[RE-wrenches] PV testing

[Chris Mason]

We use a Seaward Solar PV150 for module testing. It quickly tests a range
of data points and, when used with the irradiance meter, give a pretty good
indication that a module is performing well.
http://www.seawardsolar.com/products/pv150-solar-installation-test-kit



On Mon, Oct 5, 2015 at 10:46 AM, Starlight Solar Power Systems <
larry at starlightsolar.com> wrote:

> Bill,
>
> In the shop I have two electronic loads that I use nearly every day with
> batteries and PV modules. One is a programmable 150W, 360V that can be set
> for constant power, current or voltage (like this:
> http://www.amazon.com/Programmable-Electronic-Load-360VDC-CSI3710A/dp/B00D7QGSV4).
> It’s small enough to take to the field. The other is a 2kW model that I use
> for battery load and discharge testing. It’s too big to move.
>
> I also use the Daystar DS-05A (seen here:
> http://www.amazon.com/Daystar-DS-05A-Solar-Digital-Meter/dp/B00YVTXZJ4/ref=sr_1_fkmr0_1?s=electronics&ie=UTF8&qid=1444055204&sr=8-1-fkmr0&keywords=Daystar+PV+irradiancePV)
> irradiance meter to calculate power by holding it in the same plane as the
> module to determine actual irradiance striking the surface.
>
> Another tool I use is a simple instant read, non contact infrared
> thermometer to check the cell temperature under test.
>
> With these tools and a little information, I can measure instant power and
> calculate module degradation. Others have suggested higher cost tools but
> these low cost tools have been reliable for many years.
>
> Larry
>
> On Oct 4, 2015, at 7:56 PM, frenergy <frenergy at psln.com> wrote:
>
> Wrenches,
>
>       As time passeth, we're bumping more into older PVs/arrays that have
> questionable outputs.  After minimizing the variables (dust, temps, sun
> angle, wiring, expected deterioration with age, etc) and still coming up
> with low numbers.  Testing individual PVs' Voc and Isc don't seem to tell
> the whole story as they often look good.
>
>       Would not a definitive test be to wire a suspect PV to an
> inexpensive mppt CC (oxymoron?) and then to an orphaned battery.  The
> battery would have to have a mondo (surplus) rheostat paralleled to it to
> maintain a steady voltage during the test.  With appropriate metering in
> place, you would then have Vmmp and Immp as the rheostat is tweaked to hold
> a steady batt voltage and the CC finds the knee.
>
>       Help me here.  I know its a little spendy to cobble up but the value
> of nailing an offender might be worth it.  Am I missing something?  Is it
> common for inverters to fall off in output gradually?
>
> Bill
> Feather River Solar Electric
>
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-- 
Chris Mason
NABCEP Certified Solar PV Installer™
Solar Design Engineer
Generac Generators Industrial technician

www.cometsolar.com <http://www.cometenergysystems.com>
264.235.5670
869.662.5670
Skype: netconcepts
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