Low-Cost Tweaks Yield Big-Time Savings

Once Jack Dale Associates (JDA) quantified mechanical-system interactions for Texaco's data center, specified techniques were employed to upgrade the plant while avoiding disruptions to data-processing operations. Total construction costs for chiller-plant renovations commissioned by JDA were less than $600,000.
By Consulting Specifying Engineer Staff November 1, 2000

Once Jack Dale Associates (JDA) quantified mechanical-system interactions for Texaco’s data center, specified techniques were employed to upgrade the plant while avoiding disruptions to data-processing operations. Total construction costs for chiller-plant renovations commissioned by JDA were less than $600,000.

Procedures outlined by the engineering team improved energy efficiency and continue to save the petrochemical company more than $100,000 per year in utility costs. The design not only solved operating problems, but also improved the facility’s ability to increase its chilled-water reserve for future expansions. Best of all, the upgrades reduced energy consumption. Key features include:

The upgrades help set system demand and to ensure that only the required amount of chilled water is distributed.

Before JDA began work on the project, Texaco had received a number of proposals for resolving the facility’s system problems. The least onerous of the proposals would have required a two-week shutdown of the entire 5,000-ton chiller plant and over $2 million to complete.

Table 1 – Existing HVAC System Parameters

TimeBypass positionB riser flowB supply tempB return tempMain CHW supply temp FChilled water flow (gpm)Flow to labs (gpm)BAX flow (gpm)East-West riser flow (gpm)Main return header pressure (psi)Main supply header pressure (psi)IBM CDU flow (L/M)
13:00 Closed 1584 44.6 52.7 43.6 2778 414 617 1610 66 65 190
13:15 10% open 1665 44.7 52.1 43.7 2787 426 626 1661 65 64 190
13:20 15% open 1634 44.6 52.1 43.6 2737 432 637 1655 65 65 190
13:30 20% open 1666 45.0 52.0 43.7 2645 505 636 1704 65 65 200
13:38 25% open 1686 45.0 52.1 43.9 2655 504 630 1713 65 66 200
13:43 35% open 1669 44.4 52.3 44.0 2635 504 637 1728 65 66 200
13:49 Full open 1662 44.6 52.7 44.3 2671 502 630 1778 66 67 200
13:57 Full open 1363 44.1 54.5 44.3 2631 513 627 1864 68 68 145
14:08 Full open 1333 43.5 54.1 43.8 2611 517 635 930 69 70 130

Table 2 – Savings from Mechanical Plant Re-engineering

Original designRe-engineered design
HP kW HP kW
Subtotal: 972 611 Subtotal: 223 118
Chiller loads: 2,200 1,760 Chiller loads: 1,600 1,280
Total HP & kW: 3,172 2,371 Total HP & kW: 1,832 1,398
Dead head factor: 0.90 Pump kW saved: 973
Total kW Demand: 2,134 kW Total kW demand: 1,398
Use factor: 0.80 Use factor: 0.80
Annual pump utility cost: $235,462 Annual pump utility cost: $45,530
Added utility cost for new office space: $79,684
Net annual utility savings after chiller plant renovations: $110,248

Average cost per kWh: 0.055 $/kWh