Renewable energy Types of energy used Evaluating energy What is net energy Energy efficiency Ways to improve efficiency Solar Hydro Wind Biomass Hydrogen geothermal

Nonrenewable energy Review pros and cons of Oil Natural gas Coal Nuclear

Renewable energy 99% of energy used is from sun 1% is commercially generated from extracting and burning fossil fuels Half of the world faces a fuelwood shortage U.S. is largest energy user- 25% of world’s energy

U.S. Electricity Generation Electricity generated by source

Evaluating energy Oil will probably be depleted within years It takes roughly 50 years to phase in new energy resources To evaluate energy alternatives we consider:

Evaluating energy How much is and will be available? What is the NET ENERGY YIELD? How much will it cost to develop phase in and use? How will extracting, transporting, and using affect the environment? Will it improve sustainability

Net energy yield “It takes energy to get energy.” Think second law of thermodynamics Net energy is – the total useful energy available from the resource over its lifetime, minus the amount of energy used, automatically wasted, unnecessarily wasted in finding, processing, concentrating, and transporting it to users. It is the usable amount of high-quality energy

Net energy ratio 10 units of oil in the ground 8 units of energy spent to extract it Ratio of 10/8 can be expressed as 1.2 A higher ratio would mean a greater net energy yield So a net energy yield of 8 is better than 4 Currently oil has a higher ratio than nuclear

Energy efficiency 84% of energy use in US is energy waste 41% automatically from 2 nd law of thermodynamics 43% is wasted unnecessarily by motor vehicles, furnaces, poor insulation, poor design Lifestyle changes would be the easiest, fastest, and cheapest way to get more energy with least impact. Another way is to improve Energy efficiency

To be more energy efficient we should match quality of energy to quality of work to be done

Reducing energy waste Would: Make nonrenewable fossil fuels last longer Give time to phase in alternatives Decrease dependence on oil imports Reduce local and global environmental damage Slow global warming Save money

Ways to improve Insulate homes, eliminate leaks, install air exchangers Collect heat from machines in office buildings and use for space heating Use cogeneration in industry Ex. Steam and electricity from same fuel source Cogeneration used widely in Europe and growing in U.S.

Switch to compact fluorescent light bulbs and LEDs Computer controlled energy management systems Reusing and recycling instead of using virgin resources Improve fuel efficiency of automobiles

Energy efficiency is – the percentage of total energy input that does useful work in an energy conversion system. Although energy efficient devices may cost more initially but have a lower life cycle cost

Improvements in transportation Energy efficient trains, buses, cars, planes Improvements in building and construction Energy efficient homes and offices

Solar Energy Passive solar heating Active solar heating High temp and heat solar solutions Photovoltaic cells (solar cells) Silicon wafer which releases electrons when light falls on surface

Solar

Hydro Moving water Heat storage in water Hydroelectric dams Tide plants Wave power plants

Wind Windmills Wind farms Terrestrial / oceanic Pros and cons

Wind Farms

Biomass Gaseous or liquid biofuels Adds less pollutants than burning coal Biogas Liquid ethanol Methanol Gasohol Burning wood

Hydrogen Fuel Cells

Geothermal