For The People: Government Chillers Keep Costs Cool
It has been estimated that the equipment used to produce chilled water for HVAC systems in government facilities can account for up to 35% of a facility’s electrical energy use. When you consider that new chillers can be 35% to 40% more efficient than existing equipment, replacing the chillers may be a good idea.
In addition, there are refrigerant issues to worry about. Older chillers using CFC refrigerants may be very expensive to recharge if a refrigerant leak occurs. And if a leak does occur, venting the CFCs to the atmosphere may damage Earth’s ozone layer.
Government at various levels, from city to state to federal, are all looking to reduce costs. Replacing older equipment with new energy-efficient chillers is one of the ways facilities can reduce their utility bills and ongoing operation costs. This article will take a look at some of the chiller retrofits that have taken place recently in various government facilities.
DOE Chiller/Cogeneration ProjectSmithsonian Institution facilities along the National Mall in Washington received enhanced energy services from General Service Administration’s (GSA) modernization and expansion of its central heating and refrigeration plant.
The DOE Headquarters Forrestal Building in Washington began to reap the benefits of a privately financed energy efficiency project, and just in the nick of time. In June 2001, just days before the weather in Washington started to reach a smoldering heat index temperature of 100 degrees F, the first two of eight new 2,200-ton chillers became operational. These two chillers, part of a much larger energy efficiency project, provide cooling for the Forrestal Building.
The chillers were installed in the GSA’s central heating and refrigeration plant in Washington, which underwent a much-needed modernization and expansion process that had a price tag of approximately $64 million. The GSA and the Smithsonian Institution signed a Utility Energy Service Contract (UESC) earlier with their utility partner, Washington Gas, which provided the upfront capital costs of the improved heating and cooling equipment.
The new equipment included a cogeneration system as well as new chillers. Washington Gas acquired capital dollars for the project from a private-sector financial institution, GE Capital Potomac Federal. The Federal Government will repay the utility out of a portion of the energy cost savings resulting from the project.
The renovation is expected to result in lower emissions and operating expenses, but the plant’s capacity to meet chilled-water needs will be greater. GSA’s previous refrigeration equipment, which used ozone-depleting refrigerants, was replaced. The modernized GSA plant provides chilled water, refrigeration, and air conditioning for several federal facilities, including DOE, and eight Smithsonian Institution museums along the National Mall.
Robert Bailey, Smithsonian Institution Undersecretary for Finance and Administration, said, “This project eliminates the need for the Smithsonian to replace small, aging chiller plants in four of our museums. It also contributes to improved air quality for the region by consolidating energy output at one high-efficiency plant.”
A new cogeneration system will produce electricity and steam from natural gas, allowing GSA to meet the steam requirements of more than 100 federal and local government buildings more efficiently. The system will reduce or eliminate electricity costs while generating surplus electricity for sale to the electric power distribution grid. Using cogeneration technology and natural gas will help to improve air quality in the region by reducing emissions associated with the old system.
Dupage County Gets Hybrid System“On the hottest day of the year, we’ve got 1,000 tons of chiller capacity in reserve. That helps me feel secure,” said Dan Baran, facilities supervisor of power plant operations at the DuPage County Governmental Complex in Wheaton, IL. Baran is referring to the recent upgrade of the chiller plant and chilled water distribution system on the sprawling government campus.
The county has a municipal complex that includes 12 buildings totaling 1.5 million sq ft. These include an administration building, jail and sheriff’s office, judicial office building, health department, convalescent center, juvenile detention center, and power plant building. The chillers that served the facility are located in the power plant building that dates back to 1970.
The county recently completed an upgrade of the chiller plant and chilled water distribution system. The project involved replacing three single-stage centrifugal chillers ranging in age from 18 to 30 years and totaling 3,300 tons of capacity. According to Baran, the reasons for the replacement were a desire for greater efficiency, concern about the R-11, R-12, and R-114 refrigerants used in the old machines, and increasing concern about unit reliability because of age.
The power plant building also contains three boilers that produce high temperature hot water for building heating, domestic water heating, and laundry as well as steam for humidifiers and food service. The boilers have a dual-fuel configuration, operable on either natural gas or fuel oil.
In 1998, the county had performed an evaluation of chiller plant options, considering both electric centrifugal and hot water absorption options. Colin Oakley, facilities manager with DuPage County, had an idea to install a sophisticated hybrid system with both absorption and electric centrifugal capacity. A chilled water storage tank was being installed under an earlier contract.
The facility design, which eventually won a regional award from ASHRAE, has increased system security and improved the county’s position in contracting for energy supplies. Chilled water storage allows the county to reduce demand charges and to take advantage of off-peak energy rates. Plans were also made to upgrade the chilled water distribution network.
The electric chillers chosen were a 1,000-ton Trane CenTraVac™ centrifugal chiller and a 2,000-ton Trane duplex CenTraVac machine. The absorption machine is a 1,150-ton Trane Horizon™ two-stage absorption chiller. The existing boilers supply hot water at 360 degrees (182 degrees C) to the absorption machine. At full load, the chiller requires about half of the plant’s boiler capacity.
The three new chillers are all connected in parallel and can be operated in any combination, serving cooling load directly or delivering chilled water to the 1.2-million-gal chilled water storage tank. Cooling towers for the chillers are located next to the power plant.
According to Baran, the low temperature chilled water capability of the centrifugal chillers allows him to send water at 38 degrees to the storage tank at night, in effect banking chilled water capacity for the following day. The 10 p.m. to 9 a.m. energy rate is 2.273 cents per kWh vs. the on-peak period where the charge is 5.172 cents. These rates do not include the demand charge. This rate window allows DuPage County ample time to bring the storage tank down to temperature.
Energy efficient Upgrades For Fermilab InfrastructureThe U.S. Department of Energy’s (DOE’s) Fermi National Accelerator Laboratory (Fermilab) replaced old equipment and reduced energy consumption through a partnership with its electric utility, Commonwealth Edison. Fermilab upgraded the centralized cooling system and separated the system into two segments — a comfort system to cool the employee office space and a process system for the equipment and accelerators.
Backup cooling capacity is provided and cooling can be shifted between the process and comfort systems when necessary. The new 4,500-ton cooling system is expected to use 40% less energy and is free of ozone-depleting CFCs.
The $3.5 million project has total projected energy savings of 20 million kWh, which will result in cost savings of $900,000/year and a payback of less than five years. Installation was completed in April 1999. Actual savings have been higher than projected, in part because VSDs are running at lower speeds than anticipated.
The chillers serving the entire facility were originally interconnected into a single system in the Central Utility Building. The result of this centralization was that on occasion the accelerator would be shut down due to problems with the comfort system. The chillers had become increasingly less reliable because they were past their nominal rated useful life of 25 years. The bearings were worn and many condenser tubes were plugged, resulting in reduced chiller efficiency.
The chiller capacity control systems were failing as well. The degraded condition of the chillers became apparent when one of them failed during project installation. The failed chiller was fixed using parts from one of the chillers that had just been replaced. This kept it running for another two months until its replacement was brought on-line.
Before the energy efficiency upgrades, the cooling pumps always ran at full flow. Installation of VSDs allowed Fermilab to eliminate ten pumping stations. Actual savings to date have met or exceeded design parameters. The comfort cooling and accelerator heat rejection systems are performing as designed; the process system is doing slightly better, and the system has been running 15% to 25% more efficiently than anticipated.
Not only are the new chillers approximately 40% more energy efficient, they are also more environmentally friendly because they do not use CFCs.
The Richard B. RussellRichard B. Russell Renovation Federal Building (RBR) is a 1.25 million-sq-ft mixed use facility in downtown Atlanta that houses the U.S. District Court, Northern District of Georgia/Atlanta Division, and offices for several other federal agencies, including DOE’s Atlanta Regional Office. The RBR, which opened in 1979, has had recent upgrades in building systems, made possible via a FEMP Super Energy Performance Savings Contract (ESPC).
The RBR was upgraded to an Energy Star building, effective May 1, 2001, through a super ESPC between the GSA, Southeast Sunbelt Region, and the ERI Services Division of NORESCO (ERI), a FEMP Energy Services Contractor (ESCO).
Initially, GSA intended to have ERI modify only the Peachtree Summit building, their Sunbelt Region headquarters in downtown Atlanta, by replacing chillers and upgrading lighting. However, ERI found significant additional energy savings in the RBR and the nearby U.S. Court of Appeals, Eleventh Circuit building. As a result, the ESPC eventually included energy upgrades in all three buildings, a total of 2.35 million sq ft owned by GSA. The total ERI capital investment in the multi-building ESPC, finalized in September 1999, was $6.44 million, with GSA making payments over a 20-year period and guaranteed savings of 18%.
ERI began modifications to the RBR in the fall of 1999 and completed their work a year later. The ESCO replaced the building’s 21-year old chillers (two 1,720-ton centrifugal chillers) with three more efficient (0.636 kW/ton) 1,000-ton chillers with VFDs. The chiller replacement in January 2000 was a daunting task, since the equipment to be replaced was on the fifteenth floor in the RBR. To make the job even more difficult, ERI had to bring a mammoth crane into downtown Atlanta on a weekend when the city was hosting the Super Bowl just a block away from the RBR, and Atlanta had experienced a major ice storm that virtually shut the city down.
In spite of this adversity, ERI replaced the chillers and maintained the schedule in the ESPC. The next upgrade involved adding VFDs to the RBR AHUs. Upgrading the lighting fixtures throughout the building was the third major modification. Overall estimated energy reduction from the ESPC project amounted to 5,248,000 kWh/year for the RBR. During the one-year period from February 2000 through January 2001, when the upgrades were being made, building energy use was 3,209,219 kWh less than the previous year, and the energy performance on the RBR achieved an Energy Star rating of 79. With the modifications now complete, energy performance is expected to improve further. ES