EESC 340 Energy Resources Assessment # 1 Flashcards
What is a heat engine
Device that converts heat into work/usable energy
Describe the two types of heat engines and what makes them different?
The two primary types of heat engines are internal combustion engines and external combustion engines; where the key difference lies in whether the fuel burns inside the engine itself (internal) or outside the engine in a separate chamber (external).
External Combustion Engine:
Here, the fuel is burned outside the main engine, heating a working fluid (like steam) which then drives the engine mechanism.
Example: A traditional steam engine.
(External combustion. Steam engine ->burns fuel-> releases heat->boils water->steam moves piston. Centralized power stations.)
Internal Combustion Engine:
In this type, the fuel is ignited directly within the engine cylinder, creating pressure that drives the piston and generates power. Example: A car engine.
(Internal combustion. Internal combustion Enginges: fuel explodes -> releases heat -?-. hot gas expands inside cylinder -> expanding gas moves piston
Mobile/portable use.)
Explain Faraday’s Law of Electromagnetic Induction
Whenever a conductor is placed in a varying magnetic field, an electromotive force is produced/induced
In an electric motor, what two design factors determine how much power it can produce?
(How much current is induced?)
Depends on the
- number of turns of the coil
- the strengths of the magnetic field
**Explain the difference between AC and DC power
AC (alternating current) changes directions periodically.
- suitable for long distance transmission
- more injury per volt potential
- electronics and batteries are not compatible
DC (direct current) maintains a constant flow in one direction.
- suitable for short distances (< 2 mil) only
- less injury per volt potential
- electronics and batteries are compatible
Why did AC power win as standard for a grid?
- No energy loss in transmission lines
- transmit electricity over long distances with minimal loss/High voltage can push the current long distances
- Difficult and expensive to transform DC voltage
Explain Voltage and Current using a water analogy
- Voltage is like pressure in a pipe
- If pipe is only partly filled -> less pressure
- When opened, water will flow faster from high pressure tank
- > more volt = more current
Voltage is the push/pressure on electrons around a circuit. “how much water is in the reservoir -> more water->more pressure->more water flowing”
Current is flow of electrons .(Amperage is the rate of flow - “ the speed that the bucket fills up with water/amount of water stored”)
Explain the difference between Power and Energy, state their units, and describe how each are calculated
- Power = how rapidly energy is flowing at an instant/How quickly energy is consumed.
- Measured in Watts (V x A = W)
- Energy =quantifies the total amount that has flowed over time
- Measured in Watt hours (Wh). (V x A x hours = Wh)
Explain how high-tension power lines can carry enough electricity for an entire city through a fairly small diameter wire.
Amperage drives the cable size. To minimize cable size you can decrease the current ( flow in amps)
- Decrease Amps but
- Increase Voltage
to maintain same power.
(345,000 V “push” hundreds of miles, but only 250 A flow rate)
Compare the three main fossil fuels by
- primary use
- usage trend
- energy density
- carbon density
Natural Gas:
- primary use: electricity, heating & cooking
- usage trend: increasing
- energy density: high
- carbons intensity: low
Oil:
- primary use: transportation
- usage trend: steady
- energy density: medium
- carbon intensity: medium
Coal:
- primary use: electricity
- usage trend: falling
- energy density: low
- carbon intensity: high
List 4 generations of biofuels and give an example of each
- 1st gen: sugary/food crops: sugar cane/beet (carbon intensive)
- 2nd gen: cellulosic/non-food crops: switchgrass, giant red (less carbon intensive)
- 3rd gen: oilseed crops & algae: soybean, peanut (carbon neutral)
- 4th gen: genetically engineered crops: corn, switchgrass (carbon negative)
Describe at least 4 criteria for bio-ethanol to be considered as “low-impact”
- Biofuel crop cannot displace forests with high stored carbon
- Must have minmal/zero synthetic fertilization
- Must have minimal tractor fuel and transport costs
- Biofuel cannot compete with food
- Groundwater use must not exceed rate of recharge
Compare fossil fuels and biofuels in terms of climate impact and acid rain precursors
Fossil fuel:
- Greenhouse gases: produces CO2 (high) and N2O from fertilizer
- Land required: mined area
- Acid rain precursors: SOx (high), NOx
Biofuels:
- Greenhouse gases: no net CO2 (but increase at/after 2nd gen), N2O (fertilizer, soil)
- no SO when burning plants
- Land required: cultivated area
- Food/fuel conflict: significant potential
- Acid rain precursors: SOx (low), NOx similar to fossil fuels
Describe 2 benefits of cellulosic ethanol, relative to ethanol derived from corn
- don’t need fertilization
- less carbon intensive
- doesn’t interfere with food
Explain why biofuel production has flattened in the US
EPA’s Renewable Fuel Standard has
- limited conventional biofuel production
- focusing instead on development of cellulose biofuels and advanced biofuels
- that don’t conflict with food.
- Progress has been slow due to difficulty of creating an economically viable product (remains expensive)
