To run a desktop PC takes a fair sized solar panel, but isn't impossible. To cut power usage, use smaller LCD screens, rather than CRTs, and use parts that have passive cooling, rather than fans. Use newer parts that have low power and heat ratings in their reviews.

Also, get a power supply that is > 80% efficient. And make sure that the power supply is only rated slightly higher than your actual draw. For example, when playing Crysis on a Core 2 Duo 6850 with a GeForce 8800GT/512 and three hard disks, my machine draws about 210 watts. When just idling, it draws about 150. Thus, a 300W power supply would be totally sufficient, and you could even go as low as 280W or 250W if you wanted to cut it close. Getting a 600W power supply for that same set-up would just be wasteful, as you'd waste more power. Power supplies are more efficient when working near their rated wattage.

The other problem is that "the sun shining" and "you using your computer" are not typically happening at the same time. So, either you have to get an array of batteries, which is environmentally dubious, or you have to resolve yourself to doing a sell-back plan, where you generate electricity when it's sunny, sell it back to the power company, and then draw power when you're using your computer. However, if your goal is to be able to run the computer during a power outage, then that's not going to work.

If you're not doing it for the environment, but instead for reliability, then perhaps something like this would be the solution for you:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94935
While that is the 6 kW option, adding just a little more money can get you to 16 kW pretty easily.

[Edited by - hplus0603 on January 8, 2008 2:16:42 PM]

Another option is to go with a multi system. Combining Solar panels and a Wind generator and be very effective, but of course you will still need a battery backup array.


Honestly, I don't know why all homes aren't designed to be grid reduced, and use local fast response generators during 'bad' weather. An insane amount of fuel is wasted just to charge the high voltage transmission lines before any of the fuel can be used to actually do something useful.

Quote:I don't know why all homes aren't designed to be grid reduced, and use local fast response generators during 'bad' weather.

Because it costs more to purchase. Minimizing up-front cost is what the American market is all about (and a lot of other markets, too).

Quote:Original post by hplus0603
Also, get a power supply that is > 80% efficient. And make sure that the power supply is only rated slightly higher than your actual draw. For example, when playing Crysis on a Core 2 Duo 6850 with a GeForce 8800GT/512 and three hard disks, my machine draws about 210 watts. When just idling, it draws about 150. Thus, a 300W power supply would be totally sufficient, and you could even go as low as 280W or 250W if you wanted to cut it close. Getting a 600W power supply for that same set-up would just be wasteful, as you'd waste more power. Power supplies are more efficient when working near their rated wattage.

Actually, I don't think that's true. I've always read at many reputable hardware sites that Power supplies operate most efficiently at around 50% of there rated maximum. Also, I wouldn't recommend cutting the maximum wattage output so close to the draw, as it could cause problems at boot when everything is typically (except maybe the graphics card) spun up full-speed in the BIOS before the OS's power management can get a handle on things (e.g. all fans and probably all the drives, both hard and optical.)

The max power rating also has little if anything to do with how much wattage is actually drawn from the power source; its more a function of draw from the system and the efficiency of the CPU. All the hardware sites measure power draw from the wall when they're determining the draw of a complete system, they wouldn't have to even have that discussion if having a 600w PSU meant drawing 600w at all times.

Also, 80% efficiency isn't all that great, you can certainly find ones greater than 90%. If you can go DC-to-DC (Solar power outputs DC) you can get even more efficiency, however I've only seen smallish (low wattage) DC-to-DC PSUs, such as those designed to be powered from a car battery for in-dash computers, 200w is the largest output I've seen.

That said, if you're really serious about running a PC on solar, building a low-power system is the way to go. Via has many, low-power ITX boards that can draw as low as a dozen watts or so (CPU, RAM and Mobo included), but they're not known as powerhouse systems. You're best bet for a quite-powerful, low-wattage system would be an one of Intel's newer chips (M series, Core, Core 2) and particularly if you can get one designed for laptops, low-power servers, and/or with the ULV (Ultra-Low Voltage) spec. The smallest process and High-K metal gates will reduce power draw significantly as well. As for a motherboard, just make sure it supports the CPU you want, and doesn't have a ton of features you'll never use which you can't completely disable. You'll also generally have to give up high-performance parts. 10k RPM hard drives draw more power than 7.2k RPM drives, for example (flash drives are king for power consumption, but are pretty cost-prohibitive now.) You'll also have to give up high-end graphics, as a single high-end GPU can draw 200-300 watts on its own. Integrated graphics draw almost no power, but you'll need a low-to-mid-tier from ATI or nVidia if you need discreet graphics (ATI generally draws less power and has better price/performance ratio -- particularly in the low/middle bracket -- even though nVidia has the high-end performance crown right now and gets all the headlings.)

If you want to power a typical desktop PC via solar, you're going to need a pretty serious Solar/Battery setup, but if you build one for that purpose its a doable endeavor.

On the other hand, the easiest solution is to just run a laptop, Mac Mini, or other suitably low-power pre-built system.

[EDIT]

Forgot to add that yes, switching to LCD will also be a big win in all likelihood, especially the smaller ones (15 or 17 inches) and those with LED back-lighting (though LED back-lighting is only just now coming in portables, and may be some time in standalone LCDs). Also, if you can live without a speaker system, headphones are more efficient -- which brings to mind... if you can live without a discrete audio card, using the integrated audio will be more efficient as well, and most these days are pretty good anyhow.