Electrical Power Generation & Economy (EX-503 (A)) - Unit 5 Short Notes

UNIT 5: ELECTRICAL POWER GENERATION & ECONOMY

1.0 INTRODUCTION & OVERVIEW OF POWER GENERATION SOURCES

1.1 Classification of Energy Sources

• Conventional (Non-Renewable): Finite reserves, high pollution, established tech.

  • Examples: Coal, Oil, Natural Gas, Nuclear (Uranium/Plutonium).

• Non-Conventional (Renewable): Inexhaustible, clean, site-specific, often intermittent.

  • Examples: Solar, Wind, Hydro (run-of-river), Biomass, Geothermal, Tidal, OTEC.

1.2 Comparative Study of Major Sources

1.2.1 Merits and Demerits (Summary Table)

1.2.2 Global and Indian Energy Scenario

• Global: Shift towards renewables due to climate change (Paris Agreement). Solar & Wind leading new capacity additions. Energy transition ongoing.

• India:

  • Conventional: Coal dominant (~70%), Hydro ~12%, Nuclear ~2%.

  • Renewables: Rapid growth in Solar & Wind. Target: 500 GW non-fossil capacity by 2030 (Nationally Determined Contributions - NDCs).

  • Initiatives: National Solar Mission, Wind Power Programme, International Solar Alliance (ISA).

1.2.3 Future Energy Strategies and Prospects

• Hybrid Systems: Combine renewables (solar+wind) with storage (batteries) or conventional backup for reliability.

• Green Hydrogen: Using renewable electricity for electrolysis to produce clean fuel for industry, transport.

• Grid Modernization: Smart grids, demand response, AI/ML for forecasting and integration of variable renewables.

• Energy Storage: Pumped hydro, batteries, thermal storage for managing intermittency.

• Carbon Capture, Utilization, and Storage (CCUS): For existing fossil fuel plants.

[!TIP] Exam Focus: Always compare at least 3 sources (e.g., Thermal vs. Hydro vs. Solar) in terms of capital cost, operating cost, environmental impact, and reliability for 7-mark questions.

2.0 CONVENTIONAL POWER GENERATION TECHNOLOGIES

2.1 Hydroelectric Power Plants

2.1.1 Site Selection Criteria

1. Water Availability: High, consistent rainfall/snowmelt; large catchment area.

2. Topography: Narrow valley with steep slopes for dam construction; rocky foundation.

3. Geology: Strong, impermeable rock for dam foundation and tunnel lining.

4. Head: High hydraulic head (difference in water levels) is desirable for high power output.

5. Proximity to Load Center: Reduces transmission cost and losses.

6. Accessibility: For construction and maintenance.

7. Environmental & Social Impact: Minimal displacement, submergence of forest/arable land.

2.1.2 Typical Layout and Components

[Diagram Concept: River -> Dam/Reservoir -> Intake -> Penstock -> Surge Tank -> Turbine (in Powerhouse) -> Generator -> Tailrace -> River]

• Dam/Reservoir: Stores water, creates head, regulates flow.

• Intake Structure: Controls water entry into penstock, screens debris.

• Penstocks: Large pipes conveying water under pressure to turbine.

• Surge Tank: Function: Protects penstocks from water hammer (pressure surge) during load changes by providing a buffer. Open to atmosphere or closed (choked).

• Powerhouse: Houses turbine, generator, control equipment.

• Tailrace: Channel returns used water to river.

2.1.3 Hydraulic Turbines

2.1.4 Hydrographs, Flow Duration Curves, Power Duration Curves

• Hydrograph: Graph of discharge (flow rate) vs. time (daily, monthly, yearly). Shows river flow variability.

• Flow Duration Curve (FDC): Discharge sorted in descending order vs. % of time it is exceeded. Use: Determines dependable flow (e.g., flow available 90% of time). Shape indicates flow variability.

• Power Duration Curve (PDC): Power output sorted in descending order vs. % of time it is exceeded. Derived from FDC using $$\displaystyle P = \rho g Q H \eta $$. Use: Assess firm power, energy production potential.

2.1.5 Pumped Storage Plants (PSP)

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

• Operation:

  • Peak Load (Generation): Water from upper reservoir flows down through turbine to lower reservoir, generating power.

  • Off-Peak (Pumping): Excess grid power drives motor-pump to lift water from lower to upper reservoir.

• Merits: Excellent for peak load, load balancing, frequency control, energy storage.

• Demerits: High civil cost, energy loss in pumping cycle (~25-30%), site-specific, environmental impact.

2.2 Thermal Power Plants (Steam Power)

2.2.1 Site Selection Factors

1. Fuel Availability: Near coal mines (to reduce transport cost) or port for imported coal.

2. Water Source: Proximity to river/lake for cooling and boiler feed (large quantity needed).

3. Land: Available, cheap, and suitable for ash disposal.

4. Load Center: Near major demand centers to minimize transmission losses/cost.

5. Transport Facilities: Good rail/road/port for fuel and equipment.

6. Environmental Regulations: Away from populated areas, national parks.

7. Seismic Stability: Low earthquake risk zone.

2.2.2 Typical Layout and Main Features

[Diagram Concept: Coal Handling -> Crusher -> Pulverizer -> Boiler (Furnace, Water Walls, Superheater) -> Turbine -> Generator -> Condenser (Cooling Tower) -> Feedwater Pump -> Economiser/APH -> Boiler. Ash handling from boiler bottom.]

• Coal Handling System: Unloading, storage, crushing, pulverizing (to fine powder for efficient combustion).

• Boiler Furnace & Steam Generating System: Burns coal to produce high-pressure, high-temperature steam. Includes economiser, superheater, reheater, air preheater.

• Steam Turbine: Converts thermal energy of steam to mechanical rotation. Stages: High-Pressure (HP), Intermediate-Pressure (IP), Low-Pressure (LP).

• Condenser & Cooling Towers:

  • Condenser: Function: Converts exhaust steam from turbine to water (condensate) by cooling, creating vacuum to improve turbine efficiency.

  • Cooling Tower: Function: Cools the condenser cooling water (from once-through or recirculating system) via evaporation and air draft. Types: Natural draft (hyperbolic), Mechanical draft.

• Economiser: Function: Preheats boiler feedwater using flue gas heat before it enters the boiler. Increases boiler efficiency by recovering waste heat.

• Air Preheater (APH): Function: Preheats combustion air using flue gas heat after economiser. Improves combustion efficiency.

• Feed Water Heater (FWH): Function: Open or closed heater that uses extracted steam from turbine stages to preheat feedwater before it enters the boiler. Reduces fuel needed for steam generation, improves cycle efficiency.

• Ash Handling System: Collects bottom ash (from furnace) and fly ash (from flue gas via ESP/cyclone). Disposed in ash ponds or used in cement.

2.2.3 Water Treatment Plant in Thermal Power

• Necessity: Raw water contains dissolved salts (Ca, Mg, Na), silica, gases (O2, CO2). Causes scaling (insulation on boiler tubes), corrosion, carryover (steam impurities), and deposition in turbines. Reduces efficiency, causes tube failure, damages turbines.

• Process: Multi-stage: Clarification, Filtration, Ion Exchange (de-mineralization), sometimes Reverse Osmosis (RO). Aim: Produce ultra-pure demineralized water for boiler feed.

2.2.4 Methods to Improve Thermal Efficiency

1. Increase Steam Parameters: Higher pressure & temperature (supercritical, ultra-supercritical plants).

2. Reheat: Steam expanded in HP turbine is sent back to boiler for reheating, then expanded in IP/LP turbines. Reduces moisture content at final stages, improves efficiency.

3. Regeneration (Feedwater Heating): As above, using turbine extraction steam.

4. Reduce Auxiliary Power Consumption: Efficient pumps, fans, motors.

5. Reduce Condenser Pressure: Better cooling, larger condenser.

6. Use of Fluidized Bed Combustion (FBC): Allows burning of low-grade fuels, in-bed desulfurization.

2.3 Nuclear Power Plants

2.3.1 Basic Principle

• Nuclear Fission: Heavy nucleus (U-235, Pu-239) splits into lighter nuclei on neutron bombardment, releasing large energy and 2-3 neutrons. Chain reaction sustained.

• Nuclear Fusion: Light nuclei (H, He) combine to form heavier nucleus, releasing energy (Sun). Not yet commercially viable for power (requires extreme T&P).

2.3.2 Components of a Nuclear Reactor (Pressurized Water Reactor - PWR type)

[Diagram Concept: Fuel Rods (UO2) in Fuel Assemblies -> Reactor Core (inside Pressure Vessel) -> Control Rods (B4C, Cd) inserted/withdrawn -> Coolant (Water under high pressure) circulates -> Steam Generator (produces steam for turbine) -> Containment Vessel (thick concrete/steel) -> Shielding (Lead, Concrete) around reactor.]

• Fuel: Enriched Uranium (U-235 ~3-5%) or Plutonium. Form: Pellet in zirconium alloy cladding.

• Moderator: Function: Slows down fast neutrons to thermal energies to increase probability of fission in U-235. Materials: Light water (H2O), Heavy water (D2O), Graphite.

• Control Rods: Function: Absorb neutrons to control/stop chain reaction. Made of neutron-absorbing materials (Boron, Cadmium, Hafnium). Inserted/withdrawn to regulate power.

• Coolant: Function: Removes heat from core and transfers it to steam generator (PWR) or directly to turbine (BWR). Materials: Water (PWR, BWR), Heavy water (CANDU), Gas (CO2, He), Liquid metal (Na, NaK).

• Shielding: Function: Protect personnel and environment from ionizing radiation (gamma, neutrons). Materials: Thick layers of concrete, lead, steel.

• Pressure Vessel: Thick steel container housing core, moderator, coolant. Contains high-pressure coolant.

2.3.3 Types of Reactors: CANDU Reactor

• Full Form: CANada Deuterium Uranium.

• Layout & Working:

  • Uses Natural Uranium (0.7% U-235) as fuel (no enrichment needed).

  • Uses Heavy Water (D2O) as both moderator and coolant.

  • Pressure Tubes: Fuel channels (pressure tubes) run through a low-pressure moderator tank (calandria). Allows on-power refueling.

  • Coolant (heavy water) under high pressure flows through pressure tubes, picks up heat, goes to steam generator.

• Advantages: Uses natural uranium (fuel cost low), high neutron economy (can breed plutonium), on-power refueling (high capacity factor), proven technology.

• Disadvantages: Heavy water expensive, large size, proliferation risk (plutonium production), heavy water leakage/contamination risk.

2.3.4 Nuclear Waste Management

• Importance: Radioactive waste remains hazardous for thousands of years. Improper disposal contaminates environment (air, water, soil) and causes health hazards (cancer, genetic mutations).

• Disposal Methods:

  1. Near-Surface Disposal: For low-level waste (LLW) & some intermediate-level waste (ILW). Concrete/steel containers in engineered vaults.

  2. Geological Disposal (Deep Repository): For high-level waste (HLW) & long-lived ILW. Multiple barriers: waste form (glass), container (steel), engineered barrier (clay/bentonite), geological formation (stable rock, salt dome, clay). Most accepted long-term solution.

  3. Reprocessing: Chemically separate usable plutonium and uranium from spent fuel. Reduces volume/radiotoxicity of HLW but is expensive, proliferation-sensitive.

2.3.5 Radioactive Pollution & Environmental Aspects

• Sources: Normal operation (controlled releases), Accidents (Chernobyl, Fukushima), Waste disposal leaks.

• Pathways: Air (gaseous releases), Water (liquid discharges), Food chain (bioaccumulation of isotopes like I-131, Cs-137, Sr-90).

• Impacts: Increased cancer risk, thyroid disorders, genetic damage, land contamination for long periods.

• Mitigation: Robust containment, strict emission limits, monitoring, emergency planning, safe waste disposal.

2.3.6 Availability of Nuclear Fuel in India

• Uranium: Limited reserves (Jaduguda, Singhbhum, Tummalapalle, Lambapur). Import-dependent. Thorian reserves (monazite sands, Kerala, Odisha) are abundant. India pursuing Th-U fuel cycle (AHWR design) for long-term energy security.

• Plutonium: Produced in reactors (PHWRs) via breeding. Used in Fast Breeder Reactors (FBRs) and possibly in AHWRs.

• Strategy: Three-stage programme: (1) PHWRs (natural U, heavy water), (2) FBRs (Pu, U-238), (3) Thorium-based reactors (Th, U-233).

2.4 Other Conventional Plants

2.4.1 Diesel Power Plants

• Fuel System: Storage tank -> Filters -> Fuel pump -> Injector -> Engine cylinders.

• Exhaust System: Engine exhaust -> Silencer (muffler) -> Chimney. May have turbocharger (uses exhaust gas to drive compressor for more air intake, increasing power).

2.4.2 Gas Turbine Power Plants

• Principle: Brayton Cycle (Constant Pressure Heat Addition). Air compressed -> mixed with fuel & combusted -> hot gases expand through turbine (producing power) -> exhaust.

• Classification:

  • Simple Cycle: Compressor, Combustor, Turbine.

  • Regenerative Cycle: Uses heat exchanger (regenerator) to preheat compressed air using exhaust heat.

  • Intercooled: Cooling between multi-stage compression reduces work input.

  • Reheated: Steam from boiler used to reheat gas between turbine stages (like steam turbine).

• Layout of Simple Gas Turbine Plant:

  
  [Air Intake -> Compressor -> Combustor (Fuel injection) -> Turbine -> Exhaust]
  
  [Generator coupled to turbine shaft]
  
  [Optional: Heat Recovery Steam Generator (HRSG) for combined cycle]
  
  

• Methods to Improve Thermal Efficiency:

  1. Regeneration: Recovers exhaust heat.

  2. Intercooling: Reduces compressor work.

  3. Reheating: Increases turbine work output.

  4. Combined Cycle (CCGT): Gas turbine exhaust heat used in HRSG to generate steam for a steam turbine. Most efficient (~60%).

3.0 NON-CONVENTIONAL / RENEWABLE POWER GENERATION

3.1 Solar Energy

3.1.1 Solar Radiation: Earth-Sun Angles

• Declination (δ): Angle between sun's rays and equatorial plane. Varies ±23.45° annually.

• Latitude (φ): Angular position North/South of equator.

• Solar Altitude (α): Angle of sun's rays above horizontal. $$\displaystyle \sin \alpha = \sin \phi \sin \delta + \cos \phi \cos \delta \cos h $$, where $h$ = hour angle.

• Solar Azimuth (γ_s): Angle of sun's rays projected on horizontal plane, measured from South (N. Hemisphere). $$\displaystyle \cos \gamma_s = \frac{\sin \phi \cos \delta - \cos \phi \sin \delta \cos h}{\cos \alpha} $$.

• Insolation: Total solar radiation energy received on a surface over time (kWh/m²/day).

3.1.2 Solar Thermal Power Generation

• Principle: Concentrate solar radiation to produce high-temperature heat → generate steam → drive steam turbine → generator.

• Types of Collectors:

  • Flat Plate: Absorber plate with transparent cover. Low temp (<100°C). For water heating.

  • Concentrating: Use mirrors/lenses to concentrate sunlight.

    • Parabolic Trough: Linear focus, heats fluid in tube along focus. Common (e.g., SEGS).

    • Parabolic Dish: Point focus, heats receiver at dish focus. High temp, Stirling engine.

    • Solar Power Tower (Central Receiver): Field of heliostats reflect to central receiver on tower. Highest temp.

• Schematic Layout (Solar Thermal):

  
  [Solar Field (Mirrors/Collectors) -> Heat Transfer Fluid (HTF) Pump -> Receiver (Tower) or Tube (Trough) -> Steam Generator (Boiler) -> Steam Turbine -> Generator -> Condenser -> Cooling Tower -> HTF Pump]
  
  [Optional: Thermal Storage (Molten Salt) for dispatchability]
  
  

3.1.3 Solar Photovoltaic (PV) Systems

• Principle: Photovoltaic Effect. Photons of light strike semiconductor (Si) junction, excite electrons, create electron-hole pairs. Built-in electric field (p-n junction) separates charges, generating DC voltage/current.

• Key Elements of a PV Cell/System:

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

  • Module (Panel): Series/parallel connected cells encapsulated.

  • Array: Multiple modules.

  • Balance of System (BOS): Inverter (DC-AC), mounting structure, cables, charge controller, batteries (if off-grid), MPPT (Maximum Power Point Tracker).

• I-V Characteristics:

  • Short Circuit Current (I_sc): Current when V=0 (max current, proportional to irradiance).

  • Open Circuit Voltage (V_oc): Voltage when I=0 (max voltage, logarithmically dependent on irradiance).

  • Maximum Power Point (MPP): Point on curve where $$\displaystyle P = V \times I $$ is maximum. $$\displaystyle (V_m, I_m) $$.

  • Fill Factor (FF): Measure of "squareness" of curve. $$\displaystyle \boxed{FF = \frac{V_m I_m}{V_{oc} I_{sc}}} $$ (Typical 0.7-0.8).

  • Efficiency (η): $$\displaystyle \boxed{\eta = \frac{P_{max}}{P_{in}} = \frac{V_m I_m}{G \cdot A}} $$, where $G$ = irradiance (W/m²), $A$ = cell area.

• Factors Affecting PV Performance:

  1. Irradiance (G): Directly proportional to $$\displaystyle I_{sc} $$ and $$\displaystyle P_{max} $$.

  2. Temperature: ↑ Temperature → ↓ $$\displaystyle V_{oc} $$ → ↓ Efficiency (Si: ~ -0.4%/°C).

  3. Spectrum: Cell response varies with wavelength.

  4. Soiling/Dust: Reduces irradiance reaching cell.

  5. Shading: Can drastically reduce output (bypass diodes mitigate).

  6. Angle of Incidence: Optimal when sun's rays perpendicular to panel.

3.2 Wind Energy

3.2.1 Principle of Wind Power Generation: Betz Limit

• Power in Wind: $$\displaystyle \boxed{P_{wind} = \frac{1}{2} \rho A v^3} $$, where $\rho$ = air density (kg/m³), $A$ = swept area (m²), $v$ = wind speed (m/s). Power ∝ v³ (critical!).

• Betz Limit: Maximum theoretical fraction of wind power that can be extracted by an ideal wind turbine is 16/27 ≈ 59.3%. Real turbines achieve 35-45% (aerodynamic + mechanical losses).

• Actual Power Output: $$\displaystyle P_{turbine} = \frac{1}{2} \rho A v^3 C_p \eta_g \eta_m $$, where $$\displaystyle C_p $$ = power coefficient (≤ Betz), $$\displaystyle \eta_g $$ = generator eff., $$\displaystyle \eta_m $$ = mechanical eff.

3.2.2 Wind Energy Conversion Systems (WECS)

• Classification of Wind Turbines:

  • Horizontal Axis Wind Turbine (HAWT): Rotor shaft parallel to ground/wind. Blades upwind/downwind of tower. Most common (utility-scale). Needs yaw mechanism.

  • Vertical Axis Wind Turbine (VAWT): Rotor shaft perpendicular to ground. Omni-directional (no yaw). Types: Darrieus (lift-based), Savonius (drag-based). Lower efficiency, used for small/urban.

• Components of Horizontal Shaft Windmill:

  
  [Diagram: Tower -> Nacelle (housing) -> Rotor Hub (Blades) -> Main Shaft -> Gearbox (optional) -> Generator -> Yaw Mechanism -> Brakes -> Anemometer & Wind Vane]
  
  

  • Blades/Rotor: Capture wind energy (aerofoil shape).

  • Nacelle: Houses drivetrain (gearbox, generator), yaw system.

  • Tower: Supports rotor/nacelle at sufficient height.

  • Yaw System: Rotates nacelle to face wind (for HAWT).

  • Gearbox: Increases rotor speed (low) to generator speed (high). Direct-drive turbines eliminate gearbox.

  • Generator: Produces electricity (usually asynchronous/induction or synchronous).

• Wind Turbine Generators (WTG): Complete system including turbine, generator, control systems, and grid interface.

3.2.3 Wind Characteristics: Speed Distribution, Weibull Parameters

• Wind speed varies randomly. Probability distribution described by Weibull Distribution:

  $$\displaystyle f(v) = \frac{k}{c} \left( \frac{v}{c} \right)^{k-1} e^{-(v/c)^k} $$

  • $k$ = shape parameter (dimensionless, 1-2 typical, indicates spread).

  • $c$ = scale parameter (m/s, related to mean wind speed).

• Use: Estimate annual energy production, choose turbine cut-in/cut-out speeds.

3.2.4 Site Selection for Wind Power Plants

1. High & Consistent Wind Speed: Mean > 6-7 m/s at hub height; low turbulence.

2. Wind Rose Analysis: Prevailing wind direction, seasonal variations.

3. Topography: Hilltops, coastal areas, mountain passes (wind acceleration).

4. Accessibility: For transport/construction.

5. Grid Proximity: Near transmission lines to reduce evacuation cost.

6. Environmental & Social: Avoid bird migration routes, residential areas (noise), protected zones.

7. Land Availability: Suitable terrain, minimal obstacles.

3.2.5 Performance, Limitations & Environmental Aspects

• Performance Metrics: Capacity Factor (often 20-40%), Availability, Power Curve.

• Limitations: Intermittency, low capacity factor, visual/noise impact, need for backup/storage, grid integration challenges (voltage/frequency fluctuations).

• Environmental: Bird/bat mortality, shadow flicker, low-frequency noise, land use (minimal footprint under turbine).

3.2.6 Control Schemes for Generation & Transmission

• Pitch Control: Adjust blade angle to regulate power at high winds (above rated).

• Stall Control: Fixed-pitch blades; aerodynamic stall limits power naturally.

• Yaw Control: Align nacelle with wind direction.

• Voltage/Reactive Power Control: Using power electronics (converter) to meet grid codes (e.g., maintain power factor, low voltage ride-through).

• Power Curtailment: Deliberately reducing output during grid congestion.

3.3 Biomass Energy

3.3.1 Biomass Resources and Energy Conversion Routes

• Resources: Agricultural residues (straw, bagasse), forest residues, energy crops (sugarcane, jatropha), animal dung, municipal solid waste (MSW), industrial waste.

• Conversion Routes:

  • Thermochemical: Combustion (direct heat/power), Gasification (producer gas), Pyrolysis (bio-oil, char, gas).

  • Biochemical: Anaerobic digestion (biogas), Fermentation (bioethanol).

  • Chemical: Transesterification (biodiesel).

3.3.2 Biogas Generation: Principle with Diagram

• Principle: Anaerobic Digestion (4 Stages): 1) Hydrolysis (complex organics → simple sugars), 2) Acidogenesis (sugars → acids, alcohols), 3) Acetogenesis (acids → acetic acid, H2, CO2), 4) Methanogenesis (acetic acid, H2+CO2 → CH4 + CO2). Methanogens (archaea) in oxygen-free digester.

• Typical Biogas Plant (Deen Bandhu - Floating Drum):

  
  [Diagram: Inlet (for slurry) -> Digester Tank (underground, anaerobic) -> Gas Holder (floating drum, moves with gas pressure) -> Outlet (for spent slurry) -> Gas outlet pipe to stove/engine.]
  
  

• Types of Biogas Plants:

  • Deen Bandhu (Floating Drum): Movable steel drum on slurry. Common, low cost, but drum maintenance.

  • Pragati Design (Fixed Dome): Brick/cement masonry, fixed gas holder (gas pressure varies). More durable, lower maintenance.

• Community Biogas Plants:

  • Working: Larger scale, feedstock from multiple households/community (cattle dung, kitchen waste). Centralized collection, digestion, gas distribution.

  • Problems: Feedstock collection logistics, coordination among users, slurry disposal, high initial cost, maintenance issues, social conflicts.

• Materials for Biogas Generation: Cattle dung (most common), poultry litter, pig dung, human excreta (night soil), agricultural residues (pre-treated), food waste, municipal organic waste, aquatic weeds (water hyacinth).

3.3.3 Biomass Applications

• Direct Combustion: Burn biomass in boiler for steam/heat (e.g., bagasse in sugar mills).

• Gasification: Partial combustion at high T with limited air → producer gas (CO, H2, CH4). Used in engines/gas turbines.

• Pyrolysis: Thermal decomposition in absence of air → bio-oil (liquid), biochar (solid), syngas. Small-scale units for bio-oil production.

3.3.4 Advantages of Biomass Energy

• Renewable, carbon neutral (closed carbon cycle).

• Utilizes waste materials (MSW, agricultural residue), solving disposal problems.

• Provides decentralized energy (rural areas).

• Creates rural employment (collection, processing).

• Slurry is good organic fertilizer.

3.3.5 Environmental Problems from Agricultural/Organic Waste

• Open burning → air pollution (PM, CO, VOCs).

• Piling → methane emissions (GHG), odor, groundwater contamination (leachate).

• Attracts pests, flies, rodents → health hazards.

• Nutrient loss if not recycled as fertilizer.

• Solution: Proper collection and utilization via biogas/composting.

3.4 Geothermal Energy

3.4.1 Principle and Sources

• Principle: Harness heat from Earth's interior. Magma heats underground water/steam.

• Sources:

  • Hot Water Reservoirs: Natural aquifers with hot water (>150°C).

  • Dry Steam: Natural steam vents (rare, e.g., Larderello, Italy).

  • Hot Dry Rock (HDR): Hot impermeable rock. Requires artificial fracturing (EGS - Enhanced Geothermal Systems) and water injection.

3.4.2 Types of Geothermal Power Plants

• Dry Steam: Direct use of natural steam to drive turbine. Simplest, oldest type.

• Flash Steam: High-pressure hot water from well flashes to steam when brought to lower pressure surface. Steam drives turbine. Most common.

• Binary Cycle: Geothermal hot water heats a secondary working fluid (low boiling point: isobutane, pentane) in heat exchanger. Vapor of secondary fluid drives turbine. Can use lower temperature resources (85°C+). No direct contact, minimal emissions.

3.4.3 Potential for Geothermal Energy in India

• Moderate potential (not high like Iceland/Philippines).

• Geothermal Provinces: Himalayas (tectonic), Western India (Aravalli, Cambay, Son-Narmada), Andaman-Nicobar, Gujarat, Rajasthan, Tamil Nadu.

• Resources: Mostly low-to-medium enthalpy (<150°C). Potential for direct use (space heating, greenhouse, aquaculture) and binary cycle power. Puga Valley (Ladakh) has high potential (~150-250°C). Exploration and pilot projects ongoing (e.g., Manikaran, HP).

3.4.4 Hybrid Geothermal-Fossil Systems

• Concept: Combine geothermal heat with fossil fuel (coal, gas) boiler to increase steam temperature/pressure or supplement flow.

• Types:

  • Geothermal Preheating: Geothermal fluid preheats boiler feedwater.

  • Geothermal Supplementary Firing: Geothermal steam mixed with fossil-fired steam.

  • Bottoming Cycle: Fossil fuel generates electricity, waste heat used for geothermal binary cycle.

• Purpose: Improve efficiency, reduce fossil fuel consumption, make marginal geothermal resources viable.

3.4.5 Advantages

• Base load, reliable, high capacity factor (>90%).

• Small land footprint.

• Low emissions (mostly water vapor, traces of H2S, CO2).

• Efficient (binary cycle ~10-13%, flash ~15-20%).

3.5 Ocean Energy

3.5.1 Tidal Energy

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

• Schematic Layout of Tidal Power House:

  
  [Diagram: Basin enclosed by dam -> Sluice gates (open at high tide to fill basin) -> Turbines in dam (water flows out at low tide through turbines, generating power) -> Sea.]
  
  

  • One-way (Ebb-generation): Generate only on outgoing tide.

  • Two-way (Double generation): Turbines allow generation on both flood and ebb (special turbines).

  • Tidal Stream (Barrage-less): Underwater turbines in high-velocity tidal currents (like underwater windmills).

• Site Selection for Tidal Power Plants:

  1. High Tidal Range: > 4-5 meters (for barrage). Minimum 2m for economic viability.

  2. Large Basin Area: Behind barrage for sufficient storage.

  3. Favorable Topography: Narrow inlet to reduce dam length.

  4. High Current Velocity: For tidal stream systems (>2-3 m/s).

  5. Accessibility & Grid Connection.

  6. Minimal Environmental Impact on estuary/mangroves.

3.5.2 Ocean Thermal Energy Conversion (OTEC)

• Principle: Utilize temperature difference ($\Delta T$) between warm surface seawater (25-30°C) and cold deep seawater (5-10°C). $\Delta T$ ≥ 20°C required for viable power.

• Open Cycle (Flash Evaporation): Warm seawater enters vacuum chamber, flashes to steam (low pressure) → drives turbine → condenses (using cold seawater) → produces fresh water as by-product.

• Closed Cycle (Most Common):

  • Working Fluid: Low-boiling point (e.g., ammonia, R-134a).

  • Process: Warm seawater evaporates working fluid in evaporator → vapor drives turbine → cold seawater condenses vapor in condenser → liquid working fluid pumped back.

  
  [Diagram: Warm Surface Seawater Pump -> Evaporator (working fluid vaporizes) -> Turbine -> Generator -> Condenser (cold deep seawater cools vapor) -> Liquid Working Fluid Pump -> Evaporator.]
  
  

• Advantages of OTEC: Base load potential (if $\Delta T$ stable), produces desalinated water, aquaculture possible.

3.6 Other Renewable Sources & Concepts

3.6.1 Magneto-Hydro Dynamic (MHD) Generation

• Principle: Direct energy conversion. Ionized hot combustion gases (plasma) passed through a magnetic field. According to Faraday's Law, moving charges in magnetic field experience force → directly generates DC electricity (no moving turbine).

• Working: Seed material (e.g., potassium carbonate) added to combustion gases to increase electrical conductivity. Hot plasma flows through channel with electrodes & magnetic field.

• Advantages: Higher theoretical efficiency (no Carnot limit of turbine), no moving parts (reduced maintenance), can use coal directly.

• Status: Experimental, high temperature materials challenge, seed recovery problem. Not commercial yet.

3.6.2 Fuel Cells

• Principle: Electrochemical device converts chemical energy of fuel (H2, CH4, methanol) and oxidant (O2 from air) directly into electricity and heat. Reversible electrolysis.

• Classification (by Electrolyte):

  1. PEMFC (Polymer Electrolyte Membrane): Low T (80°C), quick start, for transport/backup.

  2. SOFC (Solid Oxide): High T (600-1000°C), high efficiency, fuel flexible, for stationary power.

  3. MCFC (Molten Carbonate): High T (650°C), fuel flexible, for utility.

  4. AFC (Alkaline): Used in space (NASA).

  5. PAFC (Phosphoric Acid): Commercialized for CHP.

• Functions: Anode (oxidation: fuel → ions + e⁻), Cathode (reduction: ions + e⁻ + oxidant → product), Electrolyte (ion conductor, e⁻ insulator).

3.6.3 Hydrogen Energy

• Advantages: Clean burning (water only), high energy density (by mass), versatile (can be stored/transported), can be produced from renewables.

• Disadvantages: Low energy density (by volume at ambient), storage & transport challenges (high pressure, liquefaction, hydrides), production cost (electrolysis), safety (flammable, explosive), infrastructure lacking.

• Storage Methods:

  1. Compressed Gas (CHG): High pressure (350-700 bar). Common for vehicles.

  2. Liquid Hydrogen (LH2): Cryogenic (-253°C). High density, but high boil-off loss.

  3. Solid State (Metal Hydrides, Chemical Hydrides): Safe, high volumetric density, but heavy/slow kinetics.

  4. Underground Caverns: Large-scale, low cost (salt caverns, aquifers).

3.6.4 Hybrid Energy Systems

• Concept: Integration of two or more renewable energy sources (e.g., solar + wind + hydro) with or without conventional backup (diesel generator) and energy storage (batteries, flywheels) to form a single, more reliable and efficient power system.

• Need: Mitigate intermittency of single renewables (solar only day, wind variable), increase overall capacity factor, improve power quality, provide 24x7 supply in remote areas (mini-grids), reduce storage requirement.

3.6.5 Cogeneration (Combined Heat and Power - CHP)

• Concept: Simultaneous generation of electrical power and useful thermal energy (heat/steam) from a single fuel source. Captures waste heat from power generation process.

• Benefits:

  • High Overall Efficiency: 60-80% (vs. 30-40% for condensing power plants).

  • Fuel Savings: Reduces primary energy consumption.

  • Reduced Emissions: Per unit of useful energy.

  • Economic: Lower energy costs for industry/commercial users.

  • Grid Support: Distributed generation.

4.0 POWER SYSTEM ECONOMICS & OPERATION

4.1 Cost Analysis of Power Generation

4.1.1 Types of Costs

4.1.2 Total Cost of Electricity Generation

$$\displaystyle \boxed{ \text{Total Cost} = \text{Fixed Cost} + \text{Operating Cost} + \text{Semi-Variable Cost} } $$

• Fixed Cost per Unit (Rs/kWh): $$\displaystyle \frac{\text{Annual Fixed Cost}}{\text{Annual Energy Output (kWh)}} $$. Decreases with higher load factor/energy production.

• Operating Cost per Unit (Rs/kWh): $$\displaystyle \frac{\text{Total Operating Cost}}{\text{Annual Energy Output}} $$. For thermal, dominated by fuel cost per kWh.

4.1.3 Depreciation Methods

• Straight Line Method: Equal depreciation charge every year. $$\displaystyle \text{Depreciation/year} = \frac{\text{Initial Cost} - \text{Salvage Value}}{\text{Useful Life}} $$.

• Diminishing Value Method (Written Down Value): Fixed percentage on remaining book value each year. Higher depreciation in early years.

• Sum-of-Years'-Digits Method: Accelerated depreciation. Sum of years digits (1+2+...+n). Depreciation fraction = (remaining life) / (sum of years).

4.2 Load Analysis & Forecasting

4.2.1 Key Curves & Definitions

• Load Curve: Load (kW or MW) vs. Time (typically 24 hrs). Shows variation of demand.

• Load Duration Curve (LDC): Load sorted in descending order vs. % of time it is exceeded. Derived from load curve. Shows firm capacity needed.

• Mass Curve (Energy Curve): Cumulative energy (kWh) vs. Time. Slope = instantaneous load. Used to determine maximum demand and load factor graphically.

4.2.2 Key Performance Factors (Definitions & Relations)

1. Maximum Demand ($$\displaystyle P_{max} $$): Highest load during a given period (e.g., daily, annual).

2. Load Factor (LF): $$\displaystyle \boxed{LF = \frac{\text{Average Load}}{\text{Maximum Demand}} = \frac{\text{Energy (kWh)}}{\text{Max Demand (kW)} \times \text{Time (h)}} } $$. Always < 1 because average load < peak load. Indicates utilization of installed capacity.

3. Diversity Factor (DF): $$\displaystyle \boxed{DF = \frac{\text{Sum of Individual Max Demands}}{\text{Simultaneous Max Demand of System}} } $$. Always > 1 because individual peaks don't coincide. Reduces required plant capacity.

4. Capacity Factor (CF): $$\displaystyle \boxed{CF = \frac{\text{Actual Energy Output}}{\text{Rated Capacity} \times \text{Time}}} $$. Always < 1 because plant doesn't run at full capacity always (maintenance, outages, load < capacity). Measures plant utilization.

5. Utilisation Factor (UF): $$\displaystyle \boxed{UF = \frac{\text{Max Demand}}{\text{Rated Capacity of Plant}}} $$. Always ≤ 1. Measures how close max demand is to plant capacity.

6. Plant Capacity Factor & Use Factor: Often used interchangeably with CF. Use Factor = (Actual operating hours) / (Hours plant could have operated at full load).

4.2.3 Reserve Capacity

• Purpose: Meet unexpected demand surges, generator outages, maintenance.

• Types:

  • Hot Reserve: Plant running at no load (synchronized), can pick up load quickly (minutes).

  • Cold Reserve: Plant shut down, can start and take load (hours).

  • Running Reserve: Difference between total capacity and current load (includes hot reserve).

• Reserve Capacity (over peak load): $ \text{Installed Capacity} - \text{Maximum Demand} $.

4.2.4 Annual Energy Production (AEP) Calculation

From factors: $$\displaystyle \boxed{ \text{AEP (kWh)} = \text{Max Demand (kW)} \times \text{Load Factor} \times 8760 \text{ h} } $$

Or from Capacity Factor: $$\displaystyle \text{AEP} = \text{Installed Capacity (kW)} \times \text{Capacity Factor} \times 8760 $$.

4.2.5 Load Forecasting

• Importance: Essential for generation scheduling, fuel procurement, maintenance planning, capacity expansion, economic operation.

• Methods:

  • Extrapolation: Trend analysis of past data.

  • Moving Average/Exponential Smoothing.

  • Regression Analysis: Relate load to factors (temperature, humidity, day type, GDP).

  • End-Use Models: Bottom-up approach from consumer categories.

  • Neural Networks/Artificial Intelligence: Modern, handle non-linear relationships.

4.3 Economic Operation of Power Systems

4.3.1 Economic Load Scheduling (Dispatch)

• Concept: Allocate total system load among available generating units to minimize total fuel cost while satisfying:

  1. Power balance: $$\displaystyle \sum P_i = P_D + P_L $$ (Demand + Losses).

  2. Generator limits: $$\displaystyle P_{i,\min} \le P_i \le P_{i,\max} $$.

• Optimization Goal: Minimize $$\displaystyle \sum C_i(P_i) $$ where $$\displaystyle C_i $$ = fuel cost function ($Rs/h$ or $Rs/MWh$).

4.3.2 Incremental Fuel Cost (λ) and Heat Rate

• Incremental Fuel Cost (λ): $$\displaystyle \lambda = \frac{dC}{dP} $$ (Rs/MWh). Marginal cost of producing next MW.

• Heat Rate (HR): $$\displaystyle \text{HR} = \frac{\text{Heat Input (kcal/kWh)}}{\text{Power Output (kWh)}} $$. Inverse of efficiency. λ is proportional to HR.

4.3.3 Economic Dispatch without Transmission Losses

• Condition: For optimal dispatch, incremental costs of all units must be equal.

  $$\displaystyle \boxed{ \frac{dC_1}{dP_1} = \frac{dC_2}{dP_2} = \lambda } $$

• Numerical Method: Given cost functions $$\displaystyle C_i(P_i) = a_i + b_i P_i + c_i P_i^2 $$ (Rs/h).

  1. Write $$\displaystyle \lambda_i = b_i + 2c_i P_i $$.

  2. Set $$\displaystyle \lambda_1 = \lambda_2 = \lambda $$.

  3. Solve: $$\displaystyle P_1 + P_2 = P_D $$ (total demand).

  4. Find $$\displaystyle P_1, P_2, \lambda $$.

4.3.4 Economic Dispatch with Transmission Losses

• Concept: Losses depend on power flows. Loss formula: $$\displaystyle P_L = \sum_{i=1}^{n} \sum_{j=1}^{n} P_i B_{ij} P_j $$ (B-coefficients, symmetric).

• Penalty Factor (β_i): Accounts for losses. Plant i's effective incremental cost = λ * β_i.

  $$\displaystyle \boxed{ \beta_i = \frac{1}{1 - \frac{\partial P_L}{\partial P_i}} } $$

• Optimality Condition: $$\displaystyle \lambda_i = \lambda \cdot \beta_i $$ for all plants. Or $$\displaystyle \frac{dC_i}{dP_i} \cdot \beta_i = \lambda $$.

• Calculation of β_i: Iterative method or using loss formula coefficients.

• Numerical Example (JUN 2025): Given $$\displaystyle \frac{\partial P_L}{\partial P_2} = 0.2 $$, find β₁.

  • Losses: $$\displaystyle P_L = P_1 \frac{\partial P_L}{\partial P_1} + P_2 \frac{\partial P_L}{\partial P_2} $$.

  • But $$\displaystyle \frac{\partial P_L}{\partial P_1} + \frac{\partial P_L}{\partial P_2} = 1 $$ (for two plants, if losses are quadratic and symmetric). So $$\displaystyle \frac{\partial P_L}{\partial P_1} = 1 - 0.2 = 0.8 $$.

  • $$\displaystyle \beta_1 = \frac{1}{1 - 0.8} = \frac{1}{0.2} = 5 $$.

4.4 Tariffs & Pricing

4.4.1 Definition and Purpose

• Tariff: Schedule of rates/charges for selling electrical energy to consumers.

• Purpose: Recover total cost (fixed + operating) + reasonable profit, promote economic use, reflect cost of service, encourage load management.

4.4.2 Types of Tariffs (Comparison)

4.4.3 Factors Influencing Tariff Structure

• Cost of generation (capital, fuel, O&M).

• Load factor & diversity factor of consumer class.

• Power factor.

• Time of use (peak/off-peak).

• Location (rural/urban, proximity to plant).

• Government policies/subsidies (e.g., agricultural subsidy).

• Competition/market forces (in deregulated markets).

• Social objectives (lifeline tariff for poor).

[!TIP] Exam Focus: For "compare tariffs" questions, create a table as above. Emphasize Two-Part Tariff as most rational for large consumers and TOD for load management.