CEM Concepts and Principles 4 â Questions and Answers
Question 1: What distinguishes a 'Type II' energy audit from a 'Type I' energy audit per ASHRAE guidelines?
- Type II focuses only on no-cost operational improvements
- Type II includes detailed analysis and savings potential for capital-intensive ECMs (Correct answer)
- Type II is limited to the building envelope, while Type I covers all systems
- Type II requires sub-metering at every major end use
Correct answer: Type II includes detailed analysis and savings potential for capital-intensive ECMs
A Type II audit (Energy Survey and Engineering Analysis) provides detailed engineering analysis and cost-benefit calculations for capital-intensive energy conservation measures.
Question 2: Which principle underlies the concept of 'combined heat and power' (CHP) systems?
- Generating electricity from waste heat of industrial processes
- Simultaneously generating electricity and capturing waste heat for useful thermal applications (Correct answer)
- Using two separate boilers to produce heat and steam independently
- Reducing peak demand by shifting electric loads to off-peak hours
Correct answer: Simultaneously generating electricity and capturing waste heat for useful thermal applications
CHP (cogeneration) captures heat that would otherwise be wasted from electricity generation and uses it for space heating, process heat, or cooling, improving overall fuel efficiency.
Question 3: What is the 'Rankine cycle' most commonly associated with in energy systems?
- Compression refrigeration in commercial HVAC equipment
- Steam-based power generation in thermal power plants (Correct answer)
- Air compression in industrial compressed air systems
- Absorption cooling using waste heat sources
Correct answer: Steam-based power generation in thermal power plants
The Rankine cycle describes the thermodynamic process used in steam power plants, where water is heated to steam, expanded through a turbine to generate work, then condensed and recycled.
Question 4: In energy management, what does 'retro-commissioning' involve?
- Installing new high-efficiency equipment to replace outdated systems
- Systematic investigation and optimization of existing building systems to restore peak performance (Correct answer)
- Commissioning a building system for the first time after construction
- Decommissioning and removing obsolete energy equipment
Correct answer: Systematic investigation and optimization of existing building systems to restore peak performance
Retro-commissioning optimizes existing building systems that were never properly commissioned or have drifted from optimal performance, typically without capital investment in new equipment.
Question 5: The 'payback period' method of evaluating energy projects has which significant limitation?
- It cannot be applied to projects with variable energy savings
- It ignores the time value of money and cash flows beyond the payback point (Correct answer)
- It requires a detailed life-cycle cost analysis to calculate
- It overestimates savings by not accounting for equipment degradation
Correct answer: It ignores the time value of money and cash flows beyond the payback point
Simple payback does not discount future savings and ignores all benefits occurring after the payback period, potentially misranking long-lived, high-return projects.
Question 6: What is 'peak shaving' in the context of electrical demand management?
- Trimming the insulation on peak-load electrical wiring
- Reducing demand during high-demand periods to lower peak demand charges (Correct answer)
- Shifting all energy use to nighttime off-peak hours permanently
- Installing capacitors to correct power factor during peak periods
Correct answer: Reducing demand during high-demand periods to lower peak demand charges
Peak shaving reduces electricity demand during the utility's peak periodsâthrough load curtailment, battery storage, or on-site generationâto minimize demand charges.
Question 7: What energy content (approximate) is equivalent to one kilowatt-hour (kWh) of electricity?
- 1,000 BTU
- 3,412 BTU (Correct answer)
- 10,000 BTU
- 100,000 BTU
Correct answer: 3,412 BTU
One kWh equals approximately 3,412 BTU, a fundamental conversion factor used throughout energy management calculations.
CEM Concepts and Principles 4
What distinguishes a 'Type II' energy audit from a 'Type I' energy audit per ASHRAE guidelines?