AP Environmental Science Net Energy & Energy Efficiency © Brooks/Cole Publishing Company / ITP

What is Net Energy? © Brooks/Cole Publishing Company / ITP NET ENERGY: the total useful energy available from a resource over its lifetime minus the amount of energy used, automatically wasted, and unnecessarily wasted to find, process, and transport it Example: if 8 units of energy are wasted for every 10 units extracted, then there is a net energy of 2 units Net energy ratio--ratio of useful energy produced to the useful energy used to produce it higher ratios = greater the net energy yield 10/8 = 1.25

Net Energy Ratios © Brooks/Cole Publishing Company / ITP Net energy ratios for various energy systems used for space heating:

Net Energy Ratios © Brooks/Cole Publishing Company / ITP Net energy ratios for various energy systems used for industry: Fig.15–3b

Net Energy Ratios © Brooks/Cole Publishing Company / ITP Net energy ratios for various energy systems used for transportation: Fig.15–3c

Energy Efficiency What is it? Energy efficiency – the percentage of total energy input that does useful work in an energy conversion system Energy efficiency of common energy conversion devices

Efficiency of Some Common Devices Device Efficiency (%)  Dry-cell flashlight battery90  Home gas furnace85  Storage battery70  Home oil furnace65  Small electric motor62  Steam power plant38  Diesel engine38  High-intensity lamp32  Automobile engine25  Fluorescent lamp22  Incandescent lamp 4

Energy Efficiency Net energy efficiency – t he net efficiency of the entire energy delivery process is determined by the efficiency of each step in the energy conversion process © Brooks/Cole Publishing Company / ITP

Energy Efficiency Energy waste 43% of the energy used in the U.S. is unnecessarily wasted by using inefficient methods to produce electricity, heat our homes, and drive our cars

Energy Efficiency The importance of reducing energy waste Nonrenewable fuels last longer Time to phase in renewable energy resources Decrease dependence on oil imports Reduce local and global environmental damage Slow climate change Create new jobs Save money © Brooks/Cole Publishing Company / ITP

You don’t have to freeze in the winter or make huge personals sacrifices. Energy conservation is implemented by using existing technologies and developing new ones

Improving Energy Efficiency Improving energy efficiency is the easiest way to make big changes in our consumption Cogeneration Fuel efficiency of motor vehicles or use of alternative fuel vehicles Slideshow: 23 Electric Cars Driving the RevolutionSlideshow: 23 Electric Cars Driving the Revolution Lighting and appliances Better insulated homes © Brooks/Cole Publishing Company / ITP

Cogeneration Cogeneration – the production of two useful forms of energy from the same fuel source-use energy converted to low energy heat to generate electricity

Fuel Efficiency First step in conservation is to increase the fuel efficiency of internal combustion cars!   Hybrid-electric internal combustion engine – internal combustion engine recharges electric battery   Fuel-cell cars – combines H 2 and O to produce water vapor and electricity

 Heat Houses More Efficiently!  Most energy efficient – Superinsulation with passive solar heat and high-efficiency (85-98%) gas furnace  Most expensive – Electric heaters!!!!  Least efficient – Electric heat supplied from nuclear power  Heat Water More Efficiently!  Tankless water heaters Lighting and Appliance Efficiency

Old tank water heater Tankless water heater

Lighting and Appliance Efficiency  Use Energy Efficient Appliances  Use Energy Efficient Bulbs!  ¼ of US electricity budget spent on lighting. 50% could be saved by changing to CFL’s  CFL’s use 1/3 the wattage of an incandescent bulb  Not all CFL’s created equal  If each house replaced ONE incan with a CFL, enough energy would be conserved to light 3 million homes and save $600 million annually  Cut Off Electrical Devices When Not In Use!—Vampire Draws

Better Insulated Homes   Insulate & Plug Leaks – 1/3 of heated air in the US leaks through closed windows, holes, and cracks in houses  Use Energy Efficient Windows – buy superinsulating glass and low-E (low-emissivity) windows that cut down on heat loss. More $ but pay for themselves as they save money.  Add more insulation to walls and ceilings  Strict Energy-Efficiency Standards for New Buildings!  Sweden has stricter standards so homes use 1/3 as much energy

A sustainable energy strategy (see Fig.16–23) © Brooks/Cole Publishing Company / ITP

Drive a car that gets at least 15 kilometers per liter (35 miles per gallon) and join a carpool. Use mass transit, walking, and bicycling. Superinsulate your house and plug all air leaks. Turn off lights, TV sets, computers, and other electronic equipment when they are not in use. Wash laundry in warm or cold water. Use passive solar heating. For cooling, open windows and use ceiling fans or whole-house attic or window fans. Turn thermostats down in winter and up in summer. Buy the most energy-efficient homes, lights, cars, and appliances available. Turn down the thermostat on water heaters to 43-49ºC ( ºF) and insulate hot water heaters and pipes. What Can You Do? Energy Use and Waste