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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."
I feel that my laptop gives me more bang for my buck. It draws much less power, and I can take it around with me. I like it much more than the cheap pc's we have at work (which would be a low power desktop) but LCD monitors are nice, but the quality of the lcd's on a laptop are just as good.
It should be obvious that there are more low power options in laptops than PCs.
However, be aware that some laptops are really just mobile desktops, in that they're fast, hot, and hungry.
There are plenty of good low power laptops out there. Just start by looking at battery life.
"Small PCs" are not necessarily better for power consumption than big boxes. It all comes down to the CPU and graphics cards, mostly. OTOH, I can attest that a lovely little Shuttle XPC with a big fat P4 will probably be enough to heat your cabin thru the coldest winter. Mine was like a hairdryer permanently on.
.sigs are for post^Hers.
Try looking at what they have here: solarpc.
They even have a complete turn-key squeak system (it's at the bottom of the page): here.
If you're just running 3-4 PCs, what's the point? Get a Belkin (cheaper) or APC (better Linux support) unit and get the same digits.
not sure how much sun exposure you have avaliable, but a laptop plugged into one of these has to last a fair while.
:-)
might even come in handy in new york next time the power goes out.
- can take it with you
- can pre-charge the batter elsewhere when possible
- has built-in "UPS"
- is specifically designed to use as little power as possible
- if you later get a generator for the rainy day, the battery gives you time to start the generator without hibernate/shutdown
- if you want the comfort of separate keyboard, bigger LCD, real mouse etc, you can still get them for laptop too (and getting that 2nd LCD may give you dual screen as a bonus) and still use less power
Whilst I can't say much about power usage I can say that a few months ago, I decided that my big old XP1600+ beast had to go and that a quieter, more bedroom friendly solution was required.
:)
I chose a laptop over a small, quiet PC mostly so I could take it to Tafe, Uni, LANs, etc on public transport, which doesn't sound like it will effect you much.
The point is, that it is quite possible to get a laptop to replace your desktop, especially since your computing power requirements seem to be similar to my own.
Personally, I managed to find a nice looking (Mac design clone) laptop with plenty of power for my needs. I was set back $2,600 Australian dollars for a Pentium M 1.5ghz, 512mb RAM, 40gb HDD, Geforce FX5200 Go and a 15.2" widescreen LCD (just as wide onscreen as my 17" CRT, slightly less tall.) Expansion wise, there is the one PCMCIA card and the internal MiniPCI slot which came with an 802.11b card inside.
My needs were also based around portability, and being a thin and light, this notebook weighs 2.7kgs. However, since you'll not likely be walking to the nearest LAN party from that location, I do think a laptop designed for good battery life will obviously use less power. Between the slower hard disk, powersaving, speedstepping CPU and powersaving motherboard, you could be using far less power than all but the best designed MiniPC. Another advantage to the laptop is that you get a few hours battery life in case your power dies or runs out of juice. Perhaps you could even take it out roaming your property if you're into that kind of thing.
Think I've rambled on a bit, but hope it's been helpful.
I'm not sure if this will produce better power savings than a decent laptop, but it should save some 30% on power if you are going to use a PC.
I assume that you use solar power to charge up 12v batteries. Running that power through an inverter only for it to eventually get converted back to DC is hugely wasteful for a variety of reasons(A horrible power factor being one of them).
I just googled around, and found this page with a variety of DC/DC PC Power supplies, with a variety of supported voltages.
Now that I think about it, if you have the capability to supply the power supply more than 12 volts(ie: 24 or 48 volts), then that will probably improve your wattage even more(as well as improve your stability if your power is "dirty").
Pair this with a small, power-saving bare-bones PC, and I would imagine you would have a setup that would be comparable in wattage to a laptop. Perhaps even better, considering that you are still using gobs of power from the DC->AC->DC conversion when charging the laptop batteries.
Finding a DC LCD Monitor may be a bit harder, but I'm sure they are out there somewhere. If you are feeling adventurous, you could even modify a monitor for DC...
— darco
Instead, get a half dozen car batteries for the same price. You'll get about a day's worth of power (IE, 24 hours).
Err, carr batteries are designed for short heavy loads - starting your car in the winter. You can run them all the way down and recharge them a couple times but then they're cooked. Substitute "marine" deep cycle batteries - the ones people use to power bass boats - same 12v lead/acid battery but the plates inside are designed for complete discharge.
At the bottom of the endless pile of paper work which characterizes all regulation lies a gun.
Alan Greenspan
A word about laptops. Most of them have two modes they operate in. While running off internal power, they run in a low power mode. This many times slows the CPU down and dims the display. Also while in battery mode the fan will run on various speeds on demand.
When they are plugged in they speed the CPU back up and brighten the display - consuming more power since it is available. I think I would probably recommend a laptop, and a few spare batteries. Then you can charge on someone else's power and bring it back home with you.
Since your laptop will use less power when running off battery you should always use your laptop on battery power. Then when you shut it off you should charge the batteries. Make sure you get a laptop with two bays.
If you go with a PC get a variable speed CPU fan with a sensor. Then it can slow down when it is not needed, saving you some juice. Since I am assuming you would be building your own system then evaluate the watt consumption of each component, and add it up getting a good quality (expensive) power supply that meets your needs without exceeding them astronomically. When possible use one component instead of two (Optical drives, hard drives, memory modules, etc.) Two will consume more juice then one (obviously) when you can get a single hard drive that is big enough to do the job.
Display brightness has a huge impact on battery life. Whatever you go with make sure your display is as dim as possible. Put your computer in a dark room.
Also, don't run SETI@Home, GIMPS or one of those other background processing systems. Those really increase your machines power consumption, as do games!
Another must have would be a good UPS with a power conditioner. Brown outs are very damaging to your computer hardware. Not that I doubt your ability to build your own power grid, but wouldn't you hate to loose your PC because of a brown out?
"Anything is possible with enough programmers, time and pizza." (Substitute caffeine for time as needed.)
I'm in the process of building (year #5, woo-hoo!) a totally off-grid home in (almost) the middle of nowhere. I've gone through this already.
The short answer is if power is all you care about, a notebook is better. My Sony TR1A consumes 13 watts of AC when plugged in at full-tilt according to my power meter, and display-off sucks just 5 watts. However, I care about more than power, like uptime/durability, ability to use off-the-shelf components, and being able to support some modest external hardware, so the actual system that stays on 24/7 is a VIA Epia 533 MHz box. It takes about 11-12 watts but can peak around 24 watts or so, plus a 15-inch LCD monitor which is pretty much never on, but consumes 16 watts when it is; so you're looking at about 30 watts with one of the lowest power desktop configurations possible.
Other odds and ends consume power as well. Inkjet printers are great (Epson C82 sucks 1 watt in standby, about 5 when printing.) Larger ethernet hub-like things are about 5 watts as well. (That'd be hubs, terminal adapters, wireless routers. nearly everything in my 3com officeconnect stack at my real house is 5W per unit.)
As far as power budgets go, it's the time the devices on that really gets you. An 18W average setup running 24 hours a day is 432 watt-hours, almost half a kilowatt hour. While I have a pretty substantial solar array (1 KW at the moment) during the winter I'm going to see maybe 4Kw-hours per day, so I'm burning nearly 10% of my capacity on just one PC.
So.... you can use your kick-ass system if you want, and if you limit it to one hour a day v. 24 hours a day, you'd be ahead.
BTW, my losses on the total system aren't bad at all. Inverters and batteries are pretty efficient these days. I'd gladly accept a 50% loss on storage and conversion, however, if I got 50% efficiency out of the panels instead of the sub-20% that's typical of solar today.
Keep in mind that while chemical-to-heat reactions can be made over 90% efficient, chemical-to-heat-to-motion reactions in a typical portable generator are more comparable to car engines - 30-40% efficient (non-portable large-scale multi-stage turbine generators can do more like 60-70%). If you're storing the resulting electricity in a lead-acid battery, that's only 70% efficient.
Assume that you have an average 35%-efficiency generator charging lead-acid batteries. That system has an efficiency of 24%.
Given that gasoline stores about 130 megajoules of energy per gallon, and you can recover 31MJ of that (same as 8.61kWh), and it costs you $1.50, then the break-even point is $1.50/8.61 (or $.174) per kWh. If you're not charging batteries, then the break-even point is $.118/kWh.
For me at least, the grid is significantly cheaper. As it should be.
Also, if you need the waste heat from the generator anyway (and can rig up a way to exchange it without dying from carbon monoxide), that could make generation a lot more worthwhile.
I have a "unabomber" shack out in the middle of nowhere, with no utilities to speak of. What you speak of is *very* doable with Solar power.
A few reflections on what I've learned.
* A PC, as you've learned, will usually consume in excess of 100W of power with the monitor on. Using aggressive settings on your power management software, a VIA EPIA motherboard, and a small LCD monitor you could probably get it around 50 watts. Such a machine is likely to feel slow.
* My Apple Powerbook is very solar-friendly. ~15W during heavy use.
* Try to get everything you need built-in. Things like PC Card devices or external storage really suck down power. The built in devices tend to be engineered for better power management profiles.
* If you find yourself needing to network, wire it. Wired networks suck less juice (at all points) than wireless. And it goes a lot faster.
* If you want to listen to music, budget that into your battery system. A laptop playing a huge MP3 playlist is never going to idle the processor down. Luckily batteries are relatively cheap, so adding just one more battery will add several hours to your runtime.
* If your situation is like mine and you will have a lot of little construction projects on your cabin while you're out there, my power use went WAAAY down when I switched from corded power tools to 18V Ryobi cordless tools. Charging the batteries did not appreciably diminish my reserves, the tools were almost as powerful as those they replaced, and they were much quieter and a joy to work with.
* Don't mess with car batteries. They are no good for this application. At the very least, look at RV/Marine Deep Cycle batteries (12V). Better yet, look at 6V Golf Cart batteries (which you pair up in series for 12V). The Golf Cart batteries will be the ones you want during those overcast weeks.
* Look into lighting, appliances, etc. that run directly off of 12VDC. There are many web sites out there that cater to hunting cabins, homesteaders, RV's, etc. You'll pay more for these appliances up front, but it is much more efficient to run most of your day to day stuff off 12VDC as you lose a lot in the inverter going up to 110VAC. The computer, however, should probably run off 110VAC if for no other reason to ensure that you're getting a steady clean feed from the inverter rather than from your PV panels & batteries, which may surge if the clouds suddenly part or what have you (the inverter will buffer this).