Central Chilled Water Distribution Systems
With chillers becoming more efficient, continued reliance on constant-flow systems, primary-secondary-tertiary complexity, and pumping horsepower, central systems are becoming the major energy consuming system on campus.Because hydraulic modeling is not a concept commonly used by design engineers, little is known of this truly useful design-build-management (D-B-M) tool. Analogous to a traveler’s roadmap and automobile, hydraulic modeling clearly identifies the management destination: peak performance at minimum operating cost. It is the accelerator set on cruise control, as well as the indicator of miles per gallon consumed. Hydraulic modeling is also the gas gauge indicating remaining capacity. And finally, it is the “idiot light” that comes on and tells you that you are having a problem in performance and/or delivery.
As a D-B-M firm, this technological breakthrough provides the facility manager with a roadmap for peak system performance that can be implemented as a single-source solution that provides the following benefits:
- Benchmark of existing conditions (gpm, pressure drop, temperature drop, installed capacity, and required capacity).
- Template by which system improvements can be made that will improve energy performance and chiller on-line management.
- Current load and future load document.
- Master planning to add or cost avoidance of adding chiller capacity.
- Allocation of chiller capacity including demand-side management of chilled water distribution during peak energy demands.
- Retro-commissioning, design intent document as well as a training document.
Through data collection of pertinent information, a D-B-M can:
- Document existing conditions;
- Document “gaps” in original design intent and the current design intent;
- Document return-on-investment opportunities; and
- Identify existing chilled water distribution problems.
From the engineering effort comes an implementation plan that will most likely be a combination of energy savings opportunities that will pay for the retrofit work in its entirety or contribute to reducing the facility manager’s five-year master plan investment requirements. A side benefit of the implementation plan is usually “out-of-sight and out-of-mind” alterations that do not impact the occupied space. These piping and control strategy modifications can be phased into place without cost impacting the occupants, thus saving on retrofit costs associated with that type of work. For the most part, all the work required to improve chilled water distribution will be done within the confines of pump and air-handling equipment rooms, in tunnels, and/or outside trenches.
Once implemented, the software model can be maintained on an as-needed basis depending on future system renovations and/or system expansion. This model can also serve as a proactive management tool to forecast and act on energy needs and consumption. Going back to the traveler with their roadmap and automobile, hydraulic modeling gets you to your destination in an efficient, controlled manner. Similarly, hydraulic modeling can be a single-source solution for hot water and steam distribution systems so, happy motoring! If you have any comments, suggestions, or questions regarding this design-build column, contact Howard McKew, P.E., CPE, 978-887-1116 (fax) or e-mail him at hmckew@sebesta.com.,/i>
