Unit 6: Energy

Apes unit 6 Terms

**Renewable Energy Source**

can be replenished naturally, at or near rate of consumption & reused

**Depletable Renewables**

can run out if overused

* Biomas (wood, charcoal, ethanol)

**Nondepletable Renewables**

do not run out if over used

* Solar, wind, hydroelectric, geothermal

**Nonrenewable Energy Sources**

exist in fixed amounts on earth & can’t easily be replaced or regenerated

**Fossil fuels**

fossilized remains of ancient biomass that take millions of years to form 

* Coal, oil, natural gas

**Nuclear**

energy generated from uranium or other radioactive fuels

**Rate of Consumption**

rate of use must be at or below rate of regeneration for renewables 

**Developed Nations**

use more energy on a per capita basis, but developed nations use more energy in total (higher pop.)

* The avg. US residents use 5x as much energy as the world avg. 

**Developing Nations**

still industrializing & pop. is till growing rapidly

* It will also increase on a per/person basis as their economics industrialize & residents achieve higher standards of living 

**Fossil Fuels**

 the most common fuel source globally 

* Oil -> gasoline; vehicles
* Coal = main fuel for electricity generation
* Natural gas = secondary fuel for electricity generation & main fuel for heating 

**Hydroelectric Energy**

dams used to create electricity; 2nd largest source

* Water spins a turbine which generates electricity

**Nuclear Energy**

3rd largest source

* Uranium fission releases

**Subsistence Fuels**

biomass that they can easily gather/purchase

* Many residents of less developed nations depend on this
* Ex. wood, charcoal, dried animal manure
* Can drive deforestation

**Development Increases FF Consumption**

econ. Development -> affluence (wealth) -> higher per capita GDP -> energy use

**Factors that Affect Energy Source Use**

availability & price

**Availability**

fossil fuels use depends on discovered reserves & accessibility of these reserves 

* Uses of FFs varies heavily with availability

**Price**

FF prices fluctuate dramatically with discovery of new reserves or depletion of existing ones

* Fracking opens new NG reserves, increasing availability, decreasing price, increasing use

**Government Regulation**

gov. Can mandate certain energy source mixes (25% renewable by 2025)

* Cannot directly raise or lower prices of energy sources (raise gas to $10/gallon)
* Taxes increase to discourage 
* Rebates, or tax credits to encourage companies building renewable energy power plants

**Subsistence Fuels**

biomass fuel sources that are easily accessible (can be found & gathered by hand); often used in developing countries as a home heating or cooking fuel

* Wood (& charcoal) are two of the most common fuel sources in developing countries
* Peat is partially decomposed organic matter )often ferns or other plants) found in wet, acidic ecosystems like bogs & moors 

**Coal Formation**

pressure from overlying rock & sediment layers compacts peat into coal over time

* In order of energy density & quality: Lignite -> bituminous -> anthracite
* Because higher energy density means more energy released when a fuel source is burned, anthracite is the most valuable form of coal (highest quality) 

**Natural Gas**

Decaying remains of plants & animals (mostly marine life) are buried under layers of rock & converted by pressure into oil (petroleum) and natural gas over time 

* Mostly methane (CH4) & is found on top of trapped oil (petroleum) deposits
* Considered the “cleanest” fossil fuel (produces the fewest air pollutants & least CO2 when burned)

**Crude Oil**

decaying organic matter trapped under rock layers is compressed into oil over time

* Extracted by drilling a well through the overlying rock layers to reach layers the underground deposit & then pumping liquid oil out under pressure
* Can also be recovered from tar sands (combination of clay, sand, water, & bitumen)

**Fossil Fuel Products**

crude oil (petroleum) is converted into lots of different products through the process of fractional distillation 

**Fracking & Shale Gas**

method of natural gas extraction that has extended access to natural gas

* Fracking natural gas from shale rock increases & extends supply of natural gas 

**Shale Gas Reserves**

FFs are non-renewable, & will eventually be depleted, but short-term economic profit still drives extraction & use

**Tar/oil Sands**

bitumen deposits where crude oil can be recovered, but w/ higher water & energy inputs 

* Canada (Alberta region) = world’s largest oil sands reserve

**Fossil Fuel Combustion**

reaction between oxygen (O2) & fossil fuels (hydrocarbons) that releases energy as heat & produces CO2 & H2O as products

* Combustion is a step in the carbon cycle
* Methane (natural gas), gasoline, propane, butane, coal are all fossil fuels (hydrocarbons) that release energy in the same way

**FF to Generate Electricity**

the #1 source of electricity production globally is coal, followed by natural gas

* These steps of electricity generation are the same, no matter what you’re burning to produce the initial heat; Heat -> Water into Steam -> Steam turns a turbine -> Turbine powers generator -> Generator produces electricity
* Coal, oil, natural gas, biomass, & trach can all be burned to drive this same process & create energy; even nuclear energy work similarity, / nuclear fission producing the initial heat

**Environmental Consequences (Coal)**

habitat destruction to clear land for mining

* Produces pollutants & releases CO2 (GHG -> global warming)

**Generating Electricity**

coal is 30% efficient as a fuel sources for generating electricity (30% of energy from the bonds in the hydrocarbons are converted to electricity)

* Much of the energy “lost” or not converted into electricity escapes as heat 

**Cogeneration**

when the heat produced from electricity generation is used to provide heat (air & hot water) in a building: CHP (combined heat & power) systems are close to 90% efficient (much better than coal/NG alone)

**Oil/Petroleum Extraction**

extracted by drilling a well through the overlying rock layers to reach the underground deposit & then pumping liquid oil out under pressure 

* Can also be recovered from tar sands (combination of clay, sand, water, & bitumen)

**Environmental Consequences (Tar Sands)**

habitat destruction to clear land for: roads, drilling equipment, digging through ground surface to reach deposits (biodiversity loss)

Ground or nearby surface water depletion (H2O needed for steam & for washing impurities from bitumen at refinery)

**Environmental Consequences (Crude Oil/Petroleum)**

possibility of spill (either from tanker ships or pipelines breaking)

* Habitat loss or fragmentation when land is cleared for roads, drilling equipment, & pipelines 

**Fracking (Hydraulic Fracturing)**

used to extract natural gas from sedimentary rock

* Vertical well is drilled down to sediment rock layer, horizontally into the rock layer

**Environmental Consequences (Fracking)**

possibility of well leaking & contaminating groundwater w/ facking fluid (salt, detergents, acids) or hydrocarbons

* Depletion of ground or surface waters nearby (as they’re drawn from for fracking fluid)

**Nuclear Fission & Radioactivity**

 a neutron is fired into the nucleus of a radioactive (unstable) element, such as Uranium

* Radioactivity refers to the energy given off by the nucleus of a radioactive

**Radioactive Half-life**

the amount of time it takes for 50% of a radioactive substance to decay (breakdown)

**Generating Electricity**

same electricity generation process as w/ FFs. just uranium fission to heat water into steam

* Heat -> water into steam -> steam turns a turbine -> turbine powers generator -> generator produces electricity
* U-235 stored in fuel roads, submerged in water in reaction core; heat from fission turns H2O -> steam

**Control Rods**

 lowered into reactor core to absorb neutrons & slow down the reaction, preventing meltdown (explosion)

**Water Pumps**

brings in cool water to be turned into steam & also cools reactor down from overheating

**Cooling Towers**

allows steam from turbine to condense back into liquid & cool down before being reused (this gives off H2O vapor) 

**Nonrenewable, but cleaner than FFs**

 nuclear energy is NONRENEWABLE because radioactive elements like Uranium are limited

* Other drawbacks of nuclear energy include possibility of meltdown & radioactive contamination

**Spent Fuel Rods**

used fuel rods remain radioactive for millions of years & need to be stores in lead containers 

**Mine Tailings**

leftover rock & soil from mining may have radioactive elements that can contaminate water or soil nearby

**Water Use**

nuclear PPs require lots of water & can deplete local surface or groundwater sources

**Thermal Pollution**

hot water from PP released back into surface water can cause thermal shock (decreased O2 & suffocation) 

**Nuclear Meltdowns**

three mile island (us), Fukushima Japan, & Chernobyl Ukraine = 3 most famous nuclear meltdowns 

* Environmental consequences of meltdowns: genetic mutations & cancer in surrounding people, animals, & plants due to radiation released from reactor core

**Three Mile Island**

partial meltdown due to testing error, radiation released but no deaths or residual cancer cases

**Fukushima (Japan)**

an earthquake & tsunami triggered cooling pump failure that lead to a meltdown (explosion of reactor core) & widespread radiation release

**Chernobyl (Ukraine)**

stuck cooling valve during test lead to complete meltdown (explosion of reactor core), several deaths, & widespread radiation release

**Contaminated Soil**

radiation can remain in soil & harm plants & animals in the future (genetic mutations)

**Radiation Spread**

radiation can be carried by the wind over long distances, affecting ecosystems far from the meltdown site 

**Biomass**

organic matter (wood/charcoal, dried animal waste, dead leaves/brush) burned to release heat-primarily for heating homes/cooking

* Utilized primarily in developing world for heating homes & cooking food

**Biofuels**

liquid fuels (ethanol, biodiesel) created from biomass (corn, sugar cane, palm oil) 

* Used as replacement fuel sources for gasoline, primarily in vehicles

**Modern vs. Fossil Carbon**

 biomass burning releases CO2, but doesn’t increase atmospheric carbon levels like FF burning does

**Modern Carbon**

CO2 that was recently sequestered, or taken out of the atmosphere

**Fossil Carbon**

stored for millions of years

**Human Health & Env. Consequences of Biomass Burning**

biomass burning releases CO, NO, PM, & VOCs (all respiratory irritants)

* Environmental consequences = deforestation & air pollutants 

**Biofuels: Ethanol & Algae**

corn & sugar can are fermented into ethanol which is mixed w/ gasoline

* Environmental consequences = all the negative consequences of monocrop agriculture

**Biodiesel**

liquid fuels produced specifically from plant oils (soy, canola, palm)

**Passive Solar**

absorbing or blocking heat from the sun, w/out use of mechanical/electrical equipment

**Active Solar**

use of mechanical/electrical equipment to capture sun’s heat (solar water heaters or CST-concentrated solar thermal), or convert light rays directly into electricity (PV cells)

**Photovoltaic Cells (PV)**

solar panels; contains semiconductor (usually silicon) that emit low voltage electrical current when exposed to the sun 

**Photons**

particles carrying energy from sun

* Causes separation of charges between two semiconductor layers(n&p)
* Electrons separate from protons & flow through circuit to load, delivering energy (as electricity)

**Intermittency**

solar energy can only be generated during the day

* Could be solved by cheaper, larger batteries that can share energy generated during the day for use at night 
* Currently these aren’t cost-effective yet 

**Concentrated Solar Thermal (CST)**

heliostats (mirrors) reflect sun’s rays onto a central water tower in order to heat water to produce steam to turn a turbine -> electricity

* Drawback: habitat destruction & light beams frying birds in mid air 

**Community (solar farm) vs. Rooftop Solar**

* Large-scale solar “farms” can generate lots of electricity, but do take up land & cause habitat loss/fragmentation
* Rooftop solar doesn’t take up land, but only produces a little electricity

**Solar Energy Pros**

no air pollutants (PM, SOX, NOX) released to generate electricity

* No CO2 released when generating electricity 
* Renewable, unlike FFs which will run out
* No mining of fossil fuels for electricity production

**Solar Energy Cons**

semiconductor metals (silicon) still need to be mined to produce PV cells (solar panels)

* This can disrupt habitats & pollute water w/ mine tailings air w/ PM
* Silicon is a limited resource
* Solar panel farms can displace habitats

**Hydroelectricity**

kinetic energy of moving water -> spins a turbine (mechanical energy) -> turbine powers generator 

* Water moves either w/ natural current of river or tides, or by falling vertically through channel in a dam
* Larger renewable source of electricity globally
* China, Brazil, & US = 3 biggest hydroelectricity producers

**Water Impoundment(dams)**

dam built in a river creates a large artificial lake behind the dam (reservoir)

**Sedimentation**

buildup of sediments behind dam

**Run of River System & Tidal Energy**

a dam diverts the natural current of a river through man-made channel beside the river 

**Tidal Power**

comes from tidal ocean flow turning turbine (coastal areas only)

**Drawbacks of Hydroelectricity Dames(ecol/env/econ)**

reservoir floods habitats behind dam (forest/wetlands -> gone; river becomes a lake

* prevents upstream migration of fish like salmon, that need to swim up to spawning grounds to reproduce
* Env. impacts = FF combustion during dam construction, increased evaporation due to larger surface area of reservoir, & methane release due to anaerobic decomposition of organic matter in reservoir
* Econ. Impacts = human homes & businesses must be relocated due to reservoir flooding, initial construction is very expensive (does create long-term jobs though), sediment buildup must be dredged (removed by crane) eventually
* Loss of ecosystem services from downstream wetlands, potential loss of fishing revenue if salmon breeding is disrupted 

**Fish Ladders**

cement “step” or series of pools that migratory fish like salmon can use to continue migration upstream, around or over dams

**Benefits of Hydroelectricity Dames**

* No GHG emissions when producing electricity (initial construction does require cement & machines that emit GHGs)
* Allows for control of downstream seasonal flooding 

**Geothermal**

natural radioactive decay of elements deep in earth’s core gives off heat, driving magma convection currents which carry heat to upper portion of mantle, close to earth’s surface 

**Geothermal for electricity**

naturally heated water reservoirs underground are drilled into & piped up to the surface (or water can be piped down into naturally heated rock layers)

**Ground Source Heat Pump**

often referred to as “geothermal” but technically the heat does not come from geologic activity (comes from the ground storing heat from the sun)

**Geothermal Heating**

true geothermal heating involves piping water deep into the ground to be heated by magma & then transferring heat from water to the building 

* Different than ground source heat pump

**Geothermal Pros**

* Potentially renewable, only if water is piped back into the ground for reuse 
* Much less CO2 emissions than FF electricity
* No release of (PM/SOx/NOx/CO)as is case w/ FFs

**Geothermal Cons**

* Not everywhere on earth has access to geothermal energy reaching close enough to surface to access it 
* Hydrogen sulfide can be released, which is toxic & can be lethal to humans & animals
* Cost of drilling that deep in the earth can be very high initially 
* Sometimes so high that it’s not even worth it 

**Hydrogen Fuel Cell**

use hydrogen as a renewable, alternative source to fossil fuel

* H2 gas enters fuel cell where it’s split into protons (H+) & electrons (e-) by an electrolyte membrane that only lets protons through
* Most common application is in vehicles 

**Creating H2 Gas**

key challenge to H fuel cells is obtaining pure H gas (b/c it doesn’t exist by itself as a gas naturally) 

* Separating H2 gas from other molecules like H2O or CH4 is very intensive
* Two main processes are steam reforming (95% of all H production) & electrolysis (less common, but more sustainable) 

**Steam Reforming**

 burning natural gas (CH4) & using steam to separate H gas from the methane (CH4)

* Emits CO2 & requires NG (FF) input

**Electrolysis**

electrical current is applied water, breaking it into O2 & H2

* No CO2 emission, but does require electricity

**Hydrogen As an Energy Carrier (Pros)**

because H2 gas can be stored in pressurized tanks, it can be transported for use creating electricity later, in a different location 

* Can also be used as a fuel for vehicles (replacing gasoline) or to create ammonia for fertilizer, or in the chemical industry

**Drawbacks of H Fuel Cells**

since 95% of H2 production requires methane (CH4), H fuel cells are based on a non-renewable & CO2 releasing energy source 

**Wind Turbine Electricity Generation**

kinetic energy of moving air (wind)spins a turbine; generator converts mechanical energy of turbine into electricity 

* Average turbine can power 460 homes

**Wind Turbine Location**

clusters in group (wind projects or farms) in flat, open areas (usually rural)

* Can share land w/ agricultural use

**Offshore Wind**

wind farms in oceans or lakes 

* Requires transmission lines built across long distances to reach land 

**Wind Energy Benefits**

non-depletable (isn’t decreased by its use) - even better than renewable energy

* No GHG emissions or air pollutants released when generating electricity
* No CO2 (climate change) or NOx/SOx/PM as w/ burning FFs
* Can share land uses (don’t destroy habitat or cause soil/water contamination

**Wind Energy Drawbacks**

intermittency (isn’t always available) can’t replace base-load power (sources that are always available like FFs, nuclear, or geothermal)

* Can kill birds & bats (especially larger, migratory birds) 
* Can be considered an eyesore or source of noise pollution by some 

**Small Scale Energy Conservation**

lowering thermostat to use less heat or use AC less often

* Conserving water w/ native plants instead of grass, low flow shower heads, efficient toilets, dishwashers, dryers
* Energy efficient appliances, better insulation to keep more heat in home 

**Large Scale Energy Conservation**

improving fuel efficiency (fuel economy) standards ex: 20 mpg -> 30 mpg

* Subsidizing (tax credits for electric vehicles, charging stations, & hybrids
* Increased public transport (buses & light rails), green building design

**Sustainable Home Design**

ways to either block out or take advantages of sun’s natural heat, or keep in heating/cooling to decrease energy required

* Deciduous shade trees for landscaping (leaves block sun in summer, but allow it in during winter)
* Using passive solar design concepts to trap sun’s heat & decrease energy from heating system (heat absorbing walls, triple or double paned windows) 
* Well-insulated walls/attic to trap heat in winter & cool air from AC system in summer 
* This decrease electricity used by AC unit & energy used by heating system

**Water Conservation**

native plants require less watering than traditional lawns (also increase biodiversity of pollinators & require less fertilizer)

* Low-flow showers, toilets, & dishwashers do the same job w/ less total water (less energy to purify & pump to homes)
* Rain barrels allow rain water to be used for watering plants or washing cars 

**Energy Conservation-Transportation**

28% of total US energy use comes from transport of goods & people 

* CAFE (corporate average fuel economy) standards are regulations set in US to require auto manufacturers to make cars that meet certain MPG standards, or pay penalties 
* Hybrids (Pruis) have both gasoline & electrical engine, enabling them to have higher MPG rating 
* Electric vehicles (EVs or BEVs) like the Tesla or LEAF use no gasoline, but still require electricity (only as sustainable as elect. source) 
* Public transit & carpooling are even better energy-saving transport options