2019 RETA Breeze Sept-Oct

Energy consumption by comparison of a highly efficient low charge ammonia system completed and the other utilizing a trans-critical carbon dioxide system.

carbon dioxide facility is appreciably less expensive to own compared to the ammonia facility. Compared with ammonia, the regula- tory burden and costs for a carbon dioxide system are virtually nil. These cost savings along with the reduction in liability for fines from EPA and OSHA, the eliminated risk of contamination of stored customer product, and the reduction in risk of employee or com- munity injuries due to exposure to a highly toxic refrigerant put the carbon dioxide system at clear advantage. Based on the above presented evi- dence, in this authors’ humble opinion the advantages of carbon dioxide far outweigh the advantages of ammonia. I expect that the industry will move in the direction of carbon dioxide for many new facilities that were previ- ously refrigerated using ammonia and HFC’s as refrigerants.

presented a great opportunity for comparative analysis between the two technologies. For the most recent 12 months of op- eration, the specific energy use at the two facilities described above can be summarized as follows in the graph above. While it is true that the carbon dioxide facility has used slightly more energy than the one using ammonia, note that compared to the industry aver- age, both of these facilities stand head and shoulders above the industry in terms of energy consumption. The ammonia system saves 78% energy while the carbon dioxide system saves 67%. Furthermore, ongoing tuning and commissioning efforts on the carbon dioxide system are providing additional savings that are projected to reduce or eliminate the ammonia energy advantage in the future. Besides energy, when operational, maintenance, water, water treatment and sewer costs are factored in, the

dry ice has returned to a liquid state and the entire tank has reached am- bient temperature before returning it to service. There are some really great videos illustrating CO2 at saturated, triple point and critical point conditions available on YouTube: https://www. youtube.com/watch?v=RmaJVxafesU or https://www.youtube.com/ watch?v=zu-S1GxmkCo. NUMBER FOUR, “Carbon dioxide systems are energy hogs”. Based on the author’s recent experi- ences with two trans-critical carbon dioxide systems installed in a frozen food warehouse, this statement is also turning out to be a myth. The construction by my company of two nearly identical facilities in virtually the same climate zone, one with an advanced and highly efficient low charge ammonia system completed in spring of 2017, and the other utiliz- ing a trans-critical carbon dioxide system completed in spring of 2018,

RETA.com 23