APES unit 6 Flashcards
renewable energy sources
can be replenished naturally, at or near the rate of consumption
depletable renewable
can runout if overused EX biomass (wood, charcoal,)
non-depletable renewable
resources do not run out EX solar, wind, hydroelectric, geothermal
non-renewable energy sources
exists in fixed amounts on earth, can’t easily be replaced or regenerated
non-renewable energy sources Fossil Fuels
fossilized remains of ancient biomass that take millions of years to form
non-renewable nuclear
energy generated from uranium or other radioactive fuels
key to renewable energy
rate of consumption must be at or below rate of regeneration for renewables
subsistence fuels
biomass fuel sources that are easily accessible (found and gathered by hand); often used in developing countries as a home heating or cooking food
wood as a fuel source in developing countries
wood is free/cheap to cut down and utilize as fuel; can cause deforestation and habitat loss
charcoal
is made by heating wood under low oxygen conditions for a long time (dehydrating wood)
peat
peat is partially decomposed organic matter (often ferns or other plants) found in wet, acidic ecosystems like bogs and moors.
– can be dried and used as fuel
coal formation
pressure from overlying rock and sediment layers compacts peat into coal over time
stages of coal formation
peat – lignight – bituminous – anthracite (oldest)
anthracite
most valuable because more energy is released when coal is burned.
coal for electricity
coal is burned to heat water into steam, to turn a turbine that generates electricity
more dense coal =
hotter, longer fires = more steam = more electricity
natural gas (methane)
decaying remains of plants and animals (mostly marine) are buried under layers of rock and converted by pressure into oil (petroleum) and natural gas over time.
what is natural gas? where is it mostly found?
natural gas is mostly methane (CH4) and is found on top of trapped oil deposits
how does natural gas form?
forms when oil is trapped in a porous, sedimentary rock, underneath harder, impermeable rock layer that doesn’t let gas escape
what is the cleanest fossil fuel?
natural gas is the cleanest: produces fewest air pollutants when burned
how does crude oil (petroleum) form?
decaying organic matter trapped under rock layers is compressed into oil over time
how is crude oil extracted?
by drilling a well through the overlying rock layers to reach the underground deposit. Then pumping liquid oil out under pressure
crude oil extraction from tar sands (intensive)
extracting and using oil from tar sands is extremely energy and water intensive.
why is extracting crude oil from tar sands water and energy intensive?
lots of water needs to be heated to create steam that’s piped down into the tar sand to melt the bitumen into a liquid that can flow up a pipe
lots more water is used to separate the oil from all the impurities
bitumen
thick, sticky, semi-solid form of petroleum (asphalt)
how are fossil fuels converted into lots of diff. products
crude oil is burned in a furnace and vapor passes into a column where diff. hydrocarbons are separated based on their boiling points
–hydrocarbons with lower at the top
–hydrocarbons with higher boiling points at bottom
co-generation
a fuel source is used to gather both usable heat and electricity
EX heat produced by a car engine can be used to run the car’s heater in winter
developed nations vs. developing energy consumption
developed nations use more energy per capita basis, but developing nations use more in total (higher pop.)
how does global energy consumption vary depending on developed nations vs. developing?
will incr. on a per/person basis their economies industrialize and residents achieve higher standards of living
most common fuel source globally
- fossil fuels:
oil - gasoline
coal - electricity generation
nat. gas - electricity and heating - hydroelectric energy:
dams used to create electricity. water spins a turbine - nuclear:
uranium fission releases heat to turn water into steam and turn a turbine
factors that affect energy source use
availability
price
gov. regulation
availability affecting energy source use
fossil fuel use depends on discovered reserves and accessibility of these reserves. use of FFs varies heavily with availabilty
price affecting energy source use
FF prices fluctuate dramatically with discovery of new reserves or depletion of existing ones – fracking opens new Nat. gas reserves, incr. availability and decr. price
gov regulation affecting energy source use
CAN mandate certain energy source mixes.
use taxes incr. to discourage companies from building FF power plants.
rebates or tax credits to encourage companies to build renewable energy power plants
CANNOT directly raise or lower prices of energy sources
global distribution of energy sources
energy sources are found all over the world
diff. countries/ region lead in certain resources
–not uniformly distributed
– depends on geologic history of area
coal energy reserves years left and most in countries
~100 - 150 yrs.
1. US
2. Russia
3. Australia
4. China
5. india
natural gas reserves years left and most in countries
~ 50-60 yrs
1. Russia
2. Iran
3. Qatar
4. US
5. Saudi arabia
oil reserves years left and most in countries
~50yrs.
1. Venezuela
2. Saudi arabia
3. iran
4. canada
5. iraq
geologic formation of oil/ nat. gas reserve layer D = source rock
dead organisms were buried under heat and pressure over millions of years; become oil/gas that flows to layer above
geologic formation of oil/ nat. gas reserve layer C = reservoir rock
layer of permeable/ porous rock where oil and nat.gas flow and collect
geologic formation of oil/ nat. gas reserve layer B = caprock
layer can be porous but not permeable; does not allow flow of oll/nat. gas to surface
fracking and shale gas
a method of natural gas extraction that has extended access to natural gas
– gas trapped in semi-permeable rock layers is releases by cracking the rock with pressurized water
tar / oil sands
bitumen deposits where crude oil can be recovered, but with higher water and energy inputs
CANADA alberta region worlds largest oil sands reserve
extends the worlds supply for crude oile
combustion formula
CxHy + O2 → CO2 + H2O + energy
biomass
organic matter (wood/charcoal, dried animal waste, dead leaves/ brush, peat)
where/ how is biomass used for fuel
utilized primarily in developing world
can be burned in power plants to generate electricity (less common than FF)
human health effects of using biomass as energy
burning biomass releases CO (deadly gas)
– especially harmful if burned indoors without proper vantilation
– solution: chimneys/ventilation, cook outside
environmental effects of using biomass as energy source
deforestation/ habitat destruction (loss of ecosystem services)
air pollution (NOx, PM, VOC contribute to smog formation)
burning biomass releases
CO2 but doesn’t incr. atmospheric CO2 levels life FF burning does
burning biomass
releases modern carbon whereas FF burning releases Fossil carbon that had been stored for millions of years
modern carbon
CO2 that was recently sequestered or taken out of the atm.
biomass is considered
is considered ‘carbon neutral’
how to think of modern carbon
spending a dollar someone just gave you vs. withdrawing from your long-term savings account
bio-fuels
liquid fuels (ethanol, biodiesel) created from biomass (corn, sugar cane, algae, palm oil)
ethanol
corn or sugar cane are fermented into ethanol which is mixed with gasoline
– has low EROEI (takes a lot of energy to grow corn, process into ethanol)
— algae produce oils that can be used as bio-fuels more sustainably than corn
biodiesel
liquid fuels produces from new and used vegetable oils ( canola, palm, soy) or animal fats (cooking greese) used as replacement for petroleum-based diesel
environmental benefits of bio-fuels
+ renewable, but only if sustainably produced
+ can use waste biomass (unconsumable parts of plants)
environmental drawbacks of bio-fuels
- soil erosion, habitat loss, GHG release, H2O use, monocrop lowers biodiversity
- lots of corn needed relative to petroleum; can compete with land for human food
- palm oil is especially harmful due to clearing forests for palm plantations
nuclear fission
neutron is fired into nucleus of a radioactive (unstable) element such as uranium. Nucleus breaks apart and releases lots of energy (heat) + more neutrons that break more nuclei (chain reaction)
radioactivity
the energy given off by the nucleus of a radioactive isotope (uranium 235).
radioactive half-life
the amount of time it takes for 50% of a radioactive substance to decay (breakdown)
generating electricity nuclear
same process just using uranium to heat water into steam.
U - 235 stored in fuel rods that are submerged in water in reaction core. heat from fission turns water into steam.
Control rods are lowered into reactor core to absorb neutrons and slow down the reaction to prevent explosion.
Water pump brings in cool water from nearby river/lake to cool reactor and prevent overheating – explosion.
cooling tower allows steam from turbine to condense back into liquid and cool down before being reused (gives of water vapot)
nonrenewable nuclear
–nuclear is non-renewable but cleaner than FFs. because uranium is limited. (limited but abundant)
–No air pollutants released when electricity is generated but mining for uranium and plant construction releases GHGs.
– only gas released is water vapor
drawbacks of nuclear energy
include possibility of reactor meltdown (which are rare) and radioactive contamination
– spent fuel rods are radioactive for millions of yrs and need to be stored in lead containers.
– mine taillings can have leftover radioactive elements (contaminate soil and water nearby)
– water use is high. PP require lots of water can deplete groundwater
– thermal pollution , hot water from PP released back into surface waters causes thermal shock and decr. 02
3 most famous nuclear meltdowns
- three mile island: partial meltdown due to testing error. radiation released but no deaths or residual cancer cases
- Fukishima: earthquake and tsunami triggered cooling pump failure leading to explosion. wide spread radiation release
- chernobyl: stuck cooling valve during test lead to complete meltdown. Several deaths and widespread radiation release
environmental consequences of meltdowns
–genetic mutations
–cancer in surrounding ppl, animals and plants due to radiation release
– contaminated soil. radiation remains in soil and harms plants and animals in future (gen. mutations)
– radiation can be carried by the wind over long distances affecting ecosystems far from meltdown site
passive solar energy
absorbing or blocking heat from sun without use of mechanical or electrical equipment
examples of passive solar energy
– using sun’s heat to cook food in a solar oven
– orienting building design to block sunlight in warmer months & allow sunlight in during cooler months
– doubled panned windows, southern facing windows with overhanging roof, deciduose shade trees, skylight to decr. electricity use, dark colored roof to absorb sunlight
active solar energy
use of mechanical/ electrical equipment to capture the sun’s heat or convert light rays directly into electricity
solar water heaters. (Active solar)
solar water heaters capture sun’s heat in water or circulating fluid & transfer heat to warm water form home. – in place of electric/gas heaters.
photovoltaic cells (PV)
solar pannels
– photons (particles carrying energy from sun) cause separation of charges between two semiconductor layers (n & p); electrons separate from protons and flow through circuit delivering energy
– PV cells on roof can either directly power building or send excess electricity back to the grid (for other users earning u credit from utility company)
drawback of PV
intermittency (solar energy can only be generated during the day)
solution: could be solved by cheaper, larger batteries that can store energy generated during the day to use at night. But aren’t currently 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 turbine etc.
drawback: habitat destruction and the light beams frying birds mid-air
community solar vs. rooftop solar
large scale solar farms can generate lots of electricity, but they do take up land and cause habitat loss/ fragmentation.
rooftop solar doesn’t take up land, but only produces a little electricity
solar energy pros
–no air pollutants releases to gen. electricity
–no CO2 released when gen. electricity
– no mining of fossil fuels for electricity production
– renewable, unlike FFs which will run out
solar energy cons
– semiconductor metals (silicon) still needs to be mined to produce panels
– can disrupt habitat & pollute water, air with PM
– solar panel farms use land and displace habitat
– initial cost to manufacture is very high
– only produces energy during the day
hydroelectric basics
kinetic energy of moving water spins a turbine(mechanical energy) and the turbine powers the generator
– water moves either with natural current of river or tides or by falling vertically through channel in dam
– by far largest renewable source of electricity globally
– china, Brazil and US are 3 biggest hydroelectric producers
water impoundment (dam)
creates a large artificial lake behind the dam (reservoir)
– enables operator to allow more or less water through the channel in the dam, incr. or decr. electricity production
– also allows for flood control downstream
– reservoirs are a source of recreation money (boating, tourism, fishing)
2 big impacts behind the dam
flooding of ecosystems behind the dam
sedimentation buildup behind dam
run of river system
pros and cons
a dam diverts the natural current of a river through man-made channel beside the river.
– natural current turns a turbine etc…
– less impactful to surrounding ecosystem since no reservoir is formed and ecosystems behind dam aren’t flooded
– doesn’t stop natural flow of sediments
– doesn’t generate as much power and may be unavailable in warmer seasons when water levels are low
tidal system
tidal power comes from tidal ocean flow turning a turbine.
(coastal areas only)
– in a bay water is trapped during high tide and then run through a turbine back into the ocean during low tide.
ecological drawbacks and impacts of hydroelectric dams
reservoir floods habitats behind dam.
– prevents upstream migration of fish like salmon that need to swim up to spawning grounds to reproduce.
–sedimentation changes upstream and downstream conditions
- upstream becomes warmer (less 02)
- downstream looses sediment (important nutrient source) decr. water level, looses streambed habitat
environmental drawbacks and impacts of hydroelectric dams
FF combustion during dam construction, incr. evaporation due to larger surface area of reservoir, methane release due to anaerobic decomposition of organic matter in reservoir
economic impacts of hydroelectric dams
human homes and businesses must be relocated due to reservoir flooding, initial construction is very expensive (++does create long term jobs++), 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 ‘‘steps’’ or series of pools that migratory fish like salmon can use to continue migration upstream, around or over dams
– enables continued breeding for salmon, food source for predators like large birds, bears and fishing for humans
–'’salmon cannon’’ is a similar alternative that enables salmon to be captured or directed into a tube that carries them over the dam
benefits of hydroelectric dams
no GHG emissions when producing elecrt. (initial construction does require cement and machinery)
– reservoir and dam can be tourist attractions
– jobs are created to maintain the dam
allows for flood control downstream seasonal flooding
geothermal basics
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,
– water can be piped down into the ground and heated by this heat from mantle
(hot water into steam, turbine, generator etc.)
geothermal for electricity
Naturally heated water reservoirs underground are drilled into and piped up to the surface (or water can be piped down into naturally heated rock layers)
– heat from magma turns water into steam which is forced through pipes to spin a turbine
– water is cooled in a cooling tower and returned to the ground to start process over
– renewable since heat from earth’s core won’t run out
ground source heat pump
–10 feet down the ground stays a consistent 50 - 60 degrees due to holding heat from sun
– heat absorbing fluid is pumped through a pipe into the ground where it either takes on heat from the ground or gives off heat to the ground
—-in summer heat from homes transfers to liquid and liquid transfers heat to ground, cooling house
—- in winter liquid takes heat from ground and transfers to the house, warming the house
geothermal heating
includes piping water deep into ground to be heated by magma and then transferring heat from water to the building
– diff. than ground source heat pump
– well must go kms down into the ground to reach heated water reservoir
– heated water is piped up to surface and sent to homes or businesses to heat them
geothermal pros
-renewable energy source
- much less CO2 emission than FF electricity
- no releases of pollutants as is case with FF
geothermal cons
— not everywhere on earth has access to geothermal energy reaching close enough to surface to access it (best near tectonic plate boundaries EX iceland)
— hydrogen sulfide can be released which it toxic and can be lethal to humans and animals
— cost of drilling that deep into earth can be very high initially (sometimes so high that its not worth it)
hydrogen fuel cell basics
most common application
use hydrogen as a renewable, alternative fuel source to FFs
— H2 gas and 02 are the inputs used to gen. elect.;; H2O is given off as a waste product.
most common application is in vehicles
— replaces gasoline, with H fuel
how does a H fuel cell work?
H2 gas enters fuel cell where it’s split into protons (H+) and electrons (e-) by an electrolyte membrane that only lets protons pass through
– electrons take an alternative route (circuit) around the membrane which gen. and electrical current
– O2 molecules enter fuel cell, break apart into individual O atoms and combine with two hydrogens (H+) to form H2O as a by product (only emission from H fuel cell)
key challenge to H fuel cells
is obtaining pure H gas cuz it doesn’t exicst by itself as a gas naturally.
– separating H2 gas from other molecules like H2O or CH4 is very energy intensive
– two main process are steam reforming (95% of all H production) and electrolysis ( less common by more sustainable)
EROEI calculation
energy obtained from fuel / energy invested to obtain = EROEI
steam reforming
burning nat. gas (CH4) and using steam to separate the H gas from methane (CH4)
– emits CO2 and requires nat. gas (FF) input
electrolysis
electrical current is applied to water, breaking it into O and H2
- no CO2 emission, but requires electricity
hydrogen as an energy carrier PROS
- Because H2 gas can be stored in pressurized tanks, it can be transported for use creating elect. later, in diff. location.
- can be used as a fuel source for vehicles or to create ammonia for fertilizer or in the chemical industry.
— as a gasoline replacement, it emits no air pollutants and only H2O, no CO2
— manufacture of many diff. industrial chemicals requires H2 gas
— can be stored as liquid or gas, making it easy to transport
— H fuel cells are ~ 80% efficient in converting chemical energy into electricity ( coal PP = 35 efficient)
H fuel cell CONS
since 95% of H2 production required methane (CH4), H fuel cells are based on a non-renewable and CO2 releasing energy source
— if electrolysis is used to produce H2, its only as sustainable as the electricity source
— widespread H fuel cell use would require building widespread H distribution network (similar to gasoline system)
— H fuel stored in gas form in vehicles would require much larger tanks that current gasoline tanks
wind turbine electricity generation
kinetic energy of moving air (wind) spins a turbine ; generator converts mechanical energy of the turbine into electricity
– blades of turbine are connected to gearbox by a shaft that rotates ; rotating gears create mechanical energy that the generator transforms into electricity.
Average turbine facts
–avg. turbine can power around 940 homes
– avg. land wind turbine has 21% - 52% capacity factor (% of total possible energy it could generate)
– only generates electricity in about 8 - 55 mph winds
– motorized drive within shaft can turn the turbine to face the wind
wind turbine location
clustered in groups (wind projects or farms) in flat, open areas (usually rural)
– locating them together makes service, repair and building transmission lines to them easier
off shore wind
= wind farms in oceans or lakes
– capitalizes on faster wind speeds
– requires transmission lines built across long distances to reach land
– higher capacity factor but more expensive to build/ maintain
wind energy benefits
–non-depletable renewable (isn’t decr. by its use)
–no GHG emissions or air pollutants released when gen. elect.
–can share land use (less habitat destruction)
–does not contaminate soil/water as FFs do
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 and bats especially large, migratory birds
–can be considered eyesore or source of noise pollution by some
small scale conservation
– lowering thermostat to use less heat or use AC less often
– conserving water with native plants instead of grass, low flow shower heads, efficient toilets, dishwashers, dryers etc.
– energy efficient appliences, better insulation to keep more heat in home
large scale conservation
–improving fuel efficiency (fuel economy) standards
– subsidizing (tax credits for) electric vehicles, charging stations, hybrids
– incr. public transport (buses), green building design
sustainable home design
– deciduous shade trees for landscape (leaves block sun in summer, but allow it in during winter)
– using passive solar design concepts to trap sun’s heat & decr. energy from heating system (heat absorbing walls, triple or double panned windows)
– well insulated walls / attic to trap heat in winter & cool air from AC system in summer
– this decr. electricity used by AC unit & energy used by heating system
water conservation
–native plants require less watering that traditional lawns (also incr. biodiversity of pollinators)
– low flow showers, toilets, and dishwashers do the same job will less total water
– rain barrels slow rain water to be used for watering plants of washing cars
energy conservation - transportation
~ 28% of total US energy use comes from transport of goods and ppl (2019)
– improving fuel economy of US fleet of vehicles conserves energy as less gasoline/diesel is needed to travel same distance
– hybrids have both gasoline and electric engine, enabling them to have higher MPG ratings
— breaking system charges the electric battery, which powers electric motor
– electric vehicles like Tesla use no gasoline but still require electricity and (are only as sustainable as its electricity source)
– public transit and carpooling are even better energy saving transportation options
sustainable building design
– green roof or walls decr. runoff and absorb sun’s heat, decr. energy needed for cooling building and surrounding area (lessens heat island effect)
– skylight on roof or windows on sides can decr. electricity used for lighting
– recycled materials can reduce energy required to produce new ones (glass, wood, even fly ash from coal can be used in foundation)
peak demand
the time of day or year (often early night time hours or very hot weather events) that electricity demand is highest
– if demand exceeds supply, rolling blackouts occur
manage peak demand
utilities will use a variable price model for electricity:
– users pay a higher rate during peak demand hours or events to discourage use
– users pay a lower rate / kWh when using a lower amount of energy (incentivizes lower overall use)
'’smart grid’’
the idea of managing demand and energy sources in a more varied way
EX using smart meters for variable price models, allowing rooftop solar to direct electricity back to grid, integrating more total energy sources (especially renewable)
