Environmental Science Energy Resources and Consumption 2 — Questions and Answers
Question 1: Nuclear fission reactors generate electricity by:
- Burning uranium at very high temperatures
- Splitting heavy atomic nuclei to release heat (Correct answer)
- Fusing hydrogen nuclei under extreme pressure
- Using radioactive decay to spin a turbine directly
Correct answer: Splitting heavy atomic nuclei to release heat
In fission reactors, heavy nuclei (typically uranium-235) are split, releasing enormous amounts of heat used to produce steam that drives turbines.
Nuclear fission reactors use controlled chain reactions in which neutrons strike uranium-235 (or plutonium-239) nuclei, causing them to split and release energy plus more neutrons that sustain the reaction. The heat produced converts water to steam, which spins turbines connected to generators. The process produces no direct CO2 emissions but generates radioactive waste that must be managed for thousands of years.
Question 2: The primary environmental concern associated with coal combustion is:
- Thermal pollution of rivers
- Emission of sulfur dioxide, nitrogen oxides, mercury, and CO2 (Correct answer)
- Radioactive waste generation
- Depletion of stratospheric ozone
Correct answer: Emission of sulfur dioxide, nitrogen oxides, mercury, and CO2
Coal combustion emits SO2 (acid rain), NOx (smog/acid rain), mercury (neurotoxin), particulates, and large quantities of CO2 (climate change).
Coal is the most carbon-intensive fossil fuel per unit of energy, releasing more CO2 than oil or natural gas. Combustion also releases sulfur dioxide (which forms acid rain), nitrogen oxides (smog, acid rain), mercury and other heavy metals (bioaccumulate), and fine particulates (respiratory illness). Fly ash disposal also poses land and water contamination risks.
Question 3: Which renewable energy technology converts sunlight directly into electricity without moving parts?
- Concentrating solar power (CSP)
- Photovoltaic (PV) cells (Correct answer)
- Solar thermal hot water collectors
- Parabolic trough systems
Correct answer: Photovoltaic (PV) cells
Photovoltaic cells use the photoelectric effect to convert photons directly into electricity through semiconductor materials with no moving parts.
Photovoltaic cells are made of semiconductor materials (commonly silicon) that absorb photons and release electrons, generating direct current (DC) electricity. An inverter converts DC to AC for grid use. Unlike concentrating solar power systems, PV has no moving parts and no thermal intermediate step. Efficiency of commercial PV panels ranges from ~15-23%, with laboratory records above 29%.
Question 4: Energy efficiency and energy conservation differ in that:
- Efficiency refers to using less energy; conservation means using better technology
- Efficiency means getting more useful output per unit of energy input; conservation means reducing overall energy use (Correct answer)
- Conservation applies only to fossil fuels; efficiency applies to renewables
- They are synonymous terms used interchangeably in energy policy
Correct answer: Efficiency means getting more useful output per unit of energy input; conservation means reducing overall energy use
Efficiency = more useful work per energy unit (e.g., LED vs. incandescent bulb); conservation = behavioral reduction in energy use.
Energy efficiency involves technological improvements that deliver the same or greater service using less energy (e.g., more fuel-efficient vehicles, LED lighting, better-insulated buildings). Energy conservation involves changing behavior or practices to reduce energy consumption (e.g., driving less, lowering the thermostat). Both strategies reduce energy demand and environmental impacts but through different mechanisms.
Question 5: Tar sands (oil sands) require more energy to process than conventional oil primarily because:
- They are located offshore at great depth
- The bitumen must be separated from sand and upgraded, requiring large energy inputs (Correct answer)
- Tar sands contain more sulfur that must be removed
- They are found at high altitudes where equipment efficiency drops
Correct answer: The bitumen must be separated from sand and upgraded, requiring large energy inputs
Bitumen in tar sands is a viscous, semi-solid hydrocarbon that must be steam-heated or mined and then chemically upgraded, consuming significant energy.
Oil sands contain bitumen, a heavy, viscous form of petroleum mixed with sand, clay, and water. Extraction requires either surface mining or steam injection (SAGD) to liquefy the bitumen in situ. The bitumen then must be upgraded to synthetic crude oil in energy-intensive upgrading facilities. The EROI of oil sands is typically 3-5:1, far lower than conventional oil's ~20:1, and production emits ~3x more CO2 per barrel.
Question 6: The rebound effect in energy economics refers to:
- The recovery of energy prices after an oil shock
- Increased energy consumption that offsets efficiency gains when energy services become cheaper (Correct answer)
- The bounce-back in renewable energy investment after a recession
- Grid stabilization after a power outage
Correct answer: Increased energy consumption that offsets efficiency gains when energy services become cheaper
When efficiency improvements lower the cost of using energy, people tend to use more energy services, partially or fully canceling the expected savings.
The rebound effect describes how efficiency gains that reduce the effective cost of an energy service can lead to increased consumption of that service. Direct rebounds: a more fuel-efficient car makes driving cheaper, so people drive more. Indirect rebounds: money saved on energy is spent on other goods that also consume energy. Economy-wide rebounds can theoretically exceed 100% (backfire), meaning total energy use rises.
Environmental Science Energy Resources and Consumption 2
Nuclear fission reactors generate electricity by: