University Switches To DC Workstations 468
An anonymous reader writes "Researchers at the University of Bath, UK are undertaking an in-depth study of energy consumption within the new network, with the aim of demonstrating that running a large network of devices on DC rather than AC is both more secure and more energy efficient. AC electric power from the grid is converted to DC and runs 50 specially adapted computers in the University Library. Students using the system have noticed that the new computers are more compact and much quieter than the previous systems. The immediate advantages of the new system are not only for the user but for the energy bill payer and the environment."
secure? (Score:4, Insightful)
There is no evidence or reason for DC to be more "secure". If some lame argument about it being harder to bring your own power source / utilise their outlets when you have a custom system is put forward, then, well... no.
I can understand the efficiency argument to a certain extent, although if a workstation needs enough power that a fanless AC PSU is unsuitable then the more efficient AC PSUs will be enjoying enough load to reach over 80% efficiency. Are the centralised rectifiers + wires + in-computer DC-to-DC converters as efficient?
Re:So... what? (Score:5, Insightful)
Truthfully both approaches are valuable, and we would be a poorer planet without either of these men. It's a shame they disliked each other so much.
Edison: "Genius is one percent inspiration and ninety-nine percent perspiration."
Edison contracted out all his perspiration. That's genius.
Re:AC vs DC (Score:4, Insightful)
The major drawback to DC power is in the wiring. Direct current requires larger gauge wiring than AC power, which increases material costs considerably. In general, DC power is economical only if the wiring between the computers and the DC source is less than 35 feet in length. More than that, AC power becomes more economical.
FTFA:
Somehow, I suspect that the cable run to the individual machines is more than 35 feet.
His figure of 35 feet is of course completely made up, or at best applies only to one very specific situation. Its a rather complex non-linear solution that depends on current level, local union labor contracts, price of copper wire, UPS and battery capacity, etc.
Obviously, if you are charging an ipod at a zillionth an amp after a 12V to 5V converter, you can run that thru thousands of feet of small gauge (cheap) speaker wire before the voltage drop will matter. And if you're doing the thousand watt gamer PC or NAS farm you'll need something approaching welding cable to keep the voltage drop low enough. In between, well, its in between. But by no means as simple as a 35 foot cutoff.
Re:So... what? (Score:4, Insightful)
You're missing the point. Much of our electronics run on 5V DC. If you put a big 5V converter on the side of your house, and a bus system to connect this to all your 5V gadgets, the losses would be greater than just having all those wall-warts. Even worse, your gadgets wouldn't work, because the voltage drop between your converter and your gadgets would be so great, you'd end up getting 4V at the gadget, and worse, the drop would vary depending on how much current that gadget is drawing (and other gadgets on that run).
If you want to be more efficient, the answer is simple: throw away all those wasteful transformer-based wall-warts, and replace them with high-quality switching wall-warts instead. They're lighter and also have better efficiency, both when under load and when not loaded. The problem is that switching wall-warts cost more than the crappy Indian and Chinese-made transformer-based ones, so gadget makers don't usually bother to include them.
Switching to DC isn't a magic bullet to solve energy efficiency problems, despite this idiotic (and just plain wrong) article.