9.3 Energy Resources

9.3 Energy Resources

1. Conventional and Renewable Energy

1. Conventional Energy:

   • Also called non-renewable or traditional energy sources.

   • Finite resources with long formation times (millions of years).

   • Types:

     • Fossil Fuels: Coal, petroleum, natural gas.

     • Nuclear: Uranium, thorium (though sometimes classified separately).

   • Characteristics:

     • High energy density.

     • Established infrastructure.

     • Cause significant environmental pollution.

     • Subject to price volatility and depletion.

2. Renewable Energy:

   • Sources that are naturally replenished on human timescales.

   • Types:

     • Solar, wind, hydro, geothermal, biomass, tidal, wave.

   • Characteristics:

     • Low or zero emissions during operation.

     • Distributed availability.

     • Intermittent nature (except geothermal and hydro).

     • Lower energy density than fossil fuels.

3. Comparison:

   • Renewables: Sustainable, clean, but intermittent, lower energy density.

   • Conventional: Reliable, high density, but polluting, finite.

2. Solar, Wind, Hydro, Bio-energy

1. Solar Energy:

   • Technologies:

     • Photovoltaic (PV): Direct conversion of sunlight to electricity.

       • Efficiency: 15-22% for commercial panels.

       • Key parameter: Solar insolation (kWh/m²/day).

     • Solar Thermal: Use sunlight for heating or to drive turbines.

       • Types: Parabolic troughs, solar towers, dish engines.

   • Advantages: Abundant, no fuel cost, low maintenance.

   • Limitations: Intermittent, requires energy storage, large land area.

2. Wind Energy:

   • Working Principle: Kinetic energy of wind → mechanical energy → electrical energy.

   • Key Equation: Power in wind: $P = \frac{1}{2} \rho A v^3$

     • $\rho$ = air density (≈1.225 kg/m³ at sea level)

     • $A$ = swept area of turbine blades = $\pi r^2$

     • $v$ = wind speed

   • Betz Limit: Maximum theoretical efficiency = 59.3%.

   • Components: Blades, gearbox, generator, tower, control systems.

   • Types: Horizontal axis (HAWT) and vertical axis (VAWT).

3. Hydro Energy:

   • Types:

     • Large-scale hydropower (>100 MW).

     • Small-scale hydro (<10 MW).

     • Micro-hydro (<100 kW).

     • Pumped storage (energy storage).

   • Power Equation: $P = \eta \rho g Q H$

     • $\eta$ = efficiency (0.8-0.9)

     • $\rho$ = water density (1000 kg/m³)

     • $g$ = gravity (9.81 m/s²)

     • $Q$ = flow rate (m³/s)

     • $H$ = head/height (m)

   • Advantages: Reliable, dispatchable, long lifespan.

   • Disadvantages: High initial cost, environmental impact, displacement.

4. Bio-energy:

   • Sources: Biomass, biogas, biofuels.

   • Conversion Methods:

     • Direct combustion: Heat → steam → electricity.

     • Anaerobic digestion: Organic waste → biogas (CH₄ + CO₂).

     • Fermentation: Sugars → ethanol.

     • Transesterification: Vegetable oils → biodiesel.

   • Advantages: Carbon neutral (in theory), waste utilization.

   • Limitations: Land use competition, emissions from combustion.

3. Nuclear Energy

1. Basic Principle:

   • Energy released from atomic nucleus via:

     • Fission: Splitting heavy nuclei (U-235, Pu-239).

     • Fusion: Combining light nuclei (deuterium, tritium) - not yet commercial.

2. Nuclear Fission Process:

   • Chain reaction: $n + ^{235}_{92}U → ^{236}_{92}U → Fission fragments + 2-3 n + Energy$

   • Energy released: ~200 MeV per fission (~80 million times chemical energy).

3. Nuclear Reactor Components:

   • Fuel rods (UO₂ pellets)

   • Moderator (slows neutrons): Water, graphite, heavy water.

   • Control rods (absorbs neutrons): Boron, cadmium.

   • Coolant: Water, liquid metal, gas.

   • Containment structure.

4. Reactor Types:

   • Pressurized Water Reactor (PWR): Most common.

   • Boiling Water Reactor (BWR).

   • Pressurized Heavy Water Reactor (PHWR): CANDU.

   • Fast Breeder Reactor (FBR).

5. Key Metrics:

   • Capacity factor: Typically 80-90% (very high).

   • Fuel consumption: 1 kg U-235 ≈ 3 million kg coal.

6. Advantages: High energy density, low operating costs, zero CO₂ during operation.

7. Challenges: Radioactive waste, safety concerns, high capital costs, proliferation risk.

4. Environmental Impacts

1. Fossil Fuels:

   • Air Pollution: SOₓ, NOₓ, particulate matter (PM).

   • Greenhouse Gases: CO₂ (main contributor to climate change).

   • Acid Rain: From SOₓ and NOₓ emissions.

   • Water Pollution: Mining runoff, oil spills.

   • Land Degradation: Mining, drilling sites.

2. Nuclear Energy:

   • Radioactive Waste: Low, intermediate, high-level waste.

   • Accident Risk: Chernobyl, Fukushima-type accidents.

   • Thermal Pollution: Waste heat to water bodies.

   • Mining Impacts: Uranium mining pollution.

3. Renewables:

   • Solar: Land use, toxic materials in manufacturing (Cd, Pb), visual impact.

   • Wind: Bird/bat mortality, visual/noise pollution, land use.

   • Hydro: Ecosystem disruption, methane emissions from reservoirs, displacement.

   • Bio-energy: Land use change, water consumption, air pollution from combustion.

4. Climate Change Connection:

   • Fossil fuels = major contributor to global warming.

   • Renewables and nuclear = mitigation options.

   • Need for lifecycle analysis of all technologies.

5. Sustainability Metrics:

   • Carbon footprint (gCO₂eq/kWh)

   • Water consumption (L/kWh)

   • Land use (m²/GWh)

   • Energy payback time (years)