Studied by 10 people
Net Energy Yield
total amount of useful, high-quality energy available from a resource minus the energy needed to make the energy available to customers
Energy return on investment (EROI)
energy obtained per unit of energy used to obtain it
First law of thermodynamics (law of conservation of energy)
it takes high quality energy to get high-quality energy
(Pumping oil from ground, refining it, and transporting it)
Second law of thermodynamics (high quality -> low quality)
some high quality energy is wasted at every step
nuclear power
Has a low net energy yield because a great deal of high quality is needed
The uranium fuel cycle is costly
Heavily subsidized
When was the first U.S. commercial oil well drilled
1859
Where was the first U.S. commercial oil well drilled
Titusville, PA
Oil is the world’s most widely used energy resource and it is used to:
heat our homes, grow most of our food, transport people and goods, make other energy resources available for use
Crude oil (petroleum)
black, gooey liquid consisting mostly of a mix of different combustible hydrocarbons along with small amounts of sulfur, oxygen, and nitrogen impurities
Crude oil (petroleum) is formed from:
decayed remains of ancient organisms that were crushed beneath layers of rock for millions of years
Crude oil cannot be used as it comes out of the ground, it must be refined into:
Petrochemicals
Availability is determined by:
1. Demand, 2. Technology, 3. Rate at which we remove the oil, 4. Cost of making oil available, 5. Market price
Proven oil reserves
available deposits from which oil can be extracted profitably; not fixed
How to avoid running out of oil:
Use unconventional heavy oil
Live with much higher oil problems
Extend oil supplies (for example, improve oil efficiency)
Use other energy sources
Use of Conventional Oil Has Environmental Costs
Land disruption, greenhouse gas emission, air pollution, water pollution, loss of biodiversity, and burning oil accounts for 43% of global CO2 emissions
Conventional Oil Advantages:
Ample supply for several decades
Net energy yield is medium but decreasing
Low land disruption
Efficient distribution system
Conventional Oil Disadvantages:
Water pollution from oil spills and leaks
Environmental costs not included in market price
Releases CO2 and other air pollutants when burned
Vulnerable to international supply interruptions
tar sands, or oil sands
mixture of clay, sand, water, and contains bitumen (a thick, sticky, and tar-like heavy oil)
Problems with extracting oil from tar sands:
Serious environmental impacts
Low net energy yield
Problems with extracting oil from oil shale rocks:
Locked up in rock; requires lots of energy, money, and water
Lots of pollution, in air and water
Low net energy yield
Heavy Oils From Oil Shale and Tar Sand Advantages:
Large potential supplies
Easily transported within and between countries
Efficient distribution system in place
Heavy Oils From Oil Shale and Tar Sand Disadvantages:
Low net energy yield
Releases CO2 and other air pollutants when produced and burned
Severe land disruption and high water use
Natural gas
Mixture of gases, 50-90% methane CH4
Medium net energy yield
Widely used for cooking, heating space and water, industrialized purposes
Provides 28% of energy consumed in US
Burns cleaner than oil and much cleaner than coal
Conventional natural gas
Often found in deposits above conventional oil, as well as shale rock
When a natural gas deposit is tapped, propane and butane gases can be liquefied under high pressure and removed as LPG and LNG
LPG
Liquefied petroleum gas (stored in tanks)
LNG
Liquefied natural gas (way by which to transport across ocean, low net energy yield)
Conventional Natural Gas Advantages
Ample supplies
Versatile fuel
Medium net energy yield
Emits less CO2 and other air pollutants than other fossil fuels when burned
Conventional Natural Gas Disadvantages
Low net energy yield for LNG
Production and delivery may emit more CO2 and CH4 per unit of energy produced than coal
Fracking uses and pollutes large volumes of water
Potential groundwater pollution from fracking
Coal bed methane gas (unconventional natural gas)
Found in coal beds near the earth’s surface; in shale beds
High environmental impacts of extraction
Methane hydrate (unconventional natural gas)
Trapped in icy water; in permafrost environments; on ocean floor
Costs of extraction is currently too high; not feasible
Coal
Solid fossil fuel formed from the remains of land plants that were buried 300-400 million years ago and exposed to intense heat and pressure over millions of years
Coal generates __% of the world’s electricity
42%
Lignite
the least desirable because of its high moisture content
Bituminous
most widely used because it is most abundant and easiest to mine
Anthracite
has the highest energy content and is cleanest burning, but is hard to obtain
Coal Advantages
Ample supplies in many countries
Medium to high net energy yield
Low cost when environmental costs are not included
Coal Disadvantages
Severe land disturbance and water pollution
Fine particle and toxic mercury emissions threaten human health
Emits large amounts of CO2 and other air pollutants when produced and burned
Conversion of solid coal to: Synthetic natural gas (SNG) by
coal gasification to remove sulfur and impurities from coal
Synthetic Fuel Advantages
Large potential supply in countries
Vehicle fuel
Lower air pollution than coal
Synthetic Fuel Disadvantages
Low to medium net energy yield
Requires mining 50% more coal with increased land disturbance, water pollution and water use
Higher CO2 emissions than coal
Coal Liquefaction
process of turning coal into liquid products resembling crude oil
Nuclear Power Plant
A highly complex and costly system designed to perform a relatively simple task: to boil water water and produce steam that spins a turbine and generates electricity
How Does A Nuclear Fission Reactor Work?
Light-water reactors; very inefficient
Fueled by uranium ore and packed as pellets in fuel rods and fuel assemblies in the core of a reactor
Control rods absorb neutrons generated in fission, regulating the rate of fission and amount of power produced
Water is in the usual coolant; keeps components from melting and releasing radioactivity into the environment
Containment shell around the reactor core to ensure radioactive materials do not escape into the environment
Water-filled pools or dry casks for storage of radioactive wastes and spent fuel rod assemblies
What is the isotope used in nuclear fission
U-235 (Uranium 235)
Nuclear Fuel Cycle
Mine the uranium
Process and enrich the uranium to make the fuel
Use it in the reactor
Safely store the radioactive waste
Decommission the reactor
Nuclear Energy Advantages
Low environmental impact (without accidents)
Emits â…™ as much carbon dioxide as coal
Low risk of accidents in modern plants
Nuclear Energy Disadvantages
Low net energy yield
High overall cost
Produces long-lived, harmful radioactive wastes
Promotes spread of nuclear weapons
Proponents of nuclear power
Fund more research and development on safer and less costly type of reactions
Pilot-plant testing of potentially cheaper and safer reactors
Opponents of nuclear power
Very expensive; does not save on oil
Questions of safety
Fund rapid development of energy efficient and renewable energy sources
Nuclear Fusion
Two isotopes (hydrogen) fused together at extremely high temperatures to form a heavier nucleus; releases energy in the process
Advantages of reducing energy waste
Usually the cheapest way to provide more energy
Reduce pollution and degradation
Slows climate change
Increase economic and national security
Energy conservation
using less energy; reducing energy use and waste
Energy efficiency
using less energy to accomplish a given task
Solutions: Improving Energy Efficiency
Prolongs fossil fuel supplies
Reduces oil imports and improves energy security
Very high net energy yield
Low cost
Reduces pollution and environmental degradation
Buys time to phase in renewable energy
Creates local jobs
Cogeneration
combined heat and power (CHP)
Two forms of electricity from the same fuel source (steam & electricity)
Conduct an energy audit:
Insulate and plug leaks
Use energy-efficient windows
Stop other heating and cooling losses
Heat houses more efficiently
Use energy-efficient appliances
Use energy-efficient lighting
Use motion sensors to turn lights on and off
Why Are We Still Wasting So Much Energy and Money?
Energy remains artificially cheap
Few large and long-lasting incentives
Lack of education
Products of Sun’s Energy
Fossil fuels
Wind
Hydroelectric
Biodiesel
Solar
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 liquid
Passive or Active Solar Heating Advantages
Net energy is moderate (active) to high (passive)
Very low emissions of CO2 and other air pollutants
Very low land disturbance
Moderate cost (passive)
Passive or Active Solar Heating Disadvantages
Need access to sun 60% of time during daylight
Suns can be blocked by trees and other structures
High installation and maintenance costs for active systems
Need backup system for cloudy days
We Can Cool Buildings Naturally
Open windows when cooler outside
Use fans
Superinsulation and high-efficiency windows
Overhangs or awnings on windows
Light-colored roof
Geothermal pumps
heliostats
mirrors
Solar thermal systems
Uses heliostats (mirrors) to concentrate the sun’s energy at a single point
Collect sunlight to boil water, generate electricity
1% of world deserts could supply all the world’s electricity
Require large amounts of water
Solar Thermal Systems Advantages
High potential for growth
No direct emissions of carbon dioxide and other air pollutants
Lower costs with natural gas turbine backup
Source of new jobs
Solar Thermal Systems Disadvantages
Low net energy and high costs
Needs backup or storage system on cloudy days
Can disrupt desert ecosystems
Photovoltaic (PV) cells
Convert solar energy to electric energy
Design of solar cells
Sunlight hits cells and releases electrons into wires
Solar Cells Advantages
Medium net energy yield
Little or no direct emissions of carbon dioxide and other air pollutants
Easy to install, move around, and expand as needed
Competitive costs for newer cells
Solar Cells Disadvantages
Need access to sun
Some designs have low net energy yield
Need electricity storage system or backup
Costs high for older systems but dropping rapidly
Solar-cell power plants could disrupt desert ecosystems
Hydropower
Uses kinetic energy of moving water
Indirect form of solar energy
World’s leading renewable energy source used to produce electricity
Large-Scale Hydropower Advantages
High net energy yield
Large untapped potential
Low-cost
Low emissions of carbon dioxide and other air pollutants in temperate areas
Large-Scale Hydropower Disadvantages
Large land disturbance and displacement of people
High methane emissions from rapid biomass decay in shallow tropical reservoirs
Disrupts downstream aquatic ecosystems
Wind energy
wind farms convert to electrical energy
Wind Power Advantages
High net energy yield
Widely available
Low electricity cost
Little or no direct emissions of carbon dioxide or other air pollutants
Easy to build and expand
Wind Power Disadvantages
Needs backup or storage systems when winds die down
Visual pollution for some people
Low-level noise bothers some people
Can kill birds if not properly designed and located
Biomass
plant materials and animal waste we can burn or turn into biofuels
creating biofuel plantations can
Degrade soil and biodiversity
Increase greenhouse gas emissions
Lead to higher food sources
Solid Biomass Advantages
Widely available in some areas
Moderate costs
Medium net energy yield
No net carbon dioxide increase if harvested, burned, and replanted sustainably
Plantations can restore degraded lands
Solid Biomass Disadvantages
Contributes to deforestation
Clear-cutting can cause soil-erosion water pollution, and loss of wildlife habitat
Can open ecosystems to invasive species
Increases carbon dioxide emissions if harvested and burned unsustainably
Biodiesel
produced from vegetable oil
Ethanol
can be made from sugarcane, corn, switchgrass, and various wastes
Cellulosic ethanol
Produced from cellulose
Problems with cellulosic ethanol
Chemical processes still being developed
Growing enough switchgrass would require too much land
Liquid Biofuels Advantages
Reduced carbon dioxide emissions for some crops
Medium net energy yield for biodiesel from palm oils
Medium net energy yield for ethanol from sugarcane
Liquid Biofuels Disadvantages
Fuel crops can compete with food crops for land and raise food prices
Fuel crops can be invasive species
Low net energy yield for corn ethanol and for biodiesel from soybeans
Higher carbon dioxide emissions from corn ethanol
With geothermal energy, heat is stored in:
Soil
Underground rocks
Fluid in the earth’s mantle
Geothermal heat pump system
continually transfers air into the ground to heat it up and brings it back up as cool air (or vice versa)
Hydrothermal reservoirs
Drill wells and extract various steams, water
Geothermal Energy Advantages
Medium net energy yield and high efficiency at accessible sites
Lower carbon dioxide emissions than fossil fuels
Low cost at favorable sites
Geothermal Energy Disadvantages
High cost except at concentrated and accessible sites
Scarcity of suitable sites
Noise and some carbon dioxide emissions
Production and storage of hydrogen
must be produced using other sources of energy
Hydrogen Advantages
Can be produced from plentiful water at some sites
No carbon dioxide emissions if produced with use of renewables
Good substitute for oil
High efficiency in fuel cells
Hydrogen Disadvantages
Negative net energy yield
Carbon dioxide emissions if produced from carbon-containing compounds
High costs create need for subsidies
Need hydrogen storage and distribution system
Note
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