1. Geothermal & Tidal Energy
Nuclear DOES NOT originate from the sun either
Renewable energy sources that do NOT originate from the Sun
 Fossil fuels, Solar, wind, biomass, hydroelectric DO

2. Geothermal Energy Energy that is generated deep within the Earth
The radioactive decay of elements amid the extremely high pressures deep in the interior of our planet generates heat that rises to the surface through magma and through fissures and cracks
Where this energy heats groundwater, spurts of heated water and steam are sent up from below
Terrestrial geysers and submarine hydrothermal vents

3. Hydrothermal vents- Chemosynthesis
Bacteria use energy stored in inorganic molecules (hydrogen sulfide H2S) to produce carbohydrates
CO2 + 4H2S + O2 -> CH20 + 4S + 3H2O
Photosynthesis: CO2 + 6H2O + sunlight-> C6H12O6 + 6O2

4. Iceland
Built from magma that came to the ocean’s surface & cooled from the Mid-Atlantic Ridge
Divergent boundary
Plates spread away from each other
Because of the geothermal heat in this region, volcanoes & geysers are numerous in Iceland
Term geyser is Icelandic.

5. Geothermal energy for heating & electricity
Uses the energy of naturally heated underground water and steam for direct heating and to turn turbines and generate electricity
Geothermal energy can be harnessed directly from the geysers at the surface, but most often wells have to be drilled down hundreds or thousands of meters toward heated groundwater

6. Geothermal energy for heating & electricity
Magma heats groundwater
Where natural fissures or cracks appear, heated water or steam surfaces in geysers or hot springs
Wells tap underground heated water or steam to turn turbines & generate power
Steam is cooled, condensed, and water is injected back into the aquifer to maintain pressure

9. Geothermal energy for heating & electricity
Hot groundwater can also be used directly for heating homes, offices, and greenhouses; for driving industrial processes; and for drying crops
Iceland started using geothermal energy in the 1940s and heats 86% of homes through direct heating with piped hot water
This is a cheaper and more efficient alternative to fossil fuels, but is only feasible in areas where geothermal energy sources are available and near where the heat must be transported

12. Geothermal ground source heat pumps (GSHPs)
GSHPs use thermal energy from near-surface sources of earth & water
The pumps heat buildings in the winter by transferring heat from the ground into buildings
They cool buildings during the summer by transferring heat from the buildings to the ground
Highly-efficient because heat is just being moved from place to place
More than 600,000 GSHPs are used to heat U.S. residences
Soil varies in temperature from season to season less than air does

13. Geothermal Power Plants
Geothermal power plants may not be capable of operating indefinitely (theoretically renewable)
1. If the plant uses heated water more quickly than groundwater is recharged, the plant will eventually run out of water
Happened in Napa Valley, California
They began injecting municipal wastewater into the ground to replenish the supply
More & more geothermal power plants throughout the world are now injecting wastewater
2. Patterns of geothermal activity in Earth’s crust shift naturally over time
Areas that produce hot groundwater now may not always do so
The Geysers in Napa Valley, CA- 1st generator built in 1960

14. Use of geothermal power is growing
In the U.S. it provides enough power to supply electricity to over 4 million people
“The Geysers” in Napa Valley, CA is the world’s largest geothermal power plant
Generating capacity has decreased by 50% since 1989
Still provides enough electricity to supply 750,000 homes
Geothermal energy provides less than 0.5% of the total energy used worldwide
It provides more power than solar and wind combined, but only a small fraction of the power from hydropower and biomass
Japan, China & U.S. currently lead world in use of geothermal power

15. Geothermal Power Reduces emissions relative to fossil fuel combustion
PRO’s
CON’s
Reduces emissions relative to fossil fuel combustion
Does release variable amounts of CO2, CH4, ammonia & hydrogen sulfide
But they are in small quantities & geothermal facilities use filtering technologies to reduce these emissions
May not always be truly sustainable
Water of many hot springs is laced with salts & minerals that corrode equipment & pollute the air
This may shorten the lifetime of plants, increasing maintenance costs & add to pollution
Limited to areas where energy can be tapped
By one estimate- each megawatt of geothermal power prevents the emission of 7.0 million kg of carbon dioxide emissions each year

16. Geothermal Power
Many hydrothermal resources remain unexploited, awaiting improved technology & governmental support for their development

17. Ocean Energy Sources
Developing ways to use the kinetic energy from the natural motion of ocean water to generate electrical power

18. Ocean Energy Sources
The rising and falling of ocean tides occurs twice each day at coastal sites
Gravitational pull of moon
Differences in height between low and high tides are especially great in long, narrow bays
Ex. Alaska’s Cook Inlet & the Bay of Fundy between New Brunswick & Nova Scotia
These areas are best for harnessing tidal energy, which is done by erecting dams across the outlets of tidal basins

20. Tidal Energy
The incoming tide flows through sluices past the dam, and as the outgoing tide passes through the dam, it turns turbines to generate electricity
Some designs allow for generating electricity from water moving in both directions
Largest tidal energy facility- France
Has operated for over 40 years
Smaller facilities operate in China, Russia & Canada
Tidal stations release few or no pollutant emissions but they can have impacts on the ecology of estuaries & tidal basins

21. Pelagic zone

22. La Rance facility in France

25. Wave Energy
Wave energy can be developed at a greater variety of sites than tidal energy
This is done by harnessing the motion of wind-driven waves at the ocean’s surface & converting this mechanical energy into electricity
Many designs for harnessing this energy exist, but few have been adequately tested

26. Wave Energy Offshore facilities
Involve floating devices that move up & down with the waves
Wave energy is greater at deep-ocean sites, but transmitting the electricity to shore would be expensive
Coastal onshore facilities
Some of these designs funnel waves from large areas into narrow channels , from which water is then allowed to flow out, generating electricity as hydroelectric dams do
Other designs use rising & falling waves to push air into & out of chambers, turning turbines to generate electricity

29. Wave Energy
No commercial wave energy facilities are operating yet, but there are demonstration projects that exist in Europe & Japan
A third way of harnessing marine kinetic energy is to use the motion of ocean currents, such as the Gulf of Mexico.
Devices look like underwater wind turbines
Currently being tested in Europe

30. Ocean stores thermal energy
Each day the tropical oceans absorb an amount of solar energy equal to the heat content of 250 billion barrels of oil– enough to provide 20,000 times the electricity used daily in the U.S.
The ocean’s surface water is higher in temperature than its deep water
The ocean thermal energy conversion (OTEC) is based on this gradient in temperature

31. Ocean stores thermal energy
Closed cycle
Warm surface water is piped into a facility to evaporate chemicals, such as ammonia, that boil at low temperatures.
These evaporated gases spin turbines to generate electricity
Cold water piped in from the ocean depths then condenses the gases so they can be reused
Open system
Warm surface water is evaporated in a vacuum and its steam turns turbines & then is condensed by cold water
Because ocean water loses its salts as it evaporates the water can be recovered, condensed & sold as desalinized fresh water for drinking/agriculture
Research into OTEC systems has been done in Hawaii & Japan, but costs remain high and there is no facility that is yet commercially operational