Renewable Energy Lecture Notes

ECOL 1000: Ecological Basis of Environmental Issues

Course Information

  • University: University of Georgia

  • Semester: Spring 2026

  • Lecture Title: Lecture 10: Renewable Energy

Renewable Energy Overview

  • Various forms of renewable energy that are currently utilized:

    • Hydropower: 57%

    • Wind: 23%

    • Solar: 9%

    • Biomass: 7%

    • Geothermal: 4%

Biomass Fuels

  • Bioenergy: Energy contained in organic materials, such as firewood and plant matter.

  • Source: Derived from solar energy.

  • Traditional Fuels: Include wood, charcoal, and animal dung.

Biofuels

  • Biofuels: Fuels derived from biological materials, such as plant materials.

  • CO2 Cycle:

    • CO2 used to make ethanol from trees comes from the atmosphere, and when burned, does not increase net CO2 levels in the air because it is part of a closed carbon cycle.

    • CO2 Origins: The CO2 is absorbed from the atmosphere by the trees.

Economic Aspects of Biofuels

  • Price Fluctuations:

    • 2002-2011: Prices varied from $0 to $7.00 per bushel.

  • Ethical Concerns:

    • Debate over using corn and other human food crops for biofuel production.

Cellulosic Ethanol

  • Sources:

    • Switchgrass: Native, low fertilizer and water needs, grows on marginal land, and is perennial.

  • Limitations:

    • Not yet produced on a large scale, no subsidies available, and expensive enzymatic processes required for production.

Algae Biofuel

  • Potential Uses: Proposed by NASA; algae can potentially clean wastewater and produce oil.

  • Process:

    1. Semi-permeable bags filled with wastewater and freshwater algae are employed.

    2. Bags allow freshwater to flow out but prevent saltwater from entering, which could kill the algae.

    3. Algae consume nutrients from wastewater and grow fatty cells rich in oil, while absorbing CO2 and releasing O2 into their environments.

  • Yield per Acre:

    • Estimated annual oil production from various plants:

    • Soybeans: 50 gallons (189 liters)

    • Canola: 160 gallons (606 liters)

    • Palms: 600 gallons (2,271 liters)

    • Algae (some types): At least 2,000 gallons (7,570 liters)

Advantages and Disadvantages of Biofuels

  • Advantages:

    • Carbon neutral, lower NOx and SOx emissions, abundant resources, domestic production.

  • Disadvantages:

    • There is debate over true carbon neutrality, costs associated with transportation and processing, and questions on net energy gain.

Wind Power

  • Mechanism for Energy Generation:

    • Blades operate like airplane wings to turn a generator.

  • Environmental Factors:

    • Geography & topography cause uneven heating of the Earth, forming winds from high to low pressure.

  • US Wind Potential:

    • Major wind farms are located in Texas, California, Minnesota, and Washington, contributing approximately 7% of global electricity.

Wind Power Advantages and Disadvantages

  • Advantages:

    • No fuel costs (i.e., no drilling, no air pollutants like CO2, NOx, SOx), domestic energy source, resilience against single energy plant disruptions.

  • Disadvantages:

    • Impact on wildlife (bird/bat deaths), aesthetic concerns, intermittent energy generation, and geographical limitations of windy areas relative to urban centers.

Hydropower

  • Mechanics:

    • Captures energy from falling or flowing water.

    • Types of hydropower plants: Impoundment (dams) and Run-of-River plants.

1. Impoundment Plants

  • Water is stored behind a dam, accumulating potential energy, which is converted to kinetic energy as it flows through a penstock to turn turbine blades connected to a generator.

    • Components:

    • Reservoir -> Intake Pipe (Penstock) -> Turbine -> Generator -> Power Transmission

2. Run-of-River Plants

  • Use runoff from rainfall and snowpack, often less costly and ecologically disruptive but dependent on a sustained water flow.

Global Hydropower Statistics

  • Hydropower contributes to 16% of the global electricity demand and 6% in the U.S.

  • Leading producers: China, Brazil, and Canada; Norway and Paraguay produce nearly 100% of their electricity from hydropower.

Hydropower Advantages and Disadvantages

  • Advantages:

    • Does not require fossil fuels, emits no pollutants, energy is cheap post-construction, can be used for flood control and water retention.

  • Disadvantages:

    • Environmental impacts on ecosystems, altered flow regimes, sediment transport changes, temperature changes affecting stream quality.

Solar Power

  • Solar Impulse:

    • A solar-powered plane completed a journey across the US, demonstrating solar energy potential.

    • Route Summary: Successful journey from California to New York, involving multiple legs with stops.

  • Energy Self-Sufficiency:

    • Example: Zion National Park’s Visitor Center utilizes solar energy extensively through photovoltaic technology and thermal mass to store and gradually release heat.

Photovoltaic Technology

  • Photovoltaic (PV) cells are experiencing rapid production growth of approximately 25% annually.

  • Alternatives include Concentrating Solar Power (CSP), which focuses sunlight onto water to produce steam for electricity generation.

Solar Power Advantages and Disadvantages

  • Advantages:

    • Renewable, with zero emissions, can be installed in various locations, and drives job growth.

  • Disadvantages:

    • High initial costs, reliance on sunlight, geographical restrictions, and hazardous materials in production.

Geothermal Energy

  • Definition: Heat energy generated and stored deep within the earth, independent of solar processes.

  • Geothermal Applications:

    • Ground Source Heat Pumps (GSHP): These are utilized for heating and cooling; they leverage stable underground temperatures.

Geothermal Energy in Iceland

  • Statistics highlight that geothermal resources are significant, with approximately 89% of heating sourced from non-renewable means and 10% from electricity.

Advantages and Disadvantages of Geothermal Energy

  • Advantages:

    • Offers reliable and inexpensive energy with low pollution levels. GSHPs use 30-70% less energy than conventional systems.

  • Disadvantages:

    • Potentially disruptive to ecosystems, replenishment rates can be slow, and high initial costs correlate with geographical limitations.

Ocean Energy

  • Mechanisms of Energy Generation:

    • Utilizes kinetic energy from tidal movements and waves.

    • Examples include tidal barrages and tidal turbines.

  • Tidal Barrage Example:

    • La Rance in France has turbines that produce electricity as water flows with tides.

    • A tidal turbine in Northern Ireland is planned to generate 1.2 megawatts, sufficient for 1,000 homes.

Ocean Energy Advantages and Disadvantages

  • Advantages:

    • Renewable and pollution-free, with low production costs.

  • Disadvantages:

    • Ecosystem disturbances in marine environments, limitations on tidal barrage systems requiring substantial tidal variations, and geographical constraints.

Conservation Savings Curve

  • Hypothetical model demonstrating energy savings potential through energy-efficient building features; indicates cost-effective energy-efficient measures based on current energy prices.

  • Future price increases in energy may make more conservation measures viable.