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To estimate potential energy savings of the refrigeration plant, we should compare plant energy use at improved set points to plant energy use at baseline set points. To get correct estimation, real life baseline set points should be chosen. Sometimes people claim that they can save 40 - 50% of energy use. Is it possible? Yes. If we choose baseline condensing pressure of 180 psig for all year around operation, 40 - 50% of total energy savings can be achieved. Did you see any ammonia refrigeration plant operating at 180 psig of condensing pressure all year around? I did not. If we compare energy use at real life average condensing pressure of 130 psig to energy use at optimum condensing pressure, total energy savings for the same plant will be in the range of 10 - 20%.

Today many companies are focused on floating condensing pressure. How much energy can be saved by floating condensing pressure?


Wet bulb temperature of ambient air changes from 60°F to 65°F. To maximize energy savings, condensing pressure should be floated from 120 psig to 130 psig by following the fluctuation of the wet bulb temperature. To estimate potential energy savings, we should compare energy use at optimum floating condensing pressure to energy use at baseline condensing pressure. This plant can have 2 baseline condensing pressures of 120 psig and 150 psig. If baseline condensing pressure is 120 psig, energy savings will be 2%. If baseline condensing pressure is 150 psig, energy savings will be 12%. Today, when many companies are focused on energy savings, majority of the refrigeration plants will have baseline condensing pressure of 120psig. It means that operation of these plants are close to the optimum (at wet bulb temperature of 60 - 65 degF) and floating condensing pressure will give you 2% of energy savings. You can get the same energy savings by lowering minimum condensing pressure by 5 psig, but you do not need sophisticated and expensive PLC for this action as floating condensing pressure is required.

To estimate real life energy savings, real life baseline set points should be chosen.


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