Renewable Energy- Exam Two

What is nuclear power and how does it generate electricity?

Nuclear power uses fission — the splitting of uranium-235 atoms — to release heat, which converts water into steam to drive turbines and generate electricity

What are major advantages of nuclear power?

• Very low greenhouse gas emissions once operational.

• Produces large amounts of baseload power.

• Reduces dependence on fossil fuels.

What are the main concerns or drawbacks of nuclear power?

• Radioactive waste disposal.

• Accidents (Chernobyl, Fukushima).

• High construction and decommissioning costs.

• Public safety and perception issues.

What happened at the Chernobyl disaster (1986)?

In Ukraine (then USSR), a flawed reactor design and operator error led to a steam explosion and graphite fire, releasing massive radiation. Caused long-term evacuations, environmental contamination, and health impacts like cancer.

What happened at the Fukushima Daiichi disaster (2011)?

An earthquake and tsunami in Japan disabled power and cooling systems, causing core meltdowns and radioactive releases. It led Japan to temporarily shut down nearly all reactors and re-evaluate nuclear safety standards.

How has nuclear energy policy shifted post-Fukushima?

Many countries (Germany, Japan) reduced or phased out nuclear programs, while others (France, China) continue development with improved safety and modular reactor designs.

How does hydroelectric power generate electricity?

Uses gravitational potential energy of elevated water. As it flows downward, energy converts to kinetic, turning turbines to generate electricity.

What are the advantages of hydroelectric power?

• Very low GHG emissions compared to fossil fuels.

• No fuel cost after construction.

• Dispatchable — electricity generation can be quickly adjusted to meet demand.

• Multipurpose (flood control, irrigation, recreation, water supply).

What are the disadvantages of hydroelectric power?

• Flooding of large areas and displacement of people.

• Ecosystem disruption (fish migration, sediment buildup).

• Siltation reduces reservoir capacity.

• Dam failures can be catastrophic.

• High capital cost and limited geographic potential.

How has hydroelectric power’s role changed in the U.S.?

• Provided 35% of U.S. power in the 1970s, but only about 6% today (≈16% globally).

• Most suitable sites already developed.

What are key regions for hydroelectric production in the U.S.?

Pacific Northwest (Columbia River), Central Valley (CA), Southern Appalachians, and New England/New York.

What are the main hydro technologies?

• Conventional dam and reservoir: stores and releases water as needed.

• Run-of-river (low-impact): diverts part of stream flow with less ecological impact.

• Pumped storage: water pumped uphill during low demand, released for peak demand.

• Tidal hydro: uses ocean tides (experimental).

What are the future challenges and directions of hydropower?

• High upfront cost and long construction times.

• Dam removals for river restoration.

• New growth mainly in developing countries.

• Lake Mead (NV/AZ) is the largest U.S. reservoir, showing both benefits and water scarcity concerns.

What is bioenergy?

Energy derived from biological sources — plants, crops, or organic waste — that can be burned directly or converted into liquid fuels like ethanol and biodiesel.

What are ethanol’s advantages?

• Cleaner-burning fuel than gasoline.

• Reduces fossil fuel dependence and enhances energy security.

• Created domestic markets for corn.

What legislation boosted ethanol use?

The 2005 Energy Policy Act, which required ethanol blending in gasoline. Led to rise in flex-fuel vehicles that can use gasoline-ethanol mixes (E85).

What are main feedstocks for ethanol?

• Corn (U.S.): about 40% of total production goes to ethanol.

• Starch (grain) ethanol: processed in Corn Belt refineries.

• Cellulosic sources (future): switchgrass, poplar, agricultural residue.

What are environmental and efficiency concerns of ethanol?

• Corn cultivation is energy intensive — yields ~1.25 units of energy per 1 input (low net gain).

• Tailpipe emissions are lower, but full life-cycle impact depends on fertilizer and energy inputs.

• Land and water use for corn farming can compete with food production.

What are the by-products of ethanol production?

Distillers grains — nutrient-rich residue used as livestock feed.

What is the main disadvantage of ethanol compared to gasoline?

Lower energy density — about 35% less energy per gallon

How is wood used as an energy source?

Burned directly for heat and electricity using stoves or industrial boilers; newer designs are much more efficient.

Where is wood energy most common?

Forested and rural regions — particularly in northern U.S., Scandinavia, and Canada.

What other biomass materials are used?

Agricultural residues, forestry waste, and energy crops (switchgrass, poplar, algae).

What are advantages of wood and biomass energy?

• Renewable if managed sustainably.

• Utilizes waste materials that might otherwise be discarded.

• Can support local economies

What are the disadvantages of wood and biomass energy?

• Air pollution (particulates, CO₂ if forests not replanted).

• Low energy density.

• May compete with land for food or biodiversity.

What is biodiesel?

A renewable fuel made from vegetable oils, animal fats, or recycled grease; can power diesel engines.

How does biodiesel differ from ethanol?

• Ethanol replaces gasoline; biodiesel replaces diesel fuel.

• Ethanol dominates in the U.S., while Europe favors biodiesel.

What are common biodiesel sources?

Soybeans (U.S.), canola (Europe), and animal waste digesters.

What are digesters, and what do they produce?

Systems that break down organic waste (e.g., manure) to produce biogas (methane) and nutrient-rich fertilizer.

What other bioenergy recovery methods exist?

Landfill gas capture and waste incineration to generate electricity.

What makes wind energy appealing?

• Fastest-growing renewable source globally.

• No greenhouse gas emissions.

• Economically competitive with fossil fuels.

• Short development time compared to nuclear or hydro.

How do wind turbines generate electricity?

Wind moves blades connected to a rotor, driving a generator that converts kinetic energy into electrical energy.

What has improved wind power’s efficiency?

• Larger turbines with taller towers and longer blades.

• Higher capacity factors (~50%) from better siting and design.

• Government tax credits and subsidies.

What are the top five U.S. wind states (2023)?

Texas, Iowa (≈58% of its power), Oklahoma, Kansas, and Illinois.

What are wind energy’s main limitations?

• Intermittency (depends on weather).

• Not dispatchable on demand.

• Noise complaints.

• Bird and bat mortality.

• Aesthetic concerns (visual landscape changes).

What are the challenges with offshore wind power?

Expensive underwater cabling and harsh marine conditions; notable examples include Block Island, RI (operational) and Cape Wind (canceled).

What is the “aesthetics of sustainability” in wind power debates?

Some people see turbines as symbols of clean energy (“thick meaning”), others as landscape intrusions (“thin meaning”). This fuels “NIMBY” (Not In My Backyard) resistance

How does solar power work?

Captures sunlight and converts it into heat or electricity via solar thermal or photovoltaic (PV) systems.

What are the two main types of solar energy systems?

• Passive solar: architectural design (windows, walls, materials) that naturally capture sunlight for heating/cooling.

• Active solar: uses mechanical systems like panels or pumps to convert and store energy

How do photovoltaic (PV) cells generate electricity?

PV cells (usually silicon) absorb photons, creating an electric current (DC electricity) that can be converted to AC for grid use.

What is Swanson’s Law?

States that the price of solar panels falls by 20% each time global production doubles — explaining rapid cost declines

What has driven the takeoff of solar energy?

• Policy support: subsidies, tax credits, renewable portfolio standards, feed-in tariffs, and net metering.

• Manufacturing expansion (especially in China).

• Technical innovations (efficiency improvements).

• Financial innovation (leasing models, investment funds).

What are environmental or technical limitations?

• Intermittent energy (daytime only).

• Land-use impacts for large solar farms.

• Material concerns (toxic chemicals in production).

• Energy storage challenges.

How does geothermal energy relate to solar?

Both are renewable, but geothermal taps Earth’s internal heat rather than solar radiation; used for direct heating or electricity.

What are its advantages and limits of solar?

Reliable baseload renewable source.

• Low emissions.

• Limited to geologically active regions (Iceland, western U.S.)