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In the solar energy industry we often want to estimate the expected energy output of a PV system. This calculation requires 2 sets of inputs. First are various physical and electrical characteristics of the PV system in question, such as solar module pitch, orientation and nominal power. The second is solar irradiance data at the PV system's location. Based on these inputs a model can calculate an expected energy output.

The lifecycle of a PV system can be divided into pre-installation and post-installation. Pre-installation the system only exists as a design on the drawing board. During this phase, we want to predict the energy output of the proposed PV system. At this point, the inputs are approximate; the PV system characteristics are planned, not physically real yet (e.g. circumstances may require the installer to place the modules at a different angle than planned), and solar irradiance data are historical averages (e.g. in the last 10 years, the average radiation incident in June was 200 W/m²). We're assuming that the historical average is a good basis for prediction. The outcome of this calculation we call predicted energy output.

Now let's say the PV system has been installed 1 month ago. We could re-do the expected energy output calculation, but now with actual inputs; we know exactly how the modules are installed and we know exactly how much solar irradiance the location received since the installation. The outcome of this calculation represents how much this PV system should have generated in normal operating conditions, given the solar irradiance actually received there. If this outcome is significantly higher than the actual kWh energy output, which is measured independently, that would indicate a technical failure of some kind (e.g. a faulty inverter).

So fundamentally there's very little difference between the two uses of the same model (pre- and post-installation), it's just that the inputs for the second describe reality better. I'm looking for adjectives to distinguish the two. I like the term predicted energy output for the pre-installation calculation, but what adjective could be used to describe the energy output from the post-installation calculation?

Expected is too ambiguous. Inferred suggests a tentative conclusion reasoned from evidence, but sounds like a bit of a stretch here. Simulated sounds better but could just as well be used to describe the pre-installation calculation. Normal, perhaps? What are your suggestions?

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    Why not say the "expected output as-built" vs. "... as-designed"
    – John Feltz
    Oct 20, 2016 at 17:12
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    You might be stuck with the mouthfuls pre-installation predicted energy output etc. Or initial predicted energy output and adjusted predicted energy output.
    – Edwin Ashworth
    Oct 20, 2016 at 17:31
  • The pre-installation energy output predictions are, in fact, simulated. For the post-installation calculations you describe, the calculations produce predicted and actual outputs.
    – JEL
    Oct 20, 2016 at 18:04
  • Initial prediction and model-adjusted prediction.
    – DyingIsFun
    Oct 21, 2016 at 2:43
  • Re the adjusted suggestions, I'd rather use a post-installation term that is meaningful without needing juxtaposition with the pre-installation term
    – Mark
    Oct 21, 2016 at 7:04

2 Answers 2

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The second go-round is called model validation analysis.

http://energy.sandia.gov/wp-content/gallery/uploads/Standardized-Approach.pdf

In general, validation is the adjective you use when you substitute real data inputs into the model and compare the results to actual recorded or real-time results.

I suppose the correct adjective is validitory, but I have never seen it in the wild.

If you want some less technical terms for customers regarding this -

So fundamentally there's very little difference between the two uses of the same model (pre- and post-installation), it's just that the inputs for the second describe reality better. I'm looking for adjectives to distinguish the two. I like the term predicted energy output for the pre-installation calculation, but what adjective could be used to describe the energy output from the post-installation calculation?

I would use "model performance based on proposed installation and regional solar radiation maps" for the first one, and "model performance based on as-build installation and measured solar radiation" for the second one. You'll want to go into some gory details about the the radiation measurements on site. It's a tricky thing do in practice unless you are in the desert or on an ice sheet.

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  • Perhaps appropriate when communicating to a fellow industry professional, but not for talking to a customer.
    – ohwilleke
    Oct 21, 2016 at 5:58
  • I thought about model validation too. One could argue about which model is being validated here (the energy calculation or the normal-operation-assumptions underlying it) but either would allow validitory to be feasible option, where it not for its obscurity and its modeling-perspective as opposed to business-perspective; I don't think people in our business would really use this word.
    – Mark
    Oct 21, 2016 at 6:32
  • @ohwilleke I added some suggestions regarding less technical language. But this isn't really a "what is the adjective for...." question. It's important to separate the physics from the installation variables.
    – Phil Sweet
    Oct 21, 2016 at 13:37
  • @Mark Yes, it is important to keep the physics, meteorology, site assessment and installation parameters separate.
    – Phil Sweet
    Oct 21, 2016 at 13:58
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I was looking for the opposite of predicted (specifically the opposite of the "pre" part):

retrodicted

to make estimates about the past using information from the present or other events from the past.

http://thefreedictionary.com/retrodict and https://en.wikipedia.org/wiki/Retrodiction

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