Renewable Power Generation (EX-503 (C)) - Unit 4 Short Notes

UNIT 4: RENEWABLE POWER GENERATION (EX-503(C))

I. INTRODUCTION & ENERGY OVERVIEW

Classification of Energy Sources:

• Conventional: Fossil Fuels (Coal, Oil, Natural Gas), Nuclear, Large Hydro.

• Renewable (Non-conventional): Solar, Wind, Biomass, Small Hydro, Geothermal, Ocean (Tidal, Wave, OTEC), Hydrogen.

Merits & Demerits (Comparative Analysis):

Indian Renewable Energy Scenario:

• Targets: 500 GW non-fossil capacity by 2030 (NDC target).

• Installed Capacity (as of ~2024): ~190 GW Renewable (Wind ~45 GW, Solar ~75 GW, Biomass/Small Hydro ~10 GW).

• Policies: National Solar Mission, Wind Power Policy, Bioenergy Programme, International Solar Alliance (ISA).

• Tamil Nadu Profile: Leader in Wind (over 9 GW, ~25% of India's wind), significant Solar potential, active Biomass (co-generation) and Small Hydro.

[!TIP] Exam Focus: Be prepared to compare two sources (e.g., Solar vs. Wind, Biomass vs. Solar) in terms of merits/demerits, or discuss India's specific targets and state-wise (especially TN) renewable profile.

Future Energy Strategies & Security:

• Focus on decarbonization, energy access, and affordability.

• Hybrid systems (solar-wind-storage) and green hydrogen for storage/transport.

• Energy Resource Reserve: Proven, probable, and possible reserves of conventional (coal, uranium) and renewable (solar/wind potential maps) resources.

II. SOLAR ENERGY SYSTEMS

Solar Radiation & Geometry:

• Key Angles:

  • Latitude (φ): Angular distance from equator.

  • Declination (δ): Angle between sun-earth line and equatorial plane. Varies ±23.45° annually.

  • Solar Altitude (α): Angle between sun's rays and horizontal plane. α = 90° - |φ - δ| at solar noon.

  • Solar Azimuth (γ): Angle between sun's projection on horizontal plane and true south (N. Hemisphere).

• Solar Time: Based on sun's position, differs from local clock time.

Solar Thermal Systems:

1. Flat Plate Collectors: Absorber plate (black surface), transparent cover (glass), insulation, casing, fluid tubes. Used for low-temp (<100°C) applications (water heating, space heating).

2. Concentrating Collectors: Parabolic trough, dish, tower. Use mirrors/lenses to concentrate sunlight onto a receiver for medium/high-temp applications (power generation, process heat).

Solar Thermal Power Generation (CSP):

• Layout: Solar field (mirrors) → Receiver/Heat Exchanger → Heat Transfer Fluid (HTF) → Steam Generator → Turbine-Generator → Condenser → HTF pump.

• Working: Sunlight concentrated to heat HTF (oil, molten salt), produces steam to drive turbine.

Solar Photovoltaic (PV) Systems:

• Principle: Photovoltaic effect. Absorption of photons by semiconductor (Si) generates electron-hole pairs → DC current.

• Key Elements:

  • Cell: Basic unit (Si, thin-film). ~0.5-0.6 V.

  • Module: Series/parallel connected cells encapsulated.

  • Array: Multiple modules.

  • Balance of System (BoS): Inverter (DC-AC), mounting, wiring, charge controller, batteries (if off-grid).

• I-V Characteristics:

  • Open Circuit Voltage (Voc): Voltage at I=0.

  • Short Circuit Current (Isc): Current at V=0.

  • Maximum Power Point (MPP): Point (Vm, Im) where Pmax = Vm * Im is maximum.

  • Fill Factor (FF): FF = (Vm * Im) / (Voc * Isc). Measures "squareness" of curve.

  • Efficiency (η): η = Pmax / (Input Solar Irradiance * Area) = (Voc * Isc * FF) / (G * A).

• Factors Affecting Performance:

  • Irradiance (G): Directly proportional to Isc.

  • Temperature (T): Increase in T → decrease in Voc (major), slight increase in Isc → net decrease in Pmax and efficiency.

  • Spectral distribution, soiling, shading, inverter efficiency.

[!TIP] Exam Focus: Numericals on Fill Factor & Efficiency are very common. Always remember units: G in W/m², A in m². Efficiency is unitless (often %).

III. WIND ENERGY SYSTEMS

Principle of Wind Power Conversion:

• Kinetic energy of wind → mechanical energy (rotor) → electrical energy (generator).

• Betz Limit: Maximum theoretical power coefficient Cp_max = 16/27 ≈ 0.593. No turbine can extract >59.3% of wind's kinetic energy.

• Power in Wind: P_wind = (1/2) * ρ * A * V^3

  • ρ = air density (kg/m³), A = swept area (m²), V = wind speed (m/s).

• Actual Power Output: P_mech = Cp * P_wind. Cp depends on Tip Speed Ratio (λ = ωR/V) and blade pitch.

Wind Turbine Types:

• Horizontal Axis Wind Turbine (HAWT): Most common. Rotor shaft parallel to ground. Requires yaw mechanism. Higher efficiency.

• Vertical Axis Wind Turbine (VAWT): Rotor shaft perpendicular to ground. No yaw needed, gearbox at ground level. Lower efficiency, higher torque ripple. (Darrieus, Savonius).

HAWT Components & Layout (Neat Diagram):

1. Rotor Blades: Capture wind energy. Aerofoil shape.

2. Nacelle: Housing containing gearbox, generator, control systems.

3. Gearbox: Increases rotor speed (low) to generator speed (high). (Direct drive eliminates gearbox).

4. Generator: Converts mechanical rotation to electricity (usually asynchronous/synchronous).

5. Tower: Supports rotor/nacelle. Height ↑ → wind speed ↑ (less turbulence).

6. Yaw System: Rotates nacelle to face wind.

7. Foundation: Concrete base.

Wind Resource Assessment & Site Selection:

• Wind Characteristics: Speed (mean, Weibull distribution k, c), direction (prevailing), turbulence intensity.

• Site Selection: High mean wind speed (>6 m/s at hub height), low turbulence, smooth terrain/offshore, proximity to grid, minimal environmental/social constraints.

Wind Power Calculations & Performance:

• Wind Power Density (WPD): WPD = (1/2) * ρ * V^3 (W/m²). Use mean of V^3, not (mean V)^3.

• Annual Energy Output (AEO): AEO = P_rated * CF * 8760 (kWh/year).

• Capacity Factor (CF): CF = (Actual Energy Output) / (Rated Power * 8760). Always < 1.

• Availability Factor: (Time available for operation) / (Total time).

Control & Grid Integration:

• Control: Pitch control (blade angle), yaw control, stall control (passive), torque/speed control.

• Grid Issues: Intermittency, voltage/frequency fluctuations. Solutions: Power electronics (converters), grid codes, forecasting, hybrid systems, storage.

Safety & Environmental Aspects:

• Noise: Aerodynamic (blade) and mechanical (gearbox).

• Visual Impact: "Skyline" clutter.

• Avian/Bat Mortality: Collision risk. Siting away from migration paths.

• Safety: Lightning protection, braking systems (aerodynamic, mechanical), fire suppression.

IV. BIOMASS AND BIOGAS ENERGY

Biomass Resources: Agricultural residues (straw, husk), forestry waste, animal dung, municipal solid waste (organic fraction), energy crops.

Environmental Problems from Waste: Open burning → air pollution (PM, CO, VOCs). Dumping → groundwater contamination, methane (GHG) emissions, disease vectors.

Biogas Generation (Anaerobic Digestion - 4 Stages):

1. Hydrolysis: Complex polymers (carbohydrates, proteins, fats) → simple sugars, amino acids, fatty acids.

2. Acidogenesis: Sugars etc. → volatile fatty acids (acetic, propionic), alcohols, H₂, CO₂, NH₃ (by acidogenic bacteria).

3. Acetogenesis: VFAs/alcohols → acetic acid, H₂, CO₂ (by acetogens).

4. Methanogenesis: Acetic acid/H₂+CO₂ → CH₄ (methane) + CO₂ (by methanogens). CH₃COOH → CH₄ + CO₂; 4H₂ + CO₂ → CH₄ + 2H₂O.

Materials for Biogas: Dung, kitchen waste, agricultural residue, sewage sludge, algae. C/N ratio ideal: 20-30:1.

Biogas Plant Designs:

1. Deen Bandhu (Floating Drum):

   • Diagram: Fixed cylindrical digester tank. Inlet, outlet. Floating gas holder (drum) on slurry.

   • Working: Feed slurry → digester → anaerobic digestion → biogas collects under floating drum, lifting it. Drum weight provides pressure. Simple, common.

2. Pragati Design (KVIC - Fixed Dome):

   • Diagram: Fixed brick dome roof. Inlet, outlet chambers. No moving parts.

   • Working: Biogas pressure pushes slurry into outlet chamber. Gas stored in top space of dome. Cheaper, but gas pressure varies, dome cracking risk.

3. Community Biogas Plants: Larger scale for village/community waste. Problems: Feedstock collection logistics, skilled operation, consistent feedstock supply, slurry disposal.

Thermochemical Conversion - Pyrolysis:

• Principle: Thermal decomposition of biomass in absence of air (inert atmosphere) at 400-600°C.

• Products: Solid (char), Liquid (bio-oil/tar), Gaseous (CO, H₂, CH₄, CO₂).

• Small-Scale Unit: Feedstock hopper → pyrolysis reactor (heater) → char removal, vapor condenser → bio-oil collection, gas cleaning → fuel gas.

Waste-to-Energy: Landfill Gas Power:

• System: Landfill → gas wells & collection pipes → vacuum/blower → gas cleaning (H₂S, moisture removal) → IC engine/gas turbine → generator.

• Advantages: Reduces GHG (methane), uses waste, base-load power, reduces odor/explosion risk.

Biomass Applications:

• Direct combustion (stoves, boilers, power plants).

• Gasification (partial oxidation → producer gas).

• Anaerobic digestion → biogas.

• Pyrolysis → bio-oil/biochar.

• Co-firing (with coal).

• Biofuels (bioethanol, biodiesel).

V. HYDROELECTRIC POWER (RENEWABLE)

Site Selection Considerations:

• Hydrological: High, reliable rainfall/snowmelt; large catchment area; favorable streamflow.

• Topographical: Narrow gorge for dam; steep valley for head; large reservoir basin.

• Geological: Sound rock foundation for dam & structures; low earthquake risk.

• Other: Proximity to load center, minimal displacement, ecological sensitivity.

Hydroelectric Plant Layout & Components (Neat Diagram):

1. Dam/Barrage: Creates reservoir, stores water, provides head.

2. Intake/Surge Tank: Controls water entry, absorbs pressure surges.

3. Penstock: Large pipe carrying water under pressure from intake to turbine.

4. Hydraulic Turbine: Converts water's pressure & kinetic energy to mechanical rotation.

5. Generator: Converts mechanical to electrical energy.

6. Tailrace: Channel returning water to river after turbine.

7. Powerhouse: Houses turbine, generator, control equipment.

Hydraulic Turbines:

• Pelton (Impulse): High head (300-2000 m), low flow. Water jets hit bucket-shaped cups on runner. Efficiency high at part load.

• Francis (Reaction): Medium head (30-300 m), medium flow. Water flows radially inward, axially out. Most common.

• Kaplan (Reaction): Low head (3-30 m), high flow. Axial flow, adjustable blades (runner & wicket gates). Efficient over wide range.

Hydrological Analysis:

• Hydrograph: Graph of discharge (flow) vs. time (daily, monthly, annual). Shows seasonal variation.

• Flow Duration Curve (FDC): Discharge ranked descending vs. percentage of time equalled or exceeded. Shows reliability of flow.

• Power Duration Curve (PDC): Corresponding power output (from FDC) vs. % time. Used for firm power estimate.

Pumped Storage Hydroelectricity (PSH):

• Layout: Two reservoirs (upper & lower) at different elevations. Reversible pump-turbine.

• Working: Off-peak (low demand): Use surplus grid power to pump water from lower to upper reservoir. Peak (high demand): Release water from upper to lower through turbine to generate power.

• Merits: Excellent peak-load response, energy storage, quick start.

• Demerits: High capital cost, 2 reservoirs needed, energy loss (~25%) in cycle.

Small-Scale Hydro (Micro/Mini): < 10 MW (micro < 100 kW). Run-of-river (no/ small dam). Low environmental impact, suitable for remote areas.

VI. GEOTHERMAL ENERGY

Resources & Potential in India:

• Types: Hydrothermal (hot water/steam), Geopressured (hot brine under pressure), Hot Dry Rock (HDR), Magma.

• Potential: Himalayas (tectonic), Aravallis, Godavari Basin, Cambay Basin, Son-Narmada-Tapi line. Low-to-medium enthalpy resources dominate. Limited commercial exploitation.

Geothermal Power Plant Types:

1. Dry Steam: Direct use of geothermal steam (>150°C) from reservoir to drive turbine. Simplest. (e.g., The Geysers, USA).

2. Flash Steam: High-pressure hot water (>180°C) from well flashes to steam in separator; steam drives turbine. Residual brine may be used in binary cycle.

3. Binary Cycle: Moderate temp (85-175°C) geothermal fluid heats a secondary working fluid (butane, pentane, R134a) with low boiling point in heat exchanger. Vapor drives turbine. No direct contact/emissions. Most common for new plants.

Binary Fluid Power Plant - Why No Flash?

• Geothermal fluid temperature/pressure is below saturation point for flashing. It remains liquid. Heat is transferred to secondary fluid via heat exchanger (ORC - Organic Rankine Cycle).

Hybrid Geothermal-Fossil Systems:

• Purpose: Boost output, improve economics, use lower temp resources.

• Types:

  • Fossil-fired (topping): Burn fossil fuel to superheat geothermal steam.

  • Geothermal bottoming: Use geothermal to heat boiler feedwater of fossil plant.

  • Mixed fluid: Combine geothermal & fossil fluids in same cycle.

Advantages & Limitations:

• Adv: Base-load, high capacity factor (>90%), small footprint, low emissions (binary), renewable.

• Lim: Site-specific (tectonic boundaries), high drilling/exploration cost, reservoir depletion risk, scaling/corrosion in pipes, moderate efficiency (~10-20%).

VII. OCEAN ENERGY

Tidal Energy:

• Principle: Harness kinetic energy of tidal currents or potential energy of tidal height difference.

• Site Selection: High tidal range (>4 m) or strong currents (tidal streams). Estuaries, narrow channels.

• Schematic Layout (Tidal Barrage): Similar to hydro dam across estuary. Gates → Basin → Turbines (bi-directional) → Tailrace. Generates during flood (inlet) and ebb (outlet) tides.

• Tidal Stream: Underwater turbines in high-current areas (no dam).

Ocean Thermal Energy Conversion (OTEC):

• Principle: Exploit temperature gradient between warm surface water (~25-30°C) and cold deep water (~5-10°C). ΔT > 20°C needed.

• Closed OTEC System (Diagram):

  • Working Fluid Loop: Low-boiling fluid (ammonia, Freon) in closed cycle.

  • Evaporator: Warm surface water heats/evaporates working fluid → vapor → turbine.

  • Condenser: Cold deep water condenses vapor back to liquid → pump → evaporator.

  • Power Output: Very low due to small ΔT → large turbines needed → high capital cost.

• Efficiency Challenge: Carnot efficiency η = 1 - T_cold/T_hot. With T_hot=300K, T_cold=280K, η_max ≈ 6.7%. Actual ~2-3%.

Wave Energy (Basic):

• Principles: Oscillating water column (air turbine), point absorber (heaving buoy), attenuator (flexible snake), overtopping device.

• Challenges: Harsh marine environment, variable waves, mooring/connection, low efficiency.

VIII. HYDROGEN AND FUEL CELLS

Hydrogen as Energy Carrier:

• Advantages: High energy per mass (120 MJ/kg, ~3x gasoline), clean combustion (H₂O), versatile (fuel, feedstock), can be produced from renewables.

• Disadvantages: Low energy per volume (liquid: 8 MJ/L, gas: low density), production cost (electrolysis), storage/transport challenges (embrittlement, leakage), safety (flammable, wide flammability range), infrastructure lacking.

Hydrogen Storage Methods:

Fuel Cells:

• Working Principle: Electrochemical device. Anode: H₂ → 2H⁺ + 2e⁻. Cathode: ½O₂ + 2H⁺ + 2e⁻ → H₂O. Electrolyte: Conducts ions (H⁺, OH⁻, O²⁻). No combustion, silent, high efficiency (40-60%, up to 85% with CHP).

• Classification by Electrolyte:

  • AFC (Alkaline): KOH electrolyte. High efficiency, used in space.

  • PEMFC (Polymer Electrolyte Membrane): Solid polymer (Nafion). Low temp (80°C), quick start, vehicles, portable.

  • SOFC (Solid Oxide): Ceramic (ZrO₂). High temp (600-1000°C), fuel flexible (can reform internally), stationary power.

  • MCFC (Molten Carbonate): Molten carbonate salts. High temp (650°C), fuel flexible, large stationary.

  • PAFC (Phosphoric Acid): Liquid H₃PO₄. Mature, commercial CHP.

IX. OTHER RENEWABLE & ADVANCED TECHNOLOGIES

Magneto-Hydro Dynamic (MHD) Generation:

• Principle: Faraday's Law of Electromagnetic Induction. Ionized hot gas (plasma) from combustion passed through magnetic field → induces EMF across electrodes → direct current.

• Working: Fuel (coal, gas) + oxidizer → combustor → seed (e.g., K₂CO₃) to ionize hot gases (~2000°C) → MHD channel (magnet + electrodes) → DC output → seed recovery → heat to steam cycle (bottoming).

• Advantages: High theoretical efficiency (~50-60% with combined cycle), no moving parts in channel, fast start.

• Challenges: Material science (high temp, corrosive plasma), seed recovery, high magnet cost, ionisation maintenance.

Cogeneration (Combined Heat and Power - CHP):

• Concept: Simultaneous generation of electricity and useful heat from same fuel source. Captures waste heat from power generation (e.g., turbine exhaust, engine jacket) for industrial processes, district heating.

• Applications: Industries (refineries, chemicals, paper), hospitals, campuses. Increases overall fuel efficiency to 70-90%.

Hybrid Renewable Energy Systems:

• Concept: Integration of two or more renewable sources (e.g., solar PV + wind + diesel + storage/battery) to overcome intermittency of single source.

• Need: Improve reliability, reduce storage size, optimize cost, meet load profile.

• Examples: Solar-wind-diesel-battery for remote villages; solar-biomass for base-load + peak.

X. CONVENTIONAL POWER GENERATION (FOR COMPARISON/CONTEXT)

Steam Power Plant (Thermal - Coal):

• Layout (Heat Line Diagram): Boiler (furnace, economizer, superheater, air preheater) → Turbine → Condenser → Feedwater pump → Feedwater heaters (open/closed) → Economizer → Boiler.

• Key Components:

  • Economizer: Preheats feedwater using flue gas → increases boiler efficiency.

  • Air Preheater (APH): Preheats combustion air using flue gas → improves combustion, reduces heat loss.

  • Feedwater Heater (FWH): Uses extracted steam from turbine to heat feedwater → reduces fuel needed in boiler, increases cycle efficiency.

  • Cooling Tower: Cools condenser cooling water via evaporation (wet) or air (dry). Reduces water consumption.

  • Condenser: Condenses exhaust steam from turbine to water (vacuum) → improves turbine efficiency, provides feedwater.

• Water Treatment: Necessity: Prevent scaling (Ca, Mg salts), corrosion (O₂, CO₂), fouling in boiler/turbine. Process: Clarification → Filtration → Softening (ion exchange) → Demineralization (mixed bed) → Oxygen removal (deaeration).

Gas Turbine Power Plant:

• Layout: Compressor (air) → Combustor (fuel + air) → Gas Turbine → (Optional) Heat Recovery Steam Generator (HRSG) → Steam Turbine (in combined cycle).

• Classification: Simple cycle, Combined Cycle (CCGT), Regenerative (recuperator).

• Efficiency Improvement: Combined cycle (gas + steam), Regeneration (preheat combustion air), Intercooling, Reheating.

Diesel Power Station:

• Fuel System: Storage tanks → filters → fuel pump → injectors.

• Exhaust System: Exhaust manifold → silencer → stack. Turbocharger often used to improve efficiency.

Nuclear Power Plant - CANDU Reactor:

• Diagram: Pressure tubes (fuel channels) in heavy water (D₂O) moderator tank. Fuel: Natural Uranium (no enrichment). On-power refueling.

• Advantages: Uses natural U, high neutron economy, online refueling, good safety record.

• Disadvantages: Heavy water expensive, large size, pressure tube design complexity, proliferation concerns (can produce Pu-239).

Nuclear Reactor Components:

1. Core: Fuel assemblies (UO₂ pellets in clad).

2. Moderator: Slows neutrons (Graphite, Heavy Water, Light Water).

3. Coolant: Removes heat (Water, Heavy Water, CO₂, Liquid Metal).

4. Control Rods: Absorb neutrons (Boron, Cadmium, Hafnium) for reactivity control.

5. Shielding: Concrete, lead, steel to absorb radiation.

6. Pressure Vessel: Contains core, coolant (PWR).

Nuclear Waste Management:

• Importance: Long-lived radioactivity (thousands of years), prevent environmental/health hazard.

• Methods:

  • Conditioning: Solidification (glass - vitrification, cement), encapsulation.

  • Storage: Interim (dry casks, pools).

  • Disposal: Deep geological repository (stable rock formation, multiple barriers). No permanent disposal facility operational yet globally.

Radioactive Pollution & Environmental Impact:

• Sources: Normal operation (traces), accidents (Chernobyl, Fukushima), waste leakage.

• Pathways: Air (gaseous releases), water (liquid effluent), food chain (bioaccumulation of I-131, Cs-137, Sr-90).

• Impact: Cancer, genetic mutations, land contamination. Requires strict monitoring and emergency planning.

Nuclear Fuel in India: Limited uranium reserves (Jaduguda, Tummalapalle). Thorium reserves abundant (world's largest). 3-stage program: PHWR (U-233) → Fast Breeder (Pu-239 + Th-232 → U-233) → Thorium-based reactors.

XI. ECONOMIC AND OPERATIONAL ANALYSIS

Cost Concepts:

• Fixed Costs (Capital/Investment Costs): Plant cost, land, buildings, equipment, interest during construction, depreciation. Independent of output.

• Operating Costs (Running/Variable Costs): Fuel, maintenance, labor, water, chemicals, waste disposal. Vary with output.

Load Characteristics & Factors:

• Load Curve: Graph of power demand (kW/MW) vs. time (hourly/daily/annually).

• Load Duration Curve (LDC): Loads ranked descending vs. percentage of time equalled or exceeded. Shows firm capacity needed.

• Flow Duration Curve (FDC): (See Hydro section).

• Definitions:

  • Maximum Demand (MD): Peak load during period.

  • Load Factor (LF): LF = (Average Demand) / (Maximum Demand) = (Energy / (MD * T)). Always < 1 because average < peak.

  • Demand Factor (DF): DF = (Maximum Demand) / (Connected Load). Always < 1 because not all connected load operates at max simultaneously.

  • Capacity Factor (CF): CF = (Actual Energy Output) / (Rated Capacity * Time). Always < 1 due to outages, maintenance, load following.

  • Utilization Factor (UF): UF = (MD) / (Rated Capacity). Can be >1 if overload possible, but usually ≤1.

• Why LF & DF < 1? Load is variable; peak is short duration; not all appliances run at once.

Economic Load Dispatch (Economic Scheduling):

• Objective: Minimize total fuel cost C_total = Σ C_i(P_i) while meeting load Σ P_i = P_D + P_L (including losses).

• Incremental Cost Theory: λ = dC_i/dP_i (Rs/MWh). Equal Incremental Cost Criterion: For optimum dispatch without losses, dC_1/dP_1 = dC_2/dP_2 = ... = λ.

• With Transmission Losses: λ = dC_i/dP_i * (1 + ∂P_L/∂P_i). (1 + ∂P_L/∂P_i) is Penalty Factor (α_i) for plant i.

• Numerical Approach (2 plants, no losses):

  • Given C₁ = a₁ + b₁P₁ + c₁P₁², C₂ = a₂ + b₂P₂ + c₂P₂².

  • dC₁/dP₁ = b₁ + 2c₁P₁ = λ

  • dC₂/dP₂ = b₂ + 2c₂P₂ = λ

  • Set equal: b₁ + 2c₁P₁ = b₂ + 2c₂P₂

  • Solve with P₁ + P₂ = P_D.

• With Losses (Penalty Factor): P_i(1 + ∂P_L/∂P_i) is effective power from plant i. Use equal incremental cost on effective power.

Tariffs and Pricing:

• Flat Rate: Fixed charge per kW of MD or per unit. Simple, not cost-reflective.

• Block Rate: Different rates for different consumption blocks (slab). Encourages conservation in higher blocks.

• Two-Part Tariff: Fixed charge (per kW MD) + Energy charge (per kWh). Most common for industrial/commercial. Recovers fixed & variable costs.

• Power Factor Tariff: Incentive/penalty based on PF (kWh vs. kVAh). Encourages reactive power management.

• Peak Load Pricing: Higher charges during system peak hours to reflect higher cost of peaking plants and incentivize load shifting.

Load Forecasting:

• Importance: Unit commitment, economic dispatch, maintenance scheduling, infrastructure planning.

• Methods:

  • Short-term (hourly/daily): Time series (ARIMA), regression (weather, calendar), machine learning.

  • Medium-term (weekly/monthly): Similar, with seasonal factors.

  • Long-term (yearly/decadal): Econometric models, trend analysis, end-use models.

XII. SITE SELECTION & ENVIRONMENTAL IMPACT

Site Selection Criteria Summary:

• Hydro: Hydrology, topography, geology, reservoir.

• Thermal: Fuel transport (coal: rail/port), water source (cooling), land, ash disposal, proximity to load.

• Nuclear: Water source, geology (seismic), low population density, security, fuel availability.

• Wind: Wind resource, grid access, land use, environmental (birds, noise).

• Tidal: High tidal range/current, estuary geometry, navigation, ecology.

• Geothermal: High subsurface temperature, reservoir permeability, water source.

Environmental & Safety Aspects:

• Nuclear: Radioactive waste (high-level, long-lived), thermal pollution, decommissioning, accident risk (meltdown). Shielding: Concrete, lead, water.

• Wind: Noise (aerodynamic, mechanical), visual impact, shadow flicker, bird/bat mortality (siting, radar).

• Biomass: Air pollution (PM, NOx, VOCs) if combustion inefficient; ash disposal; land-use change.

• General: EIA (Environmental Impact Assessment) mandatory for large projects.

XIII. REGIONAL & POLICY FOCUS: INDIA

Policies & Targets:

• National Solar Mission: Target 100 GW solar by 2022 (achieved), now part of 500 GW non-fossil by 2030. Includes rooftop, solar parks.

• Wind Energy: Wind-solar hybrid policy, repowering old turbines.

• Biomass: Co-generation policy (bagasse), agro-residue based power.

• Small Hydro: State nodal agencies, subsidy for remote areas.

• Green Energy Corridors: Strengthen grid for renewable integration.

Tamil Nadu Renewable Profile:

• Wind: #1 in India. Muppandal (Kanyakumari), Tirunelveli, Coimbatore, Pollachi. ~9 GW+.

• Solar: High potential (Tamil Nadu Solar Policy 2019). Large solar parks (Bhadla-scale in TN too).

• Biomass: Sugarcane co-generation (major), agricultural waste (cotton stalk, rice husk).

• Small Hydro: Western Ghats streams.

• Challenges: Grid stability with high wind penetration, land acquisition, evacuation infrastructure.

Challenges & Opportunities:

• Challenges: Grid integration (variability), financing (high upfront cost), technology absorption, storage cost, land acquisition, Discom financial health.

• Opportunities: Manufacturing (solar cells, wind towers), rural electrification (decentralized solar/biogas), green hydrogen production, export potential, job creation.

[!TIP] Exam Focus: Be ready to write a short paragraph on Tamil Nadu's renewable status (wind leader, solar potential, biomass from sugar) and India's national targets/policies. Link challenges to solutions (e.g., grid issues → hybrid systems, storage).