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

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

Hydropower

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

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

 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

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

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

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

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

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

Hydrogen as a Fuel Source - Electrolysis

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

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

Energy Consumption Trends and Economics

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

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

Energy Savings in Commercial Buildings

Saving Energy at Home