We at Wattminder are making an effort to address the problem of
prevalent, unknown,
or undetected under-performance of many solar generation systems.
It is largely unknown because most solar systems do not come with
monitoring
system/service. With this free service, we hope to make a difference
in the
fight against global warming.
Any solar system owner and operators can now obtain mathematical model
derived performance bench marks on line, and stop wondering about how
their system is performing.
A visitor to the website, www.wattminder.com, or www.pvperformance.com,
simply enters a brief set of values for 'vital statistics' of a solar
system. The free performance predictor will output a look-up table for
a number of environmental conditions, that this visitor's PV system
should be producing at that instance-given the Sun's position and the
solar array's location and attitude. The values provided serves as a
checkpoint for a PV system owner who does not have a monitoring
system, or if monitoring system does not indicate how well his/her
system is performing. He/She may then manually check on his system's
power meter reading, or from display on the inverter readout. If the
numbers match, or co-relate well with each other, under somewhat
different operating conditions, it would indicate his PV system is
performing reasonably well. "We hope, by providing this free bench
mark service, under-performing systems can be identified, and brought
to the attention of its install contractor, who would then correct any
performance issue, thus restoring an under-performing system to its
full capacity.
Thanks for visiting and critiqueing. MORE POWER TO YOU!
Thanks for putting this together!
It's a bright, sunny fall day here in San Jose, CA, not far from you.
There seems to be a 10 mph breeze. Temperature outside cannot be much
lower than 20 degrees C. I couldn't measure the cell temperature
easily, so took the default value of 30 C. I also have no way to
measure irradiance, so took your default value of 945 W / m^2.
The answer from your tool came up with 1653 watts as an estimate (I'm
assuming, adjusted for this time of day and season). I ran outside,
and the inverter read 1950 watts, which is in line with what the
utility meter says, accounting for the base load of our house, 200
watts. In spite of this, I think your tool is spot-on. The rebate
form for your system specified a certain energy output for the year,
and for some reason, our energy harvest for the year exceeded
prediction by exactly the proportion of 1950 / 1650 (to one decimal
place). Maybe we just got really good panels by accident. I'm pretty
sure the cell temperature is not anywhere near 0 C, which would be the
other way to get this kind of power today.
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