unit 6 energy resources and consumption

What defines a nonrenewable energy source?

It exists in a fixed amount and cannot be replenished within a human timescale.

What are examples of nonrenewable energy sources?

Fossil fuels (coal, oil, natural gas) and nuclear energy (uranium).

Are nonrenewable resources sustainable?

No, they are used much faster than they can regenerate.

What defines a renewable energy source?

It can be replenished naturally at or near the rate of consumption.

What are depletable renewable energy sources?

Biomass fuels like wood, charcoal, and ethanol that can be exhausted if overused.

What are nondepletable renewable energy sources?

Solar, wind, hydroelectric, and geothermal energy that do not run out with use.

How does energy use per capita compare between developed and developing nations?

It is higher in developed nations and lower in developing nations.

Why is total energy use often higher in developing countries?

Because they have larger populations.

What fuel types are most used globally?

Fossil fuels are the most used, followed by hydroelectric and nuclear power.

Why do developing countries rely heavily on biomass?

It's easily accessible and does not require complex infrastructure.

What is subsistence energy?

Energy sources like wood, charcoal, or dried manure used for basic survival needs.

What are the environmental effects of using wood as fuel?

Deforestation and habitat loss.

How does charcoal production affect forests?

It requires significant wood input and contributes to deforestation.

What is peat and how is it used?

Partially decomposed plant matter used as fuel; harvesting disrupts wetland ecosystems.

What are the three main types of coal, from lowest to highest energy content?

Lignite, bituminous, anthracite.

How is coal used to generate electricity?

Coal burns to heat water → produces steam → turns a turbine → powers a generator.

Where is natural gas usually found?

Trapped above oil in porous rock layers beneath an impermeable layer.

Why is natural gas considered a cleaner fossil fuel?

It produces fewer pollutants and CO₂ than coal or oil.

What are the environmental impacts of conventional oil drilling?

Land disruption and oil spill risks.

What are tar sands?

Mixtures of clay, sand, water, and bitumen used as a source of oil.

Why is tar sands extraction environmentally damaging?

It uses a lot of water and energy and creates significant pollution.

What is fractional distillation?

A process that separates crude oil into different products based on boiling point.

How is coal ranked by energy density?

Lignite (low), bituminous (medium), anthracite (high).

What is the combustion equation for fossil fuels?

O₂ + fossil fuel → CO₂ + H₂O + heat.

How efficient is coal for electricity generation?

About 30% efficient with significant heat loss.

What is cogeneration and its efficiency?

Using waste heat for energy; up to 90% efficiency.

Which fossil fuel emits the most CO₂ per unit energy?

Coal.

What are the dangers of ash from coal combustion?

It contains toxic metals like mercury and arsenic, which can leak into water.

How does fracking extract natural gas?

High-pressure fluid fractures rock layers, releasing trapped gas.

What are the main risks of fracking?

Groundwater contamination, methane leaks, and induced seismic activity.

How does nuclear fission work?

A neutron splits an unstable nucleus (e.g., uranium-235), releasing heat and more neutrons.

What is the difference between radioactive decay and nuclear fission?

Decay is natural and slow; fission is artificial and rapid.

How does a nuclear power plant generate electricity?

Fission heats water → steam turns turbine → generator produces electricity.

What is the function of control rods in a reactor?

They absorb neutrons to control the fission reaction.

What are the pros of nuclear energy?

Low emissions, high energy density, consistent supply.

What are the cons of nuclear energy?

Risk of meltdowns, radioactive waste, high costs, and thermal pollution.

What caused the Fukushima nuclear accident?

A tsunami disabled cooling systems, leading to a meltdown.

What is modern carbon?

CO₂ recently absorbed by biomass and released during burning—considered carbon neutral.

What is fossil carbon?

CO₂ from fossil fuels stored for millions of years—increases atmospheric CO₂.

What are the downsides of burning biomass?

Air pollution, deforestation, soil erosion, and health risks from indoor smoke.

How is ethanol produced?

By fermenting sugars from corn or sugarcane.

What is a major drawback of corn-based ethanol?

It competes with food production and requires significant water and land.

What makes palm oil biodiesel controversial?

It leads to deforestation and emits more GHGs than fossil fuels.

What is passive solar energy?

Using building design to naturally absorb or block solar heat.

What is active solar energy?

Using mechanical systems like solar panels to convert sunlight into electricity or heat.

What are PV cells?

Semiconductors that convert sunlight directly into electricity.

What is the duck curve?

A graph showing solar overproduction during the day and underproduction at night.

What is concentrated solar thermal (CST)?

Uses mirrors to focus sunlight, creating steam to power a turbine.

How do hydroelectric dams generate electricity?

Stored water flows through turbines → generates electricity.

What is the downside of hydroelectric dams?

Floods habitats, blocks fish migration, and traps sediment.

What are the benefits of run-of-river hydro systems?

Minimal flooding and natural sediment flow.

Why is geothermal energy renewable?

It uses Earth's internal heat and is sustainable if water is reinjected.

How do ground source heat pumps work?

Use shallow ground temperatures to heat/cool buildings.

What are hydrogen fuel cells?

They convert H₂ and O₂ into electricity, emitting only water.

How is most hydrogen produced today?

Through steam reforming of methane, which emits CO₂.

What is green hydrogen?

Hydrogen produced via electrolysis using renewable electricity—zero emissions.

What are the drawbacks of hydrogen fuel cells?

High cost, low energy density, and lack of infrastructure.

How does wind energy generate electricity?

Wind spins blades → rotates shaft → powers generator.

What are the pros of wind energy?

No emissions, renewable, and allows land-sharing with agriculture.

What are the cons of wind energy?

Intermittent supply, aesthetic concerns, and bird/bat deaths.

What are small-scale energy conservation methods?

Using LED lights, insulation, low-flow fixtures, and efficient appliances.

What are large-scale energy conservation methods?

CAFE standards, public transit, green building codes, and smart grids.

How do smart grids improve energy use?

They manage supply/demand, integrate renewables, and reduce outages.