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View Subscription Details: Letter ( 08/29/2014 ) - HTML Format

Investment in optimization


There are two steps to optimize operation of the industrial refrigeration plant.

Step 1. Initial optimization of the refrigeration plant operation. This step should be done by the operators. Typically, 5 - 10% of energy use can be saved by initial improvement of the refrigeration plant operation. However, companies should invest in education of their operators and these operators should actively participate in energy saving process.  

Step 2. Final optimization of the refrigeration plant operation. This step should be done by the experts. Additional 5 - 10% of energy will be saved without significant investments. Typical payback on investments in optimization is 2 - 3 months and this much better than payback on investments in energy saving equipment.  

Unfortunately, very rare people invest in final optimization, because they mistakenly believe that nothing can be improved in operation of their refrigeration plants. I have visited several dozens of refrigeration plants and found that operation of every plant can be improved. Look at one issue related to optimization.

Analyzing operation of the refrigeration plants, I found that almost every plant has presence of non condensable gases in the ammonia system. These gases elevate condensing pressure and energy use of the refrigeration plant increases. Why do many plants have non condensable gases in the ammonia system? This happens because very rare people check their system for the presence of these gases. Operators of the plants with positive suction pressure think that they should not have non condensable gases, because air will not go into the system during regular operation. His is correct. However, air can get into the system during maintenance. Additionally, ammonia and oil can break down and non condensable gases will be produced. Typically, people purge the ammonia system during summer operation when condensing pressure is too high. However, before this purging refrigeration plant operated for several months at elevated condensing pressure and it uses much more energy than required.

Many refrigeration plants have air purgers. If purger from time to time releases non condensable gases, people believe that purger works fine and their ammonia system is free of non condensable gases. This is not correct. I found that very often purger does not work properly, because it did not get required maintenance. Many refrigeration plants with purgers operate at condensing pressure at least 10 - 15 psig (0.7 - 1 bars) higher than saturated condensing pressure. Some may think that 10 – 15 psig is not significant. However, annual energy use of the refrigeration plant with 1000 HP of compressor power will increase by 200,000 – 300,000 kWh if condensing pressure is elevated by 10 - 15 psig. This is $20,000 - 30,000 at energy cost of 10 cents per kWh. Mentioned issue is just one of many that can be improved.

If you think that operation of your refrigeration plant is optimum and nothing can be improved, think again.

Why do you right these newsletters? I was asked this question many times.

I believe that optimization of the refrigeration plant operation is the most cost effective way to save energy in industrial refrigeration. However, this is complicated issue. To educate people, I share my knowledge and experience. Unfortunately, I can not give you all information at these free newsletters. If people require additional help in optimization, they contact me in person.


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