Low-charge packaged ammonia/NH3 (R717) refrigeration units installed at cold storage warehouses in Sioux Falls, South Dakota (U.S.), and Hamilton, Ontario (Canada) were found to have low Specific Energy Consumption (SEC) values, according to Kurt Liebendorfer, Vice President at Evapco, and Rob Adams, Principal at Ti Cold, who described these installations during a case study session at ATMO America in Alexandria, Virginia on June 7.
The conference, held June 7–8, was organized by ATMOsphere, publisher of Ammonia21.com.
Evapco supplied the ammonia units and Ti Cold built the facilities for Lineage Logistics in Sioux Falls and Sierra Supply Chain Services in Hamilton.
The high energy-efficiency of the low-charge packaged ammonia units is reflected in the SEC. A good historic SEC benchmark for a warehouse has been 1kWh/ft3/yr (35.7kWh/m3/yr), Liebendorfer explained. For the Sioux Falls facility, the freezer rooms have an SEC of 0.55kWh/ft3/yr (19.6kWh/m3/yr) and the convertible rooms an SEC of just 0.28kWh/ft3/yr (10kWh/m3/yr). When operating in full blast freezer mode, it has an SEC of 1.13kWh/ft3/yr (40.4kWh/m3/yr), which is “very, very good, given that blast operations are very heavy loading,” said Leibendorfer. The SEC of the Hamilton cooling system is very “attractive” at just 0.37kWh/ft3/yr (13.2kWh/m3/yr).
According to Leibendorfer, centralized ammonia systems have SECs typically between 0.75kWh/ft3/yr (26.8kWh/m3/yr) and 1kWh/ft3/yr. “We have seen the low-charge packaged system go lower than that because you have more compressors and they are all VFD controlled, there’s better turn down,” said Liebendorfer.
Stefan Jensen, Managing Director of Scantec Refrigeration Technologies, Brisbane, Australia, has reported that a centralized DX ammonia delivers SECs of between 20kWh/m3/yr (0.57kWh/ft3/yr) and 24kWh/m3/yr (0.68kWh/ft3/yr) when serving a distribution center with a refrigerated volume of 40,000m3 (1,553,845ft3).
Ti Cold, based in Fort Wayne, Indiana, specializes in developing and building cold storage facilities in the U.S. and Canada. The company utilizes “advanced technology solutions to create energy-efficient buildings,” and provides a full range of cold services, including master planning, site planning and operations guidance. Evapco designs and manufactures a range of industrial refrigeration systems and products for both ammonia and CO2. The company’s wide portfolio includes low-charge packaged ammonia refrigeration systems, adiabatic coolers and evaporative condensers, pressure vessels and more.
The Sioux Falls facility was an expansion project with 134,000ft2 (12,449m2) of new cold rooms, for a total size of 464,000ft2 (43,107m2). The expansion has a refrigeration load of 540TR (1,899kW) with -10°F (-23°C) freezers and -10°F/35°F (1.7°C) convertible rooms. The original facility was one of the last built by Ti Cold with a central engine room, according to Adams, who stressed that in the last three to four years the company has been installing a lot of packaged ammonia systems.
The facility, bought recently by Lineage Logistics, turned out to have insufficient capacity, and the expansion plans then left Ti Cold with a choice either to build a new engine room or go for low-charge packaged ammonia units, with the latter option ultimately prevailing. The expansion was finished in January 2022.
Ti Cold and Lineage went with eight large penthouse LCR-P dual compressor air-cooled packages from Evapco. The installation includes six units of 70TR (246kW) capacity (at -20°F/-29°C suction temperature), and two units of 60TR (211kW) capacity, both types with an ammonia charge of less than 500lbs (227kg), giving them a charge of 7.4lbs per TR (0.95kg/kW). With a 4,000lbs (1,814kg) total charge, the system required much less ammonia than a traditional centralized system. “Had this been a traditional plant, the charge could well have approached 10,000lbs,” Liebendorfer stated.
All units utilize hot gas defrost, liquid recirculation and variable frequency drive (VFD) screw compressors. For the convertible rooms, the evaporator and condenser fans are also running on VFD, making them “very energy efficient,” according to Liebendorfer.
“The low-charge packages are awesome and having these tools that are easy for our customers to understand [has] been a real plus”Rob Adams, Ti Cold
The Canadian storage facility uses the same style penthouse units as the Sioux Falls facility, though with single compressor packages. Sioux Falls uses double compressor packages. In Hamilton they have installed five rooftop penthouse ammonia units, and a sixth unit is a low-charge ammonia glycol chiller. “Penthouses are great for big rooms and cold temperatures, but they are too expensive for small rooms or higher temperatures,” Liebendorfer explained.
The Hamilton facility is 250,000ft2 (23,226m2) and includes a 30,000ft2 (2,787m2) food processing space. Total refrigeration load is 517TR (1,818kW) with -10°F freezer rooms and 35°F cold rooms, processing room and docking area. The cooling system has a total of 2,257lbs (1,024kg) charge, which equals just 4.4lbs per TR (.59kg/kW). Current freezer load is around 250,000lbs (113,398kg) per day, but the system is designed so the amount can be increased to 500,000lbs (226,796kg) per day. Construction is expected to be completed in July.
“From an ESG [environmental, social and governance] standpoint, these buildings are awesome,” Adams said, detailing how the packaged units have reduced the need for piping and created a much cleaner rooftop.
“The low-charge packages are awesome and having these tools that are easy for our customers to understand [has] been a real plus,” Adams noted.
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