Energy Conservation, Management & Audit (ME-803 (B)) - Unit 4 Short Notes

UNIT 4: ENERGY CONSERVATION, MANAGEMENT & AUDIT

I. FUNDAMENTALS & CONCEPTS

Energy Conservation vs. Energy Efficiency

[!TIP] Exam Focus: Questions often ask for distinction with examples. Use a table for clarity.

Key Terminology

• Energy Benchmarking: Comparing a facility's energy performance against a standard (e.g., SEC – Specific Energy Consumption) or similar facilities.

• Energy Cost: Total expenditure on energy purchases (electricity, fuel) including demand charges, energy charges, and penalties.

• Energy Performance: Measurable results related to energy efficiency, use, and consumption (e.g., kWh/tonne of product).

Basic Principles of Energy Policy & Planning

• Policy: Set national/industrial goals, regulations (e.g., EC Act 2001), incentives.

• Planning:

  1. Data Collection: Baseline energy use.

  2. Target Setting: Based on benchmarks.

  3. Action Plan: Identify Conservation Opportunities (ECOs).

  4. Implementation & Monitoring.

II. ENERGY AUDIT METHODOLOGY & PROCESS

Types of Energy Audits

Ten-Step Methodology for Detailed Energy Audit

1. Planning & Organizing: Define scope, team, schedule.

2. Pre-Audit Data Review: Collect past energy bills, process data.

3. Pre-Audit Walk-through: Identify major energy uses, preliminary ECOs.

4. Detailed Data Collection: Measure energy flows, process parameters.

5. Material & Energy Balance: Quantify inputs/outputs, losses.

6. Data Analysis: Identify deviations, inefficiencies.

7. ECO Identification & Evaluation: List, quantify savings, costs.

8. Report Preparation: Document findings, recommendations.

9. Management Presentation: Discuss report, secure commitment.

10. Implementation & Follow-up: Execute ECOs, monitor savings.

[!TIP] Exam Focus: "Describe ten-step methodology" is a frequent 8-mark question. Memorize the sequence.

Pre-Audit Phase: Focus Areas & Activities

• Focus Areas: Major energy-consuming equipment (boilers, motors, HVAC), utility areas, process flows.

• Activities:

  • Collect 12-24 months of energy bills (electricity, fuel).

  • Obtain process flow diagrams (PFD), single-line diagrams (SLD).

  • Identify operating schedules, production data.

  • Preliminary walk-through to spot glaring inefficiencies.

Post-Audit Activities

• Reporting & Documentation: Detailed audit report with:

  • Executive summary.

  • Current energy performance.

  • List of ECOs with investment, savings, payback.

  • Implementation roadmap.

• Monitoring, Targeting & Reporting (MTR):

  • Monitoring: Continuous tracking of energy consumption (via EMIS).

  • Targeting: Setting progressive reduction goals.

  • Reporting: Regular performance reports against targets.

• Energy Management Information System (EMIS): Integrated hardware/software for real-time data acquisition, storage, analysis, and reporting of energy metrics.

Data & Information Analysis Techniques

• Material & Energy Balance: Fundamental accounting tool.

  • General Form: Input = Output + Accumulation + Losses

  • For steady-state (no accumulation): Input = Output + Losses

• Example Problem (Mixing - Jun 2025):

  A 10% solids solution (Stream A, 5 kg/s) is mixed with a 25% solids solution (Stream B, unknown rate F_B). The mixed output (Stream C) is 20% solids. No accumulation.

  Solution:

  Material balance on solids:

$$0.10 \times 5 + 0.25 \times F_B = 0.20 \times (5 + F_B)$$

$$0.5 + 0.25F_B = 1 + 0.20F_B$$

$$0.05F_B = 0.5 \Rightarrow F_B = 10 \ \text{kg/s}$$

\boxed{F_B = 10 \ \text{kg/s}, \ \text{Output} = 15 \ \text{kg/s}}

CUSUM Analysis

• Cumulative Sum (CUSUM): Statistical technique to detect small shifts in process mean (e.g., energy consumption per unit).

• Steps:

  1. Collect sequential data (e.g., daily SEC).

  2. Calculate deviation from target/reference: Deviation = Actual - Target.

  3. Compute cumulative sum: CUSUM_i = CUSUM_{i-1} + Deviation_i.

  4. Plot CUSUM vs. time. A sustained slope indicates a shift.

• Application: Identify when a process becomes less efficient (e.g., after maintenance, fouling).

III. REGULATORY FRAMEWORK & POLICY INSTRUMENTS

Energy Conservation Act, 2001 (Key Highlights)

• Objective: Promote energy efficiency, conservation.

• Key Provisions:

  • Designated Consumers (large industries) must conduct energy audits, appoint Energy Managers.

  • Energy Conservation Building Code (ECBC) for commercial buildings.

  • Standards & Labeling for appliances.

  • Bureau of Energy Efficiency (BEE) as statutory body.

• Distribution of Powers: Central Govt. (BEE) → State Govt. (State Designated Agency).

• Roles: Energy Managers (certified by BEE) oversee compliance, audits, reporting.

Market-Based Mechanisms

• Availability-Based Tariff (ABT):

  • Rationale: Incentivize grid discipline, manage variability (especially renewables).

  • Mechanism: Electricity tariff varies by time-block (Day, Evening, Night, Morning) based on grid availability & load. Unscheduled Interchange (UI) charges for deviation from schedule.

  • Benefit: Encourages consumers to shift load to low-tariff periods, improves grid stability.

• Renewable Purchase Obligation (RPO):

  • Definition: Mandatory purchase of a specified percentage of electricity from renewable sources by distribution licensees & captive users.

  • Compliance Methods:

    1. Direct purchase of renewable power (solar, wind, biomass).

    2. Purchase of Renewable Energy Certificates (RECs) from renewable generators.

    3. Solar RECs separate from non-solar RECs.

[!TIP] Exam Focus: ABT and RPO are high-frequency 6-mark questions. Understand the "why" and "how".

IV. ENERGY AUDIT INSTRUMENTS & ANALYTICAL TOOLS

Common Energy Audit Instruments (List)

• Power Quality Analyzer

• Flue Gas Analyzer (O₂, CO, CO₂, stack temp)

• Infrared Thermometer / Camera

• Stroboscope (Tachometer)

• Clamp-on Power Meter

• Lux Meter

• Anemometer

• Pressure Gauges, Thermocouples

• Ultrasonic Flow Meter

Detailed Study of Specific Instruments

1. Infrared Thermometer (Non-contact):

   • Principle: Measures infrared radiation emitted by a surface to infer temperature.

   • Application in Audit: Detect thermal leaks (insulation failure), overheating equipment (electrical connections, bearings), steam trap failures.

   • Key Parameter: Emissivity setting (material-dependent).

2. Stroboscope (Tachometer):

   • Principle: Flashes light at adjustable frequency. When flash rate matches rotational speed, object appears stationary.

   • Application: Measure RPM of rotating machinery (motors, fans, pumps) without contact.

   • Use: Verify actual speed vs. rated speed; assess loading.

Energy Flow Visualization: Sankey Diagram

• Definition: Flow diagram where arrow width is proportional to energy quantity.

• Construction:

  1. Identify main energy inputs (fuel, electricity).

  2. Map useful output, losses (waste heat, radiation, friction).

  3. Draw arrows from input to outputs/losses, scaling widths.

• Interpretation: Visually pinpoints largest losses → priority for ECOs.

• Example: Boiler Sankey shows major loss via flue gas → focus on economizer/air preheater.

Statistical Monitoring: CUSUM Analysis

• Steps (Recap):

  1. Define baseline/target metric (e.g., kWh/tonne).

  2. For each period i, compute Deviation_i = Actual_i - Target.

  3. CUSUM_i = CUSUM_{i-1} + Deviation_i (with CUSUM_0 = 0).

  4. Plot. V-mask or tabulation used to detect significant shifts.

• Application in Energy Management: Monitor performance of a system (e.g., chiller plant) after an ECO implementation to confirm sustained savings.

V. THERMAL ENERGY SYSTEMS

A. Boilers and Steam Systems

• Boiler Performance Metrics:

  • Efficiency (η): Ratio of heat output (steam) to heat input (fuel). η = (Heat Output / Heat Input) × 100%.

  • Evaporation Ratio (ER): kg of steam generated per kg of fuel consumed. ER = (Steam output) / (Fuel consumed).

  • Relation: η ∝ ER but depends on steam parameters (pressure, enthalpy). Higher ER/η indicates better performance.

• Direct Testing Method (Boiler Efficiency):

  • Principle: Measure all inputs (fuel, air) and outputs (steam, flue gas, losses) over a period.

  • Flow Chart:

    
    Fuel → Boiler → Steam (Output)
    
                ↓
    
            Flue Gas → Stack (Loss)
    
                ↓
    
            Ash/Slag (Loss)
    
    

  • Key Measurements: Fuel flow/calorific value, steam flow/pressure/temperature, flue gas temp/O₂%, ambient conditions.

  • Formula (Input-Output Method):

$$\eta = \frac{m_s (h_s - h_w)}{m_f \times CV_f} \times 100\%$$

where `m_s`= steam mass flow, `h_s`= steam enthalpy, `h_w`= feedwater enthalpy, `m_f`= fuel mass flow, `CV_f`= fuel calorific value.

• Steam Traps (Thermostatic Type Operation):

  • Function: Discharge condensate & air while retaining steam.

  • Thermostatic Trap (e.g., Bimetallic): Uses temperature difference. Condensate cools a bimetallic element → valve opens. Steam heats element → valve closes.

• Steam Turbines (Energy Conservation):

  • Opportunities: Improve steam parameters (higher pressure/temp), reduce throttling, optimize exhaust pressure, prevent leakage, regular maintenance.

• Waste Heat Recovery (WHR):

  • Direct Benefits: Reduced fuel consumption, lower emissions.

  • Indirect Benefits: Reduced equipment size (for same output), increased capacity, improved process control.

  • Systems: Economizers (feedwater heating), Air Preheaters (combustion air heating), Waste Heat Boilers (generate steam from exhaust), Heat Pipes.

B. Insulation and Heat Transfer

• Principles: Reduce heat transfer (conduction, convection, radiation) across surfaces.

  • Fourier's Law (Conduction): Q = k A (ΔT / d)

  • Insulation increases thermal resistance R = d/k.

• Importance: Minimize losses from hot/cold surfaces → energy saving, safety, process stability.

• Five Insulation Materials with Specifications:

  1. Mineral Wool: k ≈ 0.03-0.04 W/m·K, temp. up to 250°C, fire-resistant.

  2. Calcium Silicate: k ≈ 0.06-0.07 W/m·K, temp. up to 650°C, rigid.

  3. Ceramic Fiber: k ≈ 0.1-0.2 W/m·K, temp. up to 1200°C, lightweight.

  4. Expanded Polystyrene (EPS): k ≈ 0.03-0.04 W/m·K, temp. up to 75°C, for cold insulation.

  5. Elastomeric Foam (Rubber): k ≈ 0.03-0.04 W/m·K, temp. -50°C to 100°C, flexible, vapor barrier.

C. Combustion and Solar Thermal

• Fluidized Bed Combustion (FBC):

  • Definition: Fuel burned in a bed of inert material (sand) fluidized by air jet.

  • Applications: Efficient combustion of low-grade fuels (coal fines, biomass, waste), in-situ SO₂ capture (with limestone), lower NOₓ.

• Solar Water Heaters (Energy Enhancement):

  • Techniques:

    1. Increase collector area.

    2. Use selective coating (high absorptivity, low emissivity).

    3. Reduce heat loss (better insulation, vacuum tubes).

    4. Optimize tilt angle for latitude.

    5. Use forced circulation (pump) for better heat transfer.

D. Thermal Calculations (Heat Balance)

• Heat Balance Problem (Furnace Cooling - Jun 2025):

  Furnace shell: m = 2 tonnes = 2000 kg, C = 0.2 kcal/(kg·°C), cool from 90°C to 55°C. Water inlet 28°C, max ΔT = 5°C. Neglect losses.

  Solution:

  Heat to be removed from shell:

$$Q = m C \Delta T = 2000 \times 0.2 \times (90 - 55) = 2000 \times 0.2 \times 35 = 14000 \ \text{kcal}$$

Heat absorbed by water:

$$Q = m_w C_w \Delta T_w$$

where C_w = 1 kcal/(kg·°C), ΔT_w = 5°C.

$$m_w = \frac{Q}{C_w \Delta T_w} = \frac{14000}{1 \times 5} = 2800 \ \text{kg}$$

\boxed{m_w = 2800 \ \text{kg} \ \text{or} \ 2.8 \ \text{tonnes}}

VI. ELECTRICAL SYSTEMS & MOTOR MANAGEMENT

A. Electric Motors

• Energy Efficient Motors (EEMs):

  • Higher grade materials (thin laminations, larger copper conductors).

  • Optimized design (air gap, cooling) → lower losses, higher efficiency (often IE3/IE4 class).

• Motor Loading & Efficiency:

  • Efficiency peaks at ~75-100% of rated load. Low loading (<50%) drastically reduces efficiency due to constant core/ friction losses.

• Energy Management Opportunities:

  1. Right-sizing (avoid oversized motors).

  2. Use EEMs for long-run motors.

  3. Improve power factor (reduce I²R losses in supply).

  4. Regular maintenance (bearing lubrication, alignment).

  5. Use VFDs for variable speed loads.

• Five Power Loss Areas & Improvement Measures:

  | Loss Area | Cause | Improvement Measure | |---------------------|------------------------------------|---------------------------------------------| | Stator Loss (I²R) | Resistance in windings. | Use higher conductivity copper, larger cross-section. | | Rotor Loss (I²R) | Resistance in rotor bars. | Use better conductive material (copper), optimized design. | | Core Loss | Hysteresis & Eddy currents in core.| Use thin, high-grade silicon steel laminations. | | Friction & Windage | Bearing friction, air drag. | High-quality bearings, optimized cooling fan design. | | Stray Load Loss | Harmonic fluxes, imperfections. | Improved manufacturing, design optimization. |

B. Power System Optimization

• Power Factor (PF): PF = cos φ = P / (V I) (Real Power / Apparent Power).

• Effects of Low PF:

  • Higher current for same power → increased I²R losses in cables/transformers.

  • Reduced system capacity (transformers, cables).

  • Voltage drop, poor voltage regulation.

  • Penalty charges from utility.

• Correction Methods:

  • Static Capacitors: Install near inductive loads (motors). KVAR required:

$$Q = P \left( \tan \phi_1 - \tan \phi_2 \right)$$

where `P` = real power (kW), `φ₁` = initial angle, `φ₂` = target angle.

• Synchronous Condensers: Over-excited synchronous motors.

• Phase Advancers: For induction motors.

• Incentive Structures: Many utilities offer rebates for PF > 0.95 or penalize PF < 0.9.

• Maximum Demand (MD):

  • Concept: Highest average power (kW or kVA) consumed in a defined period (e.g., 15-min or 30-min block).

  • Importance: Determines demand charge (Rs./kVA/month) → major cost component. Contract demand is agreed maximum.

• Control Methods:

  1. Load Scheduling: Shift non-essential loads to off-peak.

  2. Use of UPS/Batteries: Supply peak loads from stored energy.

  3. Demand Controller: Automatically sheds loads when approaching MD.

  4. Install High-efficiency equipment to reduce overall demand.

[!TIP] Exam Focus: The May 2023 paper had a 14-mark complex problem on PF correction with incentives and MD charges. Master the formula and incentive calculation logic.

C. Lighting and Pump Systems

• Lighting Systems: Five Conservation Measures:

  1. Replace incandescent/fluorescent with LEDs.

  2. Use occupancy sensors (auto on/off).

  3. Daylight harvesting with photo sensors.

  4. Regular cleaning of fixtures/lenses.

  5. Right-sizing illumination levels (avoid over-lighting).

• Pump Systems:

  • Head-Flow Characteristics: Pump provides head H vs. flow Q. Affinity Laws:

$$Q \propto N, \ H \propto N^2, \ P \propto N^3$$

where `N` = speed.

• System Resistance Curve: Total head required = Static Head + Friction Loss (∝ Q²).

• Sketch: Plot H_pump vs Q (downward curve) and H_system vs Q (upward parabola). Intersection = Operating Point.

• Energy Saving: Reduce speed via VFD if system allows (shift operating point along affinity laws → P ∝ N³ gives major savings).

VII. HVAC, REFRIGERATION & TRANSPORTATION

HVAC Systems: Energy Conservation Tips

• Optimize temperature set-points (summer: 24-26°C, winter: 20-22°C).

• Regular maintenance (coil cleaning, filter replacement).

• Use heat recovery (waste heat from exhaust to pre-heat/cool).

• Zoning & VAV (Variable Air Volume) systems.

• Improve building envelope (insulation, shading).

Air Conditioning

• Effect of Lower Evaporator Temperature:

  • Refrigeration effect per kg increases slightly, but compressor work increases significantly (lower suction pressure → higher compression ratio).

  • Result: Coefficient of Performance (COP) decreases → higher power consumption for same cooling.

  • COP = Cooling Effect / Compressor Work.

• Domestic Energy Saving Measures:

  1. Keep doors/windows closed.

  2. Use ceiling fans with AC (allow higher set-point).

  3. Clean filters monthly.

  4. Use "dry" mode in humid conditions (more efficient than "cool").

  5. Avoid direct sunlight on outdoor unit.

Heat Pumps

• Principle: Reverse refrigeration cycle. Extract heat from low-temperature source (ambient, ground, water) and deliver at higher temperature (for space/water heating).

• Applications: Space heating, domestic hot water, industrial process heat.

• Advantage: COP > 1 (typically 3-5) → more heat output per unit electricity than resistive heating.

Energy Conservation in Transportation

• Vehicle Level: Use fuel-efficient engines (turbocharging, direct injection), lightweight materials, low-rolling-resistance tires.

• Operational: Optimize routes, avoid idling, maintain correct tire pressure.

• Modal Shift: Promote public transport, rail/water over road for freight.

• Alternative Fuels: EVs, CNG, biofuels, hydrogen.

VIII. FINANCIAL ANALYSIS & ECONOMIC EVALUATION

Simple Payback Period (SPP)

• Concept: Time required for cumulative savings to equal initial investment.

• Calculation:

$$\text{SPP} = \frac{\text{Initial Investment}}{\text{Annual Net Savings}}$$

• Example (May 2023):

  Investment = Rs. 75 lakhs, Annual O&M = Rs. 5 lakhs, Annual Savings = Rs. 30 lakhs.

  Annual Net Savings = 30 - 5 = Rs. 25 lakhs.

$$\text{SPP} = \frac{75}{25} = 3 \ \text{years}$$

\boxed{\text{SPP} = 3 \ \text{years}}

Net Present Value (NPV) vs. Payback Period

Energy Cost Concepts & Incentive Structures

• Energy Cost Components:

  • Fixed Charges: Demand charge (Rs./kVA/month), service charge.

  • Variable Charges: Energy charge (Rs./kWh), fuel surcharge.

  • Penalties: Low PF, exceeding MD.

  • Incentives: High PF, time-of-day (TOD) consumption in off-peak.

• Incentive Example (from May 2023 problem):

  Incentive: 0.5% reduction in energy charge component for every 0.01 increase in PF over 0.95.

  If PF improved to 1.0 (increase of 0.05), incentive = 5 × 0.5% = 2.5% reduction in energy charge.

IX. MANAGEMENT TOOLS & IMPLEMENTATION STRATEGIES

Force Field Analysis

• Concept (Lewin): Any change is driven by Driving Forces (promote change) and restrained by Restraining Forces (oppose change). Equilibrium must be shifted.

• Application in Energy Management:

  1. Identify proposed ECO (e.g., install VFDs).

  2. List all driving forces (energy cost savings, policy compliance) and restraining forces (capital cost, downtime, resistance).

  3. Score strength of each force (e.g., 1-5).

  4. Strategy: Strengthen drivers, weaken/mitigate restrainers (e.g., training, phased implementation, demonstration).

Sensitivity and Risk Analysis

• Sensitivity Analysis: Determines how output (e.g., NPV, payback) changes with variation in input (e.g., energy savings, fuel cost, discount rate).

  • Method: Vary one parameter at a time (e.g., savings ±10%, ±20%) and recalculate NPV. Identify critical variables.

• Risk Analysis: Quantifies probability of adverse outcomes.

  • Methods: Monte Carlo simulation (probabilistic inputs), scenario analysis (best/worst/base cases).

  • Purpose: Assess robustness of ECOs, prepare contingency plans.

Building Energy Management (BEM) Systems

• Definition: Computer-based system (subset of BMS) focused on monitoring, controlling, and optimizing energy use in buildings.

• Functions:

  • Real-time monitoring of HVAC, lighting, plug loads.

  • Automated scheduling (HVAC on/off).

  • Alarm for abnormal consumption.

  • Data logging for MTR and verification.

  • Integration with EMIS.

END OF UNIT 4 NOTES
Aligned with RGPV ME-803(B) past papers (Jun 2025, May 2024, May 2023).