Our Alternatives to Fossil Fuels

Since early recorded history, people have been harnessing the energy of the wind.

Wind energy propelled boats along the Nile River as early as 7000 BP. By 2200 BP, simple windmills in China were pumping water, other windmills with woven reed sails were grinding grain in Persia and the Middle East.

Wind is actually a form of solar energy, when you think about it.

Wind can be used to generate mechanical energy (when you can use kinetic, or potential energy to do something physical) and electrical energyThe Betz Law

There is the little piece of bad news called the Betz' law. Back in 1919 a German physicist named Albert Betz figured out that the most you can possibly get out of wind turbine is around 59% of the power in the wind. This is an unassailable bit of physics.

First, wind speeds must exceed 12 mph in order for the turbine to even turn

• This rotates the shaft which runs through the housing nacelle

• Wind turns the rotor (blades)

• Inside the gearbox, the slow rotation is switched to a higher speed through the work of gears• The brake slows it if the wind is blowing too fast.

• The generator turns the mechanical energy into electricityA battery stores the energy for

future use.

Good

Excellent

Poor

Marginal

This was the first wind farm in Texas. The Texas Wind Power Project, located in Culberson County in West Texas, has 112 wind turbines capable of generating 35 megawatts of electricity -- enough to power 12,000 to 15,000 homes.

Altamont Pass, just east of San Francisco, California…a very windy place!

Moving water can be used to produce mechanical and electrical energy

• Energy generated using water is known as hydroelectric power

The technology we use to harness hydroelectricity is…

The TURBINE!!!

The water turbine has an efficiency rating of nearly 90%!

Prior to the invention of steam power during the Industrial Revolution, wind and water were the only sources of widespread alternative power.

Water behind a dam represents potential energy, and when we release it through the penstock which ends with a turbine, it produces electricity.

Run-of-river Plants

Run of river plants rely on seasonal flow, and are sometimes unreliable.

When the sluice is closed, the reservoir represents a huge potential energy source.

The ocean can produce two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves. Since Oceans cover more than 70% of Earth's surface, this makes them the world's largest solar collector. Just a small portion of the heat trapped in the ocean could power the world.

Ocean thermal energy (OTEC) is used for many applications, including electricity generation. There are three types of electricity conversion systems: Closed, Open, and Hybrid.

• Closed-cycle systems use the ocean's warm surface water to vaporize a working fluid, which has a low-boiling point, such as ammonia.

• Open-cycle systems actually boil the seawater by operating at low pressures. This produces steam that passes through a turbine/generator.

• And hybrid systems combine both closed-cycle and open-cycle systems. Bonus***The steam condenses within the heat exchanger and provides desalinated water in both open, and hybrid systems.Since the cost of desalination for potable water is extreme, this would tend to kill two birds with one stone!

There must be a differential of 36° F (20° C) between floor and surface, for this option to work. This is why many OTEC platforms are located in tropical regions

OTEC platform

and pipeline in the Indian Ocean

•Water near the surface of one square mile of the ocean absorbs more heat from the sun than can be produced by burning 7,000 barrels of oil• The amount of solar energy absorbed per day in the tropical oceans is more than 10,000 times the amount of heat content of the oil consumed daily in the United States

• Imagine what the development of this technology would mean to OPEC (organization of the petroleum exporting countries) and economics in general

• Could be a viable, virtually inexhaustible supply of energy for future generations.

Ocean mechanical energy is quite different from ocean thermal energy. Even though the sun affects all ocean activity, tides are driven primarily by the gravitational pull of the moon, and waves are driven primarily by the winds. As a result, tides and waves are intermittent sources of energy, while ocean thermal energy is fairly constant. • Huge potential, but still experimental

Wave energy plants are small, but can be used to power warning buoys and lighthouses.

Tides can be harnessed to produce energyAn increase of 16 feet from low to high tide is needed to make this a viable, cost efficient option.

Tidal Energy Plant in Rance Estuary, FranceNewer models are more promising, however, tidal energy still doesn’t get the attention of wind and solar.

Barrage

Target Sites1. Siberia 12. Frobisher Bay, Canada2. Inchon, Korea 13. Wales, UK3. Hangchow, China 14. Antwerp, Belgium4. Hall’s Point, Australia 15. LeHavre, France5. New Zealand 16. Guinea6. Anchorage, Alaska 17. Gujarat, India7. Panama 18. Burma8. Chile 19. Semzha River, Russia9. Punta Loyola, Argentina 20. Colorado River, Mexico10. Brazil 21. Madagascar11. Bay of Fundy

Potential global sites for the use of tidal energy are extremely limited.