1. Wind Energy No waste - clean source of energy Biggest constraints: – Cost – Public resistance (NIMBY)  Few environmental problems  Kills birds and bats

2. Hydropower Most efficient energy source (90%) Most widely used form of solar energy – 19% of world’s energy Traditional hydropower – Suited only to large dams New technology – Utilize low flow systems

3. Hydropower

4. Other Indirect Solar Energy Ocean waves – Produced by winds – Has potential to turn a turbine- and create electricity Ocean Temperature Gradients – Use difference in temperature of surface and deep water to create electricity

5. Other Renewable Energy Sources Geothermal energy – Energy from the Earth’s interior for either space heating or generation of electricity Tidal Energy – Form of renewable energy that relies of the ebb and flow of the tides to generate electricity

6.  Enormous energy source  1% of heat in upper 10 km of earth crust is equal to 500x the earth’s fossil fuel sources Geothermal Energy From Hydrothermal Reservoirs – Created by volcanoes – Reservoirs used directly for heat or to generate electricity

7. Geothermal Energy From hot, dry rock Geothermal heat pumps – Use difference in temperature between surface and subsurface – Great for heating buildings – Expensive installation

8. Tidal Energy Typical difference between high and low tide is 1–2 ft – Narrow bays may have greater variation Potential energy difference between low and high tide can be captured with – A dam across a bay – A turbine similar to a wind turbine

9. High and Low Technology Energy Solutions Most promising “energy sources” are energy conservation and energy efficiency Energy Conservation – Using less energy by reducing energy use and waste Energy Efficiency – Using less energy to accomplish a given task

10. Hydrogen as a Fuel Source Hydrogen gas (H 2 ) – Comprised of two hydrogen molecules – Large amounts of available energy – Explodes when combined with oxygen releasing energy and forming water

11. Hydrogen as a Fuel Source Advantages – Very high energy density – Can be produced from any electrical source Electrolysis (see illustration on next slide) – No greenhouse gases and few other pollutants – Can be use in vehicles Disadvantages – Highly volatile (requires special storage) – Relatively inefficient

12. Hydrogen as a Fuel Source - Electrolysis

13. Hydrogen Fuel Cell Fuel cell – Device that directly converts chemical energy into electricity  Requires hydrogen from a tank and oxygen from the air  Similar to a battery, but reactants are supplied from outside source

14. Future Applications of Fuel Cells Hydrogen Fuel Cell Vehicles – Hydrogen is not yet readily available as a fuel source 61 hydrogen fueling stations in US Batteries in cells phones or laptops

15. Energy Consumption Trends and Economics

16. Super-insulated buildings (right) Energy efficient appliances Automobiles Aircraft technology Compact Fluorescent light bulbs Condensing furnaces Energy Efficient Technologies

17. Cogeneration Production of two useful forms of energy from the same fuel – Most effective on small scale

18. Energy Savings in Commercial Buildings

19. Saving Energy at Home