UNIT 1: ELECTRICAL ENERGY UTILIZATION & ENERGY MANAGEMENT

I. ILLUMINATION ENGINEERING

Fundamental Laws of Illumination

• Inverse Square Law: Illumination $E$ on a surface normal to the ray from a point source is inversely proportional to the square of the distance $d$.

$$E = \frac{I}{d^2}$$

where $I$ = luminous intensity (candela).

\boxed{E = \frac{I}{d^2}}

• Lambert's Cosine Law: Illumination is proportional to the cosine of the angle of incidence $\theta$ (angle between ray and normal to surface).

$$E = \frac{I \cos \theta}{d^2}$$

For extended sources, integrate over area.

[!TIP] Common error: Using angle with the surface instead of normal. Always ensure $\theta$ is measured from the normal.

Lighting Schemes & Design Considerations

Types of Lighting Schemes:

• Direct: 90–100% light on work plane (e.g., downlights).

• Indirect: 90–100% light to ceiling (e.g., uplights).

• Semi-direct: 60–90% direct, rest indirect.

• Semi-indirect: 60–90% indirect, rest direct.

• General: Uniform distribution in all directions.

Design Factors:

• Required illumination level (lux) for task.

• Room dimensions, mounting height.

• Reflectance of ceiling, walls, work plane.

• Luminaire efficiency and distribution curve.

• Glare control and uniformity ratio.

Illumination Calculations

• Point source: $$\displaystyle E = \frac{I \cos \theta}{d^2} $$.

• Extended source: Sum/integrate contributions from all elements.

• Multiple lamps: Add illuminance from each source vectorially.

• Key Factors:

  • Utilization Factor (UF): Fraction of luminous flux reaching work plane (from photometric data).

  • Maintenance Factor (MF): Accounts for dirt, aging (typically 0.6–0.8).

  • Depreciation Factor (DF): Lumen depreciation over time.

Total Lamp Output Required:

$$\text{Total Lumens} = \frac{E \times A}{UF \times MF}$$

where $E$ = required illumination (lux), $A$ = area (m²).

Number of Lamps:

$$N = \frac{\text{Total Lumens}}{\text{Lumens per Lamp}}$$

[!TIP] In numerical problems, verify units: 1 lux = 1 lumen/m². Use space-height ratio for mounting height.

Energy-Efficient Lighting

• LEDs: High efficacy (100+ lm/W), long life (50,000 h), instant start, no UV/IR.

• CFLs: Compact, efficient (60–80 lm/W), but contain mercury.

• Occupancy Sensors: PIR or ultrasonic, turn off when unoccupied.

• Daylight Harvesting: Photosensors dim artificial light based on natural light.

• High-Efficiency Ballasts: Electronic ballasts for fluorescents reduce losses.

• Task Lighting: Provide light only where needed.

II. ELECTRIC HEATING

Advantages & Losses

Advantages:

• Clean, no combustion products.

• Precise temperature control.

• High efficiency (90–100%).

• Automatic operation possible.

• No standby losses.

Losses:

• Heat loss from elements to surroundings.

• Radiation and convection losses.

• Losses in wiring, contacts, and controls.

Classification of Heating Methods

1. Resistance Heating: Current through resistor ($$\displaystyle P = I^2R $$).

   • Direct: Elements immersed (e.g., water heater).

   • Indirect: Radiant or convective (e.g., space heater).

2. Induction Heating: Alternating magnetic field induces eddy currents in conductive material; also hysteresis loss in magnetic materials.

   • Applications: Melting, hardening, brazing.

   • Limitations: Only for conductors, skin effect, high initial cost.

3. Dielectric Heating: High-frequency electric field (MHz) causes molecular friction in insulators.

   • Applications: Wood, plastics, food processing.

4. High-Frequency Induction Furnace:

   • Coreless: For melting metals (steel, non-ferrous).

   • Channel: For holding and superheating molten metal.

   • Rotary: Continuous melting.

Numerical Problems

Power Calculation for Series/Parallel Elements:

Two resistors $R$ each, voltage $V$:

• Parallel: $$\displaystyle R_{eq} = R/2 $$, $$\displaystyle P = V^2 / (R/2) = 2V^2/R $$.

• Series: $$\displaystyle R_{eq} = 2R $$, $$\displaystyle P = V^2 / (2R) $$.

\boxed{P_{\text{parallel}} = 2P_{\text{series}}}

[!TIP] For identical resistors, parallel connection yields higher power. Always compute equivalent resistance first.

III. WELDING PROCESSES

Classification Based on Processes

• Arc Welding: SMAW, GMAW, GTAW, FCAW.

• Resistance Welding: Spot, seam, projection, flash.

• Gas Welding: Oxy-fuel (oxy-acetylene).

• Solid-State Welding: Friction, ultrasonic, explosion.

• Electron Beam Welding.

• Laser Beam Welding.

Detailed Study of Welding Methods

Arc Welding:

• Principle: Electric arc between electrode and workpiece melts metal.

• Consumable electrode (SMAW, FCAW) or non-consumable (GTAW).

• Shielding: flux (SMAW) or gas (GMAW, GTAW).

• Applications: Structural, pipelines, shipbuilding.

Resistance Welding:

• Spot Welding: Two electrodes apply pressure and current; local melting.

• Seam Welding: Rotating wheels for continuous weld.

• Applications: Automotive bodies, appliances.

Electron Beam Welding:

• High-velocity electron beam in vacuum chamber.

• Deep penetration, narrow weld, no filler.

• Applications: Aerospace, medical implants, thick sections.

Welding Transformers

• Step-down transformers: High current (100–1000 A), low voltage (10–50 V).

• Types:

  • Tap-changing: Adjust turns ratio for voltage control.

  • Reactor type: Series reactor for current regulation.

  • Inverter type: High-frequency, lightweight, electronic control.

• Characteristics: High duty cycle, overload capacity, rugged.

[!TIP] Welding transformers have high short-circuit impedance to limit current during shorts.

IV. ELECTROLYSIS & ELECTROPLATING

Laws of Electrolysis (Faraday's Laws)

1. First Law: Mass deposited $W$ is proportional to charge $Q$ passed.

$$W = Z Q = Z I t$$

where $Z$ = electrochemical equivalent (g/C or kg/A·s).

\boxed{W = Z I t}

2. Second Law: For same charge, masses deposited are proportional to chemical equivalents.

$$\frac{W_1}{W_2} = \frac{E_1}{E_2}$$

where $E$ = chemical equivalent (g/equivalent).

Electrochemical Equivalent & Deposition Calculations

• $$\displaystyle Z = \frac{E}{F} $$, $F$ = Faraday constant = 96500 C/mol.

• For multiple electrolytes in series, same charge deposits masses in ratio of their $E$.

Numerical Example:

Given $$\displaystyle I = 3 $$ A, $$\displaystyle t = 30 $$ min = 1800 s, $$\displaystyle Z = 0.065 $$ mg/A·s?

Assume $$\displaystyle Z = 0.065 \times 10^{-3} $$ g/A·s:
$$\displaystyle W = 0.065 \times 10^{-3} \times 3 \times 1800 = 0.351 $$ g.

[!TIP] Ensure consistent units: Convert minutes to seconds, mg to g.

Electroplating

• Process: Workpiece as cathode, metal anode in electrolyte solution. Current deposits metal coating.

• Applications: Corrosion resistance (zinc, nickel), decoration (chrome, gold), electrical conductivity (gold on contacts), wear resistance (hard chrome).

V. ELECTRIC TRACTION & DRIVES

Characteristics of a Good Traction System

• High acceleration and braking rates.

• Smooth speed control over wide range.

• High starting torque.

• Ability to operate on steep gradients.

• Regenerative braking capability.

• Reliability, safety, and low maintenance.

Speed-Time Curves

General Speed-Time Curve (Main Line):

Derivation for Trapezoidal Curve (No Coasting):

Given:

• Acceleration $\alpha$ (m/s²), retardation $\beta$ (m/s²).

• Maximum speed $V$ (m/s).

• Time for acceleration: $$\displaystyle t_a = V / \alpha $$.

• Time for retardation: $$\displaystyle t_b = V / \beta $$.

• Constant speed time: $$\displaystyle t_c $$.

• Total time: $$\displaystyle T = t_a + t_c + t_b $$.

• Distance: $$\displaystyle S = S_a + S_c + S_b $$.

From kinematics:

$$S_a = \frac{1}{2} \alpha t_a^2 = \frac{1}{2} V t_a, \quad S_b = \frac{1}{2} \beta t_b^2 = \frac{1}{2} V t_b, \quad S_c = V t_c$$

$$S = \frac{1}{2} V (t_a + t_b) + V t_c = V \left( t_c + \frac{t_a + t_b}{2} \right)$$

Solving for $V$ given $S$, $T$, $\alpha$, $\beta$.

Train Motion & Resistance

• Dead Weight ($$\displaystyle W_d $$): Total weight of train (including locomotive, coaches, fuel, water).

• Acceleration Weight ($$\displaystyle W_a $$): $$\displaystyle W_d + \text{rotating parts equivalent} $$ (typically 5–10% more).

• Train Resistance ($$\displaystyle R_t $$):

  $$\displaystyle R_t = R_{\text{mechanical}} + R_{\text{air}} + R_{\text{gradient}} $$

  $$\displaystyle R_{\text{air}} \propto v^2 $$, $$\displaystyle R_{\text{gradient}} = W \cdot \sin\theta \approx W \cdot \text{gradient} $$.

• Specific Energy Consumption: Energy per ton-km (kWh/ton-km). Includes energy for traction, auxiliary, and losses.

Electrical Braking Methods

• Plugging (Reverse Current): Reverse armature current; motor acts as brake but energy dissipated as heat in resistors.

• Dynamic Braking: Disconnect from supply, connect armature to resistor; motor generates and dissipates energy.

• Regenerative Braking: Motor acts as generator, feed energy back to supply. Most efficient, used in metros and EVs.

[!TIP] Regenerative braking saves energy, especially in hilly terrain or frequent stops.

Motors for Traction

• DC Series Motor:

  • High starting torque ($$\displaystyle T \propto I^2 $$).

  • Speed varies inversely with load (good for traction).

  • Simple speed control via series-parallel or rheostatic.

  • Robust, high overload capacity.

  Suitability: Historically preferred for DC traction systems.

• AC Motors:

  • Induction motors with VFD: Low maintenance, high speed, regenerative possible.

  • Synchronous motors: Constant speed, power factor correction.

  Modern systems favor AC for reliability and efficiency.

Electric & Hybrid Vehicles

Electric Vehicle (EV) Components:

• Battery: Li-ion (high energy density), charging system.

• Electric Motor: AC induction or permanent magnet synchronous.

• Power Electronics: Inverter (DC-AC), controller, charger.

• Transmission: Usually single-speed reduction gear (simplicity).

• Auxiliaries: HVAC, power steering (electric).

Hybrid Vehicle Types:

• Series Hybrid: Engine drives generator; motor drives wheels. Engine operates at optimal point.

• Parallel Hybrid: Both engine and motor can drive wheels directly.

• Series-Parallel: Combination, e.g., Toyota Prius. Advantages: Improved fuel economy, reduced emissions, regenerative braking, silent operation.

Load Equalization

• Use flywheel or motor-generator set to store kinetic energy during light load and release during peak load.

• Smoothes demand curve, reduces peak demand charges.

• Particularly useful in traction substations with intermittent heavy loads.

VI. ENERGY MANAGEMENT & CONSERVATION

Energy Audit

• Definition: Systematic examination to identify energy uses, quantify flows, and recommend conservation measures.

• Types:

  • Preliminary Audit: Walk-through, identify obvious savings, low cost.

  • Detailed Audit: In-depth measurement, data logging, analysis, detailed report with ROI.

• Significance: Cost reduction, environmental impact (CO₂ reduction), compliance with regulations, sustainability goals.

Energy Manager

• Roles & Responsibilities:

  • Develop and implement energy policy.

  • Conduct energy audits and analyze data.

  • Recommend and oversee conservation projects.

  • Monitor energy consumption and performance.

  • Train staff and promote awareness.

• Qualities: Technical knowledge (systems, thermodynamics), analytical skills, communication, project management, commitment.

Energy Auditing Instruments

Thermodynamics in Energy Conservation

• First Law (Energy Balance): Energy cannot be created/destroyed. For a system: $$\displaystyle \Delta U = Q - W $$.

  • Example: Boiler efficiency = (Steam energy output) / (Fuel energy input).

• Second Law: Entropy of isolated system increases; efficiency limited by Carnot cycle.

  • $$\displaystyle \eta_{\text{Carnot}} = 1 - \frac{T_c}{T_h} $$ (absolute temperatures).

  • Example: Heat engine maximum efficiency; refrigerator COP = $$\displaystyle \frac{T_c}{T_h - T_c} $$.

  • Significance: Identifies irreversibilities, guides improvement.

Demand Side Management (DSM)

• Load Curve Analysis: Plot of load vs. time (daily, seasonal). Identifies peak, off-peak, base load.

  • Importance: Basis for tariff design, load management, capacity planning.

• DSM Techniques:

  • Peak Clipping: Reduce peak demand (e.g., interruptible loads, cycling AC).

  • Valley Filling: Shift load to off-peak (e.g., storage water heaters, off-peak EV charging).

  • Load Shifting: Move load from peak to off-peak (e.g., industrial processes).

  • Strategic Load Growth: Encourage efficient loads (e.g., LED lighting).

Electricity Tariffs

• Types:

  • Flat Rate: Fixed per unit.

  • Block Rate: Increasing blocks (higher rates for more consumption).

  • Two-Part: Fixed charge + variable charge.

  • Time-of-Use (TOU): Different rates for peak, off-peak, shoulder.

• Restructuring for Conservation:

  • Higher peak rates to discourage peak usage.

  • TOU tariffs to shift load.

  • Incentives for energy-efficient equipment.

  • Penalties for low power factor.

Power Factor Improvement

• Causes of Poor PF: Inductive loads (motors, transformers) draw reactive power (Q), increasing apparent power (S).

• Disadvantages:

  • Higher current for same real power → increased $$\displaystyle I^2R $$ losses.

  • Reduced system capacity (transformers, cables).

  • Voltage drop, poor voltage regulation.

  • Penalty charges from utilities.

• Methods:

  • Shunt Capacitors: Most common; supply leading VARs locally.

  • Synchronous Condensers: Over-excited synchronous motor generates VARs.

  • Phase Advancers: For induction motors, improve PF and speed control.

  • High PF Motors: Design with lower magnetizing current.

• Improvement Calculation:

$$\text{Required Capacitor kVAR} = P (\tan \phi_1 - \tan \phi_2)$$

where $P$ = real power (kW), $$\displaystyle \phi_1 $$ = initial PF angle, $$\displaystyle \phi_2 $$ = desired PF angle.

\boxed{\text{PF} = \frac{\text{kW}}{\text{kVA}}}

Energy-Efficient Motors & Drives

Energy-Efficient Motors (EEMs):

• Higher efficiency (IE3, IE4 vs. IE1 standard).

• Better materials: copper windings, thin silicon steel laminations.

• Optimized design: larger air gap, improved cooling, reduced losses (stator, rotor, core, friction).

• Benefits: 2–8% energy saving, lower operating temperature, longer life.

Variable Speed Drives (VSD):

• Principle: Adjust frequency and voltage to control AC motor speed (VFD). For DC, adjust armature voltage.

• Benefits:

  • Energy saving: Affinity laws: $$\displaystyle P \propto N^3 $$ for fans/pumps.

  • Soft start/stop reduces mechanical stress.

  • Precise process control.

  • Power factor improvement at partial load.

• Applications: HVAC, pumps, compressors, conveyors.

Energy-Efficient Housekeeping & Maintenance

• Predictive Maintenance: Condition monitoring (vibration, thermography, oil analysis) to predict failures before occurrence.

• Preventive Maintenance: Scheduled inspections, lubrication, parts replacement based on time/usage.

• Role in Conservation:

  • Reduce downtime and energy waste from faulty equipment.

  • Maintain optimal efficiency (clean heat exchangers, aligned belts, proper lubrication).

  • Extend equipment life, reduce capital costs.

VII. INDUSTRY-SPECIFIC ENERGY CONSERVATION

Building Energy Conservation

• HVAC Systems:

  • Use high-efficiency chillers, VAV systems, heat recovery wheels.

  • Economizer cycles for free cooling.

  • Proper insulation of ducts, pipes.

  • Zoning and advanced controls (BMS).

• Lighting: LED, occupancy sensors, daylight harvesting, task lighting.

• Envelope Design:

  • Insulation (walls, roof), high-performance windows (low U-value, SHGC).

  • Shading devices, air sealing, thermal mass.

• Thermal Energy Audit in AC:

  • Assess cooling load calculation accuracy.

  • Check refrigerant charge, superheat/subcooling.

  • Inspect duct leakage, insulation, coil cleanliness.

  • Evaluate controls and scheduling.

Process Industries

Sugar Industry:

• Cogeneration using bagasse (fiber residue) in boilers.

• Multiple-effect evaporators for juice concentration.

• Back-pressure turbines for process steam and power.

• Efficient motors, waste heat recovery from flue gases.

Textile Industry:

• Energy-efficient motors and drives for spinning, weaving.

• Waste heat recovery from drying processes (heat exchangers).

• LED lighting, occupancy sensors.

• Process optimization (e.g., air-jet looms vs. mechanical).

Cement Industry:

• Preheater and precalciner to reduce kiln load.

• Kiln optimization (firing, insulation).

• Waste heat recovery from clinker cooler and kiln exhaust (WHR boiler).

• Use of alternative fuels (tyres, waste).

Agriculture & Waste Utilization

• Agricultural Waste: Bagasse, rice husk, straw, coconut husk.

• Uses:

  • Direct combustion for steam/power.

  • Biomass gasification for syngas.

  • Biogas from anaerobic digestion (cattle dung, crop residue).

• Benefits: Renewable, reduces fossil fuel use, solves waste disposal, rural employment.

Waste Heat Recovery

• Techniques:

  • Heat Exchangers: Recuperator (direct), regenerator (intermittent).

  • Waste Heat Recovery (WHR) Boilers: Generate steam from exhaust gases.

  • Thermoelectric Generators: Direct heat-to-electricity (low efficiency).

  • Organic Rankine Cycle (ORC): For low-temperature waste heat.

• Applications: Steel plants (furnace exhaust), glass furnaces, engine exhaust, kilns.

Co-generation

• Principle: Simultaneous generation of electricity and useful heat from same fuel source (e.g., steam turbine with extraction).

• Types:

  • Back Pressure Turbine: Steam expanded to process pressure, no condenser. High thermal efficiency, but inflexible.

  • Extraction-Condensing Turbine: Extract steam at intermediate pressure for process; remaining expanded to condenser. Flexible.

  • Double Extraction Back Pressure: Two extractions at different pressures.

• Benefits:

  • Overall efficiency 70–90% (vs. 30–40% for separate generation).

  • Reduced fuel cost and emissions.

  • Reliable power and process steam.

• System Diagrams:

  DiagramCANVAS: Back Pressure Co-generation: Boiler -> Turbine -> Process Steam (no condenser).
  DiagramCANVAS: Extraction-Condensing: Boiler -> Turbine -> Extraction Point -> Process Steam; Exhaust -> Condenser -> Feedwater.

VIII. PROJECT EVALUATION & ECONOMICS

Project Evaluation Methods

• Payback Period (PBP):

  • Simple: $$\displaystyle \text{PBP} = \frac{\text{Initial Investment}}{\text{Annual Savings}} $$.

  • Discounted: Cumulative discounted cash flow = 0.

  • Advantage: Simple; Disadvantage: Ignores time value, cash flows beyond PBP.

• Net Present Value (NPV):

$$NPV = \sum_{t=0}^{n} \frac{CF_t}{(1+r)^t}$$

where $$\displaystyle CF_t $$ = net cash flow at year $t$, $r$ = discount rate.

Accept if NPV > 0.

• Internal Rate of Return (IRR):

  Discount rate where NPV = 0. Accept if IRR > required rate.

• Cost-Benefit Analysis (CBA): Compare all costs and benefits (including intangibles) over project life.

• Risk Analysis:

  • Sensitivity Analysis: Vary key parameters (savings, cost) to see impact on NPV/IRR.

  • Scenario Analysis: Best, worst, most likely cases.

  • Inflation Risk: Adjust cash flows for inflation or use real discount rate.

Depreciation

• Straight-Line (SL) Method:

$$\text{Annual Depreciation} = \frac{\text{Cost} - \text{Salvage Value}}{\text{Useful Life}}$$

Equal annual charge.

• Written-Down Value (WDV) Method:

$$\text{Depreciation}_t = \text{WDV}_{t-1} \times \text{Depreciation Rate}$$

Declining balance, higher initial charges.

[!TIP] For tax purposes, WDV often used (accelerated depreciation).

Management Tools

• Matrix Chart: Prioritize projects based on criteria (cost, savings, risk, payback). Example: 2x2 matrix (effort vs. impact).

• Load Energy Balance Diagram: Sankey diagram showing energy inputs, useful output, losses (e.g., for boiler, motor system).

• Energy Flow Networks: Graphical representation of energy flows between processes, highlighting losses and recovery opportunities.

IX. CROSS-CUTTING TOPICS

Electrical Load Calculations for Air Conditioning

• Cooling Load Estimation:

  • Rule of thumb: 1 ton (3.5 kW) per 100–150 ft² (10–14 m²) for office.

  • Detailed method: Sum of heat gains from conduction, radiation, occupants, equipment, infiltration.

• Electrical Load:

$$P_{\text{electrical}} = \frac{\text{Cooling Load (kW)}}{\text{COP}}$$

COP = coefficient of performance (typically 3–4 for modern systems).

• Consider diversity factor, safety margin.

Primary Energy Resources

• Fossil: Coal, oil, natural gas (non-renewable, high emissions).

• Nuclear: Uranium (low emissions, radioactive waste).

• Renewables: Hydro, solar, wind, biomass, geothermal (sustainable, variable).

• Considerations: Availability, cost, environmental impact, reliability.

Simulation & Modeling in Energy Management

• Software Tools: EnergyPlus, DOE-2, eQUEST, HAP (HVAC), TRNSYS.

• Applications:

  • Predict building/plant energy use.

  • Evaluate conservation measures (retrofit, new design).

  • Optimize system operation.

• Inputs: Geometry, materials, systems, schedules, weather data.

• Outputs: Energy consumption, costs, emissions.

Lubrication and Tribo-logical Innovations

• Role: Reduce friction and wear in rotating equipment (motors, pumps, bearings), saving energy.

• Innovations:

  • Synthetic Lubricants: Longer life, better temperature stability, lower friction.

  • Solid Lubricants: Graphite, MoS₂ for extreme conditions.

  • Nano-lubricants: Nanoparticles enhance film strength, reduce wear.

  • Magnetic Lubrication: Magnetic fields control lubricant flow.

• Benefits: Energy saving (1–5% in some systems), reduced maintenance, extended equipment life.