With so many choices and a growing number of green alternatives, companies seeking refrigerants need to be prudent. Rajan Rajendran provides advice on how to successfully traverse the narrow path between a myriad of regulations and operational efficiency.
Environmental experts estimate refrigeration and air conditioning activities account for approximately 10 per cent of all global warming. Energy consumption is the largest driver of emissions (and operating cost) in refrigeration systems.
In typical low charge systems, 95 to 98 per cent of the indirect warming impact is from energy consumption, while only two to five per cent is attributable to direct warming through refrigerant leakage.
The most effective method of reducing these emissions is through the development of thermodynamically efficient refrigerants.
While there is no ideal refrigerant, there is a proven holistic approach to selection which can be helpful in specifying a best case solution.
In this article I have restricted comments to hydrofluorocarbon (HFC) blends and emerging ozone-neutral hydrofluoroolefin (HFO) refrigerants.
As well as protecting the environment, another area of paramount concern is the safety of personnel and property. Refrigerant safety issues fall into four major areas: toxicity (some countries permit the use of toxic refrigerant options); flammability (leakage of a flammable refrigerant could result in a fire); pressure (some refrigerants operate at high pressures only); material compatibility (material deterioration can lead to leaks).
Blends have been endorsed as safe, cost-effective substitutes for CFCs and HCFCs by the Technical and Economic Assessment Panel (TEAP) of the Montreal Protocol on Substances that Deplete the Ozone Layer (1999). Moreover, HFC systems have proven to conserve energy and reduce global warming gas emissions from electrical power-generating plants. The Alliance for Responsible Atmospheric Policy has reported that substituting blends for CFCs along with the deployment of more energy-efficient refrigeration system technology has reduced related greenhouse gas discharge by more than 80 per cent since 1990.
Based on these factors, refrigerant manufacturers and systems engineers cite the following key criteria for specifying replacement HFC refrigerants:
Global Warming Potential (GWP) – should be reviewed using the LCCP Index. The combined direct and indirect global warming impact should be as low as possible or less than the refrigerants being replaced.
Performance – the new refrigerants should be similar to those being replaced, but with zero ozone depletion and the lowest possible GWP.
Safety – new refrigerants should be non-toxic, and maximum system pressures must be no greater than the current acceptable limits for retrofit applications. Only safety, proper installation and maintenance per ASHRAE-15, ISO-5146 and European Standard EN378 should be used.
Material compatibility among the new refrigerants, lubricants and materials of construction in compressor and system components, must be maintained;
Lubricants that work with current oil-control technology should meet or exceed existing durability requirements and be backwards-compatible with mineral oil systems. It is highly desirable to have one lubricant solution that works with all alternative refrigerants, including blends and HCFC retrofit chemicals.
While RFC refrigerants are key to energy efficient refrigeration equipment, other factors also contribute to optimised energy efficiency such as responsible-use principles.
These include prompt maintenance to keep systems running longer, containment for early leak detection and repair, and all refrigerants should be recycled at the end of the system’s service life.
Although new refrigeration systems have been designed to handle these HFC refrigerants, expert consultation is often required to ensure overall LCCP objectives are met.
The best course of action in specifying refrigeration systems and refrigerants is to work closely with OEM manufacturers and their engineering specialists who can provide solutions in compliance with government regulations and industry standards.