Solar powered air conditioning

Francis · Post by **Francis** » 23 Feb 2009, 13:21

Have you heard about solar powered air conditioning? I think this is a cool and brilliant idea. Although I don't have solar powered air conditioning yet but I'm already planning to have one. What do you guys think about this?

JohnB · Post by **JohnB** » 23 Feb 2009, 15:19

Surely air conditioning is needed because of badly designed buildings that are unsuitable for the local environment. This is just a technological fix for a problem that shouldn't exist, although using solar power rather than fossil fuels or nuclear is preferable where air conditioning is used.

Aurora · Post by **Aurora** » 23 Feb 2009, 16:10

If anyone is interested, Sanyo manufacture such a system.

http://www.sanyoaircon.com/products/sol ... fault.aspx

Post by **adam2** » 24 Feb 2009, 15:43

The system linked to above is a standard electric air conditioner, used in conjunction with grid tied PV modules.
Nothing new or radical there, though it is still a good idea, and of course the PV modules will reduce the amount of utility power used, even outside the A/C season.

For very large A/C plant it is possible to raise steam useing concentrating solar thermal collecters, this then drives a compressor via a steam engine, with the exhaust steam driving an absorbtion chiller.

For smaller scale needs a standard A/C unit and grid tied solar is the way to go.

A stand alone off grid PV system can be used to power an A/C unit, but a relativly large system is required.
I use a portable air conditioner regularly on my off grid system in the summer.
Powered from an inverter, the current is about 60 amps at 12 volts, this gives a run time of least 10 hours from my 2,000 A/H battery.
In practice the run time is much better than that because the A/C is used mainly when the sun is shining and therefore most of the energy comes direct from the PV array.

Most properly designed homes should not need A/C, but my home is badly designed, and not my property to alter. Also I hate the heat and regard cooling as more important than heating, I would move to a colder country if not for family.

Post by **adam2** » 24 Feb 2009, 15:55

Francis wrote:Have you heard about solar powered air conditioning? I think this is a cool and brilliant idea. Although I don't have solar powered air conditioning yet but I'm already planning to have one. What do you guys think about this?

Are you considering a stand alone, off grid system, consisting of PV array, battery, inverter, and A/C unit?
This will be very expensive, but gives valuable independance from the grid, and if suitably sized can of course power other loads as well.
This will be a relativly large and expensive system, and will require careful design to ensure reliable service.

Alternativly perhaps you are considering a standard grid powered A/C unit, with some or all of the energy used being offset by a grid tied PV system.
This will be a cheaper and more efficient system, but has three pitfalls
1) it is totally grid reliant, and gives no backup supply whatsoever. No grid=no A/C
2) Grid tied inverters will only work if the grid voltage and frequency are well controlled, this is not the case in all countries.
3) Installing such a system will normaly require written permission from the grid operator, which in some countries may be a challenge.

Bandidoz · Post by **Bandidoz** » 24 Feb 2009, 20:53

How about Passive Solar Cooling?

http://en.wikipedia.org/wiki/Solar_chimney

Three are quite a few projects of this ilk underway in India:

http://www.igbc.in/igbc/home.jsp

AFAIK there's some info on this in Sue Roaf's "Ecohouse 2", and other similar "Passive Solar" books

http://www.DODGY TAX AVOIDERS.co.uk/Ecohouse-2-Sue- ... 0750657340

A technical "flow dynamics" report:

http://www.flomerics.com/files/casestudies/424/v41.pdf

JohnB · Post by **JohnB** » 24 Feb 2009, 21:53

Bandidoz wrote:How about Passive Solar Cooling?

It's no fun though, is it? No controls to fiddle with and flashing lights to impress people, and not using power doesn't inflate your ego like something that uses a few kilowatts

Post by **kenneal - lagger** » 25 Feb 2009, 02:38

At least PV powered air con uses the solar at a time when it's at it most efficient. Unlike ground source heaet pumps for heating. If they are solar powered not only is the solar used at its least efficient, so too is the heat pump.

John's right; aircon is a failure of design in a building.

Francis · Post by **Francis** » 02 Mar 2009, 02:23

adam2 wrote: Alternativly perhaps you are considering a standard grid powered A/C unit, with some or all of the energy used being offset by a grid tied PV system.
This will be a cheaper and more efficient system, but has three pitfalls
1) it is totally grid reliant, and gives no backup supply whatsoever. No grid=no A/C
2) Grid tied inverters will only work if the grid voltage and frequency are well controlled, this is not the case in all countries.
3) Installing such a system will normaly require written permission from the grid operator, which in some countries may be a challenge.

Yes, I'm considering a standard grid powered A/C unit. I agree with you, this kind of system is efficient but there are pitfalls we have to consider.

RenewableCandy · Post by **RenewableCandy** » 02 Mar 2009, 15:57

JohnB wrote:Surely air conditioning is needed because of badly designed buildings that are unsuitable for the local environment. This is just a technological fix for a problem that shouldn't exist, although using solar power rather than fossil fuels or nuclear is preferable where air conditioning is used.

I think Francis is in the Philipines, which have a hot humid climate, the most difficult for thermal comfort. It's probably the one location on earth even I wouldn't begrudge someone an air-con

JohnB · Post by **JohnB** » 02 Mar 2009, 16:12

RenewableCandy wrote:I think Francis is in the Philipines, which have a hot humid climate, the most difficult for thermal comfort. It's probably the one location on earth even I wouldn't begrudge someone an air-con

But hadn't many hot countries developed building methods and ways of life that coped with the heat? Surely a lot of the problem is using western building designs and lifestyles because they're modern and fashionable. Anyway, this is a UK forum, so we should be mainly discussing UK problems and solutions

.

Mitch · Post by **Mitch** » 02 Mar 2009, 21:04

I'm fully with Adam2. Also have a small standard air-con and YES - amazingly the solar P.V. works a treat for this purpose!! When it's hot enough to need the air-con, the solar P.V. actually provides all the watts required, with a fraction spare to maintain the fridge! Summer - yeah, cool boat 'n cold beers, maybe the solar p.v. wasn't such a bad buy after all.....

Francis · Post by **Francis** » 03 Mar 2009, 11:52

RenewableCandy wrote:I think Francis is in the Philipines, which have a hot humid climate, the most difficult for thermal comfort. It's probably the one location on earth even I wouldn't begrudge someone an air-con

Yes, I'm in the Philippines and the climate here is pretty hot...since summer is now approaching, we are using air-con most of the day. Using air-con everyday = pretty high electric bill. That's why if ever I see a solar powered air-con here, I would surely love to buy one.

RenewableCandy · Post by **RenewableCandy** » 03 Mar 2009, 18:23

Ah but as well as the usual combo of solar PV plus electric air-con, there is also "Absorption Chilling", which uses the high temperature (80 degC or somesuch) of a solar HW system as the "energy source" for a chill cycle, this can get down to 5 degC which (I'm reliably informed) is cool enough for a typical aircon unit.

They are MUCH cheaper to run than electric units.

Meanwhile, for any aircon, the cooler a place you can put the heat-dump bit in (e.g. in the shade, in a lake, below-ground...) the more "coolth" you'll get per unit of energy put in (i.e. Co-eff. of Performance goes up). This can give you more money returned per invested than some more complex technologies...But you knew that anyway didn't you

?

gug · Post by **gug** » 04 Mar 2009, 23:39

Mitch wrote:I'm fully with Adam2. Also have a small standard air-con and YES - amazingly the solar P.V. works a treat for this purpose!! When it's hot enough to need the air-con, the solar P.V. actually provides all the watts required, with a fraction spare to maintain the fridge! Summer - yeah, cool boat 'n cold beers, maybe the solar p.v. wasn't such a bad buy after all.....

I was getting a bit depressed about the output of my panels recently, I knew they werent at a great angle, but the most i've seen out of them so far is about half their rated power, however...

Climbed on the bathroom roof with a yet to be sited panel the other day and at 45 degrees/face on to the (rare) sun - I got nigh on 7.25 amps (max 7.5) - just doubling the tilt doubled the power. Obviously I knew this would have some effect but I hadn't bargained on just how much difference it made.

I think (and i'm not sure theres much you can do about it) the shame is, your panels point straight up (if i recall correctly).

If only you could angle the buggers towards the sun more I think you'd get much better results (sure,and i'm the 40th person thats told you this i guess)

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