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Update pvsamv1 and pvwattsv8 to linear DC degradation rather than compounding#654

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janinefreeman merged 9 commits into
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linearDegradation
Nov 12, 2021
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Update pvsamv1 and pvwattsv8 to linear DC degradation rather than compounding#654
janinefreeman merged 9 commits into
developfrom
linearDegradation

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@janinefreeman

@janinefreeman janinefreeman commented Nov 11, 2021

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Per NREL experts, updating the detailed pv model and the newest pvwatts version to apply DC degradation linearly instead of compounding. All SSC tests are passing locally. Pairs with NatLabRockies/SAM#756 PR to update defaults results and the upgrade script. Fixes #503 .

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Two questions on this prior to approving:

(1) Do we need any code protecting the output from values > 100 / analysis period? Previously the pow function would protect us from negative numbers, but we lose that with the linear formulation.

(2) Does this significantly (>0.1%) change the output in test_script_ow.lk? Based on the lack of change in the SSC tests we should be ok, but if one of us has time it might be worth running prior to merging.

@brtietz

brtietz commented Nov 12, 2021

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Question (2) makes me look like I can't read. Nevermind on that one, I've reviewed SAM 756 as well now.

@janinefreeman

janinefreeman commented Nov 12, 2021

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  1. Good catch! Looks like in the current release, entering a degradation value > 100% in the UI results in nonsensical degradation numbers that do appear to get used to produce negative energy from a system. I'll add some type of catch for that here next.

@janinefreeman

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@brtietz Updated the logic to address question 1, please review additions to lib_pv_io_manager when you get a chance. Thanks!

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The new code and warning flag work great, thanks!

@brtietz brtietz linked an issue Nov 12, 2021 that may be closed by this pull request
@janinefreeman janinefreeman merged commit a04df6b into develop Nov 12, 2021
@janinefreeman janinefreeman deleted the linearDegradation branch November 12, 2021 20:39
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DC Degradation > 100% Causes Nonsensical Outputs Compounding vs linear module degradation

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