BTU's of flat plate solar water collectors [RE-wrenches]
Dean T. Newberry
deant at dcn.org
Fri Dec 31 10:08:53 PST 2004
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Hi Todd,
The whole story on solar incident radiation is at
http://solardat.uoregon.edu/SolarRadiationBasics.html#Ref3
The short answer is the incident radiation in the atmosphere on a sunny
day on plane perpendicular to the sun beam is 1000 watts per square meter.
1 square meter = 10.76391 square feet.
That calcs to 92.9 Watts per square foot.
1kWh = 3413 Btu. So 92.9 W/M^2 / 1000 x 3413 Btu = 317.0781 Btu per
square foot per hour.
The SRCC rates collectors bases on efficiency.
The Apricus is about 66% efficient at delta T 22C and 700 watts per
square meter.
So at those conditions the Btu delivered to the heat transfer fluid is,
.7 (insolation) x .66 (collector efficiency) x 317 (Btu / sf / hr) =
146.5 Btu / SqFt / Hour.
The SunEarth Imperial with black chrome is about 57% efficient at delta
T 22C and 700 watts per square meter. So at those conditions the Btu
delivered to the heat transfer fluid is,
.7 (insolation) x .57 (collector efficiency) x 317 (Btu / sf / hr) =
126.5 Btu / SqFt / Hour.
Your collector is probably black paint. Using the SunEarth Imperial
example with black paint at 54% efficient at delta T 22C and 700 watts
per square meter. So at those conditions the Btu delivered to the heat
transfer fluid is,
.7 (insolation) x .54 (collector efficiency) x 317 (Btu / sf / hr) =
119.8 Btu / SqFt / Hour.
Your collector is 40 square feet, so the total delivered btu/hour is 40
x 119.8 = 4794 Btu/Hour normal or perpendicular to the sun.
Plug that 4794 into the System BTU input cell on the spreadsheet at
http://www.dcn.davis.ca.us/go/deant/ThermalCalc.xlt and you will get the
net heat delivered in specific hour on a day in each month for your
collectors. The spreadsheet opens with Redding sunniness and lattitude
data, 5 in 12 slope facing south with the Angle of Incidence Modifier
for Apricus turned on. Press the [Set Flat] button to get the
performance of your flat collector.
Does that help??
cul deant
*
*Tom DeBates wrote:
>Todd,
> Two groups rating collectors are
>SRCC(www.solar-rating.org) and FSEC
>(www.fsec.ucf.edu).
>
>Good Luck,
>
>Tom DeBates
>Habi-Tek
>Geneva,IL.
>
>
--
Dean T. Newberry
Marketing and Sales
Quantum Energy Group
265 Applegate School Road, P.O. Box 158
Applegate, Ca. 95703
Email: deant at dcn.org
Cell: 530 867-2392
Office: 530-878-4585
Fax: 530-878-6685
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