In my last article on energy management in the lab, I gave an overview of why labs use so much energy. In this article we will look a little deeper at one of the most energy intensive pieces of equipment in your lab and learn tips on how to reduce that energy load.
Laboratory Cold Storage
That buzzing, that awful, loud, constant sound that seems to pervade every lab space on the face of the earth. You hear it when you walk into the lab in the morning and luckily it seems to fade away as you settle into your day. Know what I am talking about? That is the sound of many refrigerators and freezer laboring away to maintain their specific temperatures and just because the sound of them may fade away, does not mean they are not still consuming energy. In fact you can probably hear one right now as you read this article.
The cold storage box is really a complex piece of machinery; there are a lot of moving parts (one of the reasons they break down so often). You have the insulated storage box, compressor(s), condenser coils, evaporator, refrigerant and the list goes on. Freezers and refrigerators maintain their temperatures by evacuating warm air out of the insulated box. Refrigerant vapor is compressed, heating it up and raising its pressure. That hot, high-pressure refrigerant travels through condenser coils where it meets with room temperature air, cooling it and becoming a liquid, while still maintaining its high pressure. This high-pressure liquid then circulates through the insulated box absorbing much of the heat inside, effectively lowering its temperature. The refrigerant returns to a vapor and circulates back to the compressor to start the process again. Every time, your refrigerator of freezer falls outside the parameters it is set to, this process happens.
To avoid spending additional resources on energy consumption from cold storage, try following these tips:
1) Dr. Gornish, identifies one method in her “3 Easy Tips to Green Your Lab” article. She says that by raising your Ultra-Low Temperature freezer’s set point from -80°C to -70°C you can reduce their consumption by 2-4 Kwh a day. This is a great start to reducing your energy use from cold storage; it is what we call a low hanging fruit or an action you can take for little effort or cost. Make sure to have an argument prepared on how this will not endanger the contents of your freezer, as it is not uncommon to find opposition to this method.
2) Know what you want in your refrigerator or freezer before opening it. For every minute the door of the cold storage box is open, it takes approximately 10 minutes to cool it down again. The longer the door is open, the longer the compressor will have to run to cool it down again.
3) Have your facilities department regularly clean the backside of your refrigerators and freezers. Dust will build up on the condenser coils, insulating them and making the compressor work harder, increasing its energy use by up to 25%. In addition to lowering the efficiency of the compressor, the increased workload will shorten the lifespan of the freezer or refrigerator.
4) Listen to your refrigerators and freezers; if you hear a compressor that is on for an extended period of time, have the maintenance department check it out. This could be a sign of an aging piece of equipment. Over time the wear and tear on a compressor can decrease the efficiency of that freezer/refrigerator by up to 35%, increasing your costs.
5) When purchasing freezers instead of looking at just the upfront cost include operating cost of the freezer. This takes energy use into consideration and can save you money over the lifetime of the freezer.
For instance, Ultra-Low Temperature (ULT) freezers or Freezers that operated at -80°C use an average of 9-22 Kwh/per day. In the course of a year a freezer that uses 22 Kwh a day will cost about $1,200 a year vs the more efficient 9 kwh/ day freezer that only costs $500. If the more efficient freezer has a price premium of $3,000 it will only take 4.3 years to recoup that cost. Considering the average lifespan of a ULT freezer is 17-20 years, you could end up saving more than $10,000 over the lifetime of that piece of equipment.
While freezers are not the most energy intensive equipment in your lab, they still do use a considerable amount of energy. By following these simple tips you can help to reduce your energy load, lower carbon emissions and save your company or institution money.