An outside air economizer like a Freeaire® system with a Polar Power® package can be a huge benefit for a server room. In fact, it is one of the most cost effective ways to utilize the cooling potential of outside air. Because a server room can safely be kept very warm, even warmer than a typical room temperature of 70°F, there are very few days per year when the outside air temperature is not cool enough to use to provide some cooling to a server room anywhere in the world. In colder climates the outside air is often cold enough to completely replace mechanical refrigeration by air conditioning systems for many days annually, especially in the winter.
This graph shows how much a Freeaire system with a Polar Power package for a small server room in Vermont room operates. You can see that in the winter, when the outside air is cold, it is being brought into the space almost all of the time. In the summer, when the outside air is sometimes too warm to use, the economizer still is on much more than it is off. In fact, there is never a day when the economizer is not operating, and the average ON percentage for the entire year is over 80% of the time. The Polar Power package is saving energy almost constantly.
Data centers in which racks of servers, routers, and computer systems receive and transmit vast amounts of electronic information are a phenomenon of the digital age. They are responsible for about 2% of the energy use in the United State, for both the server operation and the cooling equipment needed to remove the heat, and that share is growing rapidly. Whether your server room looks like the picture of the left, with its tangle of wires, or like the picture on the right, with all the wires neatly organized, , the electricity they carry still generates tons of heat that needs to be gotten rid of. Server rooms are usually cooled by air conditioning systems that have to operate 24/7/365 and that also consume prodigious amounts of expensive electricity. You are paying for that electricity twice, once to run the servers and again to operate the cooling equipment.
Whenever filtered cold or cool outside air being brought into a server room by a Polar Power package is only 4 degrees cooler than the warm air that it exhausts, it is already more efficient than the air conditioning system. As the outside air becomes colder the Polar Power gets even more efficient and takes over a larger share of the cooling from the AC. In the depths of winter in the northern US and Canada, using outside air can sometimes keep the AC off for months at a time. When the outside air being brought into a server room is 8°F cooler than the air being exhausted, the economizer is twice as efficient as an AC system. When it drops to below freezing outside a Polar Power package removes about ten times as much heat per watt as the AC.
Another way to save energy when cooling a server room is to raise its temperature setting. A common mistake is to assume that the IT equipment needs to be kept at the same 68-72°F temperature range that people find comfortable. However, since people don’t spend much time in a typical server room, the cooling needs of the servers are the more important consideration. In fact, American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) recommends a broad operating envelope of between 64.4°F to 80.6°F for every class of IT equipment. They also specify an “allowable operating range” with a higher limit of up to 89.6°F for even the most heat sensitive equipment. That means your server room can be kept much warmer than it probably is now, and you can save a lot of energy and money by doing so. The highest allowable temperature for “Class 4” equipment is over 111°F! With an operating environment that warm being OK, an air conditioning system may not be necessary at all. You should, of course, find out what class of IT equipment yours is before setting your thermostat that high.
The ASHRAE guidelines also specify the safe high and low humidity limits for IT equipment, with a similar broadening of the recommended and allowable windows of operation for the various classes. It is therefore important that the electronic controller for the economizer, such as a Freeaire Cooler Controller, monitors both temperature and humidity to ensure proper functioning.
Your air conditioning system does not have to have the entire burden of cooling your server room. Instead, let it take a backup role and use clean, cold outside air to do the job much more efficiently.