I'm looking to build a mini-ITX solution based around the Celeron 847 for an engineering project. Most of the components besides the power supply are fixed due to the constraints of the project, but not the power supply. My goal is to achieve the lowest possible power consumption at max CPU.
Would a picoPSU-80 + 60W AC adapter be enough to power that configuration? That's the puniest thing I can find with a cursory Google search. Is there another option that might offer lower consumption?
I've read that power supplies generally operate at their highest efficiency when the draw is about 70-80% of their rated wattage. From what I can tell, that configuration should draw about 40W under load.
if your goal is to achieve lowest possible power consumption then instead of just looking for a PSU with low max wattage you should also (and more importantly) be looking for a PSU with high efficiency.
if your system is drawing 40W from a 70% efficient PSU it'll be drawing 57W from the wall, or drawing 44W from the wall with a 90% efficient PSU.
PSU's must maintain their efficiency claims at 10%, 50%, and 90% load (at least to get 80plus certification), so if you figure your system will draw 40W from the PSU you'll want the highest efficiency PSU with a max load of 400W or less. something like the Sparkle R-FSP400-60ETN (400W 80plus platinum).
Not sure where you read 70-80% but it should be 50% so want to average 40-60. You can find efficiency graphs for many psus.
80+ tests are 20, 50 and 100. Having the highest efficiency does not mean you save money if the psu costs more than you will save in electricity. So platinum vs bronze at this power usage is maybe a savings of $1 per year and I'm rounding up. So if the platinum psu is $30 more, you will most likely not be using that psu for 30 years and just wasted your money. Efficiency is really not a concern at this low power. I'd be worried about quality so it doesn't die within a couple months.
FWIW the goal isn't to save money on electricity. The system is for a contest where I need to complete a certain task using as few Watt-hours as possible. The task is both I/O and CPU intensive, hence the RAID-0.
I'm now thinking it might be better to use a laptop instead, simply because they're optimized from top to bottom for high efficiency. One with a low-power CPU and two drive bays (or that can support two drives at full SATA III speeds via docking station) would work.