UNIT 2: Energy Conservation in Electrical and Industrial Systems

I. Energy Audit and Management

A. Definition, Types, and Significance

• Energy Audit: A systematic procedure to obtain knowledge of the energy consumption profile of an organization, identify and quantify energy conservation opportunities, and report the findings. It is the cornerstone of any energy management program.

• Types:

  1. Preliminary Audit (Walk-through Audit): A quick, low-cost assessment to identify obvious areas of energy wastage and major opportunities. Involves brief interviews, visual inspection, and analysis of utility bills.

  2. Detailed Audit (Comprehensive Audit): An in-depth study involving detailed data collection (sub-metering, measurements), rigorous analysis, and engineering evaluation of all Energy Conservation Measures (ECMs). Provides accurate cost-benefit analysis for each opportunity.

• Significance:

  • Identifies energy wastage and inefficiencies.

  • Quantifies potential savings (energy & cost).

  • Provides a baseline for measuring progress.

  • Prioritizes investment in energy-saving projects.

  • Enhances energy security and reduces environmental impact.

[!TIP] Exam Focus: Distinguish between Preliminary (identifies what is wrong) and Detailed Audit (quantifies how much can be saved and cost).

B. Energy Manager: Roles, Duties, and Qualities

• Roles: Acts as the champion for energy efficiency within the organization.

• Duties:

  • Develop and implement energy policy.

  • Plan and conduct energy audits.

  • Prepare energy conservation action plans and budgets.

  • Monitor and analyze energy consumption data.

  • Promote awareness and train staff.

  • Prepare reports for management.

  • Verify savings from implemented projects.

• Qualities: Technical knowledge, analytical skills, communication skills, persistence, project management ability, and commitment to sustainability.

C. Energy Auditing Process (Steps)

A systematic approach:

1. Planning & Preparation: Define scope, assemble team, gather historical data (energy bills, process data).

2. Pre-Audit (Preliminary Survey): Walk-through, identify major areas of consumption/wastage, list potential ECMs.

3. Detailed Data Collection: Measure energy use (using instruments) in key areas, collect operational data, conduct interviews.

4. Data Analysis & Evaluation: Perform material/energy balances, calculate baseline consumption, evaluate ECMs technically and economically.

5. Report Preparation: Document findings, savings potential, implementation plan, and investment requirements.

6. Implementation & Follow-up: Assist in project implementation, monitor performance, verify savings, and recommend policy updates.

D. Energy Auditing Instruments and Tools

E. Energy Efficient Housekeeping Practices

Low-cost/no-cost operational changes:

• Switch off lights, fans, equipment when not in use.

• Optimize thermostat settings (HVAC).

• Regular cleaning of lamps, fixtures, heat exchangers, filters.

• Minimize opening of doors/windows in air-conditioned spaces.

• Schedule equipment to avoid simultaneous operation of large loads.

• Ensure proper maintenance of seals on refrigerators/freezers.

F. Predictive and Preventive Maintenance

• Preventive Maintenance (PM): Scheduled maintenance at fixed intervals (time-based or usage-based) to prevent failure (e.g., lubrication, cleaning, parts replacement).

• Predictive Maintenance (PdM): Condition-based monitoring using sensors/data to predict failure and perform maintenance just in time. Techniques: vibration analysis, thermography, oil analysis, motor current signature analysis.

• Role in Conservation: Maintains equipment at peak efficiency, reduces unexpected downtime, extends equipment life, and prevents energy waste due to malfunction (e.g., dirty coils, misaligned belts, faulty bearings).

G. Energy Policy and Its Importance

• Definition: A formal statement from top management committing the organization to continuous improvement in energy efficiency, setting objectives and targets.

• Importance:

  • Demonstrates management commitment.

  • Provides a framework for action and accountability.

  • Motivates employees.

  • Essential for ISO 50001 certification.

  • Improves corporate image and stakeholder relations.

H. Primary Energy Resources and Conservation Aspects

• Primary Resources: Fossil fuels (coal, oil, natural gas), nuclear, renewable (solar, wind, hydro, biomass, geothermal).

• Conservation Aspects:

  • Fossil Fuels: Improve combustion efficiency, switch to cleaner fuels, co-generation.

  • Electricity: Reduce transmission/distribution losses, improve end-use efficiency (motors, lighting).

  • Renewables: Promote decentralized generation (solar PV), use biomass waste (bagasse, agrowaste).

  • Cross-cutting: Focus on energy efficiency as the "first fuel" – saving energy is equivalent to generating it.

II. Thermodynamics and Thermal Energy Systems

A. First Law of Thermodynamics (Conservation of Energy)

Statement: Energy cannot be created or destroyed, only transformed from one form to another. The net energy entering a system equals the change in its internal energy plus the net work done by the system.

For a closed system: $$\displaystyle \Delta U = Q - W $$

Where: $\Delta U$ = Change in internal energy, $Q$ = Heat added to system, $W$ = Work done by system.

Example (Heat Engine): Heat $$\displaystyle Q_H $$ from a hot source is partly converted to work $W$, and remainder $$\displaystyle Q_C $$ is rejected to a cold sink. $$\displaystyle Q_H = W + Q_C $$. Efficiency $$\displaystyle \eta = \frac{W}{Q_H} = 1 - \frac{Q_C}{Q_H} $$.

B. Second Law of Thermodynamics (Direction of Processes)

Statement: Heat cannot spontaneously flow from a colder body to a hotter body. It introduces the concept of entropy ($S$) – a measure of disorder/unavailability of energy.

Significance in Conservation:

1. Defines the theoretical maximum efficiency (Carnot efficiency) for any heat engine: $$\displaystyle \eta_{Carnot} = 1 - \frac{T_C}{T_H} $$ (T in Kelvin).

2. Explains why 100% energy conversion is impossible (some energy always degrades to low-grade heat).

3. Emphasizes the need for waste heat recovery to improve overall system efficiency (exergy analysis).

C. Thermal Energy Audit in HVAC Systems

1. Calculation of Electrical Loads for Air Conditioning

• Cooling Load Calculation: Sum of all heat gains.

  • Sensible Heat Gain: $$\displaystyle Q_s = U \cdot A \cdot \Delta T $$ (through walls, windows) + $$\displaystyle m \cdot C_p \cdot \Delta T $$ (from ventilation, occupants).

  • Latent Heat Gain: $$\displaystyle Q_L = m \cdot h_{fg} $$ (from occupants, infiltration, processes).

  • Total Load: $$\displaystyle Q_{total} = Q_s + Q_L $$ (in Watts or BTU/hr).

  • Electrical Power (Approx.): $$\displaystyle P_{elec} \approx \frac{Q_{total}}{COP \cdot \eta_{motor}} $$ (COP = Coefficient of Performance of chiller, $$\displaystyle \eta_{motor} $$ = motor efficiency).

2. Energy Conservation Measures (ECMs) in HVAC

• Plant Level: Use high-efficiency chillers/boilers, co-generation, variable speed drives on pumps/fans, heat recovery wheels (enthalpy wheels), economizers (use outdoor air for cooling when possible).

• System Level: Optimize water/air flow rates, reduce pressure drops, proper insulation of ducts/pipes.

• Building Level: Improve building envelope (insulation, shading), daylight harvesting, occupancy sensors, zonal control, regular maintenance.

D. Waste Heat Recovery Techniques

E. Co-generation (Combined Heat and Power - CHP)

• Principle: Simultaneous generation of electrical power and useful thermal energy (steam/hot water) from a single primary fuel source (e.g., natural gas, biomass). Recovers waste heat from power generation.

• Systems:

  1. Back Pressure Turbine: Steam expands to an intermediate pressure and is extracted for process use. No condenser. High thermal efficiency, but power output varies with heat demand.

  2. Extraction-Condensing Turbine: Steam is extracted at intermediate pressure for process, remaining steam expands to condenser vacuum. Power and heat can be controlled independently.

  3. Double Extraction Back Pressure: Two extraction points for different temperature process needs.

• Benefits:

  • Overall fuel efficiency: 70-90% (vs. 30-40% for condensing power plants).

  • Reduced transmission/distribution losses.

  • Lower greenhouse gas emissions.

  • Enhanced energy security.

  • Potential for revenue from excess power export.

[!TIP] Exam Focus: Be able to sketch and differentiate Back Pressure vs. Extraction-Condensing systems.

III. Electrical Energy Conservation in Buildings and Systems

A. Lighting Systems

1. Laws of Illumination

• Inverse Square Law: Illuminance ($E$) at a point on a plane perpendicular to the line joining the point and the source is inversely proportional to the square of the distance ($d$).

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

Where $I$ = Luminous Intensity (Candela, cd).

• Lambert's Cosine Law: Illuminance on a surface is proportional to the cosine of the angle ($\theta$) between the direction of the incident ray and the normal to the surface.

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

**Combined**: $$\displaystyle E = \frac{I \cos^3 \theta}{h^2} $$ (for a point source at height $h$).

2. Lighting Design Parameters

• Space-Height Ratio (SHR): Ratio of spacing between luminaires ($S$) to mounting height above working plane ($h$). $$\displaystyle SHR = S/h $$. Guides initial layout.

• Utilization Factor (UF): Fraction of total lumens emitted by lamps that reach the working plane. Depends on room geometry, surface reflectances, and luminaire type. (0.3 - 0.6 typical).

• Maintenance Factor (MF): Accounts for reduction in light output due to dirt accumulation and lamp depreciation. (0.6 - 0.8 typical).

• Depreciation Factor (DF): $$\displaystyle DF = UF \times MF $$.

3. Illumination Calculations (Point Sources)

• Single Point Source: Use $$\displaystyle E = \frac{I \cos^3 \theta}{h^2} $$.

• Multiple Point Sources (Point-by-Point Method): Total illuminance at a point is the algebraic sum of contributions from all sources.

$$E_{total} = \sum_{i=1}^{n} \frac{I_i \cos^3 \theta_i}{h_i^2}$$

• Room Index Method (for uniform lighting):

$$\text{Number of Lamps} (N) = \frac{E \times A}{n \times UF \times MF \times LLF}$$

Where: $E$ = Required illuminance (lux), $A$ = Area (m²), $n$ = Lumens per lamp, $LLF$ = Lamp Lumen Factor (often included in MF).

4. Energy Efficient Lighting Technologies and Methods

[!TIP] Common Pitfall: In point source calculations, $\theta$ is the angle of incidence, not just the angle from vertical. Use $\cos \theta$ where $\theta$ is angle between ray and normal to surface.

B. Electric Heating

1. Methods of Heating

• Resistance Heating: Current through a high-resistance element (Nichrome). Used in toasters, heaters, furnaces.

• Induction Heating: Eddy currents induced in a conductive workpiece by a high-frequency AC magnetic field. Skin effect confines heating to surface.

• Dielectric Heating: High-frequency AC field causes molecular friction in non-conductors (wood, plastics). Used in drying, gluing.

• Arc Heating: Heat from an electric arc (high temperature ~3000°C). Used in steel melting (arc furnaces), welding.

2. Advantages and Losses in Electric Heating

• Advantages: Clean, quiet, no combustion byproducts, precise control, high efficiency at point of use (90-95%), easy installation, safety (no open flame).

• Losses: Losses in generation (thermal power plant ~60-70% loss), transmission & distribution (~10-15% loss). Hence, overall source-to-point efficiency can be low unless electricity is from low-loss sources (hydro, renewables).

3. Induction Heating (Principle, Applications, Limitations)

• Principle: Based on Faraday's laws of electromagnetic induction. An AC current in a primary coil generates a changing magnetic field, inducing eddy currents in the conductive secondary (workpiece). $$\displaystyle I^2R $$ heating occurs in the workpiece.

• Applications: Surface hardening, melting (induction furnaces), soldering/brazing, induction cooktops.

• Limitations: Works only on conductive materials. High initial cost. Efficiency drops with non-magnetic materials. Requires high-frequency supply (using inverters).

4. Numerical Problems (Power Calculation)

• Series Connection: $$\displaystyle R_{eq} = R_1 + R_2 $$, $$\displaystyle P = \frac{V^2}{R_{eq}} $$.

• Parallel Connection: $$\displaystyle R_{eq} = \frac{R_1 R_2}{R_1 + R_2} $$, $$\displaystyle P = \frac{V^2}{R_{eq}} $$.

• Example (Toaster): Two 100Ω elements.

  • Series: $$\displaystyle R_{eq}=200\Omega $$, $$\displaystyle P= \frac{250^2}{200} = 312.5 \text{ W} $$.

  • Parallel: $$\displaystyle R_{eq}=50\Omega $$, $$\displaystyle P= \frac{250^2}{50} = 1250 \text{ W} $$.

C. Power Factor in Power Systems

1. Definition and Causes of Poor Power Factor

• Definition: Power Factor ($PF$) = $$\displaystyle \frac{\text{Real Power (P)}}{\text{Apparent Power (S)}} = \cos \phi $$ (where $\phi$ is phase angle between V and I). It is a measure of how effectively current is converted into useful work.

• Causes of Poor PF (Lagging):

  • Inductive loads: AC motors (especially under-loaded), transformers, induction furnaces, fluorescent lamp ballasts.

  • Reactive power ($Q$) consumption by these loads causes current to lag voltage.

2. Disadvantages of Low Power Factor

• Increased current for same real power: $$\displaystyle I = \frac{P}{V \cdot PF} $$.

• Higher $$\displaystyle I^2R $$ losses in conductors and transformers.

• Larger conductor size and equipment (transformers, switchgear) required.

• Voltage drop increases, leading to poor voltage regulation.

• Utilities impose penalties for PF below a certain limit (usually 0.9 lagging).

3. Improvement Methods

• Static Capacitors (Shunt Capacitors): Most common. Capacitors supply leading reactive power, canceling lagging reactive power from inductive loads. Can be individual (near load) or bank (at substation).

  • Required Capacitor kVAR: $$\displaystyle Q_c = P (\tan \phi_1 - \tan \phi_2) $$

  Where $P$ = Real Power (kW), $$\displaystyle \phi_1 $$ = initial angle, $$\displaystyle \phi_2 $$ = desired angle.

• Synchronous Condenser: An over-excited synchronous motor running without mechanical load. Supplies leading current and can be continuously adjusted.

• Phase Advancers: Used for induction motors only. Improves motor's PF by providing leading excitation.

• Synchronous Motors: Can be operated at leading PF to supply reactive power to the system.

[!TIP] Exam Focus: Always remember: Capacitor rating (kVAR) depends on real power (kW) and the change in tangent of the power factor angle.

D. Motors and Drives

1. Energy Efficient Motors (IE Standards)

• Standards: IEC 60034-30, IS 12615. Efficiency classes: IE1 (Standard), IE2 (High Efficiency), IE3 (Premium Efficiency), IE4 (Super Premium).

• Features vs Standard Motors:

  • Higher grade steel (thin laminations, lower core loss).

  • More copper in stator windings (lower $$\displaystyle I^2R $$ loss).

  • Optimized design (longer air gap, better cooling).

  • Better bearings (lower friction loss).

  • Result: 2-8% higher efficiency, especially at partial loads. Higher initial cost, lower operating cost.

2. Variable Speed Drives (VSD) - Types and Energy Savings

• Types:

  • VFD (Variable Frequency Drive): For AC induction/synchronous motors. Changes supply frequency to control speed. Most common.

  • VSD (Variable Speed Drive): Generic term, often synonymous with VFD.

  • VVVF (Variable Voltage Variable Frequency): Specific type of VFD.

  • DC Drive: For DC motors (armature voltage control).

• Energy Savings: For variable torque loads (fans, pumps, compressors), power is proportional to cube of speed: $$\displaystyle P \propto N^3 $$. A 20% reduction in speed can save ~50% energy. Eliminates throttling/damper losses.

3. Drive Selection: Individual vs Group Drive, Motor Selection Criteria

• Individual Drive: One motor per machine. Advantages: Flexible layout, independent control, high efficiency at partial loads, no single point failure. Disadvantages: Higher initial cost.

• Group Drive: One motor drives multiple machines via belts/shafts. Advantages: Lower initial cost, simpler control. Disadvantages: Inflexible, cannot start/stop individually, efficiency low if some machines idle, high maintenance.

• Motor Selection Criteria:

  1. Load Characteristics (constant/variable torque, duty cycle).

  2. Required Speed & Torque.

  3. Environmental Conditions (dust, moisture, hazardous area).

  4. Efficiency Class (IE2/IE3 preferred).

  5. Starting & Braking Requirements.

  6. Cost (initial vs lifetime).

4. Advantages of Electric Drives over Other Drives

• Clean, quiet, no exhaust.

• Precise speed and torque control.

• High efficiency over wide speed range (with VSD).

• Quick start/stop, fast response.

• Can be operated in all quadrants (4-quadrant operation with regenerative braking).

• Remote control and automation friendly.

• Lower maintenance than mechanical/diesel drives.

E. Demand Side Management (DSM)

1. Load Curve Analysis

• Load Curve: Graph of power demand (kW) vs. time (hour/day/season).

• Types: Daily load curve, seasonal load curve, annual load duration curve.

• Importance for Conservation:

  • Identifies peak demand periods (high cost, strain on grid).

  • Reveals base load and shape of demand.

  • Basis for designing DSM programs and time-of-use (TOU) tariffs.

  • Helps in capacity planning and reducing need for peaking plants.

2. DSM Techniques

3. Electricity Tariffs (Types & Restructuring)

• Flat Rate: Fixed charge per unit (kWh) irrespective of time. No incentive for load shifting.

• Block Rate: Different rates for different consumption blocks (slab system). Encourages conservation but not peak shifting.

• Time-of-Day (TOD) / Time-of-Use (TOU): Different rates for peak, normal, and off-peak periods. Most effective for DSM. Encourages shifting consumption to off-peak.

• Restructuring for Conservation:

  • Separate generation, transmission, distribution (unbundling).

  • Introduce competitive markets.

  • Mandate renewable purchase obligations (RPO).

  • Implement feed-in tariffs for renewables.

  • Use ancillary services markets to value flexibility.

IV. Electric Traction and Transportation Systems

A. Fundamentals of Electric Traction

1. Characteristics of a Good Traction System

• High starting torque to accelerate heavy trains quickly.

• Simple and robust speed control over a wide range.

• Ability to operate in all four quadrants (motoring and braking in both directions).

• High efficiency and regenerative braking capability.

• Good adhesion characteristics.

• Low maintenance, high reliability.

• Ability to handle overloads.

2. Suitability of DC Series Motor for Traction

• Speed-Torque Characteristic: $$\displaystyle N \propto \frac{(V - I_a R_a)}{\phi} $$; $$\displaystyle \phi \propto I_a $$ (for series motor). Therefore, $$\displaystyle N \propto \frac{V - I_a R_a}{I_a} $$. As load torque ($$\displaystyle T \propto \phi I_a \propto I_a^2 $$) increases, $$\displaystyle I_a $$ increases, speed $N$ drops sharply.

• Why Suitable:

  • High Starting Torque: At start ($$\displaystyle N=0 $$), back EMF $$\displaystyle E_b=0 $$, so $$\displaystyle I_a = V/R_a $$ (very high), and $$\displaystyle T \propto I_a^2 $$ → extremely high starting torque.

  • Automatic Speed Regulation: As load increases, speed decreases naturally, providing a "constant power" characteristic over a range.

  • Simple Speed Control: By varying voltage or using series-parallel control.

3. Speed-Time Curve (Trapezoidal)

• General Shape: Accelerating period (constant torque), constant speed period (constant power), coasting/decelerating period (braking).

• Trapezoidal Assumption: Constant acceleration ($\alpha$) and constant retardation ($\beta$) phases. Used for mainline service.

• Derivation for Maximum Speed ($$\displaystyle V_{max} $$):

  Let:

  $$\displaystyle t_1 $$ = Acceleration time, $$\displaystyle t_2 $$ = Constant speed time, $$\displaystyle t_3 $$ = Braking time.

  $$\displaystyle V_m $$ = Maximum speed (km/h).

  Distance $$\displaystyle D = \text{Area under speed-time curve} $$.

  For trapezoid: $$\displaystyle D = \frac{1}{2} V_m (t_1 + t_3) + V_m t_2 $$

  Also, from kinematics: $$\displaystyle V_m = \alpha \cdot t_1 = \beta \cdot t_3 $$ (if acceleration/deceleration rates are constant).

  Solving these equations gives $$\displaystyle V_m $$ and other parameters.

4. Traction Parameter Calculations

• Acceleration/Retardation: $\alpha$ or $$\displaystyle \beta = \frac{\Delta V}{\Delta t} $$ (convert km/h to m/s: divide by 3.6).

• Distance Covered ($D$): Area under speed-time curve (in km or m).

• Speed ($V$): Read from curve or calculated from $$\displaystyle V = u + at $$.

• Specific Energy Consumption (SEC): Energy consumed per tonne-km (or per km).

$$SEC = \frac{\text{Total Energy Consumed (kWh)}}{\text{Tonnes} \times \text{Distance (km)}} \text{ (kWh/tonne-km)}$$

Includes energy for traction, auxiliary loads, and losses.

5. Electrical Braking Methods

• Regenerative Braking: Motor acts as generator. Kinetic energy → electrical energy → fed back to supply system (overhead line/third rail). Most energy-efficient.

• Rheostatic Braking: Motor acts as generator. Energy is dissipated as heat in a braking resistor (grid resistor). Used when supply system cannot accept regenerated power.

• Plugging (Reverse Current Braking): Motor connections reversed while running. Creates high opposing torque. Wastes energy as heat in motor and resistors. Used for quick stops.

6. Load Equalization in Traction

• Objective: To smooth out the heavy, fluctuating current drawn by traction motors from the supply, reducing peak demand charges and voltage dips.

• Methods:

  1. Flywheel Energy Storage: A heavy flywheel on the same shaft as the motor-generator set stores kinetic energy during light load and releases it during heavy load.

  2. Motor-Generator (MG) Set with Large Rotating Inertia: The MG set itself acts as a buffer due to its high inertia.

  3. Modern: Use of power electronics (IGBT-based inverters) and battery/supercapacitor energy storage systems for more efficient equalization.

7. Factors Affecting Specific Energy Consumption (SEC)

• Train Resistance: Friction (mechanical, rolling), air resistance (∝ V²).

• Gradient: Uphill increases energy consumption, downhill can allow regeneration.

• Acceleration & Braking Rates: Higher acceleration requires more energy. Frequent braking wastes energy (unless regenerative).

• Stop Spacing: More stops → more acceleration → higher SEC.

• Auxiliary Loads: Lighting, HVAC, compressor.

• Efficiency of Traction Motors & Drives.

• Regenerative Braking Utilization.

• Train Formation (Mass).

B. Electric and Hybrid Vehicles

1. Components of Electric Vehicles (EVs)

• Battery (Energy Storage): Li-ion most common. Provides DC power.

• Electric Motor (Traction Motor): AC induction or permanent magnet synchronous motor.

• Controller / Inverter: Converts DC from battery to AC (for AC motor) with variable frequency/voltage. Also handles regenerative braking.

• Charger: Converts AC grid supply to DC to charge battery (on-board or off-board).

• Auxiliary Battery: 12V battery for lights, electronics.

• Transmission: Often single-speed reduction gear (EV motors have wide torque-speed range).

2. Energy Conservation in Transportation

• Shift to EVs: Higher well-to-wheel efficiency (~60-70%) vs. ICE vehicles (~20-30%).

• Public Transport: Mass transit (metro, BRT) moves more people with less energy per passenger-km.

• Lightweighting: Use of composites, aluminum to reduce vehicle mass.

• Aerodynamics: Reduce drag coefficient.

• Low Rolling Resistance Tires.

• Hybridization: Combine ICE with electric drive for better fuel economy.

3. Hybrid Vehicle Types

• Series Hybrid: ICE drives only a generator. Generator powers electric motor(s) which drive wheels. Battery can assist. ICE runs at constant optimal speed.

• Parallel Hybrid: Both ICE and electric motor are mechanically connected to wheels. Can operate independently or together. More common (e.g., Toyota Prius).

• Series-Parallel (Power-Split): Combines both. Uses a planetary gear set to split power. Allows ICE to run at optimal efficiency while providing variable speed to wheels.

4. Transmission Systems in EVs

• Single-Speed Reduction Gear: Most common. Simple, efficient. EV motors have wide constant torque region.

• Multi-Speed Transmission: Emerging for high-performance/long-haul EVs to improve efficiency at very high speeds.

• Direct Drive: Motor integrated into wheel hub (in-wheel motor). Eliminates differential, but unsprung mass increases.

C. Role of Electric Drives in Improving Transportation Energy Efficiency

• Enable regenerative braking, recovering 15-30% of energy.

• Provide precise torque and speed control, optimizing motor efficiency across operating range.

• Allow engine/ICE downsizing in hybrids by providing torque assist.

• Enable engine start-stop and idle-off capabilities.

• Facilitate energy management strategies (e.g., electric-only mode at low speed).

• High efficiency of electric motors (>90%) vs. ICE (~30-40%).

V. Industrial Energy Conservation and Processes

A. Industry-Specific Energy Conservation

1. Sugar Industry

• Key Processes: Cane crushing, juice extraction, clarification, evaporation, crystallization, centrifugation, bagasse (fiber) handling.

• Conservation Measures:

  • Bagasse Cogeneration: Use bagasse (primary fuel) in high-efficiency boilers (30-40 bar, 400°C+) with steam turbines for co-generation (back pressure or extraction-condensing). Export surplus power.

  • Efficient Juice Heaters & Evaporators: Multiple-effect evaporation, vapor recompression.

  • Optimize Cane Preparation & Milling: Reduce fiber content in juice.

  • Waste Heat Recovery: From flue gases (economizer), condenser cooling water.

  • Motor Efficiency: Use IE3 motors, VFDs on pumps/fans.

  • Process Control: Automate to minimize steam/energy consumption.

2. Textile Industry

• Key Processes: Spinning (ring, open-end), weaving, dyeing, printing, finishing.

• Conservation Measures:

  • Spinning/Weaving: Use efficient motors (IE3), VFDs on compressors, optimize ring frame speeds, recover waste heat from stenter.

  • Dyeing & Finishing (Major Energy User):

    • Use heat recovery from dye bath exhaust (heat exchangers).

    • Optimize steam pressure and temperature profiles.

    • Use direct/indirect fire heaters with high efficiency.

    • Recover heat from condensate (return to boiler).

    • Use low-liquor ratio dyeing machines.

    • Daylighting in large sheds.

3. Cement Industry

• Key Processes: Raw material preparation, clinker production (kiln), finish grinding.

• Conservation Measures:

  • Preheater & Precalciner: Use waste heat from kiln exhaust to preheat/carbonate raw meal before kiln. Major saver.

  • Kiln Optimization: Maintain stable coating, minimize air leakage, optimize burner.

  • Grinding: Use high-efficiency separators (e.g., roller press, V-separator), pre-grinding.

  • Waste Heat Recovery (WHR): Install WHR boilers on kiln preheater and cooler exhaust gases to generate power.

  • Alternative Fuels: Use waste-derived fuels (TDF, RDF) to replace coal.

  • Variable Speed Drives on fans and mills.

4. Utilization of Agriculture Waste for Energy

• Biomass: Crop residues (straw, husk), bagasse, animal dung.

  • Direct Combustion: In boilers for steam/heat (e.g., rice husk boiler).

  • Biogas: Anaerobic digestion of dung, crop residue → methane → used in engines for power/heat.

  • Bioethanol/Biodiesel: From sugarcane/molasses, oilseeds.

• Benefits: Reduces fossil fuel use, manages waste disposal, provides rural energy/income, carbon neutral (sustainable cycle).

B. Material and Energy Balance

• Purpose: Account for all inputs and outputs in a process to quantify losses and identify inefficiencies.

• Load Energy Balance Diagram: Sankey diagram showing energy inputs (fuel, electricity) and outputs (useful work, heat losses, radiation, exhaust). Width of arrow ∝ energy quantity.

• Material Load Energy Balance Diagram: Combines material flow (mass balance) with associated energy flows. Shows where energy is used in material transformation.

• Energy Flow Networks: System-level diagram showing energy sources, conversion devices (boilers, turbines, motors), distribution, and end-uses. Helps identify major loss points.

C. Welding and Electrolysis

1. Classification of Welding Methods

2. Welding Transformers

• Purpose: Step-down transformer to provide high current (100-600A), low voltage (15-45V) for arc welding.

• Characteristics:

  • High current, low voltage secondary.

  • Drooping Characteristic: Voltage decreases as current increases (stable arc).

  • Portable, rugged.

• Types:

  • Rectifier Type (Most Common): AC input → rectifier → DC output. Better arc stability, no magnetic losses.

  • Transformer-Rectifier: Transformer + rectifier.

  • Inverter Type: High-frequency AC → step-down → rectify. Lightweight, energy efficient.

3. Electrolysis & Faraday's Laws

• Faraday's First Law: The mass ($m$) of substance deposited/liberated at an electrode is directly proportional to the quantity of electricity ($Q$) passed.

$$m = Z \cdot Q$$

Where $Z$ = Electrochemical Equivalent (kg/Coulomb or g/A-hr).

• Faraday's Second Law: For same quantity of electricity, masses of different substances deposited are proportional to their chemical equivalent weights ($E$).

$$\frac{m_1}{m_2} = \frac{E_1}{E_2}$$

• Quantity of Electricity: $$\displaystyle Q = I \cdot t $$ (Amperes × seconds).

4. Electroplating

• Purpose: To deposit a thin layer of metal (e.g., Cr, Ni, Zn, Au) on a substrate (workpiece) for:

  • Corrosion resistance.

  • Improved appearance (aesthetics).

  • Wear resistance.

  • Better electrical conductivity.

• Process: Workpiece as cathode, metal to be plated as anode, electrolyte containing metal ions. DC current passed.

5. Numerical Problems (Weight Deposition)

• Using ECE: $$\displaystyle m = Z \times I \times t $$

  • $$\displaystyle Z = \frac{E}{F} $$ (F = Faraday constant = 96500 C/mol or 26.8 A-hr/mol).

  • $E$ = Equivalent weight = Atomic Weight / Valency.

• Example (Given): Gold (Au, At. Wt. = 197, Valency = 3). $$\displaystyle E = 197/3 = 65.67 $$. $$\displaystyle Z = 65.67 / 96500 = 6.81 \times 10^{-4} $$ g/C. $$\displaystyle I=3A $$, $$\displaystyle t=30 \times 3600 = 108000 $$ s.

  $$\displaystyle m = (6.81 \times 10^{-4}) \times 3 \times 108000 = 220.5 $$ grams.

D. Lubrication and Tribological Innovations for Energy Efficiency

• Role of Lubrication: Reduces friction and wear between moving surfaces. Friction consumes ~20-30% of world's energy.

• Energy-Efficient Lubricants:

  • Synthetic Oils: Lower friction coefficient, stable viscosity over temperature range, longer life.

  • Solid Lubricants (Graphite, Molybdenum Disulfide): For extreme conditions, reduce friction further.

  • Nanoparticle Additives: Enhance film strength, reduce wear.

• Innovations:

  • Low-Friction Coatings (DLC - Diamond-Like Carbon).

  • Textured Surfaces: Micro-dimples on surfaces to trap lubricant.

  • Active Magnetic Bearings: Eliminate mechanical contact → near-zero friction.

  • Condition-Based Lubrication: Apply lubricant only when/where needed (vs. continuous flooding).

• Impact: Reducing friction by 1% in industrial processes can save significant energy. Proper lubrication maintenance is a key low-cost ECM.

VI. Project Evaluation and Economic Analysis

A. Project Evaluation Methods

1. Payback Period (PBP)

• Simple Payback Period (SPP): Time required for cumulative net savings to equal initial investment.

$$SPP = \frac{\text{Initial Investment (₹)}}{\text{Annual Net Savings (₹/yr)}}$$

*Ignores time value of money, salvage value, and post-payback benefits.*

• Discounted Payback Period (DPP): Time required for cumulative discounted net savings to equal initial investment. Uses discount rate (cost of capital). More accurate.

2. Depreciation

• Purpose: Allocate cost of capital asset over its useful life for accounting/tax purposes.

• Straight Line Method (SLM):

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

*Equal depreciation charge each year.*

• Written Down Value Method (WDV) / Declining Balance:

$$\text{Depreciation for year } n = \text{WDV}_{n-1} \times d$$

Where $d$ = fixed depreciation rate. WDV decreases each year.

*Higher depreciation in early years, tax benefit earlier.*

3. Cost-Benefit-Risk Analysis (Including Inflation Risk)

• Cost-Benefit Analysis (CBA): Compare present value of all benefits (savings) with present value of all costs (investment, O&M). Use Net Present Value (NPV) or Benefit-Cost Ratio (BCR).

$$NPV = \sum_{t=1}^{n} \frac{B_t - C_t}{(1+r)^t} - I_0$$

Where $r$ = discount rate, $$\displaystyle I_0 $$ = initial investment.

*Accept if NPV > 0.*

• Risk Analysis:

  • Sensitivity Analysis: Vary key assumptions (energy savings, fuel cost escalation, discount rate) to see impact on NPV/PBP.

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

  • Inflation Risk: Future energy/fuel prices may escalate faster than general inflation. Use real discount rate ($$\displaystyle r_{real} = \frac{1+r_{nominal}}{1+i} - 1 $$, where $i$ = inflation rate) or escalate cash flows by expected fuel price inflation.

B. Financial Considerations for Energy Conservation Projects

• Initial Investment: Cost of equipment, installation, commissioning.

• Operating & Maintenance (O&M) Costs: Annual costs for maintenance, spare parts, labor.

• Energy Cost Savings: Primary benefit. Must be realistic (use measured data or validated models).

• Non-Energy Benefits: Improved productivity, reduced maintenance, better product quality, reduced emissions (carbon credits), improved comfort/safety.

• Financing Options: Internal funds, loans, energy service company (ESCO) contracts (performance-based).

• Incentives: Government subsidies, tax holidays, accelerated depreciation, soft loans.

VII. Advanced Tools and Techniques

A. Simulation and Modeling in Energy Management

• Purpose: To predict energy performance of systems/buildings/processes before implementation, and to optimize operations.

• Tools:

  • Building Energy Simulation: e.g., EnergyPlus, eQUEST, DesignBuilder. Model HVAC, lighting, envelope.

  • Process Simulation: e.g., Aspen Plus, HYSYS. Model industrial processes for heat integration.

  • System Dynamics: Model complex feedback loops in energy systems.

  • Computational Fluid Dynamics (CFD): Model fluid flow, heat transfer for design optimization.

• Benefits: Evaluate ECMs virtually, optimize design, reduce risk, support decision-making.

B. Matrix Charts for Energy Problem Analysis

• Purpose: Visual tool to prioritize problems/opportunities based on impact (energy savings potential) and ease of implementation (cost, complexity).

• Structure: 2x2 or 3x3 matrix.

  • X-axis: Ease of Implementation (Easy → Difficult).

  • Y-axis: Potential Impact/Savings (Low → High).

• Quadrants:

  • Quick Wins (High Impact, Easy): Implement first (e.g., housekeeping, lighting retrofit).

  • Major Projects (High Impact, Difficult): Require detailed study, capital investment (e.g., cogeneration, plant upgrade).

  • Fill-ins (Low Impact, Easy): Do if resources permit.

  • Reconsider (Low Impact, Difficult): Usually avoid.

• Use: During audit reporting to management for prioritization.

C. Energy Auditing Software and Instruments (Overview)

• Software:

  • Audit Management: e.g., ENERGY STAR Portfolio Manager, CIBSE TM54 tools.

  • Data Logging & Analysis: e.g., HOBOware, DASYLab.

  • Lighting Design: e.g., DIALux, AGi32.

  • HVAC Simulation: e.g., HAP (Hourly Analysis Program), TRACE 700.

  • Industrial Processes: e.g., Pinch Analysis software for heat integration.

• Instruments (as detailed in Section I.D): Power analyzers, thermographic cameras, data loggers, flow meters, anemometers, gas analyzers. Integration with software for automated data collection and analysis is key.

END OF UNIT 2 NOTES