Commercial Refrigeration
Technologies: Opportunities and
Best Practices for Green Design
Conventional Refrigeration Systems
Supermarkets around the world rely on refrigeration technologies
to keep produce fresh, milk cold, and icecream frozen.
In the United States, supermarkets have historically used centralized direct
expansion (DX) commercial refrigeration systems.These DX systems typically
have a charge of 3,000 to 4,000 pounds of refrigerant and can leak in excess of 20
percent of their refrigerant charge each year. Refrigerant leaks are costly and are
detrimental to the environment due to their high global warming impact.
Green DX Systems
While leaked refrigerant can be expensive to replace, centralized DX systems are
cost-effective when properly designed, installed, and maintained. Centralized
DX systems benefit from lower installation costs when compared with many
alternative commercial refrigeration technologies. In addition, centralized DX
systems can be more energy efficient than alternative systems.
Thoughtfully designed, installed, and maintained systems—referred to as 'Green
DX systems'—are a proven and reliable technology. In addition to cutting costs,
Green DX systems can help supermarkets reduce their impact on the environment
(see flip side for tips on designing a Green DX System).
Alternative Refrigeration Systems
In addition to Green DX systems, supermarkets can also adopt alternative
refrigeration designs and refrigerants. Examples of alternative refrigeration
systems include distributed systems, secondary loop systems, cascade systems,
and carbon dioxide (C02) systems. While alternative refrigeration systems often
benefit from smaller refrigerant charge sizes and lower refrigerant leak rates,
they can present other challenges related to upfront costs and technician
familiarity, and need to be carefully designed to maintain efficiency.
1 Estimated impacts are based on generalized assumptions and were calculated using the GreenChill
Climate Impact Calculator and the GreenChill Financial Impact Calculator, available online at http://
www2.epa.gov/greenchill/reports-guidelines-and-tools.
2 Estimated impacts are based on emissions of R-404A and were calculated using the Greenhouse Gas
Eguivalencies Calculator, available online at http://www.epa.gov/cleanenergy/energy-resources/
calculator.html.
Benefits of Green and
Alternative Designs
Each type of commercial refrigeration
technology offers advantages and
challenges. With many supermarkets
focused only on the challenges, the
advantages of green or alternative
designs are often overlooked. As
exemplified below, systems with
smaller refrigerant charge sizes and
lower refrigerant leak rates provide
notable financial and environmental
benefits.
Financial Impact1
Refrigerant leaks from a conventional
DX system can be up to 1,000 pounds
of refrigerant each year. At $4- $6 per
pound, leaked refrigerant translates
into a lot of money. For example, to
pay the annual replacement cost
of leaked refrigerant, a supermarket
would have to sell roughly:
• 135,000 gallons of milk, or
• 125,000 pounds of ground beef.
Environmental Impact2
The more climate-damaging
refrigerants that are commonly used
in a supermarket can mean emissions
equal to almost 1,800 metric tons of
C02.This is equivalent to:
• Annual C02 emissions from
roughly 375 passenger vehicles, or
• Annual C02 emissions from
the energy use of roughly 160
U.S. homes.
United States
Environmental Protection
Agency
October 2014
430-F-14-040
-------
Overview of System Components and Best Practices for Green Design
ROOFTOP
Condenser
Typically located outside, the condenser
transfers the heat from the high-pressure
vapor refrigerant to the surrounding air or
a water supply, causing the refrigerant to
convert back into a liquid.
Green Tip: Install the condenser as
close as possible to the compressors to
minimize the system's refrigerant charge.
Green Tip: To reduce your
system's refrigerant charge, use
split condenser piping along with
automated switching techniques to
enable the condenser to operate on
only one of the two circuits during
cold weather months. Apply industry
accepted techniques and controls
to permit pump out of stranded
refrigerant from the inactive
condenser circuit.
SALES FLOOR
Display Cases
Located throughout the sales
area, display cases are used
to store refrigerated and
frozen products.
Expansion Valve
The expansion valve, located
inside the display cases, controls
the flow of the refrigerant to
the evaporator.
Evaporators
Located inside the display cases, evaporators are used to
remove heat from the conditioned space within the display
cases. Inside an evaporator, liquid refrigerant boils, or
evaporates, absorbing heat as it changes to a vapor.
Green Tip: A variety of practices can be used to reduce the energy consumption of display cases, including the use of LED
lights, electronically commutated motors (ECMs), and no-heat glass doors. Reducing the energy load of cases reduces the
required refrigerant load, which in turn reduces the amount of refrigerant charge required of the system.
Low Pressure Vapor Refrigerant
High Pressure Vapor Refrigerant
High Pressure Liguid Refrigerant
Low Pressure Liquid Refrigerant
Often located in a machine room at the back of a
store, compressors pump the low pressure vapor
refrigerant from the evaporators and compress it to a
high pressure and temperature.
Green Tip: Compressor racks should be positioned as
close as possible to the display cases and walk-ins within
the store. They should also be positioned in such a way
so that they are easily accessible by maintenance and
service personnel.
Receiver
The refrigerant charge required of a system varies
seasonally.To accommodate this variation, additional
liquid refrigerant charge is stored in a vessel, known as
the receiver, located downstream of the condenser.
Green Tip: Oversized receivers can lead to overcharged
systems. To minimize the charge, carefully select the
vessel size to appropriately accommodate your system.
Additionally, if possible, use a vertical receiver, which
requires less charge than a horizontal receiver.
Piping
Piping is used to transfer the refrigerant from the machine room to the cases
located throughout the store. Piping also connects the compressor rack to
the condenser via the discharge and condensate line.
Green Tip: Alternative piping designs, such as suction and liquid
loop piping, can be used to reduce the linear feet of piping required by
your system as well as the number of fittings. This in turn reduces both
the charge size and leak potential of the system.
------- |