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PV panels not working properly

asked 2016-01-21 10:53:05 -0500

Jim Dirkes's avatar

updated 2016-01-21 11:22:48 -0500

I have two E+ models that are identical except for the PV generator capacity. I have defined the PV array as:

  • PhotovoltaicPerformance:Simple (90% surface fraction, 15% fixed efficiency)
  • Generator:Photovoltaic (decoupled, 1 series string, 1 module)
  • ElectricLoadCenter: Distribution (Baseload, 0W purchased electric demand limit)
  • ElectricLoadCenter:Inverter:Simple (on 24/7, .3 radiative, .9 efficiency)
  • ElectricLoadCenter:Generators (1w for one model, 50,000w for the other model)

The results are almost identical, which makes no sense to me.

I reported Photovoltaic:ElectricityProduced J for both Northern hemisphere models and see:

  • almost identical values in both models
  • hourly values are non-zero when the sun is gone (as they should be)
  • uniformly low values in both models (January is never greater than ~5,000w, July is never greater than ~8,000w)

I might be talked into believing the low values, but can't imagine or figure out why both models, which have vastly differing power output, show identical results. Help, please!

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Have you looked at the ElectricLoadCenter:Distribution output for Total Electric Energy Produced? The report for the Photovoltaic may be the DC potential of the panels.

aaron's avatar aaron  ( 2016-01-21 11:41:32 -0500 )edit

Is it possible to make a link to your model? It sounds like there may be an availability schedule limiting the PV generation time. Also, shouldn't there be zero PV electricity produced when the sun is gone? You say "hourly values are non-zero values when the sun is gone (as they should be)".

Aaron Boranian's avatar Aaron Boranian  ( 2016-01-21 11:45:45 -0500 )edit
  1. I tried Whole Building:Facility Total Produced Electric Power W - still identical results
    1. Sorry. values are zero when the sun is gone.
    2. Here is a link to both IDFs. Thanks for looking!
Jim Dirkes's avatar Jim Dirkes  ( 2016-01-21 12:55:14 -0500 )edit

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answered 2016-01-21 14:11:07 -0500

There's an important piece of info from the documentation for the "Generator Rated Electric Power Output" field of the ElectricLoadCenter:Generators object:

"This value is used only for supervisory control and generator dispatch; the actual power output for each time step is determined by the generator models."

In other words, your PV generator objects are calculating electricity generated ONLY based on collector surface area, incident radiation, and efficiency losses. The above input field will have some effects if you model storage technology, which the documentation goes on to explain. If you want to actually change the PV array's generation capabilities, either:

  • draw more collector surface area
  • increase PV generator surface fraction
  • decrease efficiency losses
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I think that will solve my problem. If I understand correctly: * I need PhotovoltaicPerformance panels of size and efficiency sufficient for my expected capacity * and the ElectricLoadCenter:Generator just manages the available power

Since I have an identical solar array surface in each model, It (now) makes sense that I have identical results. That begs the question of why the ElectricLoadCenter:Generator rated capacity field has no impact, but I'll look into it further.. As a side note, I had a lot more arrays in an earlier version and deleted them because I misunderstood this. Thank you!

Jim Dirkes's avatar Jim Dirkes  ( 2016-01-21 14:39:56 -0500 )edit

p.s., I was trying to keep things simpler by maintaining the panel geometry and adjusting only capacity. I suppose I can add a bunch of panels and then adjust efficiency to get the equivalent of different panel size....

Jim Dirkes's avatar Jim Dirkes  ( 2016-01-21 14:42:40 -0500 )edit

Yes, you understand correctly about reaching expected capacity by adjusting the PV object or collector surface directly. The simplest way to increase capacity is to increase the PV efficiency, as long as your collector surface area is large enough to provide what you desire. If not, you'll need to sketch more surface area.

Aaron Boranian's avatar Aaron Boranian  ( 2016-01-21 16:16:00 -0500 )edit

The ElectricLoadCenter:Generator object is used to dispatch all kinds of generators, not just PV. Since PV doesn't consume fuel it is assumed to always run when the sun is up and isn't really controlled like say a microturbine running on gas would be.

Archmage's avatar Archmage  ( 2016-01-22 10:21:06 -0500 )edit

"We have liftoff". The PV panels are producing electricity in a predictable fashion and life is good on that front. Thanks very much for all of the assistance. Now I can attend the ASHRAE conference with less distraction.

Jim Dirkes's avatar Jim Dirkes  ( 2016-01-22 10:52:47 -0500 )edit

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Asked: 2016-01-21 10:53:05 -0500

Seen: 1,075 times

Last updated: Jan 21 '16