AISO's Water Cooled, Environmentally Friendly Cooling Systems

Our redundant cooling systems are built by a company called Freus, Inc. The Freus systems are water-cooled air conditioning systems, that based on test results are nearly twice as energy efficient as conventional air-cooled systems. Although water is used to assist with cooling, this technology is not related to the conventional Evaporative Air Coolers often called swamp coolers. Water is used to remove heat from the refrigerant and at the same time reduce the work of the compressor. Unlike air cooled units, which lose in the range of 25 percent of their rated efficiency at temperatures exceeding 100° F relative to their SEER rating, the efficiency of the Freus evaporative water cooled units have a minimal drop.
 

The primary benefit of an evaporative water cooled condenser unit is a 25 to 40 percent reduction of overall power consumption relative to a SEER 10, and a 40 to 50 percent reduction in peak power consumption (i.e. temperatures exceeding 95° F) relative to a SEER 10. SEER or Seasonal Energy Efficiency Rating is a rating system developed to more accurately reflect overall system efficiency on a seasonal basis. Essentially, the higher the SEER, the more energy efficient the system. EER or Energy Efficiency Ratio is a ratio that compares the cooling capacity (in BTUs) to the amount of electrical power (in Watts) a system requires. It is based upon a single point measurement that is taken at an outside air temperature of 95°F. As a point of reference, systems that are over ten years old usually have an EER of about 6 to 8, while newer systems are available with EERs of 10 to 12.
 

Freus, Inc. has developed a water cooled evaporative condenser unit. A "scroll" compressor compresses the R-22 refrigerant. A small water pump(7) continually sprays water(5) over the condenser coils(6), which cools the coil primarily via conduction from the copper coil to the water sprayed on the coils, as the condensing fan(1 & 2) supplies air to the coils. The coil is solid copper; approximately three times the thickness (i.e. 0.032" vs. 0.012") of that used in air-cooled condensers, and the copper is coated to prevent corrosion. This allows the refrigerant to expel more heat by taking advantage of the use of the cooling due to evaporation. A float maintains approximately 3.5 inches of water in the bottom of the condenser. At an outdoor ambient air condition of 95° F Dry Bulb (DB) the Freus unit has an EER of about 18. As the temperature increases to 105° F the EER drops to about 17.
 

It's no secret that water-cooled systems are much more efficient in hot weather then air-cooled systems. Water removes heat from the condenser coils far more efficiently than air. The reason that water-cooled systems are more efficient is simple: It is easier to reject heat into water then into air. The energy consumption of refrigeration compressors is directly proportional to the pressure it must produce. Since water-cooled systems operate at lower condensing temperatures (90°F versus 120°F), they allow refrigeration compressors to operate at much lower pressures. This is why they require so much less energy to provide cooling. The heat transfer and evaporative process is also increased via a fan on top of the condenser. Above 95° F, a typical air cooled condenser draws approximately an additional 10% power for each 10° F increase in temperature. In contrast, an evaporative cooled condenser draws about the same power over a wide range of outdoor temperatures.

And because AISO is located in a desert area to maximize our solar panels' electricity production, we have very hot days. We also chose this location due to the great amounts of solar energy radiation the area can receive, which most of the US does not. To counter-act this heat and conserve energy while maintaining cooling, we have chosen this type of water cooled system.

"If you want to supply 65-70 degree air to the data center and it's 60 degrees outside, why don't you just take air from the outside and blow it into the data center? Why run the A/C? Its nice, you can get hundreds of hours every month where it's cold enough to blow air straight from outside." says Phil Nail, Director of Technology for AISO, referring to the custom system they have installed. We have added to the cooling systems, a custom cooling exchanger and sensors that monitor outside air temperature and when it gets 60°F or below, they suck the outside air in, filter it and direct it into the data center thus saving electricity when its cool outside. Energy savings has a positive impact on global warming and the Freus systems saves energy and water to provide a responsible way to get the cooling we need, and the electricity savings we need, while being responsible to our environment.


AIR CONDITIONING ENERGY EFFICIENCY RATIO
FREUS WATER COOLED VS. AIR COOLED