View Single Post
Old 03-01-16, 01:42 PM   #13
Mobile Master Tech
Apprentice EcoRenovator
 
Mobile Master Tech's Avatar
 
Join Date: May 2012
Location: Atlanta, Ga
Posts: 142
Thanks: 38
Thanked 41 Times in 34 Posts
Default

It is possible to run very efficient air conditioning using off-grid solar power, since the peak demand coincides with peak availability. Precool the house a bit during peak availability and have panels on more than one azimuth at least 90deg apart to get output over more of the day, eliminating or minimizing demand at other times while extending the amount of the day you have useful output. If there are clouds, your output goes down but so does the demand.

In Hotlanta, my Nordyne 23SEER central unit which can vary its output from 1.5 tons to 3.5 tons, takes around 15kwh per day to keep all 3 floors of my 5br/3.5ba house AND my garage at 74-76F. My year round demand for other electricity is around 10kwh/day.

That's within the capability of approximately a 6kw or larger PV system according to PVwatts. A couple extra panels on another azimuth is way cheaper/simpler than any kind of tracking system and adds just as much average output.

FWIW, even with all day cloud cover, I have seen system output reports that the minimum harvest you actually get is at least 20% of full sun harvest since the panels are cooler and you always get some irradiation.
__________________
"I‘d put my money on the sun and solar energy. What a source of power! I hope we don‘t have to
wait until oil and coal run out before we tackle that." Thomas Edison, 1847 — 1931

Last edited by Mobile Master Tech; 03-01-16 at 01:50 PM.. Reason: Typo
Mobile Master Tech is offline   Reply With Quote