solar storage tank

hot_rod

That's what you need to decide. 100% probably isn't do-able unless the budget is unlimited. he amount of panels and insulated storage get $$ fast. Depending on where you live 30- 40% of the load may be about right.

Are you sure about that panel output? Remember the data on the SRCC certification is per panel per day, not per hour.

hr

Mike Dunn

how to size for space heat

residential project, solar space heat, 36,500 btu/h heat loss, Question is how many panels at 18K btu per panel per hour would you use and how big of a storage tank?

Mike Dunn

output

I am shooting for 50% of the combined space heating and domestic water heating load.
As far as the SRCC #'s I calculated them like this. For my panel on a partly cloudy day it said I should get 18K btu/day/sq ft. The panel has 25 sq ft of aperature area so 18K * 25 = 450,000 btu per day / 24 hours = 18750 btu/h. If my math is wrong HR please let me know what to do as this is my first system sizing. Thanks PS how do I create paragraphs?

hot_rod

At the SRCC site

under ratings find your city or a close example. For instance Boston shows 1023 BTU per square foot per DAY. Times 25 square feet of panel would be 25,575 btu per day.

Rough numbers for a 4X8 flat panel would be 25- 32,000 BTU per day, from Solar Skies data..

To fine tune it you need the radiation info for you location, tilt, position to solar south, the return temperature to the panel, and the ambient air temperature around the panel (Ti-Ta) That's where those A-E numbers come into play on the rating sheets.

So a panel with a 110F return temperature up to it with a 20F ambient air temperature would be 110-20= 90 or column D on the SRCC rating sheet. On a typical 4x8 clear day column D notice 19,000 BTU per day.

I explain it as "where they are, and what you are asking them to do". The cooler the return to them and the warmer the air around them the higher the performance.

Keep in mind the winter sky is not as friendly, output wise. that 1023 number above for Boston is a yearly average. Go to the NASA website find the "solar energy available tables" to see how much that changes from month to month. July at my location has an isolation of 6.01, December 1.11 as a kWh/ m2/day.

When looking at solar for heating loads you get the most when you need it the least (July) :0 And vice versa.

The evac tube guys like to claim superior insulation, the vacumn makes them much superior for heating. The bottom line is there just isn't a lot of energy to be had in a cold winter N.A. sky, (thanks Dale for that line regardless of the glazing insulation difference. Careful calcs show a maybe 10% difference to the evac tubes. If they are snow free, when the sun is out.

hr