APES Unit 6
Unit 6.1: Renewable and Nonrenewable Resources
Energy resources are divided into two categories: renewable and nonrenewable
Non renewable resources - nuclear, coal, oil, fossil fuels
Hint: petroleum, petrol, gasoline
They are energy sources that exist in an fixed amount and involve energy transformation that cannot be easily replaced
We have what we have, once we run out, we run out
Renewable resources - biomass, hydroelectric, solar, wind, waves, geothermal
They are energy sources that can be replenished naturally, at or near the rate of consumption, and reused
These are energy sources, if managed correctly, can be used indefinitely
Unit 6.2: Global Energy Consumption
The use of energy resources is not evenly distributed between developed and developing countries
20% of the population uses about 80% of the energy
Since the industrial revolution (1760s) fossil fuels have dominated as being the major source of energy
Coal was the first major source of energy during the revolution, but has now been replaced with petroleum
Coal, oil, and natural gas (fossil fuels) dominate the world’s most popular energy sources
Nuclear was made popular in the 1970s but lost public faith
*Note: KNOW PERCENT CHANGE. IT WILL MORE THAN LIKELY BE ON THE EXAM
Percent Change Formula
(initial - final)/initial x 100
As a country becomes more developed, their reliance on fossil fuels for energy increases
Example: transportation in a developing country goes from walking, to bikes, to cars, to airplanes, hence using more fossil fuels as you go up the ladder
As the world becomes more industrialized, the demand for energy increases
What energy source do people use?
There are several factors:
Availability: what fuels can consumers get?
Price: supply and demand
Governmental Regulation: what fuels can consumers get?
For conversion purposes: 1 megawatt (MW) = 1000 kilowatts (KW)
Doubling Population Time Equation
70/Growth Rate %
Unit 6.3: Fuel Types and Uses
What are some types of fuels and what are they used for?
Wood and Charcoal: primarily used in developing countries
Connections: removal of trees can lead to soil erosion. Soil degradation leads to food security issues
Deforestation can decrease the amount of precipitation and CO2 sequestration
Peat: partially developed organic material that can be burned for fuel
It is a precursor to coal
Using these fuels indoors without proper ventilation can cause indoor air pollution which causes health problems
There are roughly three different types of coal used for fuel
Heat and pressure leads to the formation of these further coals
Peat: not a coal, just a precursor
Lignite: low heat capacity, low sulfur, high moisture
Bituminous: most commonly used, high heating capacity, high sulfur
Anthracite: best quality, high heating capacity, low sulfur content
The heat and pressure, the better the coal
Which is the cleanest burning fossil fuel?
Natural Gas is the cleanest fossil fuel because it does not release as many harmful emissions as the other fossil fuels
Releases negligible amounts of SO2, mercury, and particulates in comparison to coal and oil
Most methane
Still produces carbon emissions
Easily transportable
Crude oil can be recovered from tar sands, which are a combination of clay, sand, water, and bitumen
Not ideal for processing, but can be used when necessary
Crude oil is a fossil fuel that can be made into different fossil fuels
Fossil fuels can be made into specific types of fuels for specialized uses
Sample fuels: gasoline, diesel, jet fuel, heating oil, etc
Refineries take advantage of the different boiling points of the fuels
Cogeneration occurs when a fuel source is used to generate both useful heat and electricity
Unit 6.4: Distribution of Natural Energy Resources
Natural Energy Resources
Ores/Uranium - nuclear
Coal and Coke - coal
Crude Oil - oil and petroleum products
Natural Gas
Resources of energy are found all over the world
Different countries and regions lead in different resources
Oil and Natural Gas
As the geologic forms of earth changed over millions of years, sediment and living things were buried under heat and sand, and heat and pressure from the ground produced sediment pushed into the ground into oil and natural gas
Those lands were one underwater
Age of rocks determines what resources will be available
Resources are distributed, given geological formation under factors like pressure and time
Unit 6.5: Fossil Fuels
Combustion Process - a chemical process by burning fuel in the presence of oxygen, producing water and carbon dioxide
These include fossil fuels such as coal, oil and natural gas
Coal is pulverized, or made smaller
Then, burning and combustion occurs, and water is boiled which creates steam, and that steam turns to turbine, which turns into generator, which produces electricity
A reservoir is necessary to obtain water, as it is needed for boiling and cooling
Potential for Problems
Environmental problems can be found through:
Mining - digging and extraction: destruction of habitat, resources used
Pulverized Coal - small dust: flammable and harmful to respiratory systems
Heavy use of water - needed for cooling: can develop habitat for species and water resource
Carbon Dioxide - climate change gas: increases greenhouse effect globally
Other Pollutants- mercury/sulfur: released into air and water
Fossil fuels often end up being the primary source of energy, especially in the United States
Fossil fuels each have a unique method of extraction
Oil and Natural Gas
Formed from plants and animals caught under earth material
Material decays producing gas and petroleum
Liquid had to be pumped out, much drilling done at sea
Gas is collected through hydraulic fracturing
Natural gas can be found at many different locations and layers
Coal Mining
Coal has to be dug out of the ground
Depends on how deep it can be found
2 types: surface and subsurface mining
Consequences of Extraction
Coal Extraction
Surface Mining - removal of topsoil and habitat, overburden
Subsurface Mining - destruction of habitat, dangerous
Oil Extraction
Habitat destruction, potential for spills
Gas Extraction
Destruction of habitat, water contamination, earthquakes
Hydrologic Fracturing
Obtaining natural gas from the ground
Layers of rock also hold water near natural gas pockets
Steps to the Fracking Process:
Make the well with clay lining
Pipe is inserted so natural has a source to travel though
Fracking fluid is inserted which will allow the ground to break
The gas trapped in the ground will then flow out
Environmental Problems:
Well can contaminate water and destroy habitat
If the pipe is not lined properly, it may contaminate water
Fracking fluid contains volatile organic compounds (VOCs)
Natural gas may leak out of well, which could be harmful to the atmosphere
Additionally, could also cause earthquakes when breaking the ground
Unit 6.6: Nuclear Power
Nuclear Fission
Ore of uranium-235 are used to generate electricity
Nuclear power is a chemical process, generated from a chemical reaction
Similar methods are used when producing other fossil fuels
Steps:
U-235 placed into fuel rods
Struck by outside neutron
Process of splitting U-235 releases large amount of heat
Heat used to to generate stream from water
Stream turns a turbine
Turbine powers a generator
Generator makes electricity
Uranium pellets in water
Fission reaction
Stream generated
Stream —> tribune —> generator
Stream cools and can be used again
Pros and Cons of Nuclear Power
Pros
Low/No CH4/CO2 emissions
High power output
Low cost (after initial construction)
No mining for fossil fuels
No primary/secondary air pollutants
Cons
Long-lived hazardous waste/nuclear accidents
Thermal pollution
Very high initial cost (billions)
Mining for construction and uranium
Non renewable resource
Radioactive Energy
Nuclear energy emits radioactive energy
Nuclear power comes from breaking down U-235
Isotope loses energy
Emits that energy as a radioactive wave
Long term Radioactivity
Spent Uranium-235 reminds radioactive
U-235 breaks down and can’t create heat as much
This spent uranium gathers Maureen’s
Becomes heavier - like plutonium
Remains radioactive for up to 24,000 years (10 half lives)
Radioactive waste is generated in the reactor
Issues with Waste
Due to long lived waste, storage is tricky
Storage happens on site, buried deeply
Federal sit commissioned at Yucca Mountain, Nevada
Many sites means more chances of radioactive waves leaking into the environment
Radioactive energy is released from nuclear power
Radioactivity can last many years
Longevity of radioactivity leads to many issues
Nuclear Power Accidents
Nuclear power has several cases of accidents:
Three Mile Island, Pennsylvania, USA
Accident started in non-nuclear portion of reactor
Water failed to allow water in
Reactor never cooled down
Fuel began to melt down partially
No explosion or long term high radiation exposure
Chernobyl - Ukraine (USSR)
Accident arose from a safety test
Power turned off during simulation
Extra power from turbine was supposed to keep reactor powered up enough to cool
When test completed, control rods did not drop
Explosion occurred, releasing most radiation ever from an accident
Fukushima - Japan
Accident caused by a natural disaster
Earthquake and Tsunami occured in Pacific
Earthquake caused emergency shutdown
Tsunami wave flooded 4
Three nuclear reactors melted down at the same time
Accident was deemed preventable
Half-Life Radioactive Material
Half-life - is a measure of time for half of an atomic nucleus to decay
Decays into another atom, emitting radiation
Ten half-lives generally means safety
Example: cesium-137 has a half life of 30 years
How long until radioactive safety?
30x10 = 300 years
Unit 6.7: Energy from Biomass
Biomass stores energy from the sun
The First Law of Thermodynamics
Energy cannot be created or destroyed
The energy in biomass is energy from the sun
Converted during photosynthesis
Biomass is the leading renewable energy source worldwide
Burning biomass is a direct source of heat for many developing nations
Examples of biomass used as heat sources:
Wood
Peat
Charcoal
Crop residue
Manure
Positive consequences:
Easily accessible
Relatively inexpensive
Used for heating and cooking
Negative consequences:
Air pollutants
Carbon dioxide, carbon monoxide, nitrogen oxides, particulates, and volatile organic compounds
Typically burned indoors, intensifying health effect of pollutants
Over harvesting of trees for fuel wood results in deforestation
Biofuels - a liquid fuel made from plant matter that can be used as substitutes for conventional petroleum products (gasoline and diesel)
Ethanol
Made by fermenting plant-based starches into sugars and eventually alcohol
Typically mixed with gasoline to create gasohol (90% gas, 10% ethanol)
E-85 and flex-fuel vehicles can run on mixture of 85% ethanol, 15% gas
Examples:
Corn (USA)
Sugarcane (Brazil)
Sugar beets (US and Brazil)
Biodiesel
Extracted and chemically modified oil from plants
Can be a direct substitute for diesel fuel
Examples:
Soybeans (Brazil and US)
Oil palms (Southeast Asia)
Rapeseed (Europe)
Positive Consequences of Biofuel:
Combustion is carbon neutral
Modern carbon versus fossil carbon
Potentially renewable
Can be produced domestically
Negative Consequences of Biofuel:
Net energy is low
More gasohol is needed to go the same distance
Harvesting of crops for ethanol has potential for:
Increase use of fossil fuels in harvest
Increased deforestation
Reduction in fertility of agricultural land
More sustainable solutions
Ethanol
Switchgrass is being researched in the US to be produced into ethanol
Biodiesel
SVO (straight vegetable oil)
Algae
Unit 6.8; Solar Energy
Types of Solar Energy:
Photovoltaic
Transforms sunlight directly into electricity
In a photovoltaic cell, electrons are released with sunlight hits the cells
Positive Consequences:
Generation of electricity
Can reduce habitat destruction depending on installation placement
Large and small scale applications
Off the grid electricity
Negatvie Consequences:
Use is limited by the availability of sunlight
Limited lifespan of nonrenewable PV cells
Expensive
Solar farms may negatively impact fragile desert ecosystems
Active Solar
Uses a mechanical and electrical equipment to transfer solar heated liquid to transfer heat or to create electricity
Concentrated solar power - produces electricity
Heat pump - produces heat
Positive Consequences:
Generates electricity or heat
Large and small scale application
Negative Consequences:
Expensive
Requires maintenance
Solar farms may negatively impact fragile desert ecosystems
Solar farms requires high solar intensity to maximize efficiency
Passive Solar
Heat is directly absorbed from the sun without mechanical or electrical equipment
Refers to sunlight coming in through windows
Positive Consequences:
Relatively inexpensive and low maintenance
Negative Consequences:
Some aspects are difficult to implement retroactively
Energy cannot be collected or stored
Unit 6.9: Hydroelectric Power
Hydroelectricity from Dams and Reservoirs
Kinetic energy of moving water causes kinetic energy of spinning turbine
The turbine causes kinetic energy of spinning generator, which produces electricity
Hydroelectric power is used to produce electricity
Kinetic energy of moving water can be transformed into electricity
Water falls under the force of gra levity through a turbine
Kinetic energy of water converts to a kinetic energy of turbine spinning
Spinning turbine causes a generator to turn
Kinetic energy of turbine is converted to kinetic energy of magnet/wire combination inside turbine
Motion of wire and magnet converts kinetic energy to electrical energy
Electricity flows from the dam to the grid
Sources:
Dams and reservoirs
Rivers
Tidal
China’s Three Gorges Dam
Largest dam in the world
Large reservoir of water, resulted in a great deal of destruction of habitats
Amazon River in Brazil
Can affect how much water is in a habitat over the course of a number of years
Fish Ladder in Oregon
The creation of dams and reservoirs also affect the population of fish
Positive and Negative Consequences of Reservoirs
Positive Consequences
No air pollution
No waste
Relatively inexpensive electricity generation
Additional services provided by reservoir
Negative Consequences
Flooding of land for reservoir
Disruption of flow rates of river
High maintenance cost for tidal
High construction cost for dams
Most viable sites are already used
Unit 6.10: Geothermal Energy
Yellowstone National Park, Upper Geyser Basin
Example of geothermal energy
Geothermal Energy is Heat from the Earth
The Process
Water is pumped down an injection wall
Stored heat from Earth’s interior turns the water into steam
Steam rises from the production well
Kinetic energy of the steam turns into a turbine
The turbine turns a generator
The generator produces electricity
Consequences to Geothermal Energy
Positive Consequences
No combustion
No CO2 emissions
Not dependent on variable weather factors, like solar and wind
Negative Consequences
Accessibility (at reasonable cost) is limited
Release of gasses during drilling and processing
Hydrogen sulfide gas
Short-term depletion of heat possible
Impact on groundwater
Unit 6.11; Hydrogen Fuel Cell
How does a hydrogen fuel cell work?
The process is like a typical battery
A chemical reaction occurs inside the cell to create an electric current
In a typical battery, the chemicals are in a closed container
Once used, the battery must be recharged or discarded
In a hydrogen fuel cell, the chemical reactants can be added continuously
The fuel cell does not “go dead”
The Process:
Hydrogen fuel (H2) is added to the cell
This can be in liquid or gas form
In the first reaction layer, hydrogen molecules are split into protons (H+) and electrons (-)
Protons and electrons take different paths
Protons move across the membrane
Electrons are free to take an alternate route, creating a flow of electric current
In the second reaction layer, oxygen molecules (O2) are split and combine with protons and electrons
Water vapor is the only emission from the fuel cell
Renewable Energy from Fuel Cells
Hydrogen fuel cells are an alternative to nonrenewable fuel
Fuel cells combine hydrogen fuel and oxygen from the atmosphere to create electricity
Water is the only direct emission of the fuel cell
Where does the hydrogen fuel come from?
Hydrogen is usually in compounds, like water and natural gas
Typically a low environmental impact
Can come from water (H2O)
Electrolysis - electric current used to split water into hydrogen and oxygen
Can come from natural gas
Splitting methane (CH4) using heat
This results in CO2 pollution
Energy is needed to create Hydrogen Fuel
We must create the hydrogen gas that will power the fuel cell
It takes electricity or heat to break apart water or methane
This decreases the net energy of hydrogen as a fuel source
What is net energy?
It is the amount of energy produced by the source minus energy used, lost, or wasted in the process of generating the useful energy
Example: to generate electricity from coal there was mining, ore processing, transportation, losses due to the second law transformations, and losses due to power lines
Because of the second law of thermodynamics, no energy is 100% efficient
Why are fuel cells so expensive?
New technology
Research and development costs
Scale of technology
Production prices drop as more are manufactured
Raw materials
Platinum and other rare earth minerals are used as catalysts
Consequences to Hydrogen Fuel Cells
Positive Consequences
No CO2 emissions (if produced from water)
Electricity is more efficient than internal combustion
Negative Consequences
Technology is expensive
Producing hydrogen fuel from fossil fuels is not clean
Unit 6.12: Wind Energy
Energy Conversions: Electricity from Wind
Kinetic energy of moving air
Kinetic energy of spinning turbine
Kinetic energy inside generator
Produces electricity
The Growth of Wind Energy
Over the course of decades, wind power has grown exponentially
Consequences of Wind Energy
Positive Consequences
Renewable
Clean
Allows for multiple use lands
Negative Consequences
Birds and bats can be killed by turbines
Maintenance is required
Locations must have consistent winds to provide consistent power supply
Need backup power on days that are not windy
Unit 6.13: Energy Conservation
The Importance of Energy Conservation
There are negative consequences for every type of energy (nonrenewable and renewable)
We can reduce the amount of energy we use, which is energy conservation
Where can individuals make an impact?
Conserve water by taking shorter showers and doing larger loads of laundry
Conserve landscape by planting trees and reducing irrigation energy
We can also adjust our thermostats
Plant trees in front of your house to give your house more shade so you use less AC
Energy Conservation in Transportation
Fuel Economy Standards
Corporate Average Fuel Economy Standards (CAFE)
Electric Vehicles
Battery electric vehicles (BEVs or EVs) and hybrids are more efficient than the internal combustion engine
Power (electricity) can be renewably sourced
Ride sharing:
Public transportation
Carpooling
Energy Conservation in Building Design
Green building design features
Passive design elements:
Passive solar
Windows
Thermal mass
Insulation
Lighting from the sun
Green roof
Active Technologies
Heating systems (geothermal or solar)
Solar panels
Percent Change Formula
% change = new number - old number / old number