Renewable & Non-Renewable Energy

Cheatsheet Content

Introduction to Energy Sources Renewable Energy: Energy from naturally repetitive and persistent flows in the environment (e.g., solar, wind, hydro, biomass, geothermal, ocean). Non-Renewable Energy: Energy from static stores underground, requiring external action for release (e.g., fossil fuels, nuclear). Renewable Energy Sources 1. Solar Energy Description: Harnesses solar radiation via thermal or photovoltaic systems. Earth intercepts $1.78 \times 10^{17}$ W, $\approx 10,000$ times world demand. PV (Photovoltaic) Systems: Converts sunlight directly into electricity using the photoelectric effect in semiconductor cells (p-type and n-type silicon). Solar cells (PV cells) absorb photons, release free electrons, collected by bus bars as current. Individual cells form modules/panels; inverters convert DC to AC for grid use. CSP (Concentrated Solar Power): Mirrors/lenses focus sun rays onto a small area, generating high heat. Heat drives a working fluid to power a steam turbine for electricity. Technologies: parabolic trough, Stirling dish, solar power tower. Benefits: Renewable, no hazardous gas/GHG emissions, energy independence, low maintenance ($25$ year lifespan), works in various climates (snow can enhance). Disadvantages: High initial cost, intermittent (weather-dependent), low power density (needs large area), manufacturing pollution. 2. Wind Energy Description: Converts kinetic energy of wind into mechanical power, then electricity via a generator. Estimated global potential: $1.6 \times 10^{13}$ W. Types: Horizontal-axis (most common) and vertical-axis wind turbines. Components: Rotor: Blades + hub, converts wind to rotational energy. Nacelle: Houses drive train (shafts, gearbox, generator). Pitch Drive: Adjusts blade angle to optimize wind capture. Yaw Drive: Orients nacelle/rotor to face wind direction. Brake: Stops/slows rotor in emergencies. Tower: Supports components, houses controls. Working Principle: Wind creates low-pressure pocket behind blade (lift), pulling rotor to turn. Gearbox increases rotation speed for generator. Benefits: Widely available, good for remote areas (micro-grids), high conversion efficiency ($40-50\%$), clean, renewable, low operating cost, space-saving (farming below). Disadvantages: Threat to wildlife (birds/bats), noise pollution, large land requirement, unpredictable wind flow, susceptible to lightning damage. 3. Hydro Resources (Hydropower) Description: Uses natural flow of water (rivers) to generate electricity. Highly advanced and flexible. Working Principle: Dams create reservoirs, storing water at height (potential energy). Water flows through penstock to turbines (potential to kinetic energy). Turbines spin generators (kinetic to mechanical to electrical energy). Benefits: Completely renewable, no atmospheric emissions, most reliable (constant flow), adjustable output, backup power, flood control, irrigation. Disadvantages: High initial investment, limited suitable locations, environmental impacts (fish migration, habitat destruction, methane from decomposition), drought-dependent, dam collapse risk. 4. Biomass Energy Description: Energy from animal and vegetation resources (wood, crops, algae, waste). Solar energy absorbed by plants is $\approx 2 \times 10^{21}$ J/year. Forms: Can be transformed into biogas (methane), ethanol, biodiesel, charcoal. 5. Geothermal Energy Description: Energy from Earth's internal heat (decay of isotopes like Uranium, Thorium, Potassium). Status: Economically recoverable only in certain regions; negligible overall contribution but locally important. Used directly and for electricity in 24 countries. 6. Ocean Tidal Energy Description: Converts energy from tides into electricity. More predictable than wind/solar. Status: Under development, few operational plants. 7. Ocean Wave Energy Description: Harnesses energy from ocean surface waves. Shoreline potential $\approx 50,000$ MW, deep-water resources are enormous. Status: Global resource estimated $>2$ TW. 8. Ocean Thermal Energy Conversion (OTEC) Description: Uses temperature difference between warm surface and cold deep ocean water. Status: Infant stage, commercial prospects uncertain. Potential is larger than tidal/wave energy (up to $88,000$ TWh/yr). Engineering challenges limit development. General Benefits of Renewable Energy Low/No Emissions: Reduced greenhouse gases (climate change) and air pollutants (health benefits). Circular Economy: Meets objectives of a circular economy, strong driver for social and economic development. Lower Costs: Can lead to affordable energy prices, less affected by geopolitical crises or supply chain disruptions. Job Creation: Supports local economies. Accessibility: Lowest-cost new power generation, especially for developing countries and remote areas. Security & Stability: Enhances energy security and infrastructure resilience. Democracy: Supports community energy projects. General Limitations of Renewable Energy Weather Dependency: Inconsistent power generation (solar, wind). High Initial Investment: Significant upfront costs for setup. Inefficient Storage: Excess energy storage can be challenging. Limited Capacity: May have lower overall potential compared to conventional sources. Environmental Impact: Large-scale projects (e.g., hydroelectric dams) can cause habitat destruction. Non-Renewable Energy Sources Definition: Energy from static stores, requiring external action. Finite supplies. 1. Fossil Fuels (Coal, Oil, Natural Gas) Coal: India has vast reserves ($5^{th}$ largest globally), but production doesn't meet demand (import dependency $\approx 23\%$ in 2014). Oil & Natural Gas: Limited reserves in India. High import dependency (oil $75\%$, gas $25\%$). 2. Nuclear Resources Uranium: India has modest reserves ($1-2\%$ global). Infrastructure: $21$ nuclear reactors across $7$ plants. Installed capacity $5780$ MW ($\approx 2.1\%$ of total). Research: IGCAR (India Gandhi Center for Atomic Research) for nuclear energy technology development. Benefits of Non-Renewable Energy Cost: Currently cheaper than renewable sources. Efficiency: High energy density (e.g., $1$g Uranium $\to 1$ MW; $1$ tonne coal $\to 2460$ kWh). Security: Easy and convenient storage ensures availability. Convenience: Mature technology, universally available conversion and use. Transport: Raw materials (coal, petroleum, natural gas) easily transported. Location: Flexible installation, doesn't need specific geographic conditions. Limitations of Non-Renewable Energy Pollution: Main reason for pollution (carbon monoxide, other air pollutants), contributes to global warming. India $2018$ emissions: $2.299$ billion tonnes CO. Radioactive Waste: Nuclear plants generate dangerous waste (e.g., Fukushima disaster). Finite Supply: Resources will eventually run out. High Startup Cost: Thermal plant $\approx 50-70$ crores for $10$ MW; nuclear plant $\approx 60,000$ crores. Comparison: Renewable vs. Conventional Energy Sl. No. Feature Renewable Energy (Green) Conventional Energy (Brown) 1 Examples Wind, solar, biomass, tidal Coal, oil, gas, radio-active ore 2 Source Natural local environment Concentrated stock 3 Normal state A current or flow of energy. An income Static store of energy. Capital 4 Lifetime of supply Infinite Finite 5 Cost of source Free Increasingly expensive 6 Equipment capital cost per kW capacity Expensive, commonly $\approx \$1000$ Moderate, perhaps $\$500$ without emissions control; yet $>\$1000$ with emissions reduction 7 Location for use Site and society specific General and global use 8 Scale Small-scale is often economic Increased scale often improves supply costs; large-scale frequently favored 9 Skills Interdisciplinary and varied. Importance of bioscience and agriculture Strong links with electrical and mechanical engineering. Narrow range of personal skills 10 Context Well adapted to rural situations and decentralized industry Scale favors urban, centralized industry 11 Safety Local hazards possible in operation. Usually safe when out of action May be shielded and enclosed to lessen great potential dangers; most dangerous when faulty 12 Pollution and environmental damage Usually little environmental harm. Hazards from excessive wood burning, soil erosion from excessive bio-fuel use. Large hydro reservoirs disruptive. Environmental pollution common, especially of air and water. Permanent damage common from mining and radio-active elements entering water table. Deforestation and ecological sterilization from excessive air pollution. Greenhouse gas emissions causing climate change