The investment in a new stationary refrigeration system is one that has implications for many years to come. The changing regulatory framework adds to these considerations. Systems are designed for a specific refrigerant gas, and can be difficult and costly to modify.
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Unfortunately, not all gases are created equal. The damage to the ozone layer (a thin shield high up in the sky that protects all life from the sun's harmful radiation) has required the phasing out of CFCs and now HCFCs such as R-22. However, many replacements such as HFCs still pose a threat to human health in terms of climate change. The potency of HFCs, when measured in terms of how they heat the atmosphere, is typically thousands of times greater than that of carbon dioxide (CO2) on a pound-for-pound basis (see graph, below). This potency is measured as Global Warming Potential, or GWP.
Refrigerant technologies are increasingly available that are much safer for the climate, and may also save energy. Incentives are available to assist in purchasing such environmentally preferable products: Learn more about incentives.
Be advised that common replacements for R-22, such as the HFC refrigerants R-404A, R-507A, and R-407B, have been identified for restrictions by both California and the U.S. EPA because of their high GWP values and the availability of alternatives with lower GWPs.
Although some HFC refrigerants have a lower GWP than R-22, which is being phased out by , they are still high-GWP refrigerants. For example, R-134a has one of the lowest, with a GWP of 1,430. Replacement options for R-22 systems have included higher GWP gases such as R-407A (GWP of 2,107) for grocery stores and R-410A for air conditioning systems (GWP of 2,088).
Businesses need to be informed to make the best choices when purchasing new systems.
There are many alternatives to HFCs, depending on the application. Some of these have been in existence for over a century, called "natural refrigerants" because of their occurrence in nature, and are only now making a come-back due to the environmental problems with synthetic refrigerants. Examples include carbon dioxide (CO2), ammonia (NH3), water vapor, and hydrocarbons (HCs) such as propanes. New system types are emerging for specific applications. In addition a new group of low-GWP synthetic refrigerants, hydrofluoro-olefins (HFOs), are in development and already available for some applications.
The following graph illustrates the difference in global warming potential (GWP) of one pound of various common refrigerants, as compared to a pound of CO2:
The above graph illustrates the difference in global warming potential (GWP) of one pound of each of various refrigerants, as compared with a pound of CO2.
Ammonia: Ammonia has the benefit of being energy efficient and having zero impact on both climate change and the ozone layer ' unfortunately it is toxic to humans, historically limiting its applications. However, new technologies that reduce system size, safer controls and improved understanding of its application are expanding its potential. Low-charge ammonia systems are available today for a wide array of applications with favorable initial reports.
CO2: Carbon dioxide systems, particularly transcritical CO2 systems, are increasingly being used around the world, including in California. Most often used in supermarket applications in colder climates because of waste heat dissipation needs, in Europe, commercial carbon dioxide systems number in the thousands and North American market share is increasing rapidly. On both continents these systems are also making gains in southern climates.
Hydrocarbons: Hydrocarbon systems include R-290 (propane), R- (propene or propylene) and R-600a (isobutane). These refrigerants have very low GWPs and zero ozone depletion potential (ODP). In addition they have been found to have substantial energy efficiency benefits as compared to HFCs in many applications. Because they are flammable, equipment must meet UL standards. Currently these systems are limited to small commercial units such as vending machines and standalone display cases, although a SNAP application is underway () to allow larger sizes for self-contained water-cooled units in grocery stores, and a demonstration project has been installed which aim to provide whole-store solutions for commercial retail. Hydrocarbons have application in medium and low temperature applications for micro-distributed systems.
Hydrofluoroolefins (HFOs): HFOs have very low GWPs due to their very short atmospheric lifetimes. Although there are low-level flammability (A2L) issues with HFOs, some are already SNAP approved. For example, HFO-yf, with a 100-year GWP less than one (1) and similar operating properties to R-134a, is now approved for certain uses in some chillers. It is also a component of HFO-HFC blends such as R-448A and R-449A (GWPs close to 1,400) which were recently approved for retrofit of certain HFC systems. While these newly approved blends have lower GWPs than the HFC blends they replace, their use still requires great care and is already regulated under California law because they are still high-GWP refrigerants. Performance issues including energy efficiency are being evaluated. In addition, there are unresolved environmental concerns regarding HFO refrigerants such as regarding trifluoroacetic acid (TFA) buildup in water bodies. TFA is a strong acid that may accumulate on soil, on plants, and in aquatic ecosystems over time and that may have the potential to adversely impact plants, animals, and ecosystems (source: U.S. EPA, Federal Register Vol. 81, No. 74 / Monday, April 18, / Proposed Rules / p. ).
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Whatever refrigerant is used, a hybrid/cascade system that cools a secondary refrigerant with low GWP can reduce GHG emissions by reducing the overall charge and leak rate needed for a given application. These systems can also be more energy efficient, reducing the "indirect" GHG emissions caused by the generation of the electricity used to power them. Such systems are available now for use in any climate zone.
The "high side" or "primary" refrigerant used for doing the work of removing heat from the system can be any of a wide range of refrigerants including HFCs, HFOs, and natural refrigerants such as ammonia and propane. With these systems, a secondary refrigerant such as low-GWP CO2 (for both medium- and low-temperature applications) is cooled and distributed where needed. The amount of primary refrigerant can be reduced by 70% or more, and the amount of piping used for the primary refrigerant can be dramatically reduced, helping prevent emissions by reducing both leak rates and the amount of high-GWP refrigerant that can leak.
Awards and Recognition: In California and nationwide, businesses with low-GWP systems and best practices in environmental stewardship gain special recognition, such as through Store Certification Awards from the U.S. EPA's GreenChill Program as well as the Cool California Small Business Awards and other awards programs.
Here are some links to resources which may help your search for the best system choice for your application:
As far back as we can remember man has used ammonia for one reason or another. It is in fact the oldest known refrigerant. It is successfully utilized in many industries including food, petrochemical and pharmaceutical. So why is it so misunderstood?
In this article, we will attempt to clear up and demystify anhydrous ammonia, which is a formulation void of water, as it relates to refrigeration. We will discuss the benefits and drawbacks of this ammonia refrigerant as well as review leak detection and safe handling procedures.
Related service: Process Safety Management Program.
Why do we use anhydrous ammonia instead of halocarbons in industrial applications? Ammonia is cheap and extremely efficient. Ammonia is the most commonly used refrigerant worldwide for large commercial applications. The main use of ammonia is agricultural (fertilizer). More than 80 percent of the ammonia produced is utilized in this fashion due to its high nitrogen content. Since ammonia is plentiful, the cost is low. The cost for refrigerant-grade anhydrous ammonia typically is less than 50 cents a pound, compared to about $7 a pound for R4O4A and $15 a pound for R-502.
There are two primary grades of ammonia commonly available in the marketplace. There is an agricultural or commercial-grade ammonia that must contain a minimum water content of at least 2,000 ppm water (0.2 percent) with a maximum water content of 5,000 ppm (0.5 percent). The minimum water content prevents stress corrosion cracking of the metals used in equipment for the agricultural industry.
Industrial-grade anhydrous ammonia, commonly called metallurgical or refrigeration grade, has very little water contamination. Metallurgical-grade has a maximum of about 33 ppm water (0. percent) and refrigeration-grade has a maximum of about 150 ppm water (0.015 percent). For optimum efficiency and effectiveness in your industrial refrigeration system, the ammonia supplied to you for your system should meet or exceed these specifications.
In addition to the price the most compelling reason to utilize anhydrous ammonia is the fact that it has such a high latent capability per pound. Its latent capability at 5° F evaporator temperature is 565 Btu per pound. When compared with R-22, which is approximately 69 Btu per pound at the same temperature, its obvious that it takes less ammonia to do the work because it is more efficient. This means less kwh used and lower operating costs.
Because the smell of ammonia is readily perceptible, you will know it if there's even a tiny leak. With halocarbons a technician's chances of smelling a leak are low, unless it contains a lot of oil and you are near the source.
Ammonia vapor is lighter than air and in a confined area il displaces oxygen from the ceiling downward. Halocarbons are heavier than air and will displace the oxygen from the floor upward. Either situation can be fatal.
Ammonia is flammable and has a lower explosive limit (LEL) of 15 percent (150,000 ppm) and an upper explosive limit (UEL) of 28 percent (280,000 ppm). When the ammonia vapor is mixed with a mistable oil, the LEL can be as low as 8 percent (80,000 ppm).
Ammonia also will undergo what is called hazardous decomposition at temperatures above 850° F. This means it will break down into nitrogen and hydrogen gases. Hydrogen gas has a flammability range of 4 to 75 percent.
Ammonia systems generally are built around an understanding of the characteristics of anhydrous ammonia and its dangers and benefits. As with any system, the first line
of defense is the safety engineering designed into it.
Industry safety standards continue to be the main reason ammonia systems are much safer than most people are aware. Each system must meet strict safety codes, which include materials of construction as well as appropriate relief valves, ventilation, safety switches and other safety engineering concerns.
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As in any other industry, the training of operators and technicians is important. Fully trained operators and technicians are much less likely to cause a situation resulting in death or injury.
Both OSHA and U.S. EPA address training for larger ammonia refrigeration systems. If the ammonia refrigeration system has a charge of 10,000 pounds or more, you must implement or take operational and maintenance training. Many companies follow this regardless of the charge level.
Training must include standard operating procedures for every task that will be performed, as well as safe work practices, including proper line-break procedures. Line-break procedures are what a technician does each time the ammonia refrigeration system is opened for maintenance. Additionally, operating personnel must receive refresher training at least every three years.
Related service: Level I Refrigeration Operator.
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