Basics. this is a form of solar energy, as the sun drives water evaporation from the ocean and winds carry the moisture overland

Transcription

1 Hydropower

2 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

3 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

4 Ultimate source of power is the sun; aided by gravity. Dams Solar energy evaporates water Water falling on land flows downhill

5 Dams Trap water flowing downhill and use the energy to turn turbines

6 Dams Trap water flowing downhill and use the energy to turn turbines

7 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.

8 Costs of hydropower Hydroelectric is less than half the cost of fossil fuel derived electricity. Note that the difference is in fuel costs.

9 Hydropower: US Hydropower is the #1 alternative energy source (but biomass is close )

10 Hydropower: US

11 Global

12 History of hydropower

13 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

14 Pros and Cons of hydropower Pros: very clean cheap flood control (primary reason for dams) multiple crops per year possible

15 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

16 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

17 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.

18 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 during high tide Capture wave energy Use underwater propellers

19 Tidal power: propeller systems

20 Tidal power: wave systems Air driven Water driven

21 Tidal power: enclosures Power can be generated with both rising and falling tide

22 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, the higher the tide, the more useful the energy (remember height of dam issue!).

23 Tidal power: issues Due to low height of water and slack times in production, tidal dams produce about 1/3 rd the power of river dams. Tidal power is cheap, less than 1/5 th 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

24 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 very cheap to produce and maintain.