Hybrid &Electrical Vehicles (EX-703 (A)) - Unit 2 Short Notes

UNIT 2: ENERGY AUDIT AND MANAGEMENT - SHORT NOTES

1. FUNDAMENTALS OF ENERGY MANAGEMENT & AUDITING

Energy Management Concepts

• Definition: The proactive, organized, and systematic coordination of procurement, conversion, distribution, and use of energy to meet the requirements of an organization with the goal of minimizing energy costs and environmental impact.

• Objectives:

  • Reduce energy costs and wastage.

  • Improve operational efficiency.

  • Ensure energy security and reliability.

  • Minimize environmental footprint (reduce GHG emissions).

• Managerial Functions (PODSCORB):

  • Plan: Set energy policy, targets, and action plans.

  • Organize: Structure the energy management team and define roles.

  • Staff: Recruit and train personnel (Energy Manager, auditors).

  • Direct: Implement energy-saving projects and monitor progress.

  • Control: Measure, report, and correct deviations from targets.

  • Coordinate & Budget: Integrate activities and allocate resources.

• Role of Energy Manager:

  • Develop and implement energy policy.

  • Conduct/coordinate energy audits.

  • Analyze energy data and identify savings.

  • Prepare feasibility reports and manage projects.

  • Ensure compliance with regulations (BEE).

  • Promote energy awareness among staff.

Energy Audit

• Definition: A systematic procedure to evaluate an organization's energy consumption, identify areas of energy wastage, and recommend measures for improving energy efficiency. It is the "detective work" of energy management.

• Need & Benefits:

  • Identifies cost-saving opportunities.

  • Improves process/product efficiency.

  • Reduces environmental impact.

  • Enhances competitiveness and ensures regulatory compliance.

• Types of Energy Audit (Key Distinction):

• Steps for Conducting an Energy Audit:

  1. Planning & Preparation: Define scope, assemble team, collect historical data (bills, production).

  2. Data Collection (On-site): Measure energy flows (V, I, PF, flow, temp, pressure), inventory equipment, map processes.

  3. Data Analysis: Calculate baseline consumption, perform energy balance, identify losses & ESOs (Energy Saving Opportunities).

  4. Evaluation & Reporting: Quantify savings (energy, cost, CO₂), prioritize ESOs, prepare audit report with action plan.

  5. Implementation & Follow-up: Present to management, secure funding, implement projects, monitor savings.

• Barriers & Elimination:

  • Lack of Awareness/Motivation: Conduct training, demonstrate quick wins, top management commitment.

  • Financial Constraints: Highlight Life Cycle Cost (LCC), seek ESCO/soft loans.

  • Technical Complexity: Use expert auditors, standardized procedures.

  • Data Unavailability: Install sub-meters, maintain proper logs.

Environmental Aspects

• Energy Consumption (Fossil Fuels): Air pollution (SOx, NOx, PM), GHG emissions (CO₂, CH₄), water pollution, land degradation, resource depletion.

• Renewable Energy Sources:

  • Solar PV/Wind: Low operational emissions, but manufacturing impacts (silicon, rare earths), land use, visual impact, intermittency.

  • Biomass: Can be carbon-neutral if sustainably sourced, but air pollution (particulates), land-use competition.

  • Hydro: Alters ecosystems, displaces communities, methane from reservoirs.

• Systematic Environmental Assessment: Life Cycle Assessment (LCA) – evaluates environmental impacts from "cradle-to-grave" (raw material extraction → manufacturing → use → disposal).

[!TIP] Exam Focus: Be ready to compare fossil vs. renewable environmental impacts and explain LCA steps.

2. ELECTRICAL SYSTEMS & POWER QUALITY

Power Factor (PF) Improvement

• Definition: PF = Real Power (kW) / Apparent Power (kVA). It measures how effectively electrical power is used. Lagging PF indicates inductive loads (motors).

• Disadvantages of Low PF:

  • Higher current for same kW → Increased I²R losses in conductors & transformers.

  • Larger kVA demand → Higher fixed demand charges.

  • Voltage drop → Poor voltage regulation, reduced motor torque.

  • Overloaded utility infrastructure.

• Methods: Installation of Shunt Capacitors (most common), Synchronous Condensers, Phase Advancers.

• Calculation Problems (Standard Approach):

Problem Type 1: Required kVAr for PF improvement.

Given: Initial PF = cosθ₁, Target PF = cosθ₂, Real Power (P) in kW.

Steps:

1. θ₁ = cos⁻¹(cosθ₁), θ₂ = cos⁻¹(cosθ₂)

2. Initial kVAr = P × tanθ₁

3. Target kVAr = P × tanθ₂

4. Required Capacitor kVAr = P (tanθ₁ - tanθ₂)

Problem Type 2: New kVA demand after correction.

Given: Initial kVA = S₁, Initial PF = cosθ₁, Target PF = cosθ₂.

Steps:

1. P = S₁ × cosθ₁ (constant real power)

2. New kVA (S₂) = P / cosθ₂ = (S₁ × cosθ₁) / cosθ₂

Problem Type 3: Penalty Calculation.

Given: Max Demand (MD) in kVA, Avg PF, Min PF, Penalty per % dip.

Steps:

1. Calculate % dip = (Min PF - Avg PF) × 100

2. If % dip > 0, Penalty = % dip × Penalty Rate

• Location of Capacitor Banks (Best to Worst from Conservation View):

  1. At Motor Terminals: Reduces current in entire upstream circuit (most effective).

  2. At Distribution Boards/Sub-busbars: Saves energy in feeder circuits.

  3. At Main Busbar/Utility Point: Only reduces utility kVA demand, not internal distribution losses.

Harmonics

• Generation: Caused by non-linear loads that draw current in non-sinusoidal pulses. Examples:

  • Rectifiers/AC-DC drives (UPS, battery chargers, VFDs): Draw current in pulses near voltage peaks.

  • Arc furnaces, fluorescent lamps with magnetic ballasts.

  • Switched-mode power supplies (computers, TVs).

• Major Problems:

  • Additional Heating: In motors (core losses), transformers (eddy currents), capacitors (dielectric loss) → insulation failure.

  • Resonance: Harmonic frequencies coincide with system natural frequency → voltage/current magnification.

  • Malfunction: Sensitive electronics (PLC, meters), protective relays misoperate.

  • Torque Pulsations: In motors → vibration, noise.

  • Neutral Overloading: In 3-phase, 4-wire systems (triplen harmonics add in neutral).

• Harmonic Distortion Evaluation:

  • Total Harmonic Distortion (THD):

$$THD = \frac{\sqrt{\sum_{n=2}^{\infty} I_n^2}}{I_1} \times 100\%$$

(for current) or similar for voltage. I₁ is fundamental component.

*   **Measurement:** Use Power Quality Analyzer (Harmonic Analyzer).

*   **Standards:** IEEE 519-2014 sets limits on THD for different voltage levels.

• Effects on Equipment:

  • Transformers: Increased copper & core losses (K-rated transformers for harmonic environments).

  • Motors: Heating, pulsating torque, audible noise.

  • Capacitors: Excessive heating, reduced life, risk of resonance. Often detuned with series reactors.

  • Meters: Erroneous readings (electromechanical meters read high, electronic may read low).

Transformers & Distribution

• Losses:

  • Core/Iron Losses (Constant): Hysteresis & Eddy currents. Reduced by using high-grade silicon steel, thinner laminations.

  • Copper Losses (Variable): I²R loss in windings. Reduced by using larger conductor cross-section.

• Minimization Strategies:

  • Select correct kVA rating (avoid under/overloading).

  • Use low-loss transformers (Amorphous core).

  • Operate near rated efficiency point (typically 50-75% load).

  • Ensure good maintenance (tight connections, clean radiators).

• HT vs. LT Systems:

  • HT (High Tension): > 1 kV (typically 11kV, 33kV). Used for transmission/distribution. Lower current → lower I²R losses, thinner conductors.

  • LT (Low Tension): ≤ 1 kV (415V, 230V). Used for final distribution. Higher current → higher losses, thicker cables.

  • Advantages/Disadvantages of Low PF: See PF section above. Disadvantage is magnified in LT systems due to higher currents.

3. THERMAL SYSTEMS & BOILERS

Boilers (Very High Priority)

• Efficiency Calculation:

  • Direct Method (Input-Output):

$$\eta_{\text{direct}} = \frac{\text{Steam Output (kcal/hr)} \times (\text{Enthalpy of Steam} - \text{Enthalpy of Feedwater})}{\text{Fuel Input (kcal/hr)}} \times 100\%$$

    *Simple, but doesn't reveal loss reasons.*

*   **Indirect Method (Loss Method):**

$$\eta_{\text{indirect}} = 100 - (\text{Sum of all % losses})$$

    **Major Losses:**

    1.  Loss due to dry flue gas (sensible heat).

    2.  Loss due to moisture in fuel & combustion air.

    3.  Loss due to unburnt carbon in ash (fly ash, bottom ash).

    4.  Loss due to incomplete combustion (CO).

    5.  Loss due to radiation & convection from boiler surface.

    *Reveals where improvements are needed.*

*   **GCV vs. NCV Basis:**

    *   **GCV (Gross Calorific Value):** Includes latent heat of vaporization in fuel moisture/hydrogen.

    *   **NCV (Net Calorific Value):** Excludes latent heat (steam not condensed).

    *   **Conversion:** 

$$\eta_{\text{NCV}} = \eta_{\text{GCV}} \times \frac{\text{NCV}}{\text{GCV}}$$

(Since NCV < GCV, efficiency on NCV basis is lower numerically).

• Performance at Part Load: Efficiency drops at very low loads (<40%) due to fixed losses (radiation, unburned fuel) being spread over less output. There's an optimal load range (usually 70-100%).

• Economical Operation (Parallel Boilers):

  • Scenario: Two identical boilers, efficiency curve known at different loads.

  • Comparison: Running both at 50% load vs. one at 100% + other at 0%.

  • Rule: Compare total fuel consumption for the required steam output. The configuration with lower total fuel input is economical.

  • Example (from paper): For 20 TPH requirement with 15 TPH boilers:

    • Option A: Both at 10 TPH (66.7% load) → Efficiency at 75% load? (Check curve).

    • Option B: One at 15 TPH (100%), other at 5 TPH (33.3%) → Efficiency at 100% & 45% load.

    • Calculate fuel needed for each boiler in each option → Sum → Compare. % Savings = (Fuel_A - Fuel_B)/Fuel_A × 100%.

Combustion & Furnaces

• Furnace: Enclosed space where fuel is burned to generate heat. Classifications: By heat transfer (radiant, convective), by fuel (oil, gas, coal), by charging (batch, continuous).

• Minimum Excess Air:

  • Advantages: Reduces flue gas volume → lower sensible heat loss, reduces fan power, lowers NOx formation (less N₂ available).

  • Achievement: Use oxygen trim control (O₂ sensor in flue gas adjusts air supply), maintain proper burner tuning, seal air leaks.

Steam System

• Steam Traps: Automatic valves that discharge condensate, air, and non-condensable gases while preventing live steam loss.

  • Types: Mechanical (ball float, inverted bucket), Thermostatic (bimetallic, bellows), Thermodynamic (disc).

• Performance Assessment:

  • Visual/Audio: Listen for continuous blowing (failure), observe temperature difference upstream/downstream.

  • Temperature: Downstream should be near saturation temp. Large drop indicates failure.

  • Ultrasonic/Infrared: Detect high-frequency sound or temperature signature.

  • Installation of test valves for isolation and testing.

• Condensate Recovery:

  • Process: Collect condensate from steam traps, filter, pump back to boiler feedwater system.

  • Benefits: Saves water (boiler makeup), saves heat (condensate at ~100°C), reduces water treatment costs, improves boiler efficiency.

• Flash Steam Utilization:

  • Concept: When high-pressure condensate is throttled to low pressure, a portion flashes into steam.

  • Example: Condensate from a 10 bar process (sensible heat ~180°C) discharged to a 1 bar flash vessel → generates low-pressure flash steam (1 bar, ~120°C) which can be used for low-pressure heating.

• Economic Thickness of Insulation:

  • Concept: Thickness where annual heat loss cost + annual capital cost is minimized. Not maximum insulation.

  • Determination: Calculate heat loss (Q) for varying thickness (t) using

$$Q = \frac{2\pi k L (T_1 - T_2)}{\ln(r_2/r_1)}$$

. Annual heat loss cost = Q × Operating Hours × Fuel Cost. Capital cost = Insulation cost per m² × Area. Sum both → plot → find minimum.

Alternative Heating Systems

• Thermic Fluid Heating System: Uses a heat transfer oil (thermic fluid) heated in a furnace/coil, circulated to heat exchangers for process use. Operates at low pressure (even at >300°C).

• Comparison with Steam:

  • Advantages over Steam: No pressure-related safety issues (no boilers, valves, traps), no water treatment, no condensate return, precise temperature control, no scaling/fouling in coils.

  • Disadvantages: Higher initial cost, risk of oil degradation/fire, lower heat transfer coefficient than steam.

  • Preferred When: High temperature (>200°C) at low pressure, process requires precise temperature, no steam infrastructure, avoiding water treatment/condensate issues.

4. MECHANICAL SYSTEMS: MOTORS, PUMPS, FANS, REFRIGERATION

Electric Motors

• Energy Efficient Motor vs. Standard Motor:

  • Construction Differences:

    | Feature | Standard Motor | Energy Efficient Motor | | :--- | :--- | :--- | | Core Material | Conventional steel | Thinner, higher-grade silicon steel (lower core loss) | | Stator Windings | Standard copper area | ~20% more copper (lower I²R loss) | | Air Gap | Standard | Optimized (minimized) | | Bearings | Standard | High-quality, low-friction | | Design | Cost-optimized | Efficiency-optimized (longer, larger core) |

  • Advantages: 2-5% higher full-load efficiency, lower operating temperature, longer life, better power factor, lower losses at part-load.

• Motor Loading Calculation:

  • Formula:

$$\% \text{Loading} = \frac{\text{Input Power (kW)}}{\text{Full Load Input Power (kW)}} \times 100$$

*   Where, Input Power (kW) = √3 × V × I × PF / 1000

*   Full Load Input Power = Rated Output (kW) / Rated Efficiency.

*   **Example (from paper):** 20 kW motor, η_fl = 90%, V=440V, I=10A, PF=0.78.

    *   Input = 1.732 × 440 × 10 × 0.78 / 1000 = **5.95 kW**

    *   Full Load Input = 20 / 0.90 = **22.22 kW**

    *   **% Loading = (5.95 / 22.22) × 100 = 26.8%** (Severely underloaded).

Pumping Systems (High Priority)

• Factors Affecting Performance:

  • System Curve: Head required vs. flow (H = constant friction loss + static head). Friction loss ∝ Flow².

  • Pump Curve: Head vs. Flow for a given pump (decreases with flow).

  • Affinity Laws (for centrifugal pumps):

    1. Q ∝ N (Flow ∝ Speed)

    2. H ∝ N² (Head ∝ Speed²)

    3. P ∝ N³ (Power ∝ Speed³)

    Also valid for impeller diameter changes.

• Energy Conservation Opportunities:

  1. Correct Sizing: Avoid throttling. Select pump for required head/flow.

  2. Variable Speed Drives (VSD/VFD): Match pump speed to flow demand (most effective, saves power ∝ N³).

  3. Reduce System Resistance: Use larger pipes, fewer bends, clean filters.

  4. Maintenance: Impeller trimming (if oversized), seal/bearing replacement, remove scale.

  5. Parallel Operation: See below.

• Significance of Parallel Operation:

  • Provides redundancy (one can be maintained).

  • Increases flow capacity.

  • Key Point: Pumps in parallel must have similar head-capacity curves. System curve determines combined flow. Efficiency can drop if operating far from Best Efficiency Point (BEP).

Fans & Blowers

• Design/Selection: Based on required airflow (CFM) and static pressure (in. wg). Consider gas density, temperature.

• Performance Evaluation: Similar to pumps – plot system curve vs. fan curve. Operating point is intersection.

• Efficient Operation: Use inlet guide vanes (IGV) or VFDs for volume control (more efficient than outlet dampers). Ensure proper belt tension/lubrication.

Refrigeration Plants

• Factors Affecting Performance:

  • Condensing Temperature: Lower condensing temp (lower head pressure) → higher COP. Affected by ambient temp, condenser cleanliness.

  • Evaporating Temperature: Higher evaporating temp (higher suction pressure) → higher COP. Affected by cooling load.

  • Sub-cooling & Superheating: Proper levels improve efficiency and protect compressor.

  • Compressor Type & Size: Screw/scroll more efficient than reciprocating at part-load. Proper sizing is key.

• Energy Conservation:

  • Reduce condensing temperature (clean condenser, water/air flow optimization).

  • Increase evaporating temperature (raise chilled water temp if process allows).

  • Use multiple compressors with individual drives for part-load.

  • Implement economizer cycle (flash gas cooling).

  • Insulate cold pipes/equipment.

  • Regular maintenance (leak detection, oil change).

5. LIGHTING SYSTEMS

Lighting Conservation

• Scope: Optimize luminous efficacy (lumens/Watt), reduce over-illumination, use daylight, improve maintenance, employ controls.

• LED Lighting Advantages:

  • High Efficacy: 100-150+ lm/W vs. Fluorescent (60-100), Incandescent (10-15).

  • Long Life: 50,000+ hours.

  • Low Heat Emission: Reduces HVAC load.

  • Instant On/Off, Dimmable, Directional.

  • Robust, No mercury.

• Procedure to Save Energy:

  1. Audit: Measure existing lux levels, identify over-lit areas.

  2. Retrofitting: Replace inefficient lamps with LEDs or T5 fluorescents.

  3. Zoning: Separate lighting circuits for different areas/tasks.

  4. Controls: Occupancy sensors (PIR), daylight sensors (photocells), timers, dimmers.

  5. Maintenance: Regular cleaning, group relamping.

• Illumination/Lux: Luminous flux (lumens) incident per unit area (m²). 1 lux = 1 lumen/m². Required levels vary by task (e.g., office: 300-500 lux, warehouse: 100-200 lux).

Lamp Replacement Calculations (Numerical)

• Steps for Simple Payback:

  1. Annual Energy Savings (kWh): = (Number of lamps) × (Operating hours) × (W_old - W_new) / 1000

  2. Annual Cost Savings (Rs): = Annual kWh Savings × Electricity Rate (Rs/kWh)

  3. Investment Cost (Rs): = (Number of lamps) × (Cost_new - Cost_old) + Installation cost.

  4. Simple Payback Period (Years): = Investment Cost / Annual Cost Savings

• Example (from paper): Replace 500W → 350W, 350W → 150W, 125W → 60W for 4500 hrs, Rs 5.5/unit.

  • Assume equal number of each type? (Question implies overall replacement strategy). Typically, calculate savings per lamp type and sum.

  • For 500W→350W lamp: Saving per lamp = (500-350) × 4500 / 1000 = 675 kWh/yr.

  • Repeat for others. Total savings = Sum. Total investment = Sum[(Cost_new - Cost_old) × N]. Payback = Investment / (Total Savings × 5.5).

6. FINANCIAL ANALYSIS & ECONOMICS

Life Cycle Costing (LCC)

• Definition: Total cost of owning and operating an asset over its entire life (Initial Cost + Operating Cost + Maintenance Cost - Salvage Value), all discounted to present value.

• Significance: Compares alternatives based on long-term cost, not just initial investment. Essential for energy-efficient equipment with higher upfront cost.

• Process:

  1. Identify all cost components (investment, energy, maintenance, disposal).

  2. Estimate timing and magnitude of each cost over analysis period.

  3. Convert all future costs to Present Worth (PW) using discount rate.

  4. Sum all PW → LCC.

  5. Compare LCC of alternatives.

• Effect on Investment: Justifies higher initial investment for low-operating-cost options (e.g., efficient motor, LED).

Payback Period

• Definition: Time required for cumulative net cash inflows to recover the initial investment.

$$\text{Simple Payback} = \frac{\text{Initial Investment}}{\text{Annual Net Cash Inflow}}$$

• Significance of Risk Analysis: Shorter payback periods are less risky. A project with a 3-year payback is preferable to a 7-year one with same NPV, as it recovers investment faster and is less exposed to future uncertainties (energy prices, interest rates).

• Merits: Simple, easy to understand, emphasizes liquidity & risk.

• Demerits: Ignores cash flows beyond payback, ignores time value of money, arbitrary cutoff.

Net Present Value (NPV)

• Concept: Sum of all discounted future cash flows (inflows - outflows) over project life.

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

Where: $$\displaystyle CF_t $$ = net cash flow in year t, $r$ = discount rate (MARR), $n$ = life.

• Decision Rule: Accept if NPV > 0 (project adds value).

• Advantages over Payback:

  • Considers time value of money.

  • Considers all cash flows over project life.

  • Measures absolute wealth increase.

  • Aligns with shareholder wealth maximization.

• Example (from paper): Lamp cost Rs 2000, annual savings Rs 22000 for 2 years, discount rate 15%.

  • Year 0: CF = -2000

  • Year 1: CF = +22000 / (1.15) = 19130.43

  • Year 2: CF = +22000 / (1.15)² = 16635.59

  • NPV = -2000 + 19130.43 + 16635.59 = 33766.02 Rs (Positive, accept).

Internal Rate of Return (IRR)

• Definition: Discount rate at which NPV becomes zero. It is the break-even rate of return.

• Significance: Represents the project's true rate of return. Compare IRR to required rate of return (hurdle rate). Accept if IRR > hurdle rate.

• Calculation: Trial-and-error or financial calculator/Excel (=IRR(values)).

ESCO (Energy Service Company) Concept

• Basic Concept: A company that provides comprehensive energy solutions to clients. The ESCO finances, designs, implements, and guarantees energy-saving projects.

• Business Model (Performance Contracting):

  1. ESCO conducts free energy audit.

  2. Proposes guaranteed savings project.

  3. Financing: ESCO arranges/ provides project financing.

  4. Implementation: ESCO manages installation.

  5. Guarantee: ESCO guarantees a certain level of energy savings.

  6. Payment: Client pays ESCO from the actual energy cost savings over the contract period (usually 5-10 years).

  7. After contract, all savings accrue to client.

• Role: Overcomes client's lack of capital, expertise, and risk aversion. "Shared savings" model.

7. INSTRUMENTS, MONITORING & REGULATIONS

Energy Audit Instruments & Monitoring Systems

• Power Analyzer: Measures V, I, PF, kW, kVA, kWh, harmonics. Working: Uses voltage/current transformers to sample waveforms, calculates parameters digitally (DSP).

• Thermocouple/Thermometer: Measures temperature (surface, flue gas, fluid).

• Lux Meter: Measures illuminance (lux). Uses photodiode/photo cell calibrated to human eye response.

• Flow Meter (Ultrasonic, Magnetic, Orifice): Measures fluid (water, steam, fuel) flow rate.

• Flue Gas Analyzer: Measures O₂, CO, CO₂, stack temperature → calculates excess air, combustion efficiency.

• Tachometer: Measures motor/fan/pump speed (RPM).

Bureau of Energy Efficiency (BEE) Regulations

• Manners & Intervals for Energy Audit (as per BEE - Energy Conservation Act, 2001):

  • Designated Consumers (DCs): Large energy-intensive industries, commercial buildings, railways, etc.

  • Frequency:

    • Initial Audit: Within 1.5 years of being notified as DC.

    • Subsequent Audits: Every 3 years for industries, every 5 years for commercial buildings.

  • Auditor: Must be a certified energy auditor (from BEE's list).

  • Reporting: Audit report submitted to BEE and designated agency.

• Applicability: Based on annual energy consumption (in toe) or connected load thresholds specified by BEE for different sectors (e.g., > 30,000 MWh/year for industries).

[!TIP] Exam Focus: Memorize the audit frequency (3 yrs for industry, 5 yrs for commercial) and that it's mandatory for "Designated Consumers" by certified auditors.

END OF UNIT 2 NOTES