Project at a Glance
Facility: Hospital Campus
Project: Chiller and Boiler Plant Upgrades with 150,000 sf Addition and Renovations of the Main Campus
This healthcare facility, one of the largest providers of health care services in Michigan, offers a continuum of services and operates multiple campuses throughout the state. Their campus upgrades required a systems analysis and design of approved recommendations of both the chilled water plant, boiler plant that services the campus, and provide commissioning services for the major renovation and 150,000 sf inpatient expansion. The renovations of the main campus provided new state-of-the-art operating rooms, 164 all private rooms, and a 36-bed post-anesthesia care unit, or PACU; one of the largest in the country. The five-story expansion added 120 patient rooms and support spaces.
The focus of this case study documents the process that led to the upgrades made to both the Boiler and Chilled Water Plants. The performance and efficiency of these upgrades made it possible to improve service of the main campus as well as bringing on-line the 150,000 sf of new space with an actual Net Decrease in Energy Consumption and an annual savings of nearly $500,000.
The performance and efficiency of these upgrades made it possible to improve service of the main campus as well as bringing on-line the 150,000 sf of new space with an actual Net Decrease in Energy Consumption and an annual savings of nearly $500,000.
The purpose of the initial study was to present an evaluation of the existing plants and to determine if each would meet the immediate future demands of the hospital. This report also included an energy analysis which compares the efficiency, operating costs, and useful life of the existing chillers and boilers with new high-performance/efficient systems and design strategies.
The content of this study is based on:
- Field Observations
- Archive / Design drawings
- Interviews with maintenance personnel to ascertain operational concerns and deficiencies with the existing chiller plant
- Test & Balance reports
- Current utility rates
- Accepted Engineering practices
Scope of Study
- The study estimated the existing demand of the hospital by calculating that actual load.
- The new addition estimated load is added to the total existing load to determine if the existing plants have sufficient capacity.
- The condition of the equipment in each plant was evaluated to determine the viability of continued use and required improvements.
- Multiple options were then evaluated on a life cycle basis to determine the best option for improvements that met the needs of the facility including the new addition and maximize energy efficiency.
*Note: This case study first covers the chilled water plant from study through implementation and then the boiler plant concluding with before and after operational cost data.
Existing Chilled Water Plant Assessment
AS part of the Energy Center renovations, the chiller renovations involved the removal and replacement of two of the four existing chillers. Using the most recent air and hydronic balance reports, design data, as well as interviewing energy plant personnel, the actual cooling load of the hospital was able to be determined. The results show that in order to meet this cooling demand on design cooling days there would need to be 2,700 tons of nominal chiller capacity in use.
One 1,200 ton and one 1,500 ton centrifugal chiller was installed. The new chillers were needed, in part, for the added capacity of the new 150,000 square foot addition to the hospital campus and were sized to allow for additional capacity and redundancies.
The following items were additional improvements that further increased efficiency of the chilled water plant:
- Increase Capacity of Winter Cooler
- Control Valve on Steam Lines for Cooling Towers Basin Heating
- Variable Primary Pumping
- Variable Secondary Pumping
- Variable Primary Only Pumping
- Temperature Control System
- Thermal Storage
- Series Chillers
- Condenser Heat Recovery
- Decrease Steam Boiler Plant Capacity
- Remote Condenser Water Basin / Drain Back Tank
The energy economics were simulated using the Trane Trace 700 simulation program. All costs were calculated over a study life of 40 years. Estimate for equipment installation cost was based on the following:
Install cost ($) = equipment cost ($)*1.5
Basis of Calulations
Based on the results from the economic analysis (first cost ranking and economic ranking), Option A actually ranked higher than Option B. However, Option B was determined to be the best option. Although utility costs and life cycle costs are lower with Option A, when the load exceeds 2,700 tons and the backup centrifugal chiller will be required to operate to meet the demand. Therefore, if a chiller were to fail under these conditions, the chilled water plant would be unable to adequately maintain the chilled water setpoint. With Option B there is an additional 300 tons of capacity at relatively the same utility cost. The utility costs are approximately the same because there are more operating hours on the more efficient centrifugal chillers.
Included as part of the Energy Center Renovations, the entire chilled water and condensing water pump packages have been updated and replaced. These pumps are used to supply the entire buildings cooling demand to the various air handler units throughout the hospital. The pumping system change required the hospital to change from a primary/secondary system with several booster pumps located throughout the hospital to a primary pumping system utilizing three larger pumps. The pumps were connected to Variable Frequency Drives (VFDs) which control the speed of the pumps, allowing the flow of water to match the exact load that is needed. In turn, this has reduced the overall electrical demand to power the pumps.
Ice storage, or thermal storage, is a fairly old concept that involves the shifting of electrical loads from more expensive peak demand hours to less expensive non-peak demand hours through the nighttime production of ice. The ice is then stored throughout the day and used to cool the buildings chilled water supply, reducing the demand on the chillers when cooling loads are at their highest. While a direct energy efficiency gain is not realized from the production of ice, the decreased demand on the chillers, which are the number one consumer of electricity in any major facility, is reduced. In less than a year and a half, the savings from the ice storage system has more than offset the cost associated with the ice storage installation. The use of ice storage can produce 1944 ton hours of cooling for the facility.
Plate Heat Exchanger
In conjunction with the chiller and cooler tower replacement, the Energy Center plate heat exchanger has also been replaced. Because a building always has a latent heat load regardless of the time of year, a heat exchanger is used as a means of “free cooling” in the colder months of internal heating loads from MRI units, data rooms, and machine rooms. When temperatures are 48 degrees or less outside, we are able to divert the flow of water through the plate heat exchanger, reducing the overall demand on the chillers. Since the Plate Heat Exchanger has been operational, an additional 300 tons of cooling can be diverted, allowing the chillers to remain idle during this time.
Air Handler Replacement
Since 2008, twelve of the hospital existing air handling unity have been completely replaced. The new units are custom designed units that were brought into the building in multiple sections or assembled completely onsite. The fans in each unit are equipped with a VFD control module which allows the fan to operate at the exact air volume needed. Along with the VFDs, all of the AHUs are tied into the Building Automation System (BAS). With all of the new technology that was put into these units, the Facility Team was able to have a better understanding of the building’s heating and cooling needs and can respond to issues at the click of a button.
Building Automation System (BAS)
In conjunction with the AHU replacements, the controls for the units were also updated. Through the use of a Trane Building Automation System, this hospital facility’s team members are able to monitor the running conditions of all AHUs throughout the facility from a centrally located computer. This ensures that all units are functioning to their designed specifications, in turn, increasing the overall efficiency and energy savings of the unit.
The existing boiler plant consists of five water tube steam boilers (300 HP | 16,000#/HR each – 80,000#/HR combined) which provide the steam to the existing absorption chillers, steam heating coils, steam radiators, heating water heat exchangers, humidifiers, and domestic water heat exchangers. The two newest boilers are 1974 vintage. The three older boilers are 1965 vintage. Based upon the steam produced (measured by steam meter) and associated firing rates, the efficiency of each boiler is approximately 50-60%.
When considering the existing steam demand (without the absorption chillers) and the future demand of the addition, it was our recommendation to plan to replace all five existing boilers with seven new Vertical Tube, Fulton, 150HP, Steam Boilers. The Fulton Boilers are 85% efficient, high performance boilers with a total connected capacity of 41,400 #/HR. Due to the lower capacity of each boiler, the steam supply will match more effectively and equally to the steam demand.
Beyond the boilers, other systems included in the study include:
- Boiler Feed Water System
- Boiler Blow-Down System
- Ventilation | Combustion Air
- Facility Energy Management Control System
- Steam, Steam Condensate, and Heating Water Piping
- Steam | Hot Water Heat Exchangers
- Prioritized Recommendations
- Install (3) new modular steam boilers and remove B-1, B2, and B-3.
- Install new boiler feed water system.
- Install (5) additional modular steam boilers and remove B-4 and B-5 (a section of the existing roof would need to be removed if this is not complete in conjunction with the chiller plant improvements).
- Install a new boiler stack economizer in new boiler breeching. Abandon the existing chimneys.
- Take pipe samples of the heating piping to assess their condition. Focus on mains and fittings.
- Replace existing piping as required.
- Inspect hot water tubing in existing heat exchangers (check tubing thickness and tubing corrosion).
- Replace existing heat exchangers as required.
- Test the existing exhaust and intake airflows.
- Add steam pressure gauges to each side of the PRVs.
- Tear down two existing chimneys.
All five existing Cleaver Brooks boilers were replaced with eight new Vertical Tube, 150 HP, Fulton steam boilers. The new Fulton boilers are high-efficiency boilers with a small nominal capacity than the existing, allowing the steam capacity and demand to be matched more effectively. The Fulton boilers are also dual fired boilers, allowing for operation on both natural gas and fuel oil.
LEED: This project was commissioned in accordance with LEED NC v2.2 EA Prerequisite 1EA Cr 3″. Synergy also provided commissioning services for all major systems in the facility. Synergy employs one of the most comprehensive Commissioning process available to ensure that the systems installed perform as designed and met the Owner’s Project Requirements (OPR).
Continue Reading This Article...
Join our mailing list to continue reading this article and download our PDF case study.