Hydroelectric PowerJackie Richards1 & Greg Samuels2

1Department of Chemical and Biochemical Engineering, 2Department of Mechanical and Industrial Engineering,

52:133:001 Engineering Analysis of Alternative Energy Systems, http://wiki.uiowa.edu/display/greenergy/,

The University of Iowa

History BC:

700 BC: Egyptian water wheel BC-1000 AD:

762 AD: Saxons use water mill

1800’s: 1824 AD: Scottish cotton mill uses water wheel, gearing achieves 9000 RPM! 1880 AD: Michigan chair factory generates its own electricity using water turbine 1881 AD: Niagara falls hydroelectricity powers street lamps 1886 AD: 45 hydroelectric plants in U.S. and Canada

1900’s: 1907 AD: 15% of electricity generated in U.S. from hydropower 1920 AD: 25% of electricity generated in U.S. from hydropower 1929 AD: U.S.’s first pumped storage facility completed in Connecticut 1937 AD: U.S.’s first federally regulated hydroelectric facility (Bonneville Dam) in Oregon 1940 AD: 40% of electricity generated in U.S. from hydropower 1974 AD: Fish and Wildlife Coordination Act ensures environmental considerations accounted for in federal

hydroelectric facilities 1983 AD: Largest hydroelectric power plant at this time finished in Brazil at 12,600 MW

2000’s:  2008 AD: Hydroelectricity provides about 7 percent of U.S.’s electricity 2011 AD: Three Gorges Dam (China) expected to produce 22,500 MW upon installation of additional generators

Hydrological Cycle

Large-body water motion is governed by the hydrological cycle.

As long as water is available, this cycle is renewable.

How a Hydroelectric Facility WorksKinetic energy is converted to mechanical energy in turbine

machinery and then converted to electrical energy and distributed using power lines.

Power Generation Primary equation for

determining hydroelectric facility electrical output:Pactual = (ηtotal) ρ Q H g

ηtotal = combined efficiency of power generation including: Water energy extraction

efficiency Mechanical efficiencies Electrical efficiencies

ηtotal = 80-95%

Types of Hydroelectric Plants

ImpoundmentMost common type.

Uses a dam to store water in a reservoir (consistently reliable water source).

Water released from the reservoir flows through the system and turns the turbine.

Conventional flow: uses single-directional water flow.

Types of Hydroelectric Plants

DiversionFunnels a portion of river flow to

a turbine system.

Complex system of pipes used to achieve flow diversion (no dams).

Conventional flow.

Less environmental impact because it is not blocked flow, just redirecting a portion of it.

Depends on river flow rate (better on a small scale).

Types of Hydroelectric Plants

Utilizes upper and lower reservoirs and a reversible turbine to pump water in both directions (Unconventional flow).

Facility generates power during peak electrical hours (upper to lower), stores water during off hours (lower to upper).

Often used in conjunction with nuclear plants to help regulate electrical output.

Pumped Storage

Size Designations for Hydroelectric Plants

Large Hydropower 30+ MW

Small Hydropower 100 kW-30MW

Micro HydropowerLess than 100 kW

Advantages of Hydroelectric PowerHydroelectric plants can be constructed anywhere there is a

water source; so it is a secure form of domestic energy.

It is a renewable source of power.

No pollution is created by the process.

There are no carbon dioxide emissions.

Cheap to maintain a facility (about ¢0.7 per kWh), which keeps cost of electricity low to consumers

Extremely efficient conversion of hydropower to electricity

Disadvantages of Hydroelectric Power The initial construction of a plant requires a large capital cost and a lot of

time ($1700-$2300/kW).

The pay back period is 10 or more years depending on the size of the plant.

Hydroelectric dams impact the migration and population of fish because they can become obstructed in the dam.

Power plants affect the temperature of the water; adversely affecting the native plants and animals in the water and on land.

The construction of dams and reservoirs may require the destruction of homes and relocation of people.

The use of power plants is dependent on water availability (climate).

Failure of large hydroelectric facilities (dam breach) results in catastrophic damage.

Hydroelectricity in the U.S.Current U.S. hydroelectric generation amounts

to about 95,000 MW, which is enough to power 28 million households.

Hydroelectricity in the U.S.

Hydroelectricity in the U.S.

More than 75% of U.S.’s hydroelectric generation occurs in Montana, Oregon, Idaho, California, and Washington

Grand Coulee Dam, WA Largest hydroelectric facility (and largest concrete structure) in U.S. 6809 MW installed capacity

The Future of Hydroelectric Power in the U.S.

U.S. D.O.E. entire 50 states have ~30,000 MW of undeveloped potential hydroelectric capacity.

Large scale hydroelectric facilities (30+ MW) economically unattractive:high capital costs long pay back periods, and extended construction times

Development of small scale (100 kW-30MW) and micro scale (less than 100 kW) hydropower facilities have promise in the future.

Questions?

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