Energy Efficiency
-measure of how much work we can get from each unit of energy used
-each unit of energy saved eliminates the need to produce that energy and saves money
US Wasted Energy
-wastes 84% commercial energy
-41% unavoidably lost through 2nd law of thermodynamics
-43% lost unnecessarily due to inefficiency
Energy-Wasting Technologies
-incandescent lightbulb (5-10% efficient)
-internal combustion engine (wastes 80%)
-nuclear power plant (wastes 75% nuclear fuel energy, 92% including whole nuclear fuel cycle)
-coal-fired power plant (wastes 66% energy released by burning coal, 75-80% in
Advantages of Reducing Energy Waste
-saves money, reduces enviro impact, reduce pollution, quick and clean, increase economic and national security, slow climate change
Ways to Save Energy in Industry
-cogeneration
-replace energy-wasting electric motors with variable speed motors, inefficient b/c only run at full speed
-recycle materials
-switch from incandescent lighting to fluorescent or LED lighting
-electric grid system is outdated and wasteful
Cogeneration
-using combined heat and power (CHP) system, produce 2 useful forms of energy from 1 fuel source
Ways to Save Energy in Transportation
-gasoline taxes to include more of the real cost of gas
-economic incentives (fee-bate program, buyers of gas guzzlers pay high fee which go towards rebates for buyers of efficient vehicles)
Ways to Save Energy in New Buildings
-orient building to face sun
-green architecture
-living roofs (covered with soil and vegetation)
-superinsulation (so heavily insulated/airtight that heat from direct sunlight, appliances, and human bodies can warm it with little or no need for backup he
Ways to Save Energy in Old Buildings
-insulate building and plug leaks
-use energy-efficient windows
-stop other heating and cooling losses
-heat more efficiently
-heat water more efficiently
-use energy-efficient appliances and lighting
Problems with Electric Utility Companies
-have encouraged electricity use instead of efficiency
-state utility commissions should reward utilities for cutting people's bills by helping them save energy
Smart Electrical Grid
-more energy-efficient and digitally controlled
-responsive to local and regional changes in demand and supply
-use smart meters to monitor amount of electricity used and patterns of use for each customer, use this info to deliver electricity as efficient
Fuel Efficiency in the US
-corporate average fuel economy (CAFE) standards set least amount of mpg cars need
-standards have decreased to about 21 mpg
Price of Gasoline
-hidden costs from government subsidies, tax breaks, cost of pollution control and cleanup, costs of military protection of oil supplies, time wasted idling in traffic jams, and costs of illness from air and water pollution
-real cost is about $12/gallon
Hybrid Cars
-energy-efficient, gasoline-electric
-small, traditional gas-powered engine and battery-powered electric motor to provide energy for acceleration and hill climbing
-can get 50 mpg and emits 65% less CO2/km
Plug-In Hybrid Electric Vehicle
-hybrid with a second and more powerful battery
-can be plugged into electrical outlet and recharged
-but not very long travel distance on a fully charged battery
Fuel Cell Car
-fuel cells are at least twice as efficient as internal combustion engines
-could have little/no CO2 emissions
-but very expensive and negative net energy yield because uses H2 as fuel
Better Batteries
-major obstacles are storage capacity, overheating, flammability, and cost
-promising developments in lithium-ion battery and ultracapacitor
Ways to Save Energy in Your Home
-install water-saving toilets, faucets, and shower heads
-use microwave more often
-dry clothes on a rack
-use fluorescent lights or LEDs
-use high efficiency windows or insulating window covers
-turn off/unplug appliances when not in use
Why We Waste So Much Energy
-fossil fuels, nuclear power, and other widely used energy resources are artificially cheap b/c of government subsidies and tax breaks and not including harmful environmental and health costs from production and use
-few government tax breaks, rebates, lo
Advantages of Renewable Energy
-more decentralized and energy-efficient national economies that are less vulnerable to supply cutoffs or natural disasters
-could improve economic and national security
-reduce air and water pollution
-slow projected climate disruption
-create jobs
-save
Passive Solar Heating System
-absorb and store sun's heat in structure of a building
Active Solar Heating System
-pumps heat-absorbing fluid through collectors
-use some heat immediately and stores rest in insulated container
Solar Energy
-use to heat water, heat buildings, or for high-temperature heat and electricity
-works best in new homes with adequate sunlight in desert areas
Advantages of Solar Energy
-net energy is moderate (active) to high (passive)
-low CO2/air pollutants released
-very low land disturbance
-moderate cost (passive)
Disadvantages of Solar Energy
-need access to sun 60% day time
-sun can be blocked by trees/structures
-high installation and maintenance costs (active)
-need backup for cloudy days
Cool Houses Naturally
-open windows, use fans, living roof, superinsulation, block sun with window overhangs/awnings/shades, light-colored roof, geothermal heat pumps
Advantages of Concentrating Solar Energy for High-Temperature Heat and Electricity
-moderate enviro impact
-no direct emissions of CO2/other air pollutants
-lower costs with natural gas turbine backup
Disadvantages of Concentrating Solar Energy
-low net energy
-high costs
-needs backup or storage system for cloudy days
-high water use for cooling
Solar or Photovoltaic (PV) Cells
-when sunlight strikes, emit electrons
-many wired together on panel can produce electrical power
-convert solar energy to electric energy
Advantages of Solar Cells
-moderate net energy yield
-little or no direct emissions of CO2/other air pollutants
-easy to install, move around, or expand as needed
-competitive cost for newer cells
Disadvantages of Solar Cells
-need access to sun
-need electricity storage system or backup
-high costs for older systems (decreasing rapidly)
-solar-cell power plants could disrupt desert ecosystems
Hydropower
-uses kinetic energy of moving water
-indirect form of solar energy
-most common way to harness is building a dam
-leading renewable energy source for producing electricity
Advantages of Hydropower
-moderate to high net energy
-large untapped potential
-low-cost electricity
-low CO2/air pollutant emissions in temperate areas
Disadvantages of Hydropower
-large land disturbance and people displacement
-high methane emissions from rapid biomass decay, especially in tropical climates
-disrupts downstream aquatic systems
Using Tides and Waves to Produce Electricity
-use micro-hydropower generators
-put turbines underwater to get energy
Disadvantages
-few suitable sites
-high costs
-damage by storms or corrosion
Wind Energy
-wind is caused by earth's rotation and variations of solar heating
-wind turbines convert to electrical energy
-2nd fastest growing source of energy
-will reduce coal dependency
-could produce 40x world's current electricity use
-works best at sea or pla
Advantages of Wind Energy
-moderate to high net energy
-widely available
-low electricity cost
-little or no direct CO2 or air pollutant emissions
-easy to build and expand
Disadvantages of Wind Energy
-needs backup or storage system when little or no wind
-visual pollution
-low-level noise is bothersome to some
-can kill birds if not properly designed or located
Biomass
-plant materials or animal wastes that can be burned as solid fuel or converted into gaseous/liquid biofuel
-use mostly for heating or cooking, some for industrial processes and electricity, also car fuel
-need plentiful wood
-can collect by planting fast
Advantages of Biomass Energy
-widely available in some areas
-moderate costs
-no net CO2 increase if done sustainably
-plantations can restore degraded lands
Disadvantages of Biomass Energy
-moderate to high environmental impact
-increased CO2 emissions if unsustainable
-clear cutting can lead to erosion, H2O pollution, and habitat loss
-often use inefficient and polluting open fires and stoves
Biofuels
-liquid biofuels like biodiesel or ethanol
-produced from vegetable oil or plant and plant wastes
Advantages of Biofuels
-reduced CO/CO2 emissions
-high net energy yield for oil palm crops
-reduced hydrocarbon emissions
-better mileage
Disadvantages of Biofuels
-increased car emissions and smog
-low net energy yield for soybean crops
-competes with food for cropland
-clearing natural areas for plantations reduces biodiversity and increases atmospheric CO2 levels
Ethanol
Advantages
-some reduction in CO2 emissions with sugarcane bagasse
-high net energy yield from bagasse or switchgrass
-potentially renewable
Disadvantages
-low net energy yield from corn
-higher cost
-higher CO2 emissions from corn
-corn ethanol competes
Advantages of Biomass Over Gas or Diesel Fuel
-biofuel crops can be grown anywhere
-no net CO2 increase if managed properly
-available now
Use Algae for Gas and Diesel Fuel
-remove CO2 from the atmosphere and convert it into oil
-requires less land/water/other resources
-wouldn't affect food prices
-could be grown in wastewater
-but need to lower the costs, open ponds vs. bioreactors, affordable extraction, make large-scale
Use Bacteria for Gas and Diesel Fuel
-convert sugar in sugarcane juice into fatty acids that can be used as biodiesel fuel
Geothermal Energy
-heat stored in soil, underground rocks, and fluids in mantle
-use geothermal heat pump system
-use to heat/cool buildings or produce electricity
-can find suitable sites almost anywhere
Three Sources of Geothermal Energy
-geothermal heat pump system (fluid in buried pipes extracts heat, carries to heat pump, transfers heat to home's heat distribution syst)
-hydrothermal reservoirs (deeper and more concentrated, drill wells to extract dry/wet steam or hot water, use to hea
Advantages of Geothermal Energy
-moderate net energy and high efficiency at accessible sites
-lower CO2 emissions than fossil fuels
-low cost at favorable sites
Disadvantages of Geothermal Energy
-high cost/low efficiency at unconcentrated or unaccessible sites
-scarcity of suitable sites
-noise
-some CO2 emissions
Using Hydrogen for Energy
-use fuel cells to combine H2 and O2 to produce electricity and water vapor
-provides more energy per gram than any other fuel
-use for electricity and heating buildings and water
-can use large, stationary fuel cells for commercial and industrial users,
Advantages of Hydrogen
-can be produced from plentiful H2O at some sites
-no direct CO2 emissions if produced from water
-good substitute for oil
-high efficiency (45-65%) in fuel cells
Disadvantages of Hydrogen
-negative net energy yield
-CO2 emissions if produced from carbon-containing compounds
-high costs require subsidies
-needs H2 storage/distribution system
Conclusions About Future Energy Paths
-shift from large, centralized macropower systems to smaller, decentralized micropower systems
-combo of greatly improved energy efficiency and temporary use of natural gas will be the best way to make the transition to a diverse mix of locally available
Strategies for More Sustainable Energy
-improve energy efficiency
-use more renewable energy
-reduce pollution and health risks
Roles of the Government
-keep prices of selected renewable sources artificially low to encourage use
-keep prices of selected nonrenewable sources artificially high to discourage use
-emphasize consumer education