A Remedy For Real-Time Pricing Risks
The hospital's electrical distribution system consisted of a main feed from each of two different access points onto the property. Emergency generator sets consisted of one 400-kW V-12 Caterpillar generator set, and one 150-kW 6-cylinder Caterpillar generator set.
Late in 1996, computerized controls were installed. This gave operating personnel the ability to change and monitor temperature and humidity settings in the operating (main and outpatient) rooms remotely. This also permitted the ability to change, monitor, and operate three air-handling units (AHUs) and the chiller plants.
In 1997 a new Marley cooling tower was installed to replace the existing wooden cooling tower used in connection with the no. 1 and no. 2 chillers. This cooling tower was purchased with the forward planning concept of ultimately relocating to the future central energy plant.
In March of 1998 an updated, computerized preventive maintenance system was purchased, and a work order processing system was internally developed.
New Energy PlantIn late 1998, the new central energy plant came on-line. It was designed by HDR Architecture, Inc. (Omaha, NE) and installed by Alcon General Contractors (Albany, GA). The new plant houses two new, 350-hp, low-emission, Cleaver-Brooks firetube boilers each with dual-fuel capability; the existing firetube boiler was refitted with a Gordon-Piatt burner, increasing its hp rating to 350; a new deaerator; and a new, York, 800-ton, natural gas engine-driven centrifugal chiller (utilizing a new Marley cooling tower of the same model NC series as the one installed for the no. 1 and no. 2 chillers).
The gas curtailment contract ended with the installation of the gas engine-driven chiller and a favorable rate plan was established. And, the gas engine-driven chiller uses R-134a refrigerant. The controls were moved to the new central energy plant control room. The gas engine-driven chiller was placed on these controls. As the gas engine-driven chiller plant was placed in service, the steam absorption chiller unit was placed out of service.
The hospital's electrical distribution was changed drastically with the addition of the central energy plant. Both power feeds come to the plant from one access point in a common vault. Each feed has two 2,500-kW transformers, with one side redundant. The power is then fed to a centralized distribution bus. This bus is fitted with two 4,000-A breakers and one 4,000-A tie-breaker. The bus is normally split out (bus tie open). Eight new automatic transfer switches were installed throughout the hospital and central energy plant.
Two 600-kW, V-12 Caterpillar generator sets were installed, one of which is redundant. These generators are primarily set up for emergency operation in the event of a 2- to 3-sec normal power loss. They are configured to operate in a peak (parallel) mode of operation with the local power company. The generator sets are operated via an ISO phone modem to connect to the Georgia Power grid for peak-time shaving. During this operating phase, both generator sets operate at 85% capacity and reduce the hospital's demand by at least 1,015 kW. After the new generator sets were placed in operation, the old sets were placed out of service.
The central energy plant control room is equipped with fire alarm panel, medical-gas alarm panel, water testing lab with sampling points, a generator, an automatic transfer switch status panel, and a Power Logic monitoring system (for monitoring of main breaker demands, generator output, and automatic transfer switch loads).
At this time all hospital utilities feed to the main hospital via the central energy plant with the exception of domestic water.
New Emergency And Operating SuitesIn 2000, two major AHUs were replaced, and control schemes on these and approximately 60% of the total air handlers were converted to digital controls.
Then, in November of 2000, expansion construction for a new emergency department and operating suites was begun. The facilities budget for 2001 identified the need for a new, 800-ton chiller to replace the existing two 325-ton chillers that were nearing 30 years of service.
As the expansion plans developed, the chilled water supply and return lines from chiller no. 4 were found to be in the footprint of the new construction. Additional thought was given to chiller no. 4 (rated at 425 tons) and its ability to meet the expansion needs in the event of failure of any of the chillers (the unit was nearing 20 years of service). This chiller was beginning to have serious maintenance problems; plus, the cooling tower for chiller no. 4 was in need of a replacement fan motor and repair of cooling tower components.
The forward planning was then adjusted to make plans for two new, 800-ton chillers, with one being charged to the expansion project. A new cooling tower would then be purchased and primary and secondary pumps would be added to the scope necessary to make each system a standalone unit.
Siemens Building Technologies (SBT, Columbus, GA) worked very closely with the hospital staff in identifying project costs, quantifiable savings over several energy combinations, and in taking the lead for project responsibility. They worked with Total Industrial Services (TIS, McDonough, GA) who held the mechanical installation responsibilities.
TIS recommended two Carrier, 800-ton, electric motor-driven centrifugal chillers using R-134a. The new chillers would be supported by adding one primary pump, two variable-speed secondary pumps, and a new cooling tower. The total refrigerant plant consists of one 800-ton, natural gas-fired, engine-driven chiller and two 800-ton electric motor-driven chillers - making it a "hybrid" facility. The flexibility and cost saving potentials are enhanced by having a choice in which chiller to operate depending upon the rate structure for each utility for any given time frame.
SBT worked out the control logic for tying the two new chillers into the system, interlinking them with the existing chiller and supporting equipment. The control logic works with the distributed direct digital controls (ddc) for the AHUs to achieve the best practical environmental control for the facility. The new computerized facility management system monitors the chilled water supply and return temperatures and starts/stops the chillers individually or in combinations as required to maintain chilled water supply temperatures at their setpoint, thereby providing the most energy-efficient operation of the plant. The interoperability of the overall system also allows staff to monitor the addressable fire protection system, the refrigerant leak detection system, and the timed lighting systems.
The hospital also desired the backwards and forwards product compatibility the building automation system (bas) offered. Looking forward, specifically, expansion flexibility is important to St. Francis since three other sites are included in the overall system. Future plans include a systematic approach to replacing the pneumatic controls that still run a large percentage of the air and water distribution. Forward planning also includes integrating power distribution monitoring to take advantage of standby generation to further manage peak demand as the connected load increases.
Post-Op AnalysisIn March 2001, the hospital began real-time pricing (RTP) on electrical consumption. In order to accomplish a change like this from the existing power and light load (PLL) plan, a level of supply, acceptable to both parties, must be established. This level of supply known as the customer base load (CBL) generally is set from annual consumption.
Using past data, the staff expected the peak demand to decrease from 2,272 kW to 1,792 kW, a reduction of 480 kW. Compared to the PLL rates, this would yield $87,219 in peak demand charges. Under the new RTP rate, the CBL demand curve is fixed with a peak demand of 1,789 kW, just over 100% of the forecast. This means that all of the peak demand savings will be realized relative to the base year.
The use of RTP was expected to eliminate the need to run the gas engine-driven chiller during the entire summer peak demand billing period. Based on historical data, this would have required an 84% drop in run hours while still achieving the peak demand savings under the old power and light charge rate. As of August 21, 2001, the gas-fired machines had run 197 hrs.
Providentially, the hospital was experiencing problems in 1999 with the 325-ton chillers and was forced to run the new gas engine-driven chiller full time during the heat of the summer. The electric utility allowed this year to be used for establishing the CBL rate; hospital and utility records indicate the actual operating cost of the gas chiller was $102,767.
With the change to the RTP structure, St. Francis purchases any electricity above its CBL at a real-time rate that is provided at 4 p.m. each day for each hour of the next day beginning at midnight. Using a spreadsheet furnished by Siemens that takes maintenance and repair histories into account as well as the cost of fuel, the hospital uses the data to plot an hour-by-hour strategy for which chiller to run at any given time the next day. Based on the actual total hours of run time for the interval of May 18, 2001 through Aug. 21, 2001 and the actual gas costs and average RTP costs for each month, St. Francis has realized real-time savings of $69,318. Part of this savings is attributable to an aggressive effort to avoid buying RTP electricity at peak rates; the rest of the credit goes to the new electric chiller machines being rated at .58 KW/ton. The old machines were .68 and .74 KW/ton, respectively.
Comparison of actual usage patterns suggests that the old chillers consumed 43% more energy than the new chillers use (6,448,204 vs. 9,220,932 kWh under the old units' rating). The original forecast used $.025/kWh, which was the total of the actual charge and the fuel correction rate that was paid in 2000 under PLL.
Timely project execution also exacted another degree of savings. By completing the new installation in time for the 2001 cooling season, the hospital avoided rebuilding the cooling tower for the old, 450-ton chiller, saving $90,000 in capital expenditures.
ConclusionThe installation of two 800-ton electric chillers to support the existing gas chiller had been expected to generate $204,000 in savings the first year. Based on calculations of the actual first year, savings exceeded $230,000. The project increased the system's reliability by reducing the gas engine's run hours and providing a chilled-water plant with full redundancy.
St. Francis Hospital occupies approximately 500,000 sq ft. The savings generated by the CEP expansion project, including automation, will net a payback of this work in nearly 10 years.
It is anticipated that by early 2003, the generators will be available to augment the power pool of supply to the hospital allowing significant gain in electric power savings. By responding to "peak demand," or hours of high electric rates in such a manner, the generator operation will satisfy the monthly load test requirements, avoid wet-stacking, avoid load-banking requirements, and enhance reliability of operation.
St. Francis Hospital shares quality relationships with its utility providers, Georgia Power and United Cities Gas Company. While some consideration has been given to cost enhancements with other providers under the deregulated market concept, it has been found that internal and external forces do not justify change.
SFH staff has charted electrical usage information, audited rate structures, communicated with others in professional societies, and conducted an energy audit for the facilities in order to come to this conclusion. The audit was the biggest help, however, due to the identification of specific objectives that can be budgeted for in the coming years. It is a long-term effort, but well worth it.
The impact of energy savings is available to most facilities. Communicate with those in decision-making positions about the importance of implementing change in your system. ES