Nathan,
In the NREL report Photovoltaic Degradation Rates — An Analytical Review
by Dirk C. Jordan and Sarah R. Kurtz
<https://www.nrel.gov/docs/fy12osti/51664.pdf> the conclusion is that
the 0.5% or so annual degradation of PV module output is mostly due to
changes in PV module current. Other studies have come to the same
conclusion. So, long term changes in voltage might not be worth worrying
about.
Kent Osterberg
Blue Mountain Solar
On 4/10/2025 4:31 PM, Nathan J. Stumpff via RE-wrenches wrote:
Hi wrenches,
I used to do these kind of calcs all the time but am wicked rusty.
What assumptions do you use for future (degraded) hot temp Vmp of a PV
string to check if you will still be able to operate inside a given
MPPT range? Specifically interested in assumed yearly degradation to
Vmp, assumed actual operating cell temp, and if it is appropriate to
use STC value as the starting point and if not what would be better
(NOCT?)
Thanks,
-Nathan
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