>>995704
Basically, you'll need-
>UPS capable of running for 10-12hr
>Rectifier to convert DC-AC which goes to the UPS
>Solar Panels to Rectifier

Then you're going to need to figure out how many amps it draws and how many you can put back into the UPS as well as losses from the system itself.
Wind-generators are pretty fucking useless things really, solar's semi-dependable but you're going to need something fairly substantial in terms of them.

>>995722
atm its using old laptop charger which outputs 20v 4,5 amps. so i think solar panels aren't worth it as they cost a lot and are bit overkill for one pc

>>995722
>UPS capable of running for 10-12hr
>Rectifier to convert DC-AC which goes to the UPS
>Solar Panels to Rectifier

Well.. okay?
That's overcomplicating things a bit, especially in the DC-AC rectifier bit.

Basically you'd be going DC -> AC -> DC -> AC for no reason.
Now, sticking with the UPS plan, you could just buy a charge controller and hook it up directly to the UPS battery or better yet, skip buying the UPS entirely and just buy an Inverter + Battery.

Or, since we're only working with 20V output, assuming OP learns some electronics, he could just wire up two 12V (or a 24V) batteries and step down the voltage with a relatively simple circuit.

>>995731
I was guessing it'd be running on some kind of AC PSU + he would have monitors as well and most of them generally have an AC powersupply of some sort.

Other reason I like running rectifiers is that they do soak up surges from shit power sources fairly well over a long period of time and while most UPS's are pretty tough things, I've seen a lot of them die without a rectifier somewhere in the circuit. Depends really on how complicated its going to be- how many monitors, modems, speakers, external HDD's and all the other peripheral shit that hangs off it, that's what the OP needs to figure out as well as some kind of budget. When you have a budget, I can give you a fairly decent approximation of what you want and what you can get.

>>995731
so if i have 18V battery, the source of electricity and something to prevent the current from flowing back, can i hook up the battery to the source of electricity and use some magical diodes that won't burn from 18V and connect the pc to the battery (i'm not good with electronic as it shows so cut me some slack)

>>995733
i use the eee pc remotely so i won't be needing any monitors and such

>>995735
IIRC over half the power use of those things was the display and GPU.

>>995704
40 watts is quite a lot. You can run it on sun or wind provided you have enough

Check this out:
http://www.lowtechmagazine.com/2016/05/how-to-go-off-grid-in-your-apartment.html#more

To be honest, the Raspberry Pi's would probably be easier to use than this, unless there's an explicit reason you needed higher-speed local storage. RasPi 3 is voltage hungry (actually needs like 5.25V base or it's at risk of knocking out at high amps) but has built-in wifi that doesn't use the USB limits. The RasPi 2 is much less power constrained, and you'd need the extra wifi adapter (cheap if you're considering solar and shit lol), but the data transmission rates would be limited. 5 volts however is MUCH easier to deal with than 12+, and the multiple cores should guarantee your system wouldn't lock up and time out if you decided to compile something.

Additionally, for that PC, the computer is rated at 40W, but that thing would fucking roast if it used 40 watts all the time, and, that's the max consumption by the supply, not the max output to the PC. If you knew the output voltage and current limits, you could easily build an adapter yourself, as powering the AC adapter would likely instantly cost 20-50% efficiency, by the inversion stage alone, not accounting the loss in the power supply. Using linear regulators from 24->18V would be 75% efficient. Having two 90% efficient stages (if somehow your inverter and adapter were magically efficient) would be 81%, and a shitload more complicated than soldering and heatsinking a powerful regulator.

I was almost saying parallelizing regulators, but turns out there's a lot of trouble with that. A single LT1083 or LT1084 can handle the current. If the voltage was 18V you're looking at 2A max so either works stepping down 24-18, but if you're looking at 12V that's closer to 3A, so 24-12 would probably not work on the 1084, but would on the 1083.

http://cds.linear.com/docs/en/datasheet/108345fh.pdf

This was just the first one I found for high current capacity in the voltage range requierd, and since it's pretty cheap heatsink-able, that's really nice.