renewable energy types of energy used evaluating energy what is net energy energy efficiency ways to...

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 40-80 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 2nd 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