South or West for TOU (quantified) [RE-wrenches]

Antony Tersol tony at appliedsolarenergy.com
Tue Jun 15 08:09:06 PDT 2004


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Short answer: South at 35 deg tilt is better than West at it's best tilt of 15 
for San Francisco weather.  Even at 15 deg tilt, South is better.  But 
south-southwest is best.

Long answer: For San Francisco, using real weather data, running a simulation 
that calculates performance over a 365 day year, every hour, for each azimuth, 
tilt combination (for each azimuth below, the simulation was done for 19 
different tilts (every 5 degrees) x 365 days x 24 hours).

btw, this is weather dependent.  For example, for Fresno, straight south is 
optimum for total production, as opposed to SF, which favors SSW.

  Site Latitude	(lat)	36.6   degrees

The following chart shows percentage of optimum at each azim/tilt combo.
For example, for west, a tilt of 15 degrees, produces 87.1% of optimum.
For south, a tilt of 35 degrees, produces 99.3% of optimum.
The optimum is at azimuth of 15 or 20 degrees west of south, at 35 deg tilt.

Sorry if the formatting is hard to read.  Anyone wishing a nicer format email 
me, and I'll send you a .pdf file.


I ran simulation with TOU value for each of the optimums, based on an array of 
18 sharp 165, sb2500 inverter.


azim \ tilt	0	5	10	15	20	25	30	35	40	45	50	55	60	65	70	75	80	85	90

ARRAY PERFORMANCE (%)

West
	-90deg	85.6	86.5	87.0	87.1	86.9	86.2	85.2	83.9	82.3	80.5	78.5	76.3	74.1 
71.7	69.3	66.7	63.8	61.0	58.2

Optimum tilt

Total annual  energy / TOU value at 15 tilt (18 sharp 165, sb2500)
4040kwh $773.08	

Southwest
	-20deg	85.6	89.3	92.5	95.1	97.1	98.6	99.6	100.0	99.7	98.9	97.5	95.4	93.0 
90.0	86.6	82.7	78.4	73.6	68.7
	-15deg	85.6	89.3	92.5	95.2	97.2	98.7	99.6	100.0	99.8	99.0	97.6	95.6	93.1 
90.0	86.5	82.5	78.0	73.2	68.1
Total annual  energy / TOU value at 35 tilt (18 sharp 165, 
sb2500)  		4618 kwh $856.49	

South
	0deg	85.6	89.2	92.3	94.9	96.8	98.3	99.1	99.3	98.9	97.9	96.3	94.2	91.6	88.5 
84.9	80.8	76.3	71.4	66.1
Total annual energy / TOU value	at 35 tilt (18 sharp 165, sb2500)
4588 kwh $837.23

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