A One Stop Guide to Economizers

An appropriate balance of temperature and humidity control is indispensable for efficient data center operation. So it is essential to conserve the considerable investment in computer and network technology in such conveniences. On the other hand, increasing energy costs confront engineers to find the most lucrative ways to control temperature and humidity within suitable ranges. Economizers represent an effective means of increasing energy efficiency and reducing costs in data centers. The use of economizer systems is one technique that has been adopted to lower energy usage, lessen usage of meticulous air conditioning equipment and decrease operational costs.

The two chief types of economizer systems are:

  • air-side economizers and
  • fluid-based economizers

Air-side systems: These are systems which will use direct, fresh air blown into the data center with hot air take in and released back outdoors, or they may well use an air-to-air heat switch over. By means of the air to-air heat exchanger, cooler outdoor air is used to moderately or fully cool the internal data center air. Airside systems may be improved with any direct or indirect evaporative cooling, broadening their operating range. An air side system gives out a control mechanism to control the use of outside air for cooling in a room or building. It makes the most out of a system of sensors, ducts and dampers to allow admission of the suitable volume of outside air to satisfy cooling demands. The sensors quantify the outside and inside air conditions. In case outside conditions are appropriate for the use of outside air for cooling, the economizer adjusts the dampers to establish the outside air, making it the principal source of air for cooling the space. This diminishes or eradicates the need for the air conditioning system’s compressor or compressors, which results in a noteworthy energy savings for cooling the space. Air-side economizers also consists of exhaust air dampers to avoid the facility from getting over-pressurized while outsized amounts of outside air are brought in.

Water-side systems: A fluid-side economizer system is frequently referred to as water-side works in combination with a heat denunciation loop consisting of a cooling tower, evaporative cooler or dry cooler. A fluid-side economizer system is usually built-in with chilled water or glycol supported cooling system. For economizer operation, the fluid used in the cooling system goes via an additional coil to cool the room air, reducing the need for compressor operation.

The rigorous temperature and humidity requirements of data centers, coupled with the need for cooling 365 days per year and 24 hours in a day classically makes fluid-based economizers the best preferred amongst the data centers surroundings.  Fluid-based economizers also supply effectiveness in a wider section of the temperature/humidity band required by current data center computer systems. Hence they are more appropriate to a data center than dual-enthalpy control air-side economizer systems. Inside the fluid based economizer group, glycol-based systems operate efficiently at the extensive range of outdoor ambient temperatures. As economizers characterize an efficient means of increasing energy efficiency and reducing costs in data centers, there is a need for extensively using them.

The concept of economizer mode is accepted throughout the data center industry, however little has been done to homogenize the expression. This has lead to confusion in understanding the concept.  An important source of perplexity lies in the use of the term economizer to describe an element within a cooling system or a compartment of a cooling system.  An economizer is certainly not an object; it is an approach to an operation.

At the premier level ,a typical cooling system uses air, water, or refrigerant to transfer heat energy from inside to the outdoors of the data center.  The usage of terms air-side economizer and water-side economizer are frequently used to explain cooling systems with an integrated economizer mode. There are different types of economizers used in the data center. Some of them are – Direct outside air, chilled water with water-cooled chillers, chilled water with air-cooled chillers, DX with fluid economizer coil or Indirect outside air with heat wheel.

Today’s computer and communications systems necessitate a more complex and considerate approach to environmental control planning for data centers than ever earlier. In most circumstances, air-side economizer systems do not rally the rigorous temperature and humidity control requests essential for these mission-critical conveniences. Glycol-based fluid economizer systems are the most suitable choice to help reduce data center cooling costs, lessen energy usage and provide efficient, economical heat indulgence in a wide range of outdoor temperature and humidity surroundings.

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Reducing Data Center Cost Using Air Economizer – Intel

Electricity costs play a major role in the detail of the profit, loss or competence of a Data Center. Reducing them to a minimal amount is the key to an efficient and cost-effective site. Apart from the inevitable consumption of power by the server a major part of the electricity is consumed by the cooling systems. If an effectual way of achieving cooling is possible without the use of an air-conditioning system, the expenditure on cooling can be reduced considerably; here is where an Air-Economiser comes into play.

This approach to cooling has always been frowned upon by most in the industry mainly due to the feeble cooling power provided by prior prototypes of conceptually similar systems. The reliability of the servers can be questioned if proper cooling demands are not met; hence a good design towards 100 percent air cooling has never been successfully tested.

The Air-Economizer:

Typically an air-conditioning unit would draw the hot air generated by the working servers, cool it down to the set temperature and recirculate the same. Outside air would be taken at regular intervals to maintain the balance of fresh air in the Data Center. A revision in this process modifies the air-conditioning unit into an air-economizer. Here, the hot air would be expelled to the outside of the Data Center and fresh, cooler air would be drawn in, continuously or at regular intervals based on the heat generated.

The Experiment:

Intel took up a challenge to defy the common assumptions in the industry about the air-cooling technique by conducting a Proof of Concept (PoC) test. The test aimed at cooling servers at 90 degrees Fahrenheit with 100 percent outside air. Potential annual savings by achieving this could be US$2.87 Million for a 10-megawatt (Mw) plant!

The PoC was run using about 900 production Blade servers divided equally by two compartments place side by side. One was provided with warehouse grade Direct Expansion (DX) unit to recirculate the hot air and provide cooling at all times; and the other an air-economizer. The PoC was run in a dry climate over a time period of 10 months.

This is What Happened:

  • The temperature of the air supply in the economizer compartment varied between 64 and a little beyond 92 degrees Fahrenheit. Cheaper air-conditioning units with reduced response rate used in the PoC may have caused this.
  • Humidity varied between 4 to way over 90 per cent.
  • The exterior and interior of the servers were covered with a layer of dust.
  • Total power consumed was 111.78 kilowatts (KW) as compared to 500 KW for air-conditioning in both compartments. This is a 74 percent decrease in energy consumption!
  • The server failure rate in the economizer compartment was 4.46 percent as compared to the 3.38 percent in the main Data Center. The failure in the DX cooling compartment was 2.26 percent which is lesser than that of the main Data Center itself.

The Savings:

If the site of the Data Center can be located in more temperate conditions, the economizer technique can be used for more than 90 percent of the year. If 90 percent of the year a reduced power plan can be achieved and there is 74 percent savings in this plan approximately 67 percent of the total power used annually can be saved; for a 10MW plant this figure would be about US$2.87 million! Capital can be saved on building new Data Centers with fewer air-conditioning units. Potentially about 76 million gallons of water can be saved by applying the air-economizer technique.

The Catch:

Server failures remain consistent with variations with humidity, temperature and inferior air quality; hence air-economizers are suited only for drier and more temperate climates. The availability of such locations can be scarce. As the location of a Data Center is crucial for business and stable networking setting up sites at these locations if too remote is pointless.

The Cherry!

Intel plans to test the economizer technique and check for hardware degradation by using server aging analysis, they also plan on setting up a 1MW demonstration Data Center to conduct further research on this. The cost-effectiveness of the entire setup promises financial gains as well as a greener approach to Data Center construction; clearly, this is technology of the future.

Reference: Intel IT white paper


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