SPCR

This might be a little over the top, but how big and how expensive would solar panels have to be to provide enough energy to power a 300W PC under load?

According to this site, a square inch of solar panel can generate app. 45mW of energy (providing the sun is shining!). So, to generate 300W, you would need 300/0.045 = ~6700 square inches of solar panel. A 6' x 8' solar panel, measuring ~6900 sq. in. in area would generate 310W of energy.

If you add on the monitor, low power speakers, and an inkjet, I assume the total would be somewhere around 400W, requiring a panel almost 8' x 8'.

(yes, I've done some rounding. There's just no point to going to the umpteenth decimal place anymore...)

The problem becomes more complex if you want to leave the computer on 24/7 - you need more panels and batteries to store the power for usage overnight. The general theory with solar-powered homes is to use gas for heating, hot water, and cooking, while using the solar power for all the 'little' stuff.[/url]

So what your saying is replace my roof with solar panels... I understand.

I've seen roof tiles that are solar panels in disguise. Looks really nice too in the photo, no need for extra panels that stick out like a sore thumb. Don't know anyone who has it installed though.

These sites sell panels and how some info on them, although I don't know if any of them can generate 120V AC. You might be able to find something that will power a laptop. The system would work by charging a battery that will feed the power, otherwise, a passing cloud would just kill the energy source.

http://www.nationalsolarsupply.com

http://www.mrsolar.com

luckily, all of you live in relatively sunny areas (well, I'm not too sure about NJ), but in my Vancouver home it would work for 2 months or so...

What those houses actually using solar panels generally do is to set up a two way grid connection. Thus the excess power from the PV cells (converted to 110/230v ac) is fed to the grid, and there is grid power available when the PV cells aren't generating. This is far cheaper than any storage arrangement - and you get paid for the electricity you sell as well

Oh yeah, I forgot the night problem. ie, no sun in the night

So most likely you would need your attic full of batteries to save any excess energy generated by the panels.

oogabooga @ 8 x 8 inches, is that all, well thats promising.

So, what if I wanted to get 1 of them roof convertions + batteries for over night power? Any ideas on how must it would all cost?

The only problem is, Im in the UK, and we dont get many sunny days

oogabooga @ 8 x 8 inches, is that all, well thats promising.

I think he meant 8 x 8 feet....
Also, don't fill your roof with batteries - they're pretty heavy and you're likely to have the roof fall down on you if you try!

As for costs, PV cells are hugely expensive. The costs are something like $5 per watt of installed peak power. For the UK you are usually going to be running at around 10% of peak power - so a 500W (5kW peak) computer installation would cost of the order of £15,000
You can get grants from the government and the like, but even so the economics are pretty hopeless - PV is only useful for space applications and for cases where there is no grid power supply and maintenence is very expensive.

http://acre.murdoch.edu.au/refiles/pv/text.html

8 x 8 feet

£15,000

OOOKAAYYYYY, i think maybe i need another idea

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

JEN wrote:8 x 8 feet

£15,000

Is it that expensive?

I've seen a quote for about $20,000 for a fairly large system (approx 2kW) complete with batteries, inverter and installation.

I've seen 75 / 100W panels (for RV / trailers) that cost about $350 or so.

Add a few car batteries ($50 each), a charging circuit, and an inverter, and you should be able to come up with a system that cost much less than 15K quids.

As for alternatives, let's see... how many watts of electricity can a hamster running in a wheel generate? I know an adult on an exercise cycle can generate around 70 - 100W...

That was for a 5kW Peak system - it was for UK weather, and taking into account the fact that you would have to store energy, etc (assuming a 500W power draw or so).
The weather/storage issues suggest that you would be lucky to get more than 10% of peak power draw out of it. The UK weather is actually the main issue here - we just don't get the solar intensity required. Somewhere like Arizona or Tunisia you would be operating at or near peak power for much of the time - so a 2kW system would be quite feasible.

So I guess theoretically you could generate all your power needs if you wanted. Something to look into when I have a $$$ to blow.

lenny wrote:
As for alternatives, let's see... how many watts of electricity can a hamster running in a wheel generate? I know an adult on an exercise cycle can generate around 70 - 100W...

A friend of mine has rigged up a sytem to use while she's riding her recumbent excersie machine. She's got a 17" LCD mounted on a VESA mount clamped to the handlebars and uses a wireless mouse and keyboard. I've always joked with her about hooking the pedals up to a generator and powering the PC while she exercises but neither of us have the technical ability to pull it off.

Ralf Hutter wrote:

lenny wrote:
As for alternatives, let's see... how many watts of electricity can a hamster running in a wheel generate? I know an adult on an exercise cycle can generate around 70 - 100W...

A friend of mine has rigged up a sytem to use while she's riding her recumbent excersie machine. She's got a 17" LCD mounted on a VESA mount clamped to the handlebars and uses a wireless mouse and keyboard. I've always joked with her about hooking the pedals up to a generator and powering the PC while she exercises but neither of us have the technical ability to pull it off.

I'm guessing that she doens't care if that PC is silent

Hook up a VIA cpu to the generator for those days where she doesnt feel like pedaling like Lance Armstrong. Or use an AMD64 with cool-n-quiet.

Continuing even further off topic, I would think it's a lot safer to have only the LCD powered by the generator, since PCs generally don't like to have their power interrupted.

I've always thought that this is one way of getting lazy computer users to exercise more. Pedal or you don't get to see the display "Computer user collapsed from exhaustion while visiting p*rn site. News at 5!"

I'll bet maintenance would be a real pain. How long are solar panels expected to last?

Solar has the space factor. But here on earth the #1 renewable is wind. It wouldn't take much of a turbine to power a PC (obviously the wind has to blow).

If you live in the right place for it, you wouldn't need a very big turbine at all to get 300W. There is quite a range available, from very high tech - variable pitch blades etc - to plans off the internet made from a car alternator and plywood.

mrzed wrote:Solar has the space factor. But here on earth the #1 renewable is wind.

Yup - this is especially true in the UK. The hidden issue with solar and wind is regulating and storing what you produce, and providing alternatives for when the stored power runs out (mains chargers etc). One (potential) benefit of wind over solar is it may generate 24/7 so your storage can be smaller: solar is guaranteed to have nights off!

To design a system that can run 24/7/365 gets silly: if you have mains available then to design with the alternative as 'primary' source and deliberately include a mains top-up for when the wind dies down for too long is much more logical to me. Also to build a low power PC, e.g. the Epia (see SPCR reviews in the last week) where the peak system load (inc monitor, scanner etc) is easy to keep under 100W compared to a 2GHz iAMD where the peak is somewhere between 100-200 (or more if you insist on killer GPU).

IIRC Maplin used to have some wind turbines for yachts but no longer: anyway there are plenty of "marine intended" turbines available e.g. here at SailGB.com.

Correct me if I am wrong, but the point of solar panels in a home setup is not to directly power devices, but to charge batteries to power an inverter? Nobody directly powers electrical goods directly from the panels. Instead, you charge up a bank of high capacity batteries and the inverter does the work.

Likewise with wind power, except on electrical grid scale wind installations, in which the generated electricty goes more-or-less directly on the grid.