E N E R G Y E F F I C I E N C Y & R E N E W A B L E E N E R G Y
R E S O U R C E SL E C T U R E 1 2
W H Y D O W E N E E D A N E W E N E R G Y T R A N S I T I O N ?
• World is in early stages of a transition– Move from fossil fuels to energy
efficiency and renewable energy
• Cost of generating energy with solar energy fell by 82% between 2009 and 2015
– Wind costs fell 61%
• Costa Rica gets more than 90% of its energy from renewable resources
W H Y I S I M P R O V I N G E N E R G Y E F F I C I E N C Y A N D R E D U C I N G E N E R G Y W A S T E A N I M P O R TA N T E N E R G Y R E S O U R C E ?
• Improvements in energy efficiency and reductions in energy waste
– Could save at least one-third of the energy used in the world
• Up to 43% of energy used in the United States
• Many technologies exist for increasing energy efficiency of industry, vehicles, appliances, and buildings
W E WA S T E A LO T O F E N E R G Y A N D M O N E Y
• Energy efficiency – How much useful work we get from
each unit energy
• Energy conservation– Reducing or eliminating unnecessary
energy waste
W E WA S T E A LO T O F E N E R G Y A N D M O N E Y
• Some sources of waste
– Poorly insulated buildings
– Reliance on cars for getting around
– Huge data centers filled with electronic servers
• Use only 10% of energy they consume
– Motor vehicles with internal combustion engines (25% efficiency)
– Nuclear, coal, and natural gas power plants (1/3rd
electricity)
I M P R O V I N G E N E R G Y E F F I C I E N C Y I N I N D U S T R I E S A N D U T I L I T I E S
• Cogeneration– Combined heat and power
– Two forms of energy from same fuel source
• Replace energy-wasting electric motors (consume 60% of electricity used)
• Recycle materials (75% less high quality energy; 40% less CO2)
• Use energy-efficient LED lighting• Smart meter to monitor energy use• Shut down unused computers and lights
BUILDING A SMARTER AND MORE ENERGY-EFFICIENT ELECTRICAL GRID• Current electrical grid system–outdated and
wasteful
• Smart grid– Ultra-high-voltage
– Super-efficient transmission lines
– Digitally controlled
– Responds to local changes in demand and supply
– Easier to buy renewable energy
M A K I N G T R A N S P O R TAT I O N M O R E E N E R G Y – E F F I C I E N T
• Hidden costs in gasoline
– Government subsidies and tax breaks for oil companies
– All hidden costs add up to $12 per gallon
• Build or expand mass transit and high speed rail
• Carry more freight by rail instead of trucks
• Encourage biking by building bike lanes
S W I T C H I N G T O E N E R G Y -E F F I C I E N T V E H I C L E S
• Gasoline-electric hybrid car• Plug-in hybrid electric vehicle• Electric vehicle with a hydrogen fuel
cell
• Car bodies made of light, composite materials
D E S I G N I N G B U I L D I N G S T H AT S AV E E N E R G Y A N D M O N E Y
• Green architecture• Living or green roofs
– Specially formulated soil and vegetation
• Superinsulation– No need for heating system
• U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED)
– Standards
WHY ARE WE WASTING SO MUCH ENERGY AND MONEY?• Energy remains artificially cheap
– Government subsidies
– Tax breaks
– Prices don’t include true cost
• Few large and long-lasting incentives for improving energy efficiency and reducing waste
• Rebound effect (using more energy when they buy energy efficient devices)
R E LY I N G M O R E O N R E N E WA B L E E N E R G Y
• Reasons renewable energy use is not more prevalent
– Inaccurate perceptions that solar and wind energy are unreliable and intermittent
– Government subsidies and tax breaks lower for renewable energy than for fossil fuels
– Prices for nonrenewable energy do not include harmful environmental impacts
– Energy shift takes many decades
H E AT I N G B U I L D I N G S A N D W AT E R W I T H S O L A R E N E R G Y
• Passive solar heating system– Absorbs and stores heat from the
sun directly within a well-insulated structure
• Active solar heating system – Captures energy from the sun in a
heat-absorbing fluid
C O O L I N G B U I L D I N G S N AT U R A L LY
• Methods to keep a building cool– Open windows when cooler outside
– Use fans
– Superinsulation and high-efficiency windows
– Shade trees, overhangs, or window awnings
– Light-colored roof
– Geothermal heat pumps bring cool air from underground
C O N C E N T R AT I N G S U N L I G H T T O P R O D U C E H I G H – T E M P E R AT U R E H E AT A N D E L E C T R I C I T Y• Solar thermal systems
– Collect sunlight to boil water and produce steam to generate electricity
– Used in deserts and open areas with ample sunlight
– Require large volumes of cooling water for condensing steam and cleaning mirrors
• Low net energy yields
SOL AR COOKERS
• Solar cookers can replace wood and charcoal fires
USING SOL AR CELLS TO PRODUCE ELECTRICIT Y• Photovoltaic (PV) cells
– Convert solar energy to electric energy
• Design of solar cells– Sunlight hits cells and produces flow of electrons
– Systems can be connected to existing electrical grids or to batteries
USING SOL AR CELLS TO PRODUCE ELECTRICIT Y
• Solar cells made of paper-thin, rigid, or flexible sheets
– Enabled by nanotechnology and other emerging technologies
• Rural use of solar– Rooftop solar panels power LED lamps
– Solar powered microgrids
U S I N G W I N D T O P R O D U C E E L E C T R I C I T Y
• Tall, long-blade turbines can extract more energy from the wind
• Rapidly growing power source– The United States, China, and Germany
• Future is offshore wind farms• Wind power has potential to produce 40
times the world’s current electricity used
U S I N G W I N D T O P R O D U C E E L E C T R I C I T Y
• Wind is abundant, widely distributed, and inexhaustible
– Mostly carbon-free and pollution-free
• High net energy yield• Largest potential areas are usually rural
– Smart grid needed to connect
• Backup power source may be needed– Alternative: large number of wind farms in
different areas connected to smart grid
TA P P I N G I N T O T H E E A R T H ’ S I N T E R N A L H E AT
• Geothermal energy– Heat stored in soil, underground rocks, and
fluids in the earth’s mantle
• Geothermal heat pump system– Uses temperature difference between the
earth’s surface and underground
– Fluid carried through a closed loop
– Can heat a building in winter and cool it in summer
TA P P I N G I N T O T H E E A R T H ’ S I N T E R N A L H E AT
• Hydrothermal reservoirs – Drill wells and extract dry steam, wet
steam, or hot water
– The United States is the world’s largest producer
– Drilling geothermal wells is expensive
• 2015: 134 new geothermal power plants under construction or development in the United States
P R O D U C I N G E N E R G Y B Y B U R N I N G S O L I D B I O M A S S
• Biomass– Plant materials and agricultural waste
that can be burned for fuel
• Biomass plantations– Fast growing trees and shrubs for
repeated harvest
– Wood pellet production degrades forests
• Burning wood and other forms of biomass produces CO2 and pollutants
USING LIQUID BIOFUELS TO POWER VEHICLES• Ethanol
– Ethyl alcohol produced from plants
• Biodiesel– Produced from vegetable oils
• Advantages– Crops can be grown throughout the world
– No net increase in CO2 emissions under certain circumstances
– Easy to store and transport
U S I N G L I Q U I D B I O F U E L S T O P O W E R V E H I C L E S
• Brazil makes ethanol from sugarcane residue– Medium net energy
• 2014: 43% of the corn produced in the United States was used to make ethanol
– Corn-based ethanol has a low net energy
– Producing and burning corn-based ethanol adds 20% more greenhouse gases than burning gasoline
U S I N G L I Q U I D B I O F U E L S T O P O W E R V E H I C L E S
• Growing corn requires much water• Ethanol distilleries produce large
volumes of wastewater
• Cellulosic ethanol– Alternative made of inedible cellulose
– Can be made from grasses that do not require fertilizer or replanting (perennials)
• Algae can produce biofuel
P R O D U C I N G E L E C T R I C I T Y F R O M FA L L I N G A N D F L O W I N G W AT E R
• Hydropower– Uses kinetic energy of moving water
– Indirect form of solar energy
– World’s leading renewable energy source
• Top three producers– China, Canada, and Brazil
• Hydropower supplies half the electricity used on the West Coast
U S I N G T I D E S A N D W AV E S T O P R O D U C E E L E C T R I C I T Y
• Produce electricity from flowing water– Coastal bays and estuaries
• Tidal energy dams– France, Nova Scotia, and South Korea
• Challenges– Few suitable sites
– High costs
– Equipment damage from storms and saltwater corrosion
WILL HYDROGEN SAVE US?• Advantages of hydrogen as a fuel
– Eliminates most outdoor air pollution from burning fossil fuels
– Would greatly slow climate change and ocean acidification
WILL HYDROGEN SAVE US?• Some challenges
– Hydrogen chemically locked in water and organic compounds
– Negative net energy
• Serious limitation
– Fuel cells are costly
– CO2 emissions depend on method of hydrogen production
SHIFTING TO A NEW ENERGY ECONOMY
• China and the United States– Key players in making the shift to a new set of
energy resources
– Each country uses about 20% of the world’s energy
• Important actions to enable energy shift– Use full-cost pricing
– Tax carbon emissions
SHIFTING TO A NEW ENERGY ECONOMY• Important actions (cont’d.)
– Decrease and eliminate government subsidies for fossil fuel industries
– Establish a national feed-in-tariff system
– Mandate that a certain percentage of electricity generated by utility companies be from renewable resources
– Increase government fuel efficiency standards