Fujitsu’s Esprimo Green: “Zero What”?
Fujitsu announced that their showing at CeBIT 2009 will include what they call a “zero-watt PC“. The name is misleading not only that these computers draw full power except when in standby mode (or off), but also in that this may not actually save even the humble standby power drawn by a typical PC. The details will be revealed at the show, but Fujitsu will likely use technology similar to their own “zero-watt monitor” which, ”works by storing electricity into additional capacitors within the device.” Capacitors, like any means of storing electricity, have to be charged, so this is nothing more than time shifting the energy usage — not eliminating it. With the small overhead of charging and discharging, “zero standby power” devices may end up using more energy than their ordinary counterparts; the “energy savings” being analogous to saying that cell phones draw zero power from the outlet when on battery power. Standby current draw, while small, can be significant when a large number of devices add up. Still, foregoing a single use of your toaster can save more power than is used by a PC in standby uses in a week. Fujitsu’s new PC may have other power-saving features which aren’t so inconsequential. The light sensor on their zero-watt monitor, for example, can reduce brightness (and power) in accordance to ambient lighting conditions. This shows they are working on power conservation from many angles, even if some of those angles are rather obtuse. Will these new “zero-watt” computers save electricity?
All dynamic contrast LCDs save power by reducing lamp power. They can dynamically improve contrast ratios if the brightest bright and darkest dark is within the actual contrast ratio of the LCD. A side effect of this is that dynamic contrast lowers energy consumption.
Putting in an ambient light sensor will further reduce power consumption when the surrounding is dark.
Power supplies, whether switching or linear, are less efficient at low utilization. Using the main supply of the unit to charge a small battery or capacitor could be more efficient than using an always-on standby supply, which is dissipating most of its power draw as heat. Certainly batteries and capacitors are less than 100% efficient in converting energy into charge, but standby supplies are notoriously bad at converting wall power into standby power without wasting most of it as heat.
My PC, for instance, only needs about 20mW of power on standby, but the power supply dissipates 5W of power in the process. I would assume that most home appliances like TVs can make do with even less than 20mW, and their standby supplies are not much better. Today’s common switched-mode wallwarts pull 700mW-2.5W when they’re not driving a supply. I’m guessing most standby supplies have about the same minimum draw.
You’re right that power supplies are very inefficient, and you may be right that this solution ultimately does save some energy.
However, the main point is that saving a watt really isn’t that big a deal. The big culprit is inefficient computers that suck up 200 watts in idle or computers that idle in S1 mode where almost no power is being saved. The point is that putting tinted film on your windows in the summer probably saves you 200 watts continuously during the summer day.
You’re absolutely correct there, of course. I think Fujitsu is just responding to market and media pressure to address the “vampire power” problem. The gross, overall problem of inefficiency across the home and office is beyond the scope of the one TV design team. Every little bit helps, though. I’ve been replacing inefficient appliances, computers and lighting throughout my house, and that problem of gross inefficiency can only be addressed at that level: the whole home or office.
Fujitsu is responding to new EU regulations that would mandate this, so I don’t fault Fujitsu at all. This is the problem with regulators trying to do "good".
To me, any green initiative should try to get the most energy savings per dollar. If we can get consumers to spend $50 to easily cut 100W of continuous power consumption, then this should be what we should worry about. If we force people to spend that same $50 to save 1W of power consumption, then we have effectively forced a net increase in power consumption of 99 watts.