Effective/interesting domestic uses of solar power?
December 28, 2007 7:51 PM   Subscribe

What domestic devices can be operated effectively on solar power these days? Know any interesting alternative uses? Wide open question.
posted by vizsla to Technology (11 answers total) 6 users marked this as a favorite
Ed Begley Jr. runs almost his entire household on solar power (and other interesting things like bicycle power).
posted by amyms at 7:54 PM on December 28, 2007

You can use electricity from photovoltaic panels to operate any electric domestic device with an appropriate transformer. Things that run while the sun is shining will be more efficient than things that run when it isn't, because storing power is not very efficient. DC devices will be more efficient than AC devices, because solar power is DC and the conversion is not all that efficient.

For non-electric devices, gas-burning appliances (home heating and hot water heating) can be replaced by a solar hot water heating device, though for cold climates, buying sufficient vacuum collector tubes to supply all your heat needs would be very, very pricey.

If you were more specific, it might be easier to answer your questions. Are you asking for the most efficient method to use solar energy for a house? For the most cost effective uses? The simplest uses? What do you mean by alternative uses?
posted by ssg at 8:05 PM on December 28, 2007

Response by poster: ssg: All of the above. Cost effectiveness is another area of interest. Thanks.
posted by vizsla at 8:19 PM on December 28, 2007

Lots of Japanese houses have solar panels on them now. Interesting article from NPR here. An example of use on a larger scale at Aichi here.

I've met several people in Japan who have solar powered wrist watches. Here is a variety of chargers for different things, including home name plates.

Solar powered backpack from Uncommon Goods.
posted by fan_of_all_things_small at 8:39 PM on December 28, 2007

If you're interested in replacing part of your non-renewable energy use with renewable energy use, then I highly suggest a solar water heater.

I stayed at a place that has a solar water heater, and that thing is amazing.

Water is always super hot. We had 6 people living in that house at the time, and we never ran out of hot water.
posted by BeaverTerror at 9:37 PM on December 28, 2007

As BeaverTerror says, the most cost effective way to use solar energy in your house is to use it to heat your hot water. If your location is too cold and/or dark to supply all your hot water cost effectively in the winter, you can still use a normal hot water tank or an on-demand water heater to bring the water up to the required temperature. This is also the most efficient method of collecting solar energy, but it does a require a bit of a complicates system.

That said, there are other things that don't involve solar energy that can be done in the typical North American home that will be more cost effective in terms of non-renewable energy savings.
posted by ssg at 10:10 PM on December 28, 2007 [1 favorite]

If you haven't already, insulating your attic really well and switching to flourescent lighting are probably the most cost effective ways you can reduce your household energy consumption.

Tomshardware.com had an article a month or two ago about building a solar powers PC covering everything from component selection for the PC (integrated graphics and a dc-dc powersupply were key) to mounting the panels.

In general, you are probably better off, capital-efficiency-wise, sellong excess power back to the grid (assuming that you live somewhere where the utility is required to give you a good rate), and buying power when you need it, rather than paying for a big bank of batteries.

+1 on solar hot water. Passive solar heating is also worth looking in to.
posted by Good Brain at 11:16 PM on December 28, 2007

The answers are very different, even mutually exclusive, depending on whether you:

- Are interested in solar for environmental reasons, or
- Are interested in solar for self-reliance reasons.

If you're interested in green power, or you want to lower your environmental footprint, and the grid is available, the worst thing you can do is hook up a photovoltaic solar-battery-inverter system. That leaves solar heating, and photovoltaics that augment the grid (either directly, or at least without dragging unnecessary battery systems into the equation thus creating a much higher environmental cost than even dirty coal-fired grid power). Solar heating has been covered, so, photovoltaics:

Augmenting the grid directly is the best option, but is a large upfront cost (probably high four digit) that will only pay off after many years. This is where your solar panels are connected to the grid such that the grid buys any power generation that you're not using, from you. This kind of setup may be The Way Of The Future, but I'm assuming it's Too Much Too Soon for you, so I'll ignore it :)

Augmenting the grid supply to your home, but without using a battery-inverter system, cuts out a lot of what photovoltaic can do (and example of self-reliance solar being at loggerheads with environmental solar), so I would suggest building a solar charging station for charging all your battery devices (laptop, mp3, cellphone, flashlight batteries, and so on).

This is because:
- Even a small solar panel can charge these devices, it's (usually) just a matter of time
- You're already used to leaving the devices to charge when not in use, so the not-always-on nature of batteryless solar is less of an issue.
- It's really cheap and simple - just a solar panel and an inverter. No battery. No battery monitoring system, etc. Sometimes it's just a solar panel! (if your existing charger accepts 12V input and isn't too fussy about the voltage being ballpark)
- Providing it's in constant use for many years, it's about as green as photovoltaic gets.

Conversely, if you're into solar for self-reliance / self-sufficiency reasons and damn the environment, then you'll want a panel-battery-inverter system. But really, you'd be better off with grid + emergency generator, (and it might be worth your time to look into DIY wind too). This is stuff is hardly alternative though. It's a very well-trodden path

If you have a panel-battery-inverter system, then generally the first thing people migrate to the solar power is the lights, as fluorescent lights draw relatively little so even a $500 battery is decent, and it's no great crisis if the battery is drained, since lights aren't important and there are always flashlights (and the grid, if it's not a blackout).

From that point, any domestic appliance that doesn't draw much power, is good for solar. "Not much power" is a relative term, but unless you're buying serious battery storage for serious $$$, I think of "not much" as meaning a device that is "ranging from 25 watts but fairly intermittent use to less than 2 watts if in constant use", and you'll get away with higher powered items for very very short durations.

Or think of it this way: A solar panel says it is 50 Watts. If it's mounted in a fixed angle bracket rather than a motorised heliostat, you're going to get more like 30 Watts, and that's only going to be for say, five or six hours during summer (more if you're close to the equator), so 180 Watt-hours per day. Say 50% chance of cloud or rain over the year, so let's make that 100 w/h/d average. Battery charging and other losses will steal another 10-20%.
So given unlimited storage. on average you could run a single 25watt CFL bulb for a little over three hours each evening. Or two bulbs for under two hours.
Now, I just pulled those numbers out of my ass, but they are based on a fair bit of experience with solar panels, from which the consistent lesson I have learned has been that I always end up with only a fraction of the power that I feel I should have. :-)
I don't know if these guesstimate numbers are remotely accurate, but I wonder if this makes a useful rule of thunk - taking the watt output of the panel, double that number, and you get a guesstimate of the watt-hours-per-average-day. It depends greatly on where you live though.

So what's stopping you just paying more to get a bigger solar panel? There is an environmental footprint concern there, if that is an issue - if you buy more panel than you regularly use (and don't hook it up to feed back into the grid) most of its potential generation goes to waste, and since the environmental impact of panels is paid upfront, a too over-sized and under-used panel risks leaving a larger footprint than just using coal-fired grid power instead.

Like other green technology, solar is green when done right, and a waste when done wastefully.
posted by -harlequin- at 11:46 PM on December 28, 2007 [2 favorites]

As to interesting uses, it's hardly alternative, but I intend at some point to go nuts with those new paper-like photovoltaics, decoupaging them onto the surfaces of some of my battery-powered things, so that the batteries don't need charging quite so often, or even become entirely self-charging :-)
(though I expect at some point that this sort of embedded photovoltaic augmentation will eventually become not too uncommon off-the-shelf)

posted by -harlequin- at 12:09 AM on December 29, 2007

The publication Mother Earth News frequently extols the virtues and applications of solar energy. I've not used any of these techniques yet. I hope to install at least a solar hot water setup within the next year.

A few direct links to some articles I grabbed from the list:

"Water Wiser Solar Stills"
"The Vita Solar Cooker"
"Easy DIY Solar Lighting"
posted by bonobo at 1:30 AM on December 29, 2007

Also, another thing my beau and I are looking into if we build a home or additions is the Trombe wall. Related to that link is the obligatory Wikipedia category of Solar design.
posted by bonobo at 1:39 AM on December 29, 2007

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