[oasisbob]

I found that interesting too, thought it was a joke at first.

The only details I was able to dig up are in the Data Center specs [1], and they're pretty brief:

> Energy-efficient LED lighting is used throughout the data center interior. / Innovative power over Ethernet LED lighting system. / Each fixture has an occupancy sensor with manual override. / Programmable alerts via flashing LEDs.

I wondered what the justification for PoE lighting could possibly be, sounds like all the lighting is also functional as instrumentation.

Anyone know more?

[1] http://opencompute.org/specs/Open_Compute_Project_Data_Cente...

[chopsueyar]

A couple of guesses. They probably have a lot more cat5/cat6 around than 3-conductor 12 gauge copper wire (not sure if it is cheaper by the foot).

Also, the network switches can output the PoE, so maybe it is easier to wire into/from the racks or overhead than a seperate AC line with conduit.

Labor installation and material costs may be less.

Also, since it is DC, and not an AC lighting source, interference may be less (just a guess).

And as you mentioned, the lighting as instrumentation.

[bhousel]

All true. Right now 14/3 Romex costs about 3x more than Cat5. Copper is expensive!

LED lamps use DC power. The LED lamps that you can buy that screw into a standard Edison socket contain electronics to convert the AC line voltage into DC. This is inefficient -- generates heat and wastes power (though still not nearly as much as a traditional incandescent bulb).

By using power over Ethernet for their lighting, the datacenter can use cheaper, cooler, more efficient bulbs, and save a lot of money on the wiring too.

I can definitely foresee a future where new construction includes wiring for both line voltage AC and also low voltage DC. It could eliminate all the bulky transformers scattered around a typical house and save energy and money.