EMP Sustainable Practices & Conservation 3 — Questions and Answers
Question 1: A chiller's coefficient of performance (COP) is 4.5. What does this mean?
- For every 4.5 kW of cooling, 1 kW of heat is rejected
- For every 1 kW of electrical input, 4.5 kW of cooling is produced (Correct answer)
- The chiller operates at 45% of rated capacity
- The chiller rejects 4.5 times more heat than it absorbs
Correct answer: For every 1 kW of electrical input, 4.5 kW of cooling is produced
COP is the ratio of useful cooling output to electrical energy input; a COP of 4.5 means 4.5 units of cooling per unit of electricity consumed.
Question 2: Which renewable energy certificate (REC) policy mechanism requires utilities to obtain a specified percentage of power from renewable sources?
- Feed-in Tariff (FIT)
- Renewable Portfolio Standard (RPS) (Correct answer)
- Net Energy Metering (NEM)
- Power Purchase Agreement (PPA)
Correct answer: Renewable Portfolio Standard (RPS)
A Renewable Portfolio Standard mandates that a percentage of a utility's electricity supply come from eligible renewable energy sources.
Question 3: Which heat recovery technology extracts energy from exhaust air to pre-condition incoming fresh air in an HVAC system?
- Variable refrigerant flow (VRF) system
- Energy recovery ventilator (ERV) (Correct answer)
- Cooling tower with condenser water reset
- Dedicated outdoor air system (DOAS) without heat exchange
Correct answer: Energy recovery ventilator (ERV)
An ERV transfers both sensible heat and latent moisture between exhaust and supply airstreams, reducing conditioning energy.
Question 4: A facility's monthly electric bill shows a 35% demand charge based on peak 15-minute interval. Which strategy BEST reduces this charge?
- Installing higher-efficiency motors
- Staggering start times of large loads to flatten demand peaks (Correct answer)
- Increasing operating hours to spread load
- Switching to a time-of-use rate without demand charges
Correct answer: Staggering start times of large loads to flatten demand peaks
Staggering large load starts reduces the coincident peak demand during the billing period, directly lowering demand charges.
Question 5: What is the primary environmental benefit of using low-global-warming-potential (low-GWP) refrigerants in HVAC systems?
- Improved system COP
- Reduced contribution to climate change from refrigerant leaks (Correct answer)
- Lower refrigerant purchase cost
- Compliance with ASHRAE 90.1 energy efficiency requirements
Correct answer: Reduced contribution to climate change from refrigerant leaks
Low-GWP refrigerants minimize climate impact when refrigerant leaks occur, since their warming potential is far less than legacy HFCs.
Question 6: In a simple payback analysis, a lighting retrofit costs $50,000 and saves $12,500 per year. What is the simple payback period?
- 2 years
- 4 years (Correct answer)
- 5 years
- 6.25 years
Correct answer: 4 years
Simple payback = initial cost ÷ annual savings = $50,000 ÷ $12,500 = 4 years.
Question 7: Which water conservation measure also provides the greatest indirect energy savings in a facility?
- Replacing landscaping with drought-tolerant plants
- Installing low-flow fixtures in restrooms
- Reducing hot water consumption through fixture retrofits and insulation (Correct answer)
- Harvesting rainwater for cooling tower makeup water
Correct answer: Reducing hot water consumption through fixture retrofits and insulation
Reducing hot water use saves both the water itself and the energy needed to heat it, yielding the highest combined water-energy savings.
EMP Sustainable Practices & Conservation 3
A chiller's coefficient of performance (COP) is 4.5.
What does this mean?