California Data Centers Expect to Cut Energy Usage By 75 Percent

Aug 10, 2010California's Department of General Services (DGS) is equipping 12 of the state's data centers with an RFID-based temperature-control system intended to reduce energy consumption. The installations follow the 2008 implementation of the same system at the state's Franchise Tax Board in Sacramento, where it has reduced the use of energy in the agency's data center from 59 kilowatts to 15. In the meantime the state continues to install the system, supported by funding from the U.S. Department of Energy. The system, known as the Data Automation Software Hardware (DASH) is designed and installed by Federspiel Controls, and includes 900 MHz active RFID tags and readers from Dust Networks.

Data center operators have a tendency to set the cooling units' temperatures excessively low to ensure that the hottest server equipment is sufficiently cooled. This practice, however, wastes energy.

Since the tax board's RFID-based temperature-control system went live at the end of 2008, Federspiel has installed temperature sensors wired to RFID tags at four other California government sites, with eight more in the works for agencies that include California's Secretary of State, Department of Transportation and Department of Health Services. In each case, the DASH system depends on sensor modules with temperature probes wired to Dust Networks active 900 MHz RFID tags complying with a proprietary air-interface protocol. The modules attach with Velcro to racks in data centers, where the probes measure temperature and the RFID tags transmit that temperature data to a reader, with tags often acting as intermediary, receiving data from a neighboring tag and forwarding that information to adjacent tags until it reaches a reader. If one sensor tag fails, the network "heals itself" and continues to transmit around that tag. The reader, known as the wireless gateway, receives the temperature data and sends that data to the software residing on a dedicated server on the data center's back-end system via an Ethernet cable.

In addition to implementing the RFID system, the Tax Board repositioned floor tiles to improve air distribution, and mounted flexible curtains to isolate servers' hot-aisle airflow, says Jim Durborough, the Franchise Tax Board's senior information systems analyst and data center facilities manager.

For the RFID portion, Federspiel Controls installed wireless temperature sensor modules in the tax board's 10,000 square foot facility. Each module has two thermistors, one for the top of a server rack and one for the bottom. A sensor module was also installed on each of a dozen 22-ton air-handling units, which use chilled water to cool the air. In total, 23 sensor modules measuring temperatures at 46 locations are being used. In conjunction with the sensors, the center installed variable frequency drives (VFDs) for the coolers to control the fan speeds and water flow into the coolers.

If a sensor detects a temperature exceeding an acceptable threshold, the Federspiel Controls software determines the response, based on the specific temperature measured and the tag's location. For example, a specific chiller may need to increase its fan speed or increase its flow of cold water, and that would need to be accomplished by a specific percentage based on that temperature reading. The system then instructs that chiller's VFDs to adjust those settings accordingly. The software can also alert staff as to the changes in settings, and they can continue to monitor the response and ensure that temperature drops appropriately in accordance to the adjusted settings.

"We took that success and began working with the Department of General Services," says Mark Housley, CEO of Federspiel Controls. In late 2009, Federspiel made the proposal to install the DASH system, consisting of Dust Technologies hardware and its own software, at 12 more data centers operated by state agencies. By the end of the year, he says all 12 sites will be completed.

Each data center is different and requires planning, Housley says. "These are 24/7 operations, so we do these installations with a lot of care and deliberation." Because each center has a different physical lay-out, the company must determine the most effective location of each tag to collect temperature data throughout the room, as well as determine whether to have the software respond to temperature changes by automatically adjusting fan speeds and water flow or by alerting staff and allowing them to change settings manually on coolers or other equipment. "Each installation is unique. We see different rack configurations, different combinations of DX units, or chilled-water units," he says.

Most of the installations will include 50 to 200 sensor modules, some with racks that have doors, and others without, although the tags can transmit through the doors, Housley says. The tags can also be linked to other sensor data beyond temperature such as air pressure, humidity, or in the case of the chillers, the water flow. Federspiel configures the beacon rate of the tags.

Housley says he expects energy usage at all the California agencies' data centers to drop by about 75 percent, as a result of the DASH deployments.

At the Franchise Tax Board, for example, "the peak energy usage before the DASH system was installed was around 59 kilowatts," says Durborough. "The kilowatt usage with the DASH installed varies from 19 to 15." These readings were taken off an E-mon D-mon electric meter, he says, which is monitoring that usage.

"The project is expected to save the tax board $42,700 per year by reducing energy consumption," says Durborough.