Small solar panels
July 20, 2011 8:27 AM   Subscribe

Are there decent small-sized, even portable solar panels that deliver safe, reliable (when the sun is out, that is) power? (enough to run, say, a stereo system/tv). I live on the top floor of a building, and have a small terrace; I can't install large permanent panels, but I get so much sun it seems a waste not to try and harvest it in some sense. But is installation tricky, and how do you actually connect it into your system etc.
posted by dearleader to Technology (6 answers total) 3 users marked this as a favorite
You are looking for something like this:

Installation should be simple, but the catch is it outputs 12V DC power. This is good enough to recharge battery, or connect to other 12V appliances. You can also connect this to a power inverter and get 120V AC output. However, it'll be costly to actually connect this to your house system.
posted by curiousZ at 8:55 AM on July 20, 2011

Before you get your hopes up, portable solar charging systems are very expensive. They make sense if you are far off the electrical grid (e.g. camping) but a few grand to run your stereo probably isn't worth it. Plus the whole 12V thing.

But you could spend a hundred bucks or so and get a cell phone or laptop charger just for fun, basically.

However, if you have a huge budget, you have to shlep your own power, and your life is on the line - in other words, you are the US Marine Corps in Afghanistan - you would love your portable solar chargers. Which is to say that hopefully economy of scale will kick in at some point and make systems like these more affordable for everyday use.
posted by Quietgal at 9:05 AM on July 20, 2011

Crap ...a COUPLE hundred bucks...
posted by Quietgal at 9:08 AM on July 20, 2011

You can make tea in the sun or dry laundry on a rack.
posted by theora55 at 9:08 AM on July 20, 2011 [1 favorite]

You'd connect your solar panels to a battery using an appropriate solar controller. You'd then need a power inverter to change the battery's stored, low voltage DC power to 110 VAC, 60Hz power (or 240 VAC, 50Hz power, if you live in England, etc). Ideally, your solar controller could sense when your battery is being discharged by your inverter, and isolate the solar cells from the load, beyond their maximum efficiency and to protect their life.

Often, you can buy a whole package containing the solar panels, mounting hardware, solar controller, battery/batteries and inverter, all sized to drive a particular wattage load for a particular length of time daily, and with overall warranty coverage, from a solar products distributor. Powering a 32 inch LCD HDTV might take around 100 Watts of power, which is going to use the full day's charging output of 2 or 3 average size solar photovoltaic panels, in a couple hours of TV viewing. Most household loads are going to discharge the battery faster than a small area of solar cells can charge it, but as an apartment dweller with limited external panel size and mounting options, that's going to be a fact of life for any system you're likely to find for your use.

If you buy components carefully, and do the integration yourself, a small system for driving a 100 watt sized load for a few hours every evening might not cost more than a few hundred dollars to assemble.
posted by paulsc at 9:12 AM on July 20, 2011

Pretty much what curiousZ said. You can buy the same component parts separately, but panels that size are about $80 each so you may as well buy the set. You also need a charge controller, which is included with that. You'll need a 12 volt battery. Without a battery, you can only run things that use the amount of power you're making at the time and any power that's not used goes to waste -- save it up in a battery and use what you need, when you need it. You're best off just running things that use 12 volts and avoiding a power inverter if possible (an inverter will allow you to plug in "regular" things, but they tend to have relatively high draws and there's some inefficiency associated with the inverter itself). You can easily rig up a stereo -- a car stereo works great. You can buy light bulbs (incandescent, florescent, or LED) that run on 12 volts. And you could run a small 12 volt LCD or LED TV marketed for automotive use.

If you do this, and I highly recommend it, you should view it as a fun experiment and learning experience as opposed to a way to save money or power.

Alternatively, if you want to dumb it down for starters, get a single 15 watt panel and wire it directly to a small 12 volt fan. No battery or charge controller needed. The fan will spin only when you're making adequate power for it, so it turns on and off "automatically" based on the sun. A radiator fan from the salvage yard works -- this is what I use for ventilation in my greenhouse -- or you can find tons of nicer looking choices just by doing a search. My best guess is that a single panel will power a fan 10-12 inches in diameter.
posted by LowellLarson at 2:39 PM on July 20, 2011 [1 favorite]

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