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

Tue Jun 15 10:08:09 PDT 2004

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When using TOU metering and a ground mount, we always try for SSW @ 35
degrees. We find that this makes a big difference in net energy savings for
our Ag. Customers when we can convince them to do irrigation at night or
early morning.

On another note, we just got an article from a German energy on-line
magazine describing China's implementation of the German model for solar and
wind energy policy. WOW! My first reaction was to imagine that every solar
chip in creation would go to China (those that haven't gone to Germany,
Spain and Italy, that is); but after calming down a bit I believe that this
might actually spur the Chinese to produce highly efficient modules of their
own, which in turn may eventually find their way to this market and possibly
bring the cost of solar down a bit. Hope springs eternal.

Matt T

-----Original Message-----
From: Antony Tersol [mailto:tony at appliedsolarenergy.com] 
Sent: Tuesday, June 15, 2004 8:09 AM
To: RE-wrenches at topica.com
Subject: RE: South or West for TOU (quantified) [RE-wrenches]

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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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