Energy Management: Your questions answered

Webcast presenter Tom Wenning from Energy Efficiency Research & Analysis (EERA) answered additional questions about topics such as artificial demand, dilute/dense phase transport replacement, and why you shouldn't open manual drain valves.

By Tom Wenning, Energy Efficiency Research & Analysis (EERA) May 10, 2018

The "Energy Management" webcast was presented live on May 3, 2018, by Tom Wenning, program manager, Energy Efficiency Research & Analysis (EERA). The webcast can be found here. He supplied written answers to some of those questions that weren’t addressed from the webcast attendees:

Question: What should be the standard kwh consumption for full capacity running of centrifugal compressors?

Answer: A centrifugal compressor’s operating efficiency is typically around 16 to 20 kW/100 cfm. I’d recommend visiting the Compressed Air and Gas Institute ( and checking out their compressor performance data sheets.

Q: What is artificial demand?

A: Artificial demand is defined as the excess volume of air that is consumed when supplying higher pressure than necessary for applications – unregulated and/or regulated to higher than necessary.

Q: What is a replacement for dilute/dense phase transport?

A: An alternative is a low- or high-pressure blower or a low pressure air compressor. You may want to take a look at the DOE’s compressed air sourcebook: "Improving Compressed Air System Performance"

Q: Why should you not open manual drain valves?

A: There are four main methods for draining condensate from the system: manual valves, level-operated mechanical traps, electrically operated solenoid valves and zero air-loss traps. While manual valves can be effective, they may be very costly from an air-loss perspective. They should never be permanently "cracked open" to allow continuous condensate removal – this is extremely costly. The best solution from an energy/cost viewpoint is a zero air-loss trap.

Q: From your audits, do you have some examples of typical savings from energy recovery?

A: Heat recovery efficiencies can range a tremendous amount depending upon the equipment and end-use of the heat. The recovery can range anywhere from 50 to 90% of the available thermal energy, but again, it depends. I would recommend taking a look at the Heat Recovery factsheet in the DOE’s compressed air sourcebook: "Improving Compressed Air System Performance

Q: What is the most common ECM that you have dealt with, with respect to compressed air systems?

A: The most common are reducing leaks, reducing system pressure, modifying/improving compressor control and eliminating inappropriate uses.