Quote Originally Posted by GCAP CoolCast View Post
yes that paper was written by Joe Phillis who if I remember correctly works for Frick or maybe Johnson Controls.

PG&E in california put out an 86 page report march 30 of 2009 using real world testing at a US Cold Storage facility that conflicts with Joe's report.

they did a 5 month study using flow meters, power meters, etc. they found that the CO2 cascade system using recips was at a much lower kW/Cube than a two stage ammonia system.

another independant study was done as well by Vacom Technologies. Their website is http://www.vacomtech.com/

also Greg Robinson from M&M refrigeration asked me to post his phone number so that anyone who had question or doubts about CO2's energy efficiency could give him a call for more information.

Greg Robinson
Email gregr@mmrefrigeration.com
Work 410-754-8005
One end user, one contractor, one consultant. It looks like they work as a team.
I didn't see this report. However, to do it right they should compare apple and apple. It looks like CO2 recip. compressors were compared to NH3 screw compressors. Definitely, part load efficiency of recip. is better than part load of screw. However, if you put VFD for screw it will be close. Another issue is condensing pressure. NH3 system require hot gas defrost. Some people do defrost at 150 psig, others at 120 psig. I saw plant that was defrosted at 80 psig of condensing pressure. What pressure did they choose for this study? Probably, 180 psig for NH3 plant and 100 psig for CO2. In this case you will get 30% of energy savings. CO2 plant has electrical defrost. No limitation to the condensing pressure. However, they have to change elec. heaters very often.