Unit 6: Energy Resources and Consumption

Notes

Overview

• Conservation: management or regulation of a resource so that its use does not exceed the capacity of the resource to regenerate itself

• Preservation: maintenance of a species or ecosystem in order to ensure their perpetuation, with no concern to their potential monetary value

• Natural resources: a/biotic ecosystems

• Ecosystem capital: natural resources described in terms of their value

• Energy: capacity to do work

• Potential energy: stored energy; energy at rest (can be converted to kinetic energy)

• Kinetic energy: energy inmotion

• Radiant energy: sunlight

• Convection: transfer of heat by the movement of the heated matter

• Conduction: transfer of energy through matter from particle to particle

• Energy quality: higher energy quality produces more heat

• Net energy yield: comparison between the cost of extraction, processing, and transporting the amount of useful energy derived from the fuel

Laws of thermodynamics

1. First Law of Thermodynamics: energy can neither be created nor destroyed; it can only be transferred and transformed (ex. photosynthesis: radiant energy is converted to chem energy in the form of bonds that hold together atoms in carbs)

2. Second Law of Thermodynamics: entropy (disorder) of the universe is increasing

1. In most energy transformations, a sig fraction of energy is lost to the universe as heat

2. Ex. 10% rule

Resources

• Renewable sources

• Resources such as plants and animals

• Can be regenerated quickly

• Nonrenewable resources

• Minerals and fossil fuels

• Typically formed by very slow geological processes

• Incapable of being regenerated within the realm of human existence

• Consumption: of natural resources is the day to day use of env resources

• Production: use of env resources for profit

Fossil fuels

General notes

• Formed from the fossilized remains of once-living organisms

• Over time, organic matter is exposed to intense heat and pressure → organic molecules broken down into oil, coal, and natural gas

• Oil/petroleum: made of long chains of hydrocarbons

• Coal: mixture of carbon, hydrogen, oxygen, and other atoms

• Found in long continuous deposits called seams at various depths underground

• Natural gas: methane gas with mixture of other gases

• Oil and nat gas formed in same areas

• Deep in the earth under both land and ocean floor (stored in the pores between rocks)

Oil

• Crude oil: oil pumped fresh from a reserve

• Three diff methods of extracting oil

• Primary extraction: oil easily pumped to surface

• Pressure extraction: use mud, saltwater, CO2 to push out oil from reserve

• Steam extraction: uses steam, hot water, hot gases to partially melt very thick crude oil and make it easier to extract

• Drilling for oil is only moderately damaging the env bc little land is needed to drill

• Oil is transported thousands of miles by tankers, pipelines, trucks, etc → risk of explosion, oil spill

Coal

• Types of coal (order of purest)

• Anthracite: pure carbon

• Bituminous

• Subbituminous

• Lignite

• Coal mining

• Strip mining

• Removal of earth’s surface

• Coal is removed then the earth that was removed is replaced, topped with soil → area is contoured and re-vegetated

• Underground mining

• sinking of shafts to reach underground deposits

• networks of tunnels are dug or blasted and humans enter tunnels to manually retrieve the coal

• After production in mines stops, cave-ins occur

• Env MPX

• Contribute to air pollution (CO2, nitrogen oxides, mercury, sulfur dioxide are released as by-products)

• Produces fly ash and boiled residue as waste products

• Coal contains a sig amount of sulfur (iron sulfide, organic sulfur)

• Major source of mercury pollution → airborne mercury pollution can deposit in the ground as a result of rainfall → flows into lakes, streams, bodies of water both from rainfall and runoff → mercury travels → accumulate in fish → eaten by ppl

• Solutions

• Scrubbers: some by products can be removed through the actions of scrubbers (contain alkaline substances that precipitate out much of the sulfur dioxide)

• Burn coal with limestone: liberated sulfur combines with calcium in the limestone to form calcium sulfate → can't be released

• Wet scrubbing: fine mist of water to transform sulfur oxides from an air pollution issue to either a water pollution issue or to a commercial product → sulfuric acid

• Baghouse/cyclo scrubbers: filter or spin particulates out of the effluent gases

• Electrostatic filters: use electric charge to attract dust particulates to metal surfaces where they can be gathered and disposed of as solid waste

Natural gas

• Methane, pentane, butane, several other gases

• Simple molecular struc → nat gas produces only CO2 and water when it burns (don’t produce oxides of nitrogen and sulfur)

• Env MPX

• In an uncontrolled release, can cause violent explosions

• More difficult to transport than coal or oil

• Tanks can only hold a small amount of gas → nat gas is liquified by putting it under high pressure (LNG - liquefied natural gas) → requires a lot of energy

• Transported by pipes: risks of leaks and explosions → damaged habitats when building pipe sys

Nuke energy

General notes

• Primary non-fossil fuel non renewable energy source

• Fission: uranium 235 isotope split up (key reaction in production of nuke eng)

• Breeder reactors: generate new fissionable material faster than they consume material

• Nuclear fusion: fusing two nuclei (most likely 2 isotopes of hydrogen → tritium-2 neutrons and deuterium-1 neutron)

• Half-lives: tie it takes for half of the radioactive sample to degrade

• Good: produces no sulfur dioxide or nitrogen oxide; less CO2 than fossil fuels

Types of reactors

• Boiling water reactors

• Use heat of reactor core to boil water into steam → steam piped directly to turbines → steam spins turbines that generate electricity → water is cooled back to a liquid → pumped back to the core to be turned into steam again

• Uses 2 water circulation sys: (1) makes steam and carries it to the turbine (2) cools water form the core so it can be turned back into steam

• Pressurized water reactor

• Use eat from core to heat second water water supply via a heat exchanger

• Second water sys provides steam to spin turbines

• Third water circulation sys cools steam from the turbines (by using 2nd heat exchanger) → used to make steam again

• Uses 2 water circulation sys: (1) cools the core (2) makes steam (3) cools steam back into water to be made into steam again

Safety issues

Renewable energy

Biomass

• Includes woods, charcoal, and animal waste products

• Gasohol

• gasoline extender made from a mix of 90% gasoline and 10% ethanol

• Obtained by ferementing ag crops or crop wastes

• Partly derived from organic substrate

• Higher octane than has and burns more slowly, cooly and completely → reduced emissions of some pollutants

• Vaporizes more readily than gas → potential to aggravate ozone pollution in warm weather

• Ethanol/methanol

• Surface carbon and carbon based → add no net carbon to the atmo

• CO2 is released during combustion

• More expensive and energy intensive to produce (one bushel of corn produces only 2.5 gallons of ethanol)

• Biodiesel: new product made largely from waste vegetable oils

Hydroelectric energy

• Generated as moving water turns turbine

• ADV

• Production releases no pollutants

• As water is held behind dams, new habitats in the forms of wetlands are created

• Env MPX

• Produces thermal pollution

• Requires that rivers are dammed → change rates at which rivers flow; destroys habitats

• Silting: as water sits behind dams, normal sediments it carries have time to sink to the bottom → additional weight on struc

• Structures have to be strong enough to hold back many tons of sediment

• Sediment isn't passed farther down the river → sediment is used to fertilize floodplains of river

• Reservoirs have greater surface area = higher rate of evaporation and water loss

• Fish that spawn in the normally silty river no longer have a place to do so; dams prevent fish from returning to their hatching streams

• SOLUTION: fish ladders- let some fish return upriver, BUT … number of fish that get thru is limited so pop still decline

• Limited number of rivers = limited hydroelectricity

Solar energy

• Passive solar energy collection: use of building materials, building placement, and design to passively collect solar energy that can be used to keep a building warm or cool (ex. windows)

• Active collection: use of devices that collect, focus, transport, or store solar energy (ex. solar panels)

• Solar panels

• absorb solar energy and pass the energy onto tubes in which water is circulating → heated water can be stored for later use

• Photovoltaic cells (PV cells): produces electricity which is then stored in batteries

• When sunlight hits PV cells, electrons energized and flow freely → produces electric current

• Produces no air pollutants, BUT… production of PV cells requires the use of fossil fuels

• PV cells use no moving parts, require little maintenance, are silent

• Not every location in the US receives enough sunlight to make solar panels worthwhile

Wind energy

• Wind blows into wind turbine that spins the blades - machinery inside base of windmill (nacelle) rotates

• Wind farms: groups of placed modern wind turbines

• Can be located offshore in the ocean

• DAs

• More costly than using fossil fuels bc of the initial outlay of capital that must be invested in order to build them

• What happens when there’s no wind?

• Birds could be cut up and killed by blades

• SOLUTION: stop placing wind turbines in the middle of migration routes

• Produces no harmful emissions

Geothermal energy

• Produced by harnessing the earth’s internal heat

• Interior of earth is still warm due to radioactive decay

• Greatly elevated temperatures within earth result in a buildup of pressure → some of this heat escapes through fissure and cracks to the surface (ex. geysers, hydrothermal vents, hot springs)

• Naturally heated water and steam from the earth’s interior turn turbines to create electricity

• Wells are typically drilled down into the earth thousands of meter to water that's 300-700℉ → brought to surface and converted to steam → powers the turbine

• Concerns

• Limited bc only few areas have geothermal sources to tap

• Salts that are dissolved in the water corrode machinery parts

• Some gases (methane, CO2, hydrogen sulfide, ammonia) that are trapped in the water may be released as the water is utilized

Ocean tides

• Tidal movements of ocean water can be tapped and used as a source of energy

• Dams erected across outlets of tidal basins → incoming tides are sluiced through the dam → outgoing tides turns turbines and generates electricity

Hydrogen cells

• Hydrogen is obtained from fossil fuels by a process called reforming

• Hydrogen is very difficult to store and not very energy dense, BUT… hydrogen fuel cells are considered to the best, cleanest, and safest fuel source

• Free hydrogen not found on earth, but can be released thru the process of electrolysis (hydrogen atoms are stripped from water, leaves the oxygen atom)

• Hydrogen can also be obtained from organic molecules (but the use of organic sources can release pollutants)

• Once free hydrogen is released, it can be stored and then used to generate electricity through reverse reaction of electrolysis

• Good: only waste from the fuel cell is water vapor

• Bad: high cost of fuel cell and lack of hydrogen fuel stations limit tech

Energy conservation

• Practice of reducing our use of fossil fuels and reducing the MPX we have on the env as we produce and use energy

• Hybrid vehicles: built with one electric and one gas-powered engine

• Good gas mileage, produce less CO2 pollution

• Diesel-fueled cars: pure diesel fuel, switch to biofuel

• CAFE (Corporate Average Fuel Economy) standards

• Set mile per gallon standards for a fleet of cars

• Goal: reduce energy consumption by incr fuel economy of cars and light trucks

• Mass transit

Env policy

Major acts

Green taxes

• Lowers taxes on income (payroll/income), raises taxes on consumption

• List of taxes

• Carbon taxes on the use of fossil fuels

• Taxes on the extraction of mineral, energy, and forestry products

• License fees for fishing and hunting

• Taxes on tech and products associated w sub neg externalities

• Garbage disposal taxes

• Taxes on effluents, emissions, and other hazardous wastes

• Goals of green taxes

• Generation of revenue to correct past pollution damage and reduce future pollution

• Change behavior

• Use funds received from taxes for restoration

• Market permits: cap and trade permits

• Companies allowed to buy permits that allow them to discharge a certain amount of substances into certain env outlets

• If they can reduce discharge, allowed to sell remaining portion of permit to another company

• Economic incentive for companies to sell = decr discharge

Int’l agreements