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study 1a Faced with ever increasing energy costs the Sheraton Hotel sought the services of Jardine-Trane Technical Services. The Trane Tracer Summit System and Danfoss VLT frequency converters were installed on the existing two 700 ton CenTraVac chillers and secondary chilled water pumps. This letter reproduced below was from the Chief Engineer to the Management group. |
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"Congratulations" You may recall in September 1996, The Sheraton Grande Laguna Beach Resort initiated a project to install several building automation systems within the hotel. These systems included a Trane Tracer Summit Package which optimises the centralvac chiller operation including chiller soft start-cool down control, chilled water reset control, electrical demand limiting and automatic scheduling of air handling units throught the property. The second item included in the project was Variable Speed Drive Units for the chilled water pumps. I am happy to report that the actual return of investment was realised in August 1997, only 11 months after installation. I have included graphs detailing Kilo Watt hour usage, Kilo Watt hour demand, savings per month and average monthly Kilo Watt hour usage for your information. The savings are calculated comparing previous year monthly usage versus current month usage and multiplying the units saved by the current month electrical charges. In other words if we had not implemented this project the hotels electricity bill would have been significantly higher over the 11 month period. I would like to take this opportunity to congratulate every one on their insight and support for this project, and hope every one feels as I do, the pleasure of knowing we have not only saved costs, but also contributed, if in only a small way, to reduce environmental degradation. Best Regards, see attachments below. |
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Electricity KWH Usage
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Electrical Demand
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| Using the Trane Tracer
Summit Chiller
plant optimisation system and Danfoss VLT
frequency converter on the secondary chilled water pumps
a simple payback period of 11 months was achieved.. Environmental impact By improving the efficiency of the chiller plant, the Sheraton Hotel will prevent the following pollution from entering the atmosphere:
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Case study 1b
| Danfoss "VLT" Variable Speed Drives were installed on three secondary chilled water pumps and two condenser water pumps with a total kilowatt rating of 275kW using Variable Speed Drives. | It can be seen that by reducing the speed/flow of the pumps by 20% that the energy consumption has been reduced from 100% to 52%. | This is a significant saving and shows the potential energy savings in a decoupled system Variable speed drives versus constant flow. |
Cost comparison: Variable speed drives versus 100% flow/speed
Motor kW: 275 cost per kWh: 1.07 Baht total annual running hours 8760
Variable speed drive
| % flow/speed | % Energy consumption | kW | % Operation time | Annual running hours | Hrs x kW x unit cost | Total cost |
80o |
52 |
143 |
100 |
8,760 |
8,760 x 143 x 1.07 |
1,340,368 |
Total energy consumption (Baht) 1,340,368
Alternative - 100% flow speed
| % flow/speed | % Energy consumption | kW | % Operation time | Annual running hours | Hrs x kW x unit cost | Total cost |
100 |
100 |
275 |
100 |
8,760 |
8,760 x 275 x 1.07 |
2,577,630 |
Total energy consumption (Baht) 2,577,630
Annual energy saving (Baht) 1,237,262
Note: The above calculation does not take into account peak demand charges or oil fluctuation prices when these are factored into the calculation even greater savings can be achieved.
