Last night I went to Comtec's new data centre facility in Reigate. It's a pretty impressive place, with some interesting bits and pieces in the actual computer room (and NOC). There's an efficient 'hot corridor' layout with multiple coolers, Blade Ready systems, and doesn't rely on tidy under-floor cabling.
The best bit is just outside the main computer room. It's a hydrogen fuel cell - one of only three in the UK, and apparently the only one that actually works in a live environment.
Basically, it looks like an ordinary tall 19" rack cabinet. When the power fails, conventional UPSes take up the load in the computer room, while the fuel cell fires up. It's divided into three pieces, each of which starts up in turn. It's actually quite an underwhelming experience, because all you really see or hear is a few fans starting up and some icons on a monitoring computer screen changing. But this is good news - there's no diesel generator, no complex moving parts and an incredibly small carbon footprint.
It's nice to see something real going on to make data centres more 'green'.