Visualizing Environmental Science
Renewable Energy Resources
Chapter 18
Chapter 7
[chapter opener image]
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Reducing Heat Loss
– Two strategies to decrease reliance on fossil fuels
• Developing alternative energy sources
• Reducing energy use
– Thermal images show
heat escaping from a
building
• Dark blue and green
represent cold
• Reds and yellows represent
heat
• Allow homeowners to
detect where heat is
escaping their home and
insulate, caulk, replace old
windows
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
• Direct solar energy
– Always available, not like fossil and nuclear fuels
– Solar energy must be collected and transformed
into other forms for it to be useful as an energy
source for human use
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
• Heating buildings and water
– Active solar heating
• Collectors absorb solar energy and pumps and fans
distribute the collected heat
• Primarily used for heating water
– Household use
– Swimming pools
– Can provide a family with hot water year-round
• More than 8% of energy consumed in the U.S. goes
toward heating water
• Not used as much for space heating, but may become
more important as oil, gas, electricity prices rise
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
Active Solar Heating
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
• Passive solar heating
– Does not require mechanical devices to distribute
the collected heat
– Design features are used to warm buildings in the
winter and keep them cool in the summer
• South facing windows receive more sunlight
– Sunlight provides heat, stored in floors and walls
– Heat is transmitted by convection
• Must be well-insulated to maintain heat
• Passive heating can save as much as 80% of heating
costs
• About 7% of new homes built have passive heating
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
House designed
with passive solar
heating
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
• Photovoltaic solar
cells
– A wafer/thin film
of solid-state
materials; treated
with certain metals
it generates
electricity when
solar energy is
absorbed
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
• No pollution, minimal maintenance
• Absorbs sunlight even on cloudy or rainy days
• Currently limited by low efficiency
• Large-scale power generation requires too much land
to generate sufficient electricity
• Can be economical in rural areas of developing countries
vs. installing power lines
Energy Consumption
• Cost of manufacturing PV
units has steadily decreased
over the past 35 years
• PV cells incorporated into
roofing tiles may provide
substantial power production
in future
– California residents have installed over 1000MW
solar capacity on roofs by late 2012
– Japan considering policy requiring PV on new
building rooftops by 2030
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
• Solar thermal electric generation
– Means of producing electricity in
which the sun’s energy is concentrated
via mirrors or lenses onto fluid-filled
pipes
– Becoming cost-competitive with fossil
fuels
– No pollution, acid deposition, or
climate change
– Does require alternate energy source
(natural gas) at night or on cloudy days
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
• Solar-generated hydrogen
– Hydrogen—fuel of the future
• Abundant, easily produced
• Electricity from any source can split water into oxygen
and hydrogen gases
• Hydrogen itself is a clean fuel
– Produces water and heat as byproducts
– Potential to provide energy for transportation,
heating buildings, producing electricity
• Solar electricity must be used immediately, whereas
hydrogen can be stored and transported by pipeline
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Some renewable energies use the sun’s energy
indirectly
– Combustion of biomass (organic matter)
• Plants use solar energy for photosynthesis and store
the energy as biomass
– Wind energy
• Uses wind to generate electricity
– Hydropower
• Uses dammed rivers and streams to generate electricity
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Biomass energy
– Plant and animal material used as fuel
• Crop wastes, sawdust, wood, charcoal, peat, animal
dung
– At least half of the world’s population relies on
biomass fuel
• Wood is the primary fuel for cooking and heat in many
developing countries
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Biogas
– Biomass can be converted into a mixture
of gases
– Mostly methane
– Biogas digesters produce gas for cooking
and lighting, by microbial decomposition
of wastes
• Several million used in China and India
• Solid remains can be used as fertilizer
– Biogas has the potential to power fuel
cells to generate electricity
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Biomass can also be converted into liquid fuels
– Methanol
– Ethanol—can replace gasoline in internal
combustion engines
– Biodiesel—made from plant or animal oils
• Biomass is attractive to politicians and
consumers as source of energy
© 2014 John Wiley & Sons, Inc. All rights reserved.
Power Generation from Wood Chips
12-17
Indirect Solar Energy
• Problems with biomass
– Use of land and water that might be dedicated to food
production
• Higher food prices
• Reduced food supplies
– Unsustainable use of wood
• Trees are cut faster than replanted
• Severe damage to environment
– Erosion, desertification, deforestation, etc.
– Harm to soil quality
• Crop residues are not left for conservation tillage
– Increases likelihood of erosion and mineral depletion
– Reduces productivity
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Wind energy
– Wind turbines are huge, and becoming
more efficient (100m tall)
• $0.40/kwh in 1980 to $0.04–0.07/kwh now
• Cost competitive with most conventional
energy
– Most profitable in areas with consistent
winds
• Coastal areas, mountain passes, islands,
grasslands
• U.S., Germany, Denmark are main wind
electricity producers
– Denmark produces 21% of its energy by wind
• China expanding wind energy capacity
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Best locations for wind energy in U.S.
– ND, TX, SD, MT, NE, WY, OK, MN, IO, KS
– If we developed wind energy in ND, TX, and KS, we
could supply enough electricity to meet the current
needs of the entire U.S.
• Projects are underway
• Currently, wind power is captured and placed in
regional electricity grids
– Requires development of distribution methods
• No waste, clean energy
– Every kwh of wind electricity reduces release of 2.2lb
of CO2 from fossil fuels into the air
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Problems with wind turbines
– Can cause bird kills if turbines are on bird migration
pathways (Altamont Pass, CA)
• Can be corrected by not placing turbines on those sites,
painting blades, using anti-perching devices, and shutting
down during peak migration periods
• Developers currently conduct voluntary wildlife studies to
locate sites away from bird and bat routes
– Aesthetic issues
• Maple Ridge Wind Farm in Upstate NY
– Some residents welcome extra money from wind leases
– Others complain that turbines ruin their view of Adirondacks
• Nantucket Sound residents oppose off-shore wind project in
MA, because tourists may find it offensive
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Hydropower
– Potential energy of water held
back by a dam can be
converted into electricity
– More efficient than any other
source of energy
• 90% of potential energy is
converted to electricity
– Generates about 19% of
world’s electricity
• 7% in U.S.
© 2014 John Wiley & Sons, Inc. All rights reserved.
Indirect Solar Energy
• Problems with hydropower
– Dams change natural flow of rivers
• Water backs up, floods large areas of land to form
reservoir, destroys plant and animal habitats
• Downstream lands no longer receive nutrient-rich silt
• Earthquakes may occur and damage dams in areas of
seismic activity
• In some areas, there is greater evaporation of water
• Displaces people when reservoir is created
© 2014 John Wiley & Sons, Inc. All rights reserved.
Other Renewable Resources
• Geothermal energy
– Energy from the Earth’s
interior, used for space
heating or generation of
electricity
– Just 1% of the heat
contained in the uppermost
layer of the Earth’s crust is
500 times the energy
contained in all of Earth’s oil
and natural gas resources
© 2014 John Wiley & Sons, Inc. All rights reserved.
Other Renewable Resources
• U.S. is largest producer of geothermal
electricity
– The Geysers geothermal power plant, in CA
provides electricity to 1.7 million consumers
• Geothermal energy is renewable on a human
timescale
– Water used to transfer energy is not inexhaustible
• Some geothermal systems recirculate water back to
underground reservoir
– Considered environmentally benign
© 2014 John Wiley & Sons, Inc. All rights reserved.
Other Renewable Resources
• Heating and cooling buildings
with geothermal energy
– Ground-effect heat pumps
(GHPs) take advantage of the
difference in temperature
between Earth’s surface and
subsurface
• Underground pipes with
circulating liquids extract natural
heat in winter, transfer excess
heat underground in summer
• Heating systems can be modified
to provide supplemental hot
water
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Consumption
Electricity
generation costs
© 2014 John Wiley & Sons, Inc. All rights reserved.
Other Renewable Resources
• Tidal energy
– Tides are caused by the gravitational
pull of the moon and sun
– A dam across a bay can harness the
energy of large tides to generate
electricity
• Water at high tide gets trapped on land
side, as tide recedes, the water falls
through the dam’s spillway and turns a
turbine
• France, Russia, China, Canada have tidal
power plants
– Problems
• Few places in the world have tides large
enough to support this mode of energy
• High economic cost
• Potentially high environmental costs in
estuaries
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Solutions
• Energy conservation
– Using less energy; reducing energy use and waste
• Energy efficiency
– Using less energy to accomplish a given task
• Consumption trends and economics
– Even though U.S. has become more energy
efficient, consumption has increased
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Solutions
• Energy-efficient
technologies
– Refrigerators today use
80% less energy than in
early 1970s
– Automobile efficiency has
improved dramatically
since 1970s—lighter
materials and dragreducing design
• Fuel efficiency doubled between mid 70s and mid 80s
• Declined after that as larger vehicles became popular
• Autos with fuel efficiencies of 60 mpg will be possible in
next decade
© 2014 John Wiley & Sons, Inc. All rights reserved.
Energy Solutions
• Energy-efficient technologies
– Appliances, automobiles,
buildings, industrial processes
– CFLs produce light
comparable to that of
incandescent light bulbs, but
require only 25% of energy
and last up to 15% longer
– Condensing furnaces require
30% less fuel
– ‘Superinsulated’ buildings use
70–90% less energy
© 2014 John Wiley & Sons, Inc. All rights reserved.
Potential Renewable Energy Mix
12-32