Lighting controls company Redwood Systems has done a number of installations in data centers.

To improve the efficiency and control over commercial lighting, Redwood Systems is plugging light fixtures into the computer network.

The company's DC (direct current) lighting control system is used by a number of data center customers, including Facebook, which installed it in its Prineville, Ore., data center. Sam Klepper, the chief marketing officer at Redwood, said yesterday that Facebook intends to expand its use of the control system as it adds to the Oregon site and builds another data center in North Carolina.

Efficient LED lighting is an active area for green-technology start-ups like Redwood because lighting upgrades can have rapid return on investments. Redwood doesn't make light fixtures themselves but a control system for managing lights.

In the case of Facebook, the company is using Redwood's controls with LED light fixtures for improved efficiency and with sensors to automatically adjust light when people enter a data center aisle and to monitor the temperature at different points. Data center customers appear willing to spend for the new functionality, such as high temperature alerts, as much as for increased efficiency, Klepper said.

The Redwood system uses a rack-mounted server that supplies power to light fixtures through direct current, rather than the AC (alternating current) used in buildings. Having a low-voltage DC line to lights, using Ethernet cables, improves the energy efficiency, Klepper said. Direct current is used in some data centers as a way to reduce the losses from converting from a buildings alternating current to the direct current that electronics run on.

In addition to converting from AC to DC, the Redwood central control can gather information from sensors, placed on the ceiling, or cameras and control lighting based on motion of light levels, for example. There is also a Web-based application for setting schedules and monitoring energy use.

If a company is upgrading lighting, the return on investment in a lighting control system can be instant or up to five years depending on conditions and power prices, Klepper said. Much of the energy savings comes from the installation, he added. Because the controls use Ethernet and direct current, some equipment, such as junction boxes and relays, can be avoided and the labor costs are lower.

Updated at 12:30 p.m. PT.

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Martin LaMonica is a senior writer for CNET's Green Tech blog. He started at CNET News in 2002, covering IT and Web development. Before that, he was executive editor at IT publication InfoWorld.