Hydropower Statistics

8/20/2019 Hydropower Statistics

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Hydropower


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Basics•this is a form of solar energy, as the sun drives water

evaporation from the ocean and winds carry the moisture

overland

•largest form of alternative energy used today (but only 2%

of global energy)

•industrialized countries have already tapped most of their

potential

•non-industrialized countries have most of the untapped

potential


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More basics

•Energy is converted from potential energy of water at some

height to other forms of energy as water drops... electrical

energy, mechanical energy....

•most water power is tapped via dams ... these hold enough

water to outlast periodic droughts and help to control flooding

•tidal power and wave power are an ocean forms of water

power


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Dams

Ultimate source of

power is the sun;

aided by gravity.

Solar energyevaporates water

Water falling on

land flows

downhill


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DamsTrap water flowing downhill and use the energy to turn turbines


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DamsTrap water flowing downhill and use the energy to turn turbines


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Dams

Height of dam and mass of water behind the dam

determine useful energy.

Efficiency is very good to excellent, generally 80 to

90% efficient in converting potential energy to

electrical energy.


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Costs of hydropower

•Hydroelectric is less than half the cost of fossil fuel derived

electricity.

•Note that the difference is in fuel costs.


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Hydropower: USHydropower is the #1 alternative energy source (but

biomass is close…)


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Hydropower:

US


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Global


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History of hydropower


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History of hydropower

Percentage of electricity from hydropower has declined

because the total amount of electricity produced has risen,

while electricity for hydropower remained nearly constant

Very little new hydropower added after 1975

Fluctuations in amount of hydropower after 1975 are due

variations in rainfall… climate


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Pros and Cons of hydropower

Pros:

•very clean•cheap

•flood control (primary reason for dams)

•multiple crops per year possible


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Pros and Cons of hydropower Cons:

•potential is limited globally to about 5 to 10% of energy needs

•dependability is an issue; prolonged droughts can cut electrical

production in half or more

•dams have drawbacks, including...

!loss of nutrient flow down river

!loss of sediment flow down river

!sedimentation behind the dam limits lifetime of the dam

flooding of scenic areas

!ecosystem below the dam is usually changed by having

colder, nutrient poor water

!aesthetics… loss of wild rivers


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Potential for hydropower

Industrialized world is about tapped out… maybe a

30% increase possible.

•currently 3% of total energy

•so 5% of today's energy is possible

•but as needs increase, this percentage goes down

•maximum of 3% is realistic


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Potential for hydropower

Developing world has more potential

•less than 1% of energy from hydropower

today

•could be as much as 10%

•as developing countries develop, however,

this percentage will drop, maybe 5% or less.


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Tidal power

Form of hydropower, but uses gravitational

energy, the pull of the moon on water

Concept is simple.

•build a dam across an inlet with a large tidal

range, or

•Build an enclosure that can be filled duringhigh tide

•Capture wave energy

•Use underwater propellers


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Tidal power: propeller systems


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Tidal power: wave systems

Air driven

Water driven


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Tidal power:

enclosuresPower can be generated

with both rising and

falling tide…


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Tidal power: issues

Tides cycle every 12.5 hours, so daily peak production

times and slack times vary, this causes a mismatch in

supply and demand, as industrial demand is high during

the day and low at night.

Tides vary seasonally and monthly as well.

The tidal range is about 2 feet to about 20 feet, thehigher the tide, the more useful the energy (remember

height of dam issue!).


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Tidal power: issues

Due to low height of water and slack times in

production, tidal dams produce about 1/3rd the power of

river dams.

Tidal power is cheap, less than 1/5th the cost of fossil

fuel power.

Problems include hindered ship traffic and ecological

damage to marine ecosystems and especially migrating

fish species.

Wave generating systems dependent on weather


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Tidal power: bottom line

Tidal power has a potential equal to only 1 to 2

percent of current global energy use, but , it is

useful in certain coastal settings, and is verycheap to produce and maintain.

Hydropower Statistics

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