APES - Chapter 15 & 16 Test Review

Net Energy Yield

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:

1. Use unconventional heavy oil

2. Live with much higher oil problems

3. Extend oil supplies (for example, improve oil efficiency)

4. 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

1. Mine the uranium

2. Process and enrich the uranium to make the fuel

3. Use it in the reactor

4. Safely store the radioactive waste

5. Decommission the reactor

Nuclear Energy Advantages

• Low environmental impact (without accidents)

• Emits ⅙ 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