Three steps

Typically, there are three steps to an energy efficient refrigeration plant.

Step 1. Initial optimization of the refrigeration plant operation.

Operating engineers can improve the operation of their refrigeration plants and energy will be saved. This step does not require significant investments. Typical investment at this stage of the optimization is from $0 to $10,000. Some companies believe that optimization of the refrigeration plant operation is the duty of the operating engineers. Other companies try to encourage their operating engineers to actively participate in the energy saving process. I think that this encouragement can be helpful to maximize the efficiencies of the many refrigeration plants. Typically operating engineers can achieve up to 30 - 40 % of total energy savings.

Step 2. Final optimization of the refrigeration plant operation.

This step should be done by a consultant. Unfortunately, many companies miss this energy saving step because they mistakenly believe that full optimization of the refrigeration plant operation was done by operating engineers.

Example.

Majority of the refrigeration plants are operated at minimum condensing pressure of 110 - 120 psig. During winter operation, reduction of this pressure can significantly improve efficiency of every refrigeration plant. However, majority of the operating engineers never seen the operation of the refrigeration plant at condensing pressure 100 psig or lower. They believe that this is impossible. My experience has shown that many refrigeration plants can be operated at condensing pressure below 100 psig. I have seen plants operated at 60 psig of the condensing pressure. However, there are several barriers to operate plants at such low condensing pressure but every barrier has a solution.

Where is the border between step1 and step 2? I suggest to every company to optimize operation of their refrigeration pants for 1 year. Usually, after achieving initial energy savings, you are stuck. This is the point at which step 2 should be initiated. Find the right person who will be able to help you to continue optimization. However, do not assume that every professional engineer or every consultant will do this job. Optimization of a refrigeration plant operation is a relatively new direction in industrial refrigeration and just a few people can do it right.

Typical investment at this step is $10,000 - 20,000 and additional 30 - 40% of total energy savings can be achieved.

Step 3. Investments in VFDs.

Compressor, condenser fan and evaporator fan VFDs can improve efficiency of the refrigeration plant. However, significant capital investments are required. Typical investments are $100,000 - 200,000. Mentioned VFDs can save up to 20 - 30% of total energy savings. I think this step should be done after full optimization (steps 1, 2) of the refrigeration plant operation. Surprisingly, some companies invest in VFDs before initiating optimization (step 1). However, it is not a surprise that they achieved limited energy savings.

Choose the right steps in the energy saving process.