Lecture 3 Renewable Energy

Renewable Energy

Nonrenewable Energy Sources

  • Definition: Energy sources formed over millions to billions of years, which are unsustainable and nonrenewable.

  • Types:

    • Fossil Fuels:

      • Oil: Extracted through drilling below Earth's surface.

      • Coal: Considered the dirtiest burning fuel; extracted through harmful methods.

      • Natural Gas: Collected by fracturing the Earth, using water pressure.

Renewable Energy Sources

  • Definition: Energy collected from resources naturally replenished on a human timescale.

  • Common Types:

    • Wind: Wind turbines rotate to generate electricity.

    • Solar: Utilizes solar panels to absorb sunlight for energy.

    • Hydroelectric: Uses flowing water to spin a generator.

    • Geothermal: Uses heat from the Earth’s core for energy.

  • Other Sources:

    • Biogas

    • Biomass

    • Biofuels

    • Hydrogen fuel cells

    • Nuclear fusion

    • Ocean waves and tidal energy

    • Small-scale hydroelectric

Comparison of Renewables and Non-Renewables

  • Future Projections: EIA forecasts renewables could provide nearly half of global electricity by 2050.

    • Graphs indicate trends in World net electricity generation (1990-2050).

    • Significant increase in renewable energy share by 2050.

Biogas

  • Definition: Methane gas produced by bacteria from organic material in the absence of oxygen.

  • Process:

    • Organic materials are processed in anaerobic digesters, and microorganisms are added.

    • Methane is collected for energy, and solids can be repurposed.

  • Pros and Cons:

    • Pros: Reduces reliance on traditional fossil fuels.

    • Cons: Not efficient on large scales and emits methane.

Methane Emissions from Landfills

  • Data: Estimated methane emissions map shows varying emissions by state, highlighting high emissions in certain areas.

Biomass

  • Definition: Biological material from living or recently living organisms (e.g., wood chips, yard clippings).

  • Stats: Accounts for about 40% of the world’s renewable energy supply.

  • Process: Burned to heat water, producing steam for turbine generation.

    • Sources: Can be grown from various plants including switchgrass and hemp.

  • Pros and Cons:

    • Pros: Can be cultivated on non-arable land.

    • Cons: Requires land use and may contribute to air pollution.

Biofuels

  • Definition: Fuels made from living organisms processed chemically.

  • Examples: Bioethanol and biodiesel, most used in the USA and Brazil.

  • Process: Fermentation and transesterification of plant materials.

Algal Biofuels

  • Process Overview:

    • Algal growth, harvesting, extraction of oil, followed by conversion to biodiesel or bioethanol.

Pros and Cons of Biofuels

  • Pros: Biodegradable and can power various vehicles.

  • Cons: Requires significant land, water, and resources, which may lead to deforestation.

Geothermal Energy

  • Definition: Energy sourced from underground heat.

  • Process: Pockets of steam drive turbines for electricity.

  • Location: Commonly found in tectonically active areas like California and Iceland.

  • Pros and Cons:

    • Pros: Reliable and produces little air pollution.

    • Cons: Potential water contamination and may be site-limited.

Hydroelectric Power

  • Process: Dams trap water released to turn turbines generating electricity.

  • Stats: Accounts for about 22% of U.S. energy production.

  • Pros and Cons:

    • Pros: Effective flood control, no emissions.

    • Cons: Alters ecosystems and can create stagnant waters, promoting pathogen growth.

Dam Impacts

  • Upstream Effects: Reduced water quality, increased pollutants, and loss of natural sediment transport.

  • Downstream Effects: Warmer water temperatures and unnatural riverbed changes.

Flood Control

  • Causes of Floods: Include dam failures, snowmelt, and heavy rainfall.

  • Mitigation Techniques: Employing levees, reservoirs, catchment basins, and permeable surfaces.

Economic Benefits of Large Dams

  • Benefits: Storage for agriculture, flood control, energy production.

Solar Energy

  • Active Solar: Mechanically collects solar energy (e.g., photovoltaic cells).

  • Passive Solar: Utilizes design and materials for heating/cooling without mechanical systems.

  • Pros and Cons:

    • Pros: Abundant and clean energy source.

    • Cons: High initial costs, efficiency drops in limited sunlight areas.

Wind Energy

  • Process: Wind turns turbines connected to electricity generators.

  • Pros and Cons:

    • Pros: Potential to meet U.S. electrical needs.

    • Cons: Requires consistent winds, can be noisy, impacts local wildlife.

Future Renewable Energy Sources

  • Expanding Options: Hydrogen fuel cells, nuclear fusion, tidal energy, and small-scale hydroelectric.

Hydrogen Fuel Cells

  • Reaction: Combines hydrogen and oxygen to produce water and energy.

  • Pros and Cons:

    • Pros: Minimal waste, reduced pollutants.

    • Cons: Expensive to produce, storage issues.

Nuclear Fusion

  • Definition: Fusing nuclei generates energy; still under development with no commercial plants yet operational.

  • Pros and Cons:

    • Pros: Low waste and greenhouse gas emissions, easier control.

    • Cons: Expensive development and infrastructure.

Wave and Tidal Energy

  • Definition: Uses natural movements of tides and waves to generate electricity.

  • Pros and Cons:

    • Pros: No pollution, minimal impact.

    • Cons: High construction costs, limited sites.

Small-Scale Hydroelectric Power

  • Definition: Utilizes small turbines to generate electricity in streams.

  • Benefits: Minimal impact on stream navigation.

Energy Sources in Less Developed Countries

  • Primary Energy Source: Often biomass used for domestic energy needs, such as wood, charcoal, and manure.