Research shows how energy targets can be achieved.
by Kyle Delpiano
September 3, 2018

The combination of VFDs and PICVs provided the most savings in terms of electricity consumption, detailed in Images 4 through 6. “A robust monitoring effort was essential to developing these fundamental understandings and the data needed to form analyses and to develop energy conservation measures,” Waite said.

“This study further illustrates that replacing constant speed pumps with more appropriately sized equipment can significantly reduce their energy usage. Replacing the constant speed, constant flow primary HW and condenser water (CW) pumps provided estimated annual electricity savings of 20 percent in primary HW pumping and 29 percent in CW pumping,” Waite said in his thesis.

water distributionImage 6. Total annual cooling system pumping energy.

Doing the Math

With all retrofits considered, the total annual cooling pumping energy reduction was computed to be 36.1 percent compared to the original system (see Image 6).

The data analysis of the pre- and post-retrofit conditions formed the basis for the mathematical model to assess energy consumption, calculating the following:

  • pump power at thermal loads within monitoring range
  • pump power at loads beyond monitoring range
  • system hydraulic behavior
  • pump power

The mathematical model can provide a fast and accurate energy assessment of a hydronic system. From there, the team can install sensors at various points and recommend specific system improvements that can immediately reduce energy consumption and costs.

Monitoring system behavior at Astor Place yielded three primary benefits: determine if equipment was operating as designed; assess the amount of energy being used and the dynamic adjustments to the load’s demands; and gain a broader understanding of system behavior, the last of which is most intriguing for Waite.

“This will allow us to develop theories on how systems behave as a whole rather than a collection of individual parts,” Waite said.

For Related Management Company, the granular focus of the project was insightful. The project gave the company the opportunity to establish a clear chain of cause and effect when dealing with energy efficiency while driving value to the condo owners through energy savings.

Future Implications

As owners seek to improve efficiency of building systems, HVAC upgrades are often last on the list due to perceived high upfront costs. The results from the Astor Place Energy Improvement Project can help inform decisions about new equipment and the potential for energy savings.

“It’s not cost effective to replace a large pump as a stand-alone efficiency measure,” Waite said. “But if your BMS tells you that over a decade a 25-hp pump never operated over 15 hp, you can replace it with properly sized equipment that’s both cost effective and energy efficient.”

References
1. (Waite M.B. Analyses of energy infrastructure serving a dense urban area: opportunities and challenges for wind power building systems and distributed generation (Doctoral dissertation). Columbia University. 2016)

2. (Waite M, Deshmukh A and Modi V. Experimental and analytical investigation of hydronic system retrofits in an urban high-rise mixed use building. Energy and Buildings 2017;136:173-188.)

3. (Copeland C. Improving Energy Performance Of NYC’s Existing Office Buildings. ASHRAE Journal 2012.)

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