6. Energy Management

Efficiency Measures — Quiz

Test your understanding of efficiency measures with 5 practice questions.

Practice Questions

Question 1

An industrial compressor consumes 100 kW at full speed. After installing a VFD, it operates at 60% of rated speed for 8000 hours per year. Assuming power ∝ (speed)^3, what is the annual energy saving in kWh?

Question 2

A building has a 250 kW cooling load operating 2000 hours per year. A chiller upgrade improves COP from 3.2 to 4.2 at a cost of \\$75,000; electricity costs \\$0.10/kWh. What is the simple payback period in years?

Question 3

A flat roof area of 250 m^2 is retrofitted from U=1.5 W/m^2·K to 0.5 W/m^2·K. If the indoor–outdoor temperature difference is 12 K and heating season is 1800 hours per year, what is the annual heating energy saving (in kWh)?

Question 4

A pump delivers 10 kW of hydraulic power. Motor efficiency is upgraded from 70% to 85%, and it operates 6000 hours annually. What is the annual energy saving (in kWh)?

Question 5

A 250 kW motor operates at power factor 0.70. After correction to 0.95, what is the reduction in reactive power (in kVAR)?