Unit 6 Test Pt. 2 Flashcards
Fission vs. Fusion
Fission ~ splits atoms anything heavier than iron, to create new energy
Nuclear fission involves shooting a neutron into an unstable isotope of Uranium (235) causing the nucleus to break down and thus lose mass
This mass loss creates lots of energy, which can, in a chain reaction, be used to break the nucleus apart further- thus, a nuclear chain reaction
Fusion - put atoms together , changing elements, law of conservation of matter doesn’t matter creating new things and destroying things, cannot fuse things to create new energy past iron (anything heavier
How nuclear energy works
Primary system
Nuclear reactor fuels nuclear fission reaction in fuel rods, creates lots of energy located in water, going into a steam generator
Secondary system
Turbine spins due to steam creates kinetic energy which creates electricity that goes into the transformer, cold water goes through condensers where steam turns back into water and goes back to the primary other steam gets let go through a huge pipe
Fuel cells are where reactions happen- they are submerged in a coolant solution, such as water
Water heats up and vaporizes, steam is collected and used to spin a turbine, which can generate electricity
Tertiary system
Water can be recycled back into the system via a condenser, or can be stored separately to cool
Cold water normally from a river or stream
advantages of nuclear energy
Relatively little air pollution (generation of nuclear energy does not emit carbon dioxide or other GHGs other than water vapor)
Incredibly energy dense- 1 gram of uranium produces 20 million Kcalories
Clean energy sources → does not produce emissions/pollution, sometimes called green energy source, sometimes not
drawbacks of nuclear energy
NOT renewable! There is only so much U-235 and other radioactive material
Unlike solar wind which is renewable
Mining this stuff does emit GHGs and disrupts biodiversity
The greenhouse gases which this cause is from the mining
Risk of a meltdown- small, but has happened and could happen again
Chernobyl, Three Mile Island, Fukushima
Reminds radioactive for thousands of years
Spent fuel rods and mining waste is radioactive
Water use is high
Can harm aquatic life
Thermal pollution - all the heat that gets discharged into bodies of water can harm aquatic life
Mining the uranium has negative environmental effects
Energy From Biomass
Remember NPP? It’s back
NPP is biomass, or the amount of stuff produced by an ecosystem
NPP can be burned for energy, as it is made of combustible hydrocarbons
It’s really no different from coal- except the energy is less compacted
Biofuels and Carbon Cycle
Why is burning biofuels carbon neutral?
Just putting carbon back into the area that was once there, few years
Why aren’t fossil fuels carbon neutral?
You are putting carbon into the air that has been out of the system for a very long time (millions of years), not the same as just putting carbon from biomass back into the atmosphere
Fossil fuels - carbon in the atmosphere a LONG time ago → not neutral
Ethanol
Corn or glucose can be fermented and then mixed with gasoline, usually around 10%.
Our cars literally eat corn, too!
Burning ethanol does not introduce new carbon into the atmosphere, but food production has a carbon and land use footprint so is arguably not all that sustainable
Ethanol ~ grain alcohol (specifically often from fermented corn)
Problems with corn, you use fossil fuels to make corn, water, fertilizer, land
Biofuels Consequences of Use
All the negative consequences of agriculture- if using monocultures to plant crops like corn for ethanol- so habitat loss, low biodiversity, soil degradation, water use, etc.
Burning subsistence fuels introduces lots of carbon dioxide into the atmosphere and particulate matter that can worsen asthma, bronchitis, etc. Also carbon monoxide (toxic), nitrous oxides, volatile organic compounds
Removal of woody biomass for burning threatens biodiversity and contributes to deforestation in areas where regulation is weak
Renewable Energy
Replenishable at the rate of use
Solar, hydro, geothermal, and wind are the four major categories- each with benefits and drawbacks
Sources of Energy Waste
Keep on Anything like lights, cars, fridge
Leaving stuff plugged in
Car idle
Too many baths
Manufacturing single use items
Food waste
Drafts, lack of insulation, heat getting wasted
running water
Energy efficiency
energy return on investment
EROI is one measure of energy efficiency, which gets at how much energy is required to produce a unit of energy (it should be a low ratio)
Higher EROI - more cost efficient
Hydroelectric - high upfront cost but not much cost to keep it running (has a high EROEI)
1:10 (putting in 1 unit of energy to get 10 units of energy ), 1:50 is a better ratio (putting in 1 unit of energy to get 50 units of energy)
Energy is also lost at consumer levels, too
Leaky Windows
Poorly Insulated Homes
“Gas Guzzlers”- vehicles or machines that are inefficient or unnecessarily large/powerful
Inefficient appliances or even light bulbs
Old lightbulbs are worse
Food waste (consumer or industrial)
Efficiency by fuel type EROEI
Higher EROEI the most economically beneficial
Ways that energy can be lost
Waste can come from heat production as a byproduct that is lost
When you are using heat, heat gets leaked out and released into the environment
Mining energy
Construction, operation, and maintenance of equipment needed
Faulty power distribution networks/grid/storage
Variable output (especially with solar, wind, and hydro)
We can’t control environmental factors
Conservation Strategies
We (U.S.) waist 40% of our energy by stuff that’s not necessary
Raising every vehicle’s fuel efficiency by 2 mpg would do more in a few months than drilling the Arctic NWR in its entirety would
Light Bulb switches (incandescent light would require 700 lbs of coal to run for a year- LED would maybe be 15-20 lbs)
Cogeneration- where the heat that is lost in electricity production is pumped and used as heat- would help drive up efficiency
Better insulation on homes and better sealing on windows, especially where climate is harsh and temperature control is needed.
Use of public transit
Tradeoff: Harsh Realities and Dark Side of Green Energy?
So is green energy still “worth it”??
YES!
Climate change aside (which is a huge aside- but that comes later in the course)- we will run out of fossil fuels in the next ~100 years! We love energy and the only way to be able to continue using it at incredibly high levels over the next generation is to go green.
These problems point to a need to invest in technologies that are better and globally strategize ways to minimize environmental and human harm. All energy comes at a cost- even green energy. This should surprise nobody.
electric cars pros and cons
pros
Over certain amount of years or miles it does break even (in terms of benefits vs weight on environment) but takes time
cons
Battery is made of rare earth minerals
Productions of batters use minerals that are more intensive/expensive to obtain
Where is the electricity generated as some of it might not be clean
Isn’t enough electricity for everyone to have electric cars
Complications with green energy
NYC 90% non renewable as you need space to create green energy, we have bad electric grid meaning that we can’t move electricity around that well
We would need to build new infrastructure (in electric grid) in order to have the US be fully powered by green energy
Green energy relies on mineral resources - sketchy environmental and ethical issues that come with getting these minerals, but we can’t have green energy without them, how are we going to manage that?
Not ready for green energy, need to get ready
Energy has become increasingly partisan and some harsh realities are being ignored - fossil fuels are not forever - and green energy clearly needs investment to fix some of its own problems
