General Aspects of Energy Management & Energy Audit Available here with full solutions — 55 questions recovered from the 2025 exam:
Objective (1 mark)
50 of 50
Short (5 marks)
5 of 8
Long (10 marks)
0 of 6
This is not the complete paper. The questions below are the ones we could recover and verify; the rest of that year’s paper is not reproduced here. Every answer shown is checked against the 2014 BEE guidebook and carries its book section reference and an explanation.
Full paper pattern: Section-I 50×1 = 50 marks · Section-II 8×5 = 40 · Section-III 6×10 = 60 · Total 150, pass mark 75, 3 hours. ▶ Practice these interactively
Other years
Objective questions (1 mark) — 50
📖 §1.13 Electricity Pricing in India — demand side management
1. Energy saving through DSM is treated as equivalent to:
A reduction in electricity tariff
New additions on the supply side in MWs
Import of cheaper electricity
Government subsidies
Answer: B) New additions on the supply side in MWs
Confirmed — a MW of demand avoided by DSM removes the need to build a MW of new generating capacity, so DSM savings are counted as equivalent to new supply-side additions in MW (this is the standard 'negawatt' treatment used in the exam). It is not a tariff reduction, an import, or a subsidy.
📖 §1.12 Long Term Energy Scenario — APDRP / R-APDRP
2. What is the main aim of the Accelerated Power Development and Reform Programme (APDRP)?
To eliminate subsidies for agricultural consumers
To privatize all power plants in India
To promote only renewable energy in the power sector
To cut AT&C losses by audits and system improvements
Answer: D) To cut AT&C losses by audits and system improvements
Confirmed vs Book-1 §1.12 — APDRP was introduced by the Ministry of Power in 2002-03 to improve distribution reliability and utility viability, 'targets towards the commercial viability of the utilities by reducing their Aggregate Technical & Commercial (AT&C) losses to 15%', with technical, commercial, financial and IT interventions. It is neither a privatisation nor a renewable-only programme.
4. A process receives 1000 kg/hr of raw material. The hourly outputs are 700 kg of product, 200 kg of waste, and 50 kg stored. What is the unaccounted loss?
📖 §3.2 Work, Energy and Power — W = F·s, P = W/t, 1 kWh = 3.6 MJ
5. A boiler receives 100 MJ of fuel energy. The steam output is 70 MJ, the flue gas loss is 20 MJ and the radiation plus unaccounted loss is 10 MJ. What is the boiler efficiency?
65%
60%
70%
75%
Answer: C) 70%
Confirmed vs Book-1 §3.2 — Efficiency = useful output/input = 70/100 = 70%. Book-1 Ch.3, Work, Energy and Power — W = F·s, P = W/t, 1 kWh = 3.6 MJ.
📖 §3.4 Specific heat — Table 3.1 Specific heat of common substances
7. Maximum specific heat among the following:
Water
Lead
Mercury
Iron
Answer: A) Water
Confirmed vs Book-1 §3.4 — Water has the highest specific heat (~1 kcal/kg°C) among the listed substances. Book-1 Ch.3, Specific heat — Table 3.1 Specific heat of common substances.
Confirmed vs Book-1 §10.4 — The main chemical responsible is chlorofluorocarbons (CFCs) from refrigerators and air conditioners; UV frees a chlorine atom that destroys ozone catalytically. A single CFC molecule can destroy up to 100,000 ozone molecules.
📖 §6.1 / §6.2 - Figure 6.1 Energy Action Planning Steps; Top Management Commitment and Support
9. The first step in an energy action plan is:
Recognition of achievements
Designing monitoring reports
Selecting new technologies
Top management commitment
Answer: D) Top management commitment
Confirmed vs Book-1 §6.1 / §6.2 — Figure 6.1 lists 'Top Management Commitment and Support' as the first of the six energy action planning steps - without it there is no authority, funding or manpower for the programme. Recognising achievements (a) is the LAST step, and monitoring reports (b) and technology selection (c) belong to later evaluation and implementation stages.
11. Calculate the quantity of water evaporated when 100 kg of feed containing 6% solids is concentrated to 30% solids.
600 kg
180 kg
80 kg
800 kg
Answer: C) 80 kg
Confirmed vs Book-1 §5.5 Ex.5.6 (book's own numbers): Solids in feed = 100 × 0.06 = 6 kg and are conserved. Output = 6/0.30 = 20 kg. Water evaporated = 100 − 20 = 80 kg. Option (c).
📖 §6.4 Energy Policy and Planning - Force Field Analysis (prioritising forces)
12. In force field analysis, which approach is usually more effective for achieving a goal?
Strengthening forces that are already positive
Minimising negative forces that act as barriers
Ignoring external factors and focusing only on internal ones
Changing the organisational goal
Answer: B) Minimising negative forces that act as barriers
Confirmed vs Book-1 §6.4 Energy Policy and Planning — The book's explicit tip: 'It is usually more effective to attempt to minimize negative forces than to try to strengthen forces that are already positive.' Option (a) is the tempting reverse of that tip; ignoring external factors (c) contradicts the instruction to identify both internal and external forces, and changing the goal (d) defeats the purpose of the analysis.
13. Which of the following is NOT a conventional financing option?
Debt financing
Performance contracting
Retained earnings
Stock buyback
Answer: D) Stock buyback
Confirmed vs Book-1 §7.6 — Book, Section 7.6, lists the conventional financing options: debt financing, equity financing, retained earnings, capital lease, true lease and performance contracting.
Stock buyback is a distribution of surplus to shareholders, not a source of funds for capital investment.
📖 §7.3 Comparison between Net Present Value and Internal Rate of Return
14. Two projects: X (IRR=40%, NPV= Rs 50,000/-) and Y (IRR=30%, NPV= Rs 1,20,000/-) having same life, no finance limit. Choose the best project.
X
Y
Cannot decide
Question invalid
Answer: B) Y
Confirmed vs Book-1 §7.3 — Book: 'The higher the net present value, the more attractive is the proposed project'; NPV measures absolute wealth added and is the comparison tool between projects.
With equal life and no financing constraint, choose Y (NPV Rs.1,20,000) over X (NPV Rs.50,000) even though X has the higher IRR - the book warns a high IRR alone is not a desirable feature.
Confirmed vs Book-1 §7.7 — Book: 'Most assets used in the course of a business decrease in value over time. Tax law permits reasonable deductions from taxable income to allow for this. These deductions are called depreciation allowances.'
Discounting/compounding relate present and future values, and inflation is a general price effect - only depreciation is the loss of asset value with time.
📖 §4.9 Maximizing System Efficiencies (TPM practice; six big losses not listed in Ch4 text)
16. In Total Productive Maintenance (TPM), which of the following is not one of the six big losses that lower equipment efficiency?
Breakdowns
Idling and minor stoppages
Reduced speed
Excessive overtime hours
Answer: D) Excessive overtime hours
Confirmed vs Book-1 §4.9 — The six big losses in TPM are breakdowns, setup and adjustment, idling and minor stoppages, reduced speed, process defects/rework and reduced yield (start-up) losses — all of which lower Overall Equipment Effectiveness. Excessive overtime hours is a manpower/cost issue and is not one of the six equipment losses.
17. Fixed energy consumption can be determined from:
Bar chart
Vertical line chart
Pie chart
XY coordinate system
Answer: D) XY coordinate system
Confirmed vs Book-1 §9.6 — plotting energy (y) against production (x) on an XY coordinate system and extending the best-fit line to zero production gives the intercept C = fixed energy consumption. Answer (d).
18. Carbon capture from point sources and storage is called:
Carbon sequestration
Carbon sink
Carbon capture
Carbon adsorption
Answer: A) Carbon sequestration
Confirmed vs Book-1 §10.5 — Carbon sequestration is the removal of CO2 from large point sources (power plants, refineries, industry) and its storage in geologic formations — depleted oil and gas reservoirs, deep coal seams or saline reservoirs. A carbon sink is a natural absorber (oceans, biomass).
19. Why is an energy baseline established in Monitoring and Targeting (M&T)?
To record only monthly electricity bills
To fix a reference point for measuring energy performance improvements
To eliminate the need for energy performance indicators
To avoid sharing information with managers and stakeholders
Answer: B) To fix a reference point for measuring energy performance improvements
Confirmed vs Book-1 §9.4 — 12-24 months of energy and output data are regressed to obtain the standard energy performance, which 'provides a base line for the assessment of future performance' and can be used as an initial target. The baseline is therefore the reference for measuring improvement. Answer (b).
📖 §7.4 Cash Flow — Capital Investment Considerations
20. Life-cycle costing is better than simple purchase cost because it:
Includes operation, maintenance and energy costs over life
Ignores maintenance costs
Forces single-supplier bidding
Cuts down procurement cycle time
Answer: A) Includes operation, maintenance and energy costs over life
Confirmed vs Book-1 §7.4 — Book, Section 7.4, requires all four elements to be considered - initial capital cost, net operating cash inflows, economic life and salvage value - not the purchase price alone.
Life-cycle costing therefore adds operating, maintenance and energy costs over the whole economic life to the first cost, which is why it is the sounder basis for a decision.
Corrected (was c) — Book-1 §11.6 Biomass Energy (Gasification of Biomass):
Book: ‘The products of combustion are combustible gases like Carbon monoxide (CO), Hydrogen (H₂) and traces of Methane (CH₄)’, and the chapter-end key to objective Q.10 is ‘CO, H₂ and CH₄’.
The methanation reaction C + 2H₂ = CH₄ in the reduction zone supplies the methane, and Typical Producer Gas Composition lists CH₄ = 3 ± 1%.
So producer gas is CO + H₂ + CH₄ — option a, not ‘CO, H₂’ only.
22. Work Breakdown Structure (WBS) is mainly used for:
Combining small tasks into one large project
Dividing complex projects into simpler, manageable tasks
Preparing cost estimation only
Eliminating tasks from the project
Answer: B) Dividing complex projects into simpler, manageable tasks
Confirmed vs Book-1 §8.3 — Book-1: 'WBS is the process of dividing complex projects to simpler and manageable tasks... much larger tasks are broken down to manageable chunks of work' that can be easily supervised and estimated.
Hence option (b).
23. What is a major limitation of the Gantt chart in project management?
It does not show the duration of activities
It does not clearly show logical dependencies between activities
It cannot be used for construction projects
It requires advanced statistical methods for preparation
Answer: B) It does not clearly show logical dependencies between activities
Confirmed vs Book-1 §8.3 — Book-1, 'Limitation of Gantt chart': 'The Gantt chart does not normally show the logical interdependencies between the predecessor and successor activities very well.'
Duration IS shown by the bar length, so (a) is wrong → option (b).
24. In a project network diagram, why is a dummy activity used?
To represent an activity with very small duration
To show logical dependency between activities with the same start and end nodes
To reduce the total project duration
To allocate additional resources to critical activities
Answer: B) To show logical dependency between activities with the same start and end nodes
Confirmed vs Book-1 §8.3 — Book-1: 'Dummy activity is required if two or more activities having identical starting and ending events... shown as dotted line to ensure that activity C starts only after activity B and activity D are completed.'
A dummy has ZERO duration and consumes ZERO resources; it only preserves logic → option (b).
📖 §11.2 Fundamentals of Solar Energy (Fundamentals of Solar Energy)
25. Solar radiation consists of:
X-rays, Gamma rays, and Microwaves
Ultra-violet, Visible, and Infra-red radiation
Visible, Infra-red, and Radio waves
Ultra-violet, X-rays, and Cosmic rays
Answer: B) Ultra-violet, Visible, and Infra-red radiation
Confirmed vs Book-1 §11.2 Fundamentals of Solar Energy (Fundamentals of Solar Energy) —
Book opens §11.2: ‘Solar radiation is radiant energy emitted by the sun comprising of ultra-violet, visible and infra-red radiation.’
X-rays, gamma rays, microwaves and radio waves are not the constituents named by the book.
Answer b.
26. Which of the following are basic objectives of sustainable development?
Economic security and prosperity
Social development and advancement
Environmental sustainability
All of the above
Answer: D) All of the above
Confirmed vs Book-1 §10.13 — 'Sustainable development encompasses three basic and inter-related objectives: economic security and prosperity; social development and advancement; environmental sustainability.' All three are therefore correct. The Brundtland Commission report 'Our Common Future' (1987) gives the definition.
27. Select the correct statement about the Critical Path Method (CPM):
CPM is a deterministic model that does not take into account variation in completion time
CPM is a probabilistic model that takes into account variation in completion time
CPM is a probabilistic model that does not take into account variation in completion time
CPM is a deterministic model that takes into account variation in completion time
Answer: A) CPM is a deterministic model that does not take into account variation in completion time
Confirmed vs Book-1 §8.3 — Book-1: 'CPM is a deterministic model that does not take into account variation in the completion time, so one fixed time is used for an activity.'
PERT, by contrast, is the probabilistic model using three time estimates → option (a).
28. Acceptable delay time (slack time/float) is equal to:
Time between Earliest Finish and Latest Finish
Time between Earliest Start and Latest Start
Both a and b
None of the above
Answer: C) Both a and b
Confirmed vs Book-1 §8.3 — Book-1: total float is 'the time between its earliest and latest start time, OR between its earliest and latest finish time', i.e. Float = LS − ES = LF − EF.
The worked example confirms it: for activity C, LS(8) − ES(5) = LF(12) − EF(9) = 3 weeks.
Both expressions are valid and equal → option (c) Both a and b.
29. The objectives of Standards & Labeling (S&L) programme aim to:
Set sulphur standards for coal-fired power plants
Provide informed choice about energy saving
Enforce penalties on renewable obligation non-compliance
Fix tariff slabs for power-intensive industries
Answer: B) Provide informed choice about energy saving
Confirmed vs Book-1 §2.3.2 — The stated objective of S&L is 'to provide the consumer an informed choice about the energy saving and thereby the cost saving potential of the marketed household and other equipment'. Sulphur norms are pollution control, RPO enforcement is under the Electricity Act 2003 and tariff slabs are set by regulatory commissions — none is an S&L objective.
30. Is the activity critical, given ES = 8 days and LS = 10 days?
Yes
No
More details required
Next activity details required
Answer: B) No
Confirmed vs Book-1 §8.3 — Float = LS − ES = 10 − 8 = 2 days. A critical activity must have ZERO float (ES = LS and EF = LF).
Since the float is 2 days (> 0), the activity is not on the critical path → option (b) No.
📖 §1.13 Electricity Pricing in India — What is ABT?
32. Availability Based Tariff (ABT) was introduced in India to:
Encourage solar roof-top for industries
Reduce dependence on oil imports
Subsidise rural electrification
Improve grid discipline and frequency control
Answer: D) Improve grid discipline and frequency control
Confirmed vs Book-1 §1.13 — 'Introduction of Availability Based Tariffs (ABT) and unscheduled interchange charges for power, introduced in 2003 for inter-state sale of power, have reduced voltage and frequency fluctuations.' ABT enforces day-ahead schedules with rewards and penalties, i.e. grid discipline and frequency control — it has nothing to do with rooftop solar, oil imports or rural subsidies.
33. In a 'Guaranteed Savings' ESCO project, the ESCO company would not be involved in:
Project design
Project finance
Project implementation
Verifying energy savings
Answer: B) Project finance
Confirmed vs Book-1 §2 (general) — In the Guaranteed Savings model the CUSTOMER arranges and carries the project financing, while the ESCO designs, implements and guarantees — and therefore also verifies — the savings. Confusing it with the Shared Savings model, where the ESCO finances the project, is the trap.
📖 §1.7 Indian Energy Scenario — Energy Supply (India R/P ratios)
34. The Reserves-to-Production (R/P) ratio of coal in India is high compared to oil and gas. This implies:
Coal reserves can provide secure supply for decades
India has surplus oil reserves to meet its demand
Natural gas is India's most secure long-term option
India's coal imports will vanish completely
Answer: A) Coal reserves can provide secure supply for decades
Confirmed vs Book-1 §1.7 — India's coal R/P is about 100 years against oil 17.5 years and gas 40.2 years, so coal reserves can secure supply for decades. India has no oil surplus (it imports over 75% of crude) and gas reserves are only 0.7% of the world's, so (b) and (c) are wrong; and the book expects coal imports to rise, not vanish.
📖 §1.11 Energy Intensity on Purchasing Power Parity (PPP)
35. The use of Purchasing Power Parities (PPPs) in energy intensity calculations ensures that:
GDP comparisons reflect only exchange rate fluctuations
GDP of all countries is valued at a uniform price level, showing only differences in real economic volume
GDP is measured exclusively in domestic currency terms
GDP comparisons ignore differences in goods and services consumed
Answer: B) GDP of all countries is valued at a uniform price level, showing only differences in real economic volume
Confirmed vs Book-1 §1.11 — 'The use of PPPs ensures that the GDP of all countries is valued at a uniform price level and thus reflects only differences in the actual volume of the economy.' Using market exchange rates instead would overstate the GDP of high-price countries, which is exactly the distortion option (a) describes.
36. Which statement best describes the relationship between energy conservation and energy efficiency?
Energy conservation and energy efficiency are identical and interchangeable terms
Energy efficiency refers to reducing energy intensity per unit of output, while energy conservation refers to reducing overall consumption.
Energy efficiency requires lowering comfort levels, while energy conservation does not
Energy conservation excludes energy efficiency measures from its scope
Answer: B) Energy efficiency refers to reducing energy intensity per unit of output, while energy conservation refers to reducing overall consumption.
Confirmed vs Book-1 §1.15 — energy conservation is achieved when the GROWTH of energy consumption is reduced in physical terms, while energy efficiency is achieved when the energy intensity of a product or process is reduced WITHOUT affecting output, consumption or comfort levels. That rules out (c); and since the book calls efficiency 'an integral part of energy conservation', (a) and (d) are also wrong.
37. 'Designated Consumers' under EC Act are classified mainly because:
They are exempted from energy audits
They focus only on renewable generation
They represent small artisan industries
They are users of energy in an energy intensive industry
Answer: D) They are users of energy in an energy intensive industry
Confirmed vs Book-1 §2.1 — 'Designated consumer means any user or class of users of energy in an energy intensive industry and other establishments specified in the Schedule as designated consumer.' They are therefore large energy users who must appoint energy managers, get accredited audits done and meet norms — not exempted, not small artisan units and not renewable-only entities.
📖 §4.4 Step 6 Analysis of energy use / energy balance (Sankey detail in Book-1 Ch5 & Ch9)
38. Sankey diagrams help energy managers by:
Prioritizing improvements based on visualized energy losses
Reducing the need for energy audits
Replacing thermodynamic calculations
Eliminating the use of performance indicators
Answer: A) Prioritizing improvements based on visualized energy losses
Confirmed vs Book-1 §4.4 — A Sankey diagram draws each energy stream with a width proportional to its magnitude, so the largest losses are immediately visible and improvement effort can be prioritised where the money is. It supplements — never replaces — the energy audit, the thermodynamic calculations behind the balance, or the performance indicators used to track progress.
📖 §4.12 Energy audit instruments — Electrical Measuring Instruments
39. Which instrument measures power factor directly?
Ammeter
Wattmeter
Lux meter
Power analyzer
Answer: D) Power analyzer
Confirmed vs Book-1 §4.12 — Book §4.12: electrical measuring instruments (power analyzers) measure "KVA, KW, PF, Hertz, KVAr, Amps and Volts" on-line without stopping the motor, so power factor is read directly. An ammeter gives current only, a wattmeter active power only (PF then has to be computed with kVA) and a lux meter measures illumination.
📖 § Chapter IV — Sec 13, Powers and Functions of the Bureau
40. What is the mission of the Bureau of Energy Efficiency (BEE) under the Energy Conservation Act 2001?
To regulate electricity tariffs at the national level
To promote renewable energy by providing capital subsidies
To develop policies and strategies that reduce the energy intensity of the Indian economy
To license only energy auditors and energy managers
Answer: C) To develop policies and strategies that reduce the energy intensity of the Indian economy
Confirmed vs Book-1 §2.3 (Sec 13) — BEE's mandate under Sec 13 is to develop policies, strategies, standards, codes and capacity that reduce the energy intensity of the Indian economy — recommending norms and labels, notifying DCs, ECBC guidelines, awareness, training and certification. Electricity tariff regulation belongs to CERC/SERCs and renewable capital subsidy to MNRE, and certification is only one of BEE's many functions, not its whole mission.
📖 § 2.3.1 Energy Conservation Building Codes (ECBC)
41. What is the main purpose of the Energy Conservation Building Code (ECBC)?
To set minimum energy efficiency standards for commercial buildings
To fix electricity tariffs for buildings
To mandate use of only renewable energy in construction
To regulate real estate prices
Answer: A) To set minimum energy efficiency standards for commercial buildings
Confirmed vs Book-1 §2.3.1 — ECBC was developed to deal with rapidly rising energy consumption in commercial buildings and 'sets minimum energy efficiency standards for design and construction of commercial buildings', with norms per square metre by climatic region. It does not fix tariffs, does not mandate renewables-only construction and has nothing to do with real-estate prices.
42. 'Daylight harvesting' in lighting systems means:
Collecting solar energy for night lighting
Using flat plate collectors for heating
Adjusting artificial lighting based on natural daylight
Storing energy in battery banks
Answer: C) Adjusting artificial lighting based on natural daylight
Confirmed vs Book-1 Ch.3 — Daylight harvesting dims/switches artificial lighting in response to available natural daylight to save energy. Book-1 Ch.3, Book-3 Ch.8 Lighting System (outside Ch-3 text).
43. In a cumulative sum chart, a horizontal graph indicates:
Nothing can be said
Energy consumption is reduced
Specific energy consumption is increasing
Actual and calculated energy consumption are the same
Answer: D) Actual and calculated energy consumption are the same
Confirmed vs Book-1 §9.6 — a flat (horizontal) CUSUM means the running Σ(E_act - E_calc) is unchanged, i.e. actual equals calculated consumption each period and performance is exactly on target. Rising = worsening, falling = savings. Answer (d).
📖 §1.3 Commercial Energy and Non Commercial Energy
44. Which of the following is non-commercial energy?
Lignite
LPG
Solar energy for water heating
Hydro power
Answer: C) Solar energy for water heating
Confirmed vs Book-1 §1.3 — the book's own examples of non-commercial energy include 'firewood and agro waste in rural areas, SOLAR ENERGY FOR WATER HEATING, electricity generation, and for drying grain…', i.e. energy sourced within a community and not traded in the market. Lignite, LPG and hydro power are all sold for a definite price and are therefore commercial energy.
📖 § Measurement & Verification in performance contracting (general)
47. The main purpose of Performance Measurement and Verification (PMV) is to:
Establish new project costs
Ensure that guaranteed savings have been achieved
Increase the baseline consumption
Eliminate the need for utility bills
Answer: B) Ensure that guaranteed savings have been achieved
Confirmed vs Book-1 §2 (general) — Performance measurement and verification compares post-implementation consumption against an agreed baseline to confirm that the savings guaranteed by the project have actually been achieved — that is what triggers payment in a performance contract. It neither establishes project cost nor raises the baseline, and utility bills remain the primary data source.
📖 §7.3 Financial Analysis Techniques — Return on Investment (ROI)
48. ROI for an investment of Rs 1,00,000 with an annual return of Rs 20,000 per year is_______
1%
10%
20%
200%
Answer: C) 20%
Confirmed vs Book-1 §7.3 — ROI = (Annual net cash flow / Capital cost) x 100 = (20,000 / 1,00,000) x 100 = 20%.
Cross-check with the inverse relation: payback = 1,00,000/20,000 = 5 years, and 1/5 = 20%.
📖 §11.6 Biomass Energy (Average conversion efficiency of a gasifier)
49. Biomass gasifier using 1 kg wood (4,000 kCal/kg) producing 2 m³ gas (1,000 kCal/m³). What would be the efficiency?
25%
50%
75%
100%
Answer: B) 50%
Confirmed vs Book-1 §11.6 Biomass Energy (Average conversion efficiency of a gasifier) —
Book formula: ηgas = (calorific value of gas per kg of fuel) / (avg. calorific value of 1 kg of fuel).
Gas energy = 2 m³/kg × 1000 kcal/m³ = 2000 kcal; fuel energy = 4000 kcal/kg.
η = 2000/4000 = 50%. Answer b. (Compare the book's solved example: 46,000/64,000 = 71.88%.)
📖 §4.4 Step 8 Cost benefit analysis / §4.8 Matching energy usage to requirement (VSD retrofit)
1. A centrifugal pump (30 kW motor) runs 16 h/day, 300 days/yr at 65% loading and 88% efficiency with no flow control. A VFD retrofit (cost ₹1,50,000) is expected to cut energy by 10%; power cost ₹7.0/kWh. Find (a) current annual energy, (b) annual saving, (c) annual cost saving, (d) simple payback.
Model answer: (a) Current annual energy = (30 × 0.65 / 0.88) × 16 × 300 ≈ 106,364 kWh. (b) Energy saved with VFD = 106,364 × 0.10 ≈ 10,636 kWh/yr. (c) Annual cost saving = 10,636 × ₹7.0 ≈ ₹74,455. (d) Simple payback = 1,50,000 / 74,455 ≈ 2.01 years (≈ 24 months).
Work in a fixed order and show each line: input power -> annual energy -> energy saved -> money saved -> payback. Each step carries marks even if a later number is wrong.
Input power = rated kW x loading / efficiency. Loading is multiplied, efficiency is DIVIDED - swapping them is the commonest error in this question type.
Annual hours = hours/day x days/year (16 x 300 = 4800 h). Do not use 8760 unless the question says continuous running.
Simple payback (years) = Investment / Annual cost saving. Quote it in years and, if asked, x12 for months. This is §4.4 Step 8 cost-benefit applied to a §4.8 matching-energy-to-requirement measure.
📖 §8.3 CPM benefits & essential difference between CPM and PERT
2. What are the benefits of the Critical Path Method (CPM)? Explain how PERT differs from CPM.
Model answer: CPM benefits: it provides a graphical view of the project, predicts the time required to complete the project, and shows which activities are critical to the schedule and which are not (it also identifies float/slack and the minimum project duration). CPM uses deterministic single-time estimates and considers time and cost (origin: DuPont 1957). PERT differs in that it is probabilistic: it uses three time estimates (optimistic, most likely, pessimistic) combined as TE = (To + 4Tm + Tp)/6 to account for uncertainty, and is suited to research/novel projects with uncertain durations (origin: US Navy Polaris).
Reported in the Sep 2025 paper. Answer assembled from the book's CPM benefits and CPM-vs-PERT material.
3. A facility has connected load 500 kW and contract demand 500 kVA. Monthly maximum demand approx 350 kW at 0.85 PF. Demand charge is Rs 300 per kVA/month and minimum billing demand is 80% of contract demand. a) Determine the current demand in kVA. b) Calculate excess demand charges above minimum billing demand. c) Find the minimum power factor required to avoid excess demand charges.
Model answer: a) Actual kVA demand = kW/PF = 350/0.85 = 411.76 kVA. b) Minimum billed demand = 500 x 0.8 = 400 kVA; excess demand = 411.76 - 400 = 11.76 kVA; excess charges = 11.76 x 300 = Rs 3528/month. c) Minimum PF to keep demand at 400 kVA = 350/400 = 0.875.
Three relations do the whole sum: kVA = kW/PF, minimum billing demand = 80% of contract demand, and required PF = kW ÷ billed kVA. Common mistake: comparing 350 kW against the 500 kVA contract — demand is billed in kVA, so convert with the power factor first. Note that raising PF from 0.85 to 0.875 alone removes the penalty; that is the answer to part (c).
📖 §1.15 Energy Conservation and its Importance (Book-1 Ch.1 EOC L-1)
4. Explain the difference between energy conservation and energy efficiency with a suitable example.
Model answer: Energy conservation and energy efficiency are separate but related concepts. Energy conservation is achieved when the growth of energy consumption is reduced in physical terms; it can result from several processes such as productivity increase or technological progress. Energy efficiency is achieved when the energy intensity of a specific product, process or area of consumption is reduced without affecting output, consumption or comfort levels. Energy efficiency simply means using less energy to perform the same function. Promotion of energy efficiency contributes to energy conservation and is therefore an integral part of conservation policy. Example: replacing a 60 W incandescent lamp with an 8 W LED giving the same 800 lumens uses about 1/8th of the energy (and cuts CO2 emissions proportionately) - an efficiency measure that leads to conservation.
Efficiency = same output with less energy; conservation = the broader reduction it produces.
5. An energy-efficient air compressor costs Rs.6,00,000, saves Rs.1,80,000/yr for 3 years, with annual maintenance of Rs.10,000 from year 2 onward, salvage Rs.50,000 at end of year 3, discount rate 10%. Find (a) net annual cash flow from year 2, (b) NPV, (c) economic acceptability.
Model answer: (a) Net cash flow from year 2 = 1,80,000 − 10,000 = Rs.1,70,000. (b) PV: Yr0 −6,00,000; Yr1 1,80,000×0.909 = 1,63,636; Yr2 1,70,000×0.826 = 1,40,420; Yr3 (1,70,000+50,000)×0.751 = 2,20,000×0.751 = 1,65,220. NPV = (1,63,636+1,40,420+1,65,220) − 6,00,000 = −Rs.1,30,724. (c) NPV is negative, so over 3 years at 10% the project does not recover its cost and is not economically acceptable.
Add salvage to final-year inflow; negative NPV → reject.