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View Subscription Details: Letter ( 06/30/2014 ) - Plain Text Format Energy Audit

An energy audit is an inspection, survey and analysis of energy flows for energy conservation. The goal of every energy audit is to identify energy saving measures. Potential energy savings and costs of implementing identified measures should be estimated as well. In real life not every energy audit is good. The quality of an energy audit should be evaluated by two criteria. The first criterion is the magnitude of the identified energy savings. Second criterion is payback of investments to implement identified energy savings measures. An energy audit is a plan to maximize energy efficiency of your refrigeration plant. This plan can be good or bad. A bad plan will lead to a bad energy efficiency project. Review examples of bad energy audits.
Example 1. An energy audit identified that $10,000 of energy costs can be saved. To achieve these savings $20,000 should be invested. Payback of investments is 2 years. This is relatively good payback, but potential energy savings are limited. Most likely more energy can be saved for this refrigeration plant.
Example 2. Identified potential energy savings are $100,000. However, to achieve these savings $1,000,000 should be invested. Payback of these investments is 10 years. This payback is too long. Many companies will not invest in energy efficiency projects which have payback longer than 2 years.
How can you get a good energy audit? You should find the right people. Today many companies claim that they have done dozens of energy audits for the buildings, for commercial refrigeration, and for industrial refrigeration. However, there is huge difference between these energy audits. To do a good energy audit, someone should be an expert in the particular area of refrigeration. You can not be an expert in every area of refrigeration. Good energy audit should include optimization of the refrigeration pant operation. We can have a look at a few differences between commercial and industrial refrigeration.
1. They have different refrigerants. Commercial plants have freons. Industrial plants have ammonia. Choice of refrigerant will influence the oil return or oil recovery. This issue will influence the energy saving approach.
2. Commercial refrigeration plants have air condensers. Industrial refrigeration plants have evaporative condensers. To maximize energy efficiency of your refrigeration plant, it should be operated at optimum condensing temperature approach. However, optimum approaches will be different for commercial and industrial refrigeration, because performance of the air condenser depends on dry bulb temperature and performance of evaporative condensers depends on wet bulb temperature of ambient air.
3. Usually, commercial plants have reciprocated compressors and industrial plants have screw compressors. Part load operation of these compressors is different. This means that different operating strategies should be chosen.
Recently, I talked to one expert who visited one industrial refrigeration plant. Management of this plant invested a lot of money in VFDs. However, after installation of VFDs energy use has increased by 10% compared to initial baseline. They did not realize that to get energy savings from VFDs the right operating strategy should be chosen. This expert helped them to choose the right strategy and energy use was reduced by 15% compared to the initial baseline.
An energy audit is not expensive, typical costs are $5,000-10,000. If you are not sure that your first energy audit is good, do a second one. Very often, it will save you several hundred thousand dollars in unnecessarily investments. Unfortunately, we have many examples of poor investments in energy efficiency of industrial refrigeration plants.
To achieve a successful energy efficiency project, it is very important to find the right people who will be able to do a good energy audit for you.
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