100-Year-Old Refrigeration Techniques Are Obsolete

Vapor compression refrigeration systems use 23 percent of all electric energy in the United States. Add the millions of gallons of gasoline burned to power automobile air conditioners, and it is clear that any increase in efficiency could lead to tremendous societal benefits. Unfortunately, decades of attempts to improve the vapor compression refrigeration system by reducing chloroflurocarbon (CFC) emmissions have not resulted in increased efficiency or reduced environmental impact of this system. Typically, reductions in CFC emissions lead

to decreased efficiency, requiring the use of more electric power as well as the emission of more environmental toxins from the electric-power-generation process.

Efficient, Cleaner Refrigeration Through EERC

Calmac developed an ejector expansion refrigeration cycle (EERC) process to improve the efficiency of vapor compression refrigeration by recovering energy typically lost during the process. Specifically, the EERC process uses the energy normally lost in the expansion process to help compress the gas entering the compressor.

The EERC expands the liquid refrigerant in two steps. The first step is through a specifically designed nozzle where the liquid is used to increase the pressure of the gas returning to the compressor. After this stage, the liquid refrigerant is collected in a receiver where it is metered into the evaporator by conventional methods.

Prior Success Indicates Goals Are Possible

Before applying for ATP funding, Calmac had expended significant internal resources to overcome prior EERC failures in the industry. For example, industry efforts to achieve EERC had not generated sufficient pressure within the ejector nozzle to enhance refrigeration efficiency. Calmac, however, had developed techniques to achieve a six-percent improvement in energy expended for refrigeration through the use of the EERC. That level of improvement was not high enough to make the technology cost effective, but, with further research and refinement, Calmac expected a 10-percent improvement for air-conditioning and up to a 20-percent improvement for other, lower temperature applications. Moreover, more efficient refrigeration would reduce both the size of the equipment needed in the process and the potential release of CFCs into the environment. When improvements reached the 10-percent threshold, cost savings would then be high enough to encourage original equipment manufacturers (OEMs) to use the EERC process. At that point, economic and environmental spillover could be achieved.

Limited internal funds had hindered efforts, however, to reach the commercially viable 10-percent improvement stage. Furthermore, given the previous failures to develop EERC technology within the industry, external funds through the private market were not available to Calmac.

Improved Refrigeration Efficiency Has Potential Spillover Benefits

Because refrigeration is used in almost every residential and commercial structure, and because it accounts for such a high percentage of the nation's consumption of electric power, improvements in refrigeration efficiency could result in lower overhead costs across many

Unforeseen Obstacles Block Increased Efficiency and Commercialization

In the first 18 months of the project, Calmac engineers researched materials and engineering advances that had the potential to push the EERC above the 10-percent efficiency improvement threshold. The following six months were spent integrating these innovations into the EERC technology. At the start of the third year of the project, however, Calmac encountered unforeseen instability in the ejector's operation. Three sources of the instability were examined, but Calmac was unable to completely pinpoint and solve the problem. The specific operating parameters needed in the ejector for the EERC operation introduced inherent instabilities to the system outside this design window.

Calmac conducted research into the cause of the instability and generated extensive documentation of its findings. However, the company could not make the EERC operate efficiently for the equipment's complete range of operation.