Laptop vs. Small Desktop: Best Bang Per Watt?

Deagol writes "Tomorrow I take possession of a remote, wooded lot with a cabin. 15 miles to the nearest utility pole, my electricity options are limited to those I can generate myself, solar being my primary goal. I'm sitting here staring at my power meter, seeing my desktop & monitor draw about 250W -- a non-trivial amount to generate over a 8-to-12 hour workday. I'd be happy with equivalent computing horsepower (1.4GHz T-Bird, 512M RAM, though more is always better). Should I get a small PC with an LCD monitor, or should I get a laptop? Will laptops draw less power (in general), and if so, will losing the modularity and lower cost of commodity PC parts be worth it? I'd love opinions from those who have been in a similar situation."

Comments

One word: Batteries!

[metrazol]

The big problem you'll face on solar is the ol' "It don't work when the sun ain't around." That means you're better off getting a laptop for a few reasons. 3 or more hours of battery life can be very handy and you can march around with it, meaning you could leave lights off at your desk and stroll over to the kitchen with your laptop, saving electricity in two ways, the lights and that stored in the batteries.

Another option is get a UPS for your desktop. You can run the machine off of that when the power goes out, night, etc. and they are relatively cheap...if you get a 4 hour one... and can power other devices. The laptop and the UPC will trickle charge while juice is flowing, so you can be pretty sure that when the sun does set, you won't miss a beat with your tech.

Now... how exactly are you going to get on the net? Satellite? Pigeon?

Any rivers?

[nocomment]

If there's any rivers nearby, you could relatively easily make a multiple solution generator. Build a small water-wheel type generator, a windmill, and a solar generator. Then run these into a UPS (or 2), and you should have power as long as

• you have daylight
• the river is flowing
• there is a breeze

If all of the above fail, you have 2-8 hours of UPS power (depending on how big and how many UPSs you get), and 2-3 hours of battery in the laptop (make that 4-6 if you get a spare battery). You could make it through a frozen, long, dark, and still Alaskan night with that setup. You'll be set...and still nerdy ;-)

Re:Both have big energy loss

[Bishop]

but they basically take the power in and put it right to the motherboard and components.

This is incorrect. Standard computers use 12v, 5v, 3.3v, -5v, and -12v power. 5v and 3.3v supply the majority of the power used. Additionally the 12v as supplied by cars and boats is not 12v, it can be anywhere from 10.5v (mostly dead) to 14.5v (chargeing). 12.66v is the actuall full charge potential of a lead acid battery. The power from an engine altenator is also not nearly clean enough for use in a computer.

A 12VDC power supply as discussed by the parent is a DC-DC converter. Typically the DC input will be inverted (converted into AC) so that a transformer can be used to generate the various required voltages. After the transformer the power supply is very similar to standard switching power supply found in computers. A good DC-DC power supply will be slightly better then an inverte and standard power supply. Typically either will be equally efficient.

A car is a really terrible generator. Most have trouble keeping their own batteries charged. An inexpensive generator will do far better.

The original poster should really figure out what they plan to do for power first. Depending on the power source they may not have to compromise.

Solar cells sound great in theory, but in practice leave a lot to be desired. Especially if the cabin is not located in a desert with lots of sun. Even if sun is plentifull it is hard to show that solar cells plus a bank of batteries are more environmentally friendly then an old fashioned disel generator running on dead dinosaurs. A properly installed generator running on biodisel with heat recapture, for hot water and heating, would be better. Although expensive a fuel cell generator (as posted elsewhere) is also worth looking at. Again heat recapture can be used. If the fuel cell is the propane type, the same propane can be used for cooking, refrigeration, and additional heating. Hydro is also worth looking into if there is water nearby. Bonus points for useing a windmill to pump water back up to the resevior for reuse.

Re:Both have big energy loss

[jonbrewer]

What you should do is get yourself a computer with a 12VDC power input. They sell power supplies that take in 12VDC and have standard motherboard power connectors (although the last time I shopped for one it was using AT connectors).

Both satisfied by VIA EPIA and Procase 12V DC-DC converter board (included in their Mini-ITX cases). I purchased a couple of these to play with in designing an outdoor router. (One with a lot more oomph than the commercial alternative, the routerboard)

The DC-DC board presents at one end a 12V 4.5A input, and at the other an ATX power connector and power for 3-4 peripherals (in my case, only one is used to power an IDE-CF adapter)

The only great problem I have is with 12V 5A power supplies - they're damn near impossible to find! (guys at Dick Smith say, "you mean .5 amps" and I sigh.)