Low-Cost Tweaks Yield Big-Time Savings
-- Consulting-Specifying Engineer, 11/1/2000
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:
- Bidirectional hydraulic decoupling bridges that assist in setting demand.
- Installation of variable-frequency drives to reduce the pumping horsepower throughout the complex by 950 hp (see Figure 2, page 64 ).
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.
Time | Bypass position | B riser flow | B supply temp | B return temp | Main CHW supply temp F | Chilled 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 |
Original design | Re-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
