs the Environment
The Case of Hydroelectric Power
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 hydro-production has leveled off and therefore becomes
an increasingly smaller percentage of the US energy budget.
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 hydro-potential in the US has been tapped
Why is Hydro so attractive?
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
720 watts x 24 hours/day x 30 days/month = 518 KWH/month.
Power generating capacity is directly proportional to the height
the water falls. For a fall of say only 3 m, 30 times less
electricity would be generated (e.g. 17 KWH/month) - but this
is just for a miniscule flow rate of 1 kg/sec.
Capacities of some large dams:
Grand Coulee 1942 6500 MW
John Day 1969 2200 MW
Niagara (NY) 1961 2000 MW
The Dalles 1957 1800 MW
Chief Joseph 1956 1500 MW
McNary 1954 1400 MW
Hoover 1936 1345 MW
Glen Canyon 1964 950 MW
Three Gorges 2000 18000 Mw
Pacific Northwest has 58 hydroelectric dams 63% of total
electricity generated. Most of the rest comes from coal fired steam plants
(e.g. Centralia Washington).
Note, the Trojan Nuclear Power Plant was relatively easy to shut down
because replacement power was immediately available.
Again the main advantages of Hydro are a) its renewable and b)
there is a lot of energy available:
Some Real Disadvantages:
Dams are frequently located upstream from major population centers:
Hydroelectric Power - The Risks:
- 1918--1958: 33 Major dam failures resulting in 1680 documented
- 1959--1965: 9 major dams failed throughout the world
- 1976: Teton Dam failure in Idaho
- Most of the dams on the Colombia have been built since 1950
and are not close to their failure points
- The Salmon Problem:
- Extremely Emotional Issue --> icon of the PNW
- Some Federal Dam Licenses can now be lost because of
salmon migration problems
- Some studies suggest Federal dams are mostly responsible
for drop from 16 million to 300,000 wild fish per year
- Actual Salmon Count data is available for these dam sites:
- Estimated that to improve migration, utility rates will
rise in the PNW by 8%
- There are lots of other factors at work as well:
- El Nino
- Aggressive Fishing
- Poor logging practices and increased soil erosion
Note that reservoirs offer expanded habitat for geese, pelicans,
eagles, osprey. They also help with flood control thus minimizing
soil erosion in the watershed.
Adverse effects of dams on salmon:
- migratory barrier
- killed in turbines (especially young ones swimming downstream)
- super-saturation of air in water (high pressure of water falling
down forces air into the solution)
- reduced oxygen content if river flow is reduced (summer) due
to separation of warm and cold water; cold water doesn't mix to
be aerated (this is mostly a problem in the Tennessee Valley)
- Build fish "passages" to direct them towards tributaries
this has proven successful for trout in Oregon
- Better turbine design and screen systems can help eliminate
fishkill on the downstream migration
- Minimize turbulence in the operation of the turbine
- Have better flow control
How will potential lost power be compensated for?
- energy conservation?
- sale of hydro to the US by Canada?
- Import of Natural Gas (from Canada) for new generation of gas-fired
- Coal-fired plants?
Overview of Hydropower and the Issues
The Columbia River Salmon Passage model (CRiSP)