Where can I find the most affordable solar panels to power my dorm room?

June 23, 2007 7:23 PM

Where can I find the most affordable solar panels to power my dorm room?

I'm in the business to purchase the most affordable (new or used) solar panels. I'm on an extreme budget and want to get about 100 watts. Any suggestions welcome!

posted by peetle to technology (24 comments total)

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Give the guy a break! Your answers aren't very useful. Maybe he just wants to power stuff via the sun. Nothing wrong with that.

Have you seen this guy's Cheap Solar Power System. Might be a bit much for a dorm room, but could be a start.
posted by ArcAm at 8:24 PM on June 23, 2007

I don't think this is such an awful question. maybe he has valid reasons. any panel's power output is going to depend a lot on local conditions, though. honestly I know just enough about solar power to be a nuisance, but I'd say that RI doesn't get enough sun to make solar viable. your results will probably be disappointing.
posted by Chris4d at 8:26 PM on June 23, 2007

Don't forget, you'll need to also get a deep cycle battery for storage, and a power inverter if you want to run AC appliances. Since 100+ watt panels are sort of expensive (around the $500-$700 range), I'm not sure how conducive this project is to a tight budget.

Are you really sure you want to do this? Unless you actually get permission to mount a panel on the roof of the dorm and then to run wires through your window or something, this isn't really going to work very well. How about scaling down your needs, or just building a small proof of concept for fun instead?
posted by tracert at 8:27 PM on June 23, 2007

I don't think this is such an awful question. maybe he has valid reasons.

hmm, lets re-read the question:

I'm on an extreme budget and want to get about 100 watts.

bonus:
Any suggestions welcome!

Solar just isn't a viable solution for the average consumer, much less a dorm dweller.
posted by b1tr0t at 8:29 PM on June 23, 2007

Sundance Solar sells mini solar panels which are well under $100 (though I don't know what that size of panel could power), as well as showers, radios, cell phone chargers, and a bunch of other electronic thingies.

As a former dorm RA, though, I urge you to not tweak with the electrical system in a building you share with others; it will be noticed, and it will annoy your RA or get you in trouble with the housing office, the fire department, or really anyone who cares to bother you. I had a resident who thought I didn't smell her very not allowed toaster every morning - that is, until she got fined after I asked her to stop using it multiple times and she ignored me. Bwahaha.

I also wouldn't have wanted to have to deal with kicking a resident out if that person was trying to power some, oh, I dunno, lights or something off the grid so as not to be noticed. Do tread lightly, please! :)
posted by mdonley at 8:59 PM on June 23, 2007

The first thing you'd have to do is talk to Brown and see whether they'd mind you hanging a big solar wing out of your window, keeping one or more charged car batteries sitting around in your room, and running your own amateur electrical system.

The answer to all three is probably "OH MY GOD YES WE MIND," but it is Brown

The thing you should do is get together with others to agitate for Brown to either install its own solar, or arrange to purchase renewable-source electricity.
posted by ROU_Xenophobe at 9:29 PM on June 23, 2007

The first thing you'd have to do is talk to Brown and see whether they'd mind you hanging a big solar wing out of your window...

It is easier to ask forgiveness than permission.

Since 100+ watt panels are sort of expensive (around the $500-$700 range)

Current ebay prices, if you buy smart, are about $300 for ~100W.
posted by Chuckles at 10:03 PM on June 23, 2007

It is easier to ask forgiveness than permission.

It is much cheaper to ask permission than to shell out several hundred dollars for something you can't use.
posted by ROU_Xenophobe at 12:01 AM on June 24, 2007

The thing you should do is get together with others to agitate for Brown to either install its own solar, or arrange to purchase renewable-source electricity.

UChicago just did this for us--whatever we saved in a month they bought in renewable wind energy. See if you can get StuGov to run a Green Campus campaign/competition. It's worth more in the long run, anyway.
posted by rhoticity at 12:02 AM on June 24, 2007

The cheapest way I've seen is that sometimes on ebay, someone will sell a box weighing X pounds of loose photovoltaic cells. (Never buy this if the cells are assorted sizes or shapes - only if they are the same)
This route means that you will have to mount the cells on some kind of backing panel, put a protective window on it, and wire them all up to turn the solar cells into a solar panel, etc. This is not hard to do, but it is very time consuming, and if you don't plan carefully, you might find yourself spending more money on the hardware supplies to make the frame, etc, than you anticipated. It is, however, cheap, and you have the advantage of being able to arrange the cells how and where you want, to output the voltage that best suits you, etc.

Note that these bulk purchases of cells will contain many broken or non-functioning cells, and you will want to test each one for current output in order to match the highest performing ones with each other. To do this, I wait until night, and use a single incandescent bulb in the room, and measure the output of each cell at exact the same distance and angle to the light, via a multimeter. Though even your posture as you read the meter may affect the reading. The bulb does not have the same spectra as the sun, so this method isn't ideal, but it will find the major dud cells and identify the really good ones.
posted by -harlequin- at 1:57 AM on June 24, 2007

Another trick for budget PV is mirrors. Since mirrors are cheaper than PV cells, buy fewer cells, and put mirrors beside them to reflect additional light onto them. There are limits to this though - the cell efficiency drops the hotter they get, too much concentrated sun and they'll be running very poorly. Also, the sun tracks over the sky, so mirror systems work best with a clockwork or other motorized mount to keep the panels+mirrors facing the sun.
The typical mirror arrangement is a mirror on each side of the cell at 30 degrees from perpendicular to it.

Generally, mirrors are used where sun collecting area is larger than that of the available solar cells. Whereas in situations where the PV budget is large enough that the available sun-collecting area is the limiting factor (such as most NASA devices), obviously mirrors would be disadvantageous.
posted by -harlequin- at 2:09 AM on June 24, 2007

Basically, most solar solutions require a series of panels (probably 12 sq. ft for 100W but possibly 36 if you want 24x7 power), an inverter and sometimes a battery. However, I'm pretty sure you shouldn't hook an inverter into your dorm system and feed power back into the grid, so you'll definitely need the battery. Do you need this 100W power source 24x7, and are you powering DC or AC devices (if the former, you won't need an inverter).

Read this, and this.

If you are doing this for environmental reasons, please consider how much fossil fuel energy went into the production of the panels. Better environmental solutions often focus on conservation, especially changing lighting to LED or CFL.

My apologies if the following is OT:
If you are doing this for grow lights (hinted at above by mdonley), consider energy efficient LED grow lights (I have no experience with these, but the theory sounds good), which would reduce your wattage requirements considerably. I assume unless told otherwise that you are growing something legal. Don't tell me otherwise. You could probably safely use grow lights without generating an investigation worthy night time power draw by setting up a battery charger on a timer so that it just charges from 8 AM to 9 PM and then use batteries to power the lights.
posted by BrotherCaine at 2:29 AM on June 24, 2007 [1 favorite]

Ignore my previous power output estimates, as this map says RI gets around 4kWh/day/sq.meter of panel on the worst month of the year.
posted by BrotherCaine at 2:39 AM on June 24, 2007

Also, if you are powering an audio or computer device you may need a pure sine-wave inverter which is a bit pricey.
posted by BrotherCaine at 2:40 AM on June 24, 2007

We've installed solar panels on the roof of our campus-owned (and Housing-managed - ugh) house, and it was a minor pita, but Housing eventually caved and let us have them. Our RAs also can't fine/bust you for alcohol or drugs/etc, so we may be in the minority.

I'd bet Brown, out of any school, would be likely to have similar attitudes. You can get away with quite a lot if you're reasonably smart about it. If you're doing this to grow, though, it'll probably get uncovered, so start out with a legit reason.

And, as a reference point, we have 4 large solar panels, and that's enough, in sunny weather, to power a few highly energy efficient, dimmish lights, and heat some hot water.
posted by devilsbrigade at 8:34 AM on June 24, 2007

If you are doing this for environmental reasons, please consider how much fossil fuel energy went into the production of the panels.

This is a misunderstanding of the production process. Solar panels are made from the offcuts of the semiconductor industry - the bulk of the manufacturing energy input occurs during the semiconductor production process, and thus that energy would simply be going to waste if the solar panels were not made.

Also, if he sets up a 100W system in his dorm, that's not the kind of thing you just throw away when you graduate. That panel might see use for decades.

(But obviously the final application of the solar panel does make a difference. For example, solar powered garden/path lights trade a simple length of wire running under the grass and a few hours sweat installing it, for a solar panel that charges a cheap cadmium battery every day such that the battery is ruined within a year. The device then no-longer works, and so it typically becomes landfill - despite the amount of toxic cadmium it contains, and that it also contains a solar panel could produce another 30 years of energy. So in case of cheap garden lights, solar panels are clearly enabling a convenience that is environmentally harmful)
posted by -harlequin- at 9:17 AM on June 24, 2007 [2 favorites]

It's Brown? Dude, set up a GISP with a nice prof and get credit for trying to get the university to do it on a larger scale. Or look to moving to one of the co-ops or the eco house and set it up there. Then you don't have to pay for it and it has a wider effect. But seriously? Shit like this is why GISPs were invented.
posted by dame at 9:56 AM on June 24, 2007

I also wouldn't have wanted to have to deal with kicking a resident out if that person was trying to power some, oh, I dunno, lights or something off the grid so as not to be noticed. Do tread lightly, please! :)

Just to set things straight since he hasn't posted a follow up yet -- as far as I know he's not planning to grow anything at all. It's about the possibility of using renewable energy in the dorm, not covert power usage.

(I speak as a fellow Brown student and girlfriend of the original poster.)
posted by puffin at 10:33 AM on June 24, 2007

You might be interested in this PDF on solar system sizing and pricing and this briefing PDF on non-grid solar systems, both from the lovely and talented CD3WD, a compilation of bootstrap hooks for the third world.

I would make a point of filling out the 'A first checklist' quiz on Pg 2 of the briefing link, though. From my reading, it sounds like you get a 'no' for at least five of the questions, any one of which would disqualify you.
posted by Orb2069 at 6:47 PM on June 24, 2007

The whole "solar panels take more power to make than they will ever generate" thing is conservative FUD, and hasn't been true for twenty years. Current figures here.
posted by flabdablet at 1:37 AM on June 25, 2007 [1 favorite]

I stand corrected, but still think it is worth doing some analysis. This is definitely not a cookie cutter solution. My friends who've installed solar solutions with batteries have not gotten the same payoff as an inverter only solution.
posted by BrotherCaine at 4:09 AM on June 25, 2007

No offense intended with my insinuation of botanical shenanigans - just trying to make sure you don't end up on the street/in the hoosegow mid-semester.

What's the roof like? While your room might be too small a unit to provide an independent power source for, could the roof be covered with enough solar panels to provide power for something near the dorm, like a lighted basketball court or a street light?

Since they'd be used by more people, the college might be more interested in funding something like that, and perhaps the state would give them some sort of rebate. Here's an article about a university in Scotland (even less sunny than Providence) using solar panels to power a computer lab.
posted by mdonley at 8:05 AM on June 25, 2007

The whole "solar panels take more power to make than they will ever generate" thing is conservative FUD, and hasn't been true for twenty years.

I've heard both sides of this repeated, but one thing sticks in my thoat (from your linked article)...

As noted in Alsema (2000), these differences can partly be explained by different assumptions for process parameters, but they mostly appear to arise from estimates for the silicon purification and the crystallisation process. The majority of silicon solar cells are made from off-spec material rejected by the micro-electronics industry, which introduces the question of whether to include process steps required for micro-electronics wafers in the energy requirements for the PV modules.

If they're saying that the reason the 'Requires more fuel to build than it puts out' comment is off is because their estimates use semiconductor waste as feedstock instead of raw silicon.... Well, I guess it's true up to a point. That point being when the falling slope of semiconductor waste (Due to process optimization) meets the rising slope of PV demand...

Personally, I think that, if PV is going to save the day, it's going to be a new PV tech, like thin film, not glass plates - and encouraging people to make or buy glass plates is (IMO) throwing good money after bad. I liked Don Lancaster's take on it: "You will know when this(Net Solar output greater than input) happens by (a) pv being used to fully produce pv, and (b) by aisle 13 at Wal-Mart being clogged with 110 vac, 1 kw plug-and-go home panels." (PDF here)
posted by Orb2069 at 4:54 PM on June 25, 2007

Don Lancaster is apparently conflating Energy Return on Energy Investment (EROEI) with economic return on investment (ROI). At present, EROEI for solar panels is something of the order of 800%. Economic ROI, though, is nowhere near that - largely because we're still paying for non-renewable energy at a price that reflects its fuel extraction cost, rather than its fuel replacement cost.

1kw plug-and-play solar panels will not turn into a commodity item until they start offering an economic ROI that even Joe Sixpack can work out will save him money, and quickly. To make that happen, electricity is going to need to cost about twice what it does now; or, China is going to need to start making mass quantities of cheap thin-film solar panels.

We're also going to need a certain amount of infrastructure support, as in widespread adoption of grid-interactive meters. Without those, everybody with panels would also need batteries, and that makes things more expensive.
posted by flabdablet at 10:36 PM on June 25, 2007