December 27, 2018 | by Greg Marsicek, Energy Engineer, Seventhwave.

In the past, energy efficiency in commercial buildings was often dominated by the primary systems – envelope, lighting and HVAC. This was logical as these systems dominated the energy consumption of most commercial buildings. With technology and design advancements as well as code improvements, the energy end uses impacted by these systems (heating, cooling, lighting) have shrunk significantly – which means other end uses such as plug loads have become an increasing larger percentage of a building’s total energy use. In a standard office building of the past, plug loads may have contributed to 5-10% of the total building end use. For modern, more efficient office buildings, this number has increased to 20%. For high performance office buildings plug loads potentially could reach 40-50%. These trends all point to the importance of controlling plug loads in all modern buildings – especially those with high performance targets or net-zero goals.

What can be done? Is there hope? After visiting several office buildings in Minnesota and studying occupant’s workstations – the future looked grim. Space heaters? Check. Fans? Check. No computer power management settings? Check. But this presents an energy saving opportunity by controlling the plug loads at workstations. Recent improvements in plug load control technology has led to the tier 2 advanced power strip – a device that controls both the computer power settings and peripherals at a workstation.

This field study involved testing tier 2 advanced power strips by visiting three commercial office buildings in Minnesota and installing approximately 80 power strips. We measured energy usage for two months at the workstations – the first month without the tier 2 advanced power strip and the second month with the tier 2 advanced power strip. We wanted to quantify the energy savings of these devices. However, we also worked to summarize the other important aspects of these devices. How easily can they be implemented in a typical office building? Who should be involved in the implementation? Are they cost effective? Are users receptive to using these devices?

Our research found that these devices can save on average 100 kWh at a workstation. This number is primarily driven by the computer power management aspect of the device – as the computer is the largest energy consumer at a workstation. In addition, workstations that are energy intense (those with large desktops) have larger energy savings. Another key aspect is how receptive were users to these devices? Our feedback survey found that typically users are not receptive to computer power management (whether it is implemented through a tier 2 advanced power strip or simply with the onboard Window’s settings). However, the energy savings potential makes continued efforts to improve acceptance worthwhile.

These devices are readily available on the market today. We found that it is critical that IT personnel are onboard with the implementation of these devices. In addition – having a champion in the office also increases the acceptance of these devices. The champion is often a supervisor or energy efficiency advocate within the company. This individual can help promote the benefit of the devices in addition to providing input on how to use the devices.

Want more info on this field study? Check out the live webinar on Thursday, Feb. 7 from 11 a.m. – noon. Can’t make it? The webinar will be housed on our education page to view on-demand.

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Greg Marsicek

ABOUT THE AUTHOR

Greg uses energy modeling software (TRNSYS, eQuest, and others) to analyze buildings and energy systems. He uses this information to help buildings owners and design teams make informed design decisions. No building or project is the same and thus there are no “cookie-cutter” solutions or modeling approaches. Greg is an experienced TRNSYS user and has FORTRAN programming knowledge. He is an active ASHRAE member. Greg earned his bachelor’s and master’s degrees in mechanical engineering from the University of Wisconsin–Madison.