a serious thread about air conditioning via solar...

[IGBT]

We ran our 6000 BTU window unit purely on solar during 105 degree weather in Eastern Washington this past summer.

It can be done but requires a lot of solar.  We have four 270 watt panels on the roof producing a max of 1080 watts (but I saw about 900 watts).

The A/C was using about 700 watts and the other 200 watts was float charging the batteries.   That was at the high noon sun.

We ran the A/C from 11am to about 5pm.   I shut the A/C off when the batteries were starting to provide 20% of the power needed and the remaining evening sun charged them back to 100%.    Our battery bank is only 250AH Lifeline AGM.

The A/C did not keep the camper cold but did keep it at about 78 degrees inside.   Everyone else at the rally without A/C was really dying with 90 degree temps inside their campers.

I rate it as doable, but only in certain situations.

 

[eDJ_]

A number of years I was dating a Girl when I lived in Central Ohiio.   We had both become interested in passive solar heating of a "salt box" type of home.  Active solar was much more expensive and the market for it wasn't so well developed back then.   Most of what we were finding were experiments published in "Mother Earth News" and it was a great stimulation for my imagination.  (going on the theory,  that if you can imagine it you can do it".)

This would be for those who have a piece of land of their own to build this project so they could have heat or
A/C from this source when they park there.

One of the first articles was about an experiment where a small basement was insulated with foam panels and lined with 4 mil plastic.  Then a system of PEX tubing was built with a manifold of thin wall 6" plastic pipe with
elbow's to move air through.  Pumps would pump swimming pool antifreeze (non toxic) in a 50/50 solution.

Once the system was set in place mud was mixed and poured into the structure to fill it.  So there were three levels of PEX tubing in the mud and three levels of the pcv pipe manifold.  The Solar was active and tied into the  PEX.   The plastic was joined so that there was one fan input and the output of air to go into the small home beside this structure.  During the night,  the solar would pump the antifreeze into the panel and the heat in the mud pit would be radiated into the darkness of space via the panel exchange.  (this was the process the article described)  in the daytime air from the home would be exchanged through the PCV pipe in the cold mud pit. (I could see some problems with this with condensation etc but the article didn't address this)   I would see it working better for heating but this was early experiments. 

Here is a link to an article where it was used with a Greenhouse for climate control.  This is solar using a mud medium.

http://www.motherearthnews.com/home...k/solar-greenhouse-zmaz78mjzgoe.aspx?PageId=2


Companies like Lennox are now experimenting with Solar A/C for domestic applications

http://www.lennox.com/products/heating-cooling/solar-ready


Here is an article which may be of interest in a Tiny Home publication.  It regards small Japanese manufactured
Solar A/C units.  It may be of some interest and more directed to this thread.  I'm sure that if the Japanese
are making something this small, they will find a way to make it smaller.

Air Conditioning on Solar Power

http://thetinylife.com/air-conditioning-on-solar-power/


Solar Air Conditioner Heat Pump

http://www.hotspotenergy.com/solar-air-conditioner/


My thoughts are that if I had a couple of small rural plots of ground,  in the north and south that I would snow bird from,  I'd be inclined to attempt this "mud pit" system using the Solar to power small efficient fans and pump motors to circulate the air and cooling/heating medium from the active Solar Panel.  The Solar photovoltaic would generate the electric for them.  The Van, tiny house, etc would be adapted with a port in the front and back to transfer the air through it.  Insulated flex/duct would connect the vehicle to the mud pit manifold.

 

[eDJ_]

Although this isn't a solar powered product,  it may be possible to build it small enough and efficient enough that it could run on propane gas to heat, air condition, and provide hot water.  

a Vuilleumier heat pump (VHP)
which includes novel improvements that
will yield higher performance than the
already high COP results of previously
developed VHP. The heat pump will use
natural gas to provide heating, cooling, and
hot water with a single device

See the graphics etc on the page link below. (if this is developed it may be a less expensive way to have heat, a/c, and hot water than the solar option)

http://www.energy.gov/sites/prod/fi...r Review Presentation - ThermoLift 4.4.14.pdf

 

[thatswhatsup]

posted two weeks ago..


http://www.gonewiththewynns.com/off-grid-solar-rv-air-conditioning

I know they have lots more solar and batts than a van could ever handle... but at least people are still trying..
now we just need to wait for panels and batteries at get a little stronger, and smaller. ..cheaper would also be nice. Not counting on that.

 

[BradKW]

I've watched a couple of their solar related vids, including the solar AC one. Aside from being really nice people that I enjoy following, they are basically clueless in this department, saying things that are just blatantly incorrect. Really cute couple though, and I'm jealous of their lithium battery bank

 

[thatswhatsup]

I figured it wasn't really new info.. they do seem a bit inexperienced.
I'm glad they gave it a shot though

 

[cognitive dissonance]

The obvious downside of PV solar powered A/C is that you can't park in the shade!  One thing no one mentioned yet is insulation.  To me, really good insulation may be the difference between failure and success if you want to run A/C on PV.  For me, the only choice would be closed cell spray polyurethane foam...

Insulating the roof matters the most, but the walls and floor still account for nearly half of your heat gain or loss.  If I was contemplating PV powered AC (and I am, on my school bus) I'd go for at least 4" of foam sprayed in the ceiling.  I'd want at least 3" in the rest of the vehicle.

My next consideration would be shading the sides of the vehicle. What the sun doesn't hit will never get hotter than ambient temperature, which greatly reduces the cooling load. This means an awning that is as long as possible and parking so that it helps you.  (Shading the roof is largely accomplished by your PV array.)

Third would be window area.  Windows have far lower thermal efficiency than insulated walls.  Obviously, the less window area you have, the lower your heat loss/gain.  All windows that aren't shaded by the awning should be protected with reflective/insulated shades.  (I like a nice bright space, but lack of window area can mostly be made up for with LED lighting, which uses very little electricity and produces very little heat. A strategically placed mirror works wonders for roominess as well...)  

I would be just as concerned with these things as the size of my battery bank, the number of PV modules or the efficiency of my air conditioner.  And, speaking of that, I plan to take my Kill-A-Watt to a couple of appliance stores and do my own testing before I buy an A/C unit...

 

[ascii_man]

I've watched a couple of their solar related vids, including the solar AC one. Aside from being really nice people that I enjoy following, they are basically clueless in this department, saying things that are just blatantly incorrect. Really cute couple though, and I'm jealous of their lithium battery bank  

Yeah, they're kind of an Onion story: "Scientists discover that extremely rich and extremely attractive people don't need technical knowledge."