Solar Pathfinder Results

MacPHJr

I have been messing around with the Solar Pathfinder at my fathers house for when we eventually do his system. However my solar fraction is very low. I know the house has a great southern exposure with minimal shading. In order to gain a solar fraction over 80 I would need to install 5 Vitsol 30 tube panels to heat 79 gallons of water. It doesnt seem right and I must have  done something wrong. Anyone else experience this.

hot_rod

where are you located?

and what is the load you are trying to cover?



Solar Energy Available info like this pic below will tell you what is available in your area. Go to the NASA website and plug in your location.



Also try one of the solar simulation software programs. www,retscreen, F-chart, T-sol. They all have a free demo version.



Here is a sample of the quick calculator at T-sol www.valentin.com



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MacPHJr

Retscreen Results

I used Retscreen last night and got a Solar Fraction of 59%, just about double the fraction I recieved from the Solar Pathfinder Survey. Still seems a bit low to me. The only wat to get a better solar fraction would be to add a panel and the manufacturer told me that would over kill for a typical domestic hot water system.

Kind of frustrating and i'm having my doubts about solar in general.

hot_rod

adding collectors

will take that SF up, no doubt. But it may push you into a situation where you need to shed or dump heat in the summer months. Then you end up spending power to get rid of "free" solar, so it just depends on your area, load, and expectations. What do the 3 or 4 summer months look like currently and with an extra collector? 100% SF? How often?



Generally when we run RET on our systems the SF goes from mid to high 50's to 70 or so SF, by adding an additional collector. But run the calc for your exact application. That's the beauty of the simulation programs.



Also look at the difference in economics when you change the system SF.



If you do boost up the collector sq. footage to storage ratio, I'd consider a drainback type of system so you don't run the risk of glycol breakdown and dumping to prevent excessive stagnation in a closed loop glycol system.



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