Cheap Solar Cooling Solution?

An anonymous reader asks: "I would like to use solar panels to generate enough power to run an air-conditioner that is only needed when the sun is out. The problem lies in the cost of the battery bank, where one can quickly run to thousands if not tens of thousands of dollars. Given the state of current solar panel technology, what kind of unique solutions have people come up with to handle the voltages of this setup WITHOUT the use of a battery bank?"

"I realize that the photovoltaic array will have to be of sufficient size to offer more power than will be consumed by peak load, causing excess power, that will need to be dealt with. Also, there will need to be some monitor so that if the available energy doesn't meet the minimum threshold, then the appliance is shut off (or the juice to the circuit is cut), and vice versa. As temperatures approach 120F and more this summer, I'm putting more aside for this project and at this point am not concerned with any but simple methods of using up 'excess' energy. Though thoughts have rattled around about a Linux controlled shading system to adjust the raw juice coming off the panels through selective shading."

If the concern is cooling, then one way of burning off any "excess" power might be creative use of fans (either single fans or a bank of them; small or large, depending on the amount of excess power available). What other ways might such "excess" power be used?

Comments

Good luck with that

[Smidge204]

A 12,000 BTU air conditioner (Good for about 400sq.ft. of your typical home) with a SEER of 10 (Minimum efficiency rating for sale in the USA) will consume 1 watt per 10 BTUs of cooling. That works out to about 1200 watts. Figure 100 watts per square foot of sunlight and a panel efficiency of 10%, and you're looking at about 120 square feet of solar panel to cool 400 square feet of living space.

In other words, take the total square footage of the area you want to cool and divide it by 3. That's a rough estimate of the square footage of solar panel you'll need. (Of course, the math WILL change depending on your installation: more efficient panels, better sunlight, more efficient AC unit, etc). This estimate is a worst-case scenario, and I can easily see getting a factor of 5 or better.

As for excess energy... if you anticipate needing a LOT of cooling, one option may be to "store" some of that cool. Use the extra juice to run refrigeration units to chill tanks filled with brine or antifreeze solution. Help cool off/dehumidify your house by running this chilled solution through some radiator coils. (Add small fans for better results!) The pump and fans can also be powered from the "extra juice" if there is any.

The added benefit here is that you can use energy collected in early morning/late evening hours to help reduce cooling load during the really hot parts of the day, allowing you to get away with smaller AC units and less solar panels.

...might wanna check with local building codes, though. Some places get pretty anal about liquid storage!
=Smidge=

Re:Think Outside the Suburb

[Anonymous Coward]

If you've ever been to a _really_ hot country, the first thing you do is put a canopy over your house. Something like the tented airport in Saudi Arabia. Get everything to be light colored, to reflect the sun. Painting the streets white sounds like a stupid idea, but those streets soak up a lot of solar energy, and re-radiate it into the surroundings. Cities are much hotter than the surrounding area, and part of the problem is all that pavement and dark-colored roofs heating things up.

If you want solar, then build the solar array a couple of feet, at least, above your house. That way, your house will be in the shade created. You're smart enough to not stand out in the sun when it's really hot, but why do you make your house stand out in the sun all day, then expect it to be cool? If there's enough water around, plant tall trees that will shade the house. Keep windows and drapes closed on the sunny side of the house. Make sure your attic space is ventilated, or even power vented. Have canopies, or shades, on the outside of the house, that keep sun out of the windows.

Next, _build_ your own house. Use stack effect cooling. Insulate heavily. Insulation slows heat transfer, which means it will slow down the heat getting in. (Most people think you should only insulate in cold climates.)

Somehow, people survived for thousands of years without air conditioning. Could it be that "modern" housing design, where one style suits the entire country, isn't the best idea?