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transfer surplus electricity in the house to power grid

asked 2023-11-26 20:53:36 -0500

sheida's avatar

updated 2023-11-28 13:26:24 -0500

how can I get output for the amount of electricity transferred by the power generator from the grid?

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answered 2023-11-28 14:35:20 -0500

updated 2023-11-29 06:29:20 -0500

If you have, for instance, excess PV generation (with or without storage), this would show up in the eplustbl.htm file under "Electric Loads Satisfied", as illustrated here. Compare "Electricity Coming From Utility" vs "Surplus Electricity Going To Utility". The latter seems to be what you're after (based on the title of your question).

If the "Electricity Coming From Utility" is 0 (or nearly), then the PV kit (array/inverter/distribution/storage) is sufficient to render the building model "off-grid". If the PV kit is instead insufficient, EnergyPlus will draw from the utility to meet demands, as explained here and here (search for "All demand not met by available generator capacity (or storage) will be met by purchased electrical").

You may find this paper of some interest.

EDIT: Add the following to an .idf file to get monthly tallies of "Electricity Coming From Utility" vs "Surplus Electricity Going To Utility"

  *,                                           !- Key Value
  Facility Total Purchased Electricity Energy, !- Variable Name
  Monthly;                                     !- Reporting Frequency

  *,                                           !- Key Value
  Facility Total Surplus Electricity Energy,   !- Variable Name
  Monthly;                                     !- Reporting Frequency

Look up the last 12 occurrences of each output variable in the generated .eso file.

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thanks for your complete explanation, if I want to get output for a month to show `how much electricity transfer from PV to the grid" and vise versa, which variables show these amounts for me better?

sheida's avatar sheida  ( 2023-11-28 23:55:27 -0500 )edit

@sheida, I edited my initial answer (to get monthly tallies).

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-11-29 06:32:55 -0500 )edit

Thanks for your help, I got it :) what about transfer electricity from PV panels to the grid? the variable for surplus energy shows that, am I right?

sheida's avatar sheida  ( 2023-11-29 20:03:17 -0500 )edit

@sheida, both (annual) "Surplus Electricity Going To Utility" and (here, monthly) "Facility Total Surplus Electricity Energy" show excess PV generation exported to the grid. This is documented in the E+ Input/Output Reference Manual, here and here (CTRL-F "Electric Loads Satisfied").

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-11-30 06:03:16 -0500 )edit

what about transformer? does it shows the electricity transfer from building to the grid and vise versa?or it is just to balance the voltage? could you please take a look on the result I got.

sheida's avatar sheida  ( 2023-11-30 15:38:37 -0500 )edit

answered 2023-11-30 15:54:21 -0500

sheida's avatar

updated 2023-11-30 15:54:46 -0500

Based on what you said I got these results, but my big question is that, why although we have surplus energy made by PV we have have electricity coming from utility yet?!image description(/upfiles/17013812497317174.png)image description

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From your June results, one can clearly see evenings/nights/mornings when there's electricity consumption in the home (when the PV array isn't generating); if storage is inadequate (size, charge/discharge characteristics), E+ will necessarily draw from the utility (possibly a virtual utility if the house is meant to be off-grid). You can track storage outputs. Either reconsider storage parameters, or constrain loads when it's dark.

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-12-01 07:16:56 -0500 )edit

A side note: It would be preferable to EDIT your initial question (similar to how I edited my initial answer), than to ask a follow-up question as an answer. Something to consider in the future.

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-12-01 07:22:14 -0500 )edit

I uploaded the results I got from charge/discharge of battery, I don't know why the results I got from figures are different from the "Electric Loads Satisfied" table. I will be appreciated if you say what is the problem.

sheida's avatar sheida  ( 2023-12-01 15:59:59 -0500 )edit

@sheida, does the sum of monthly "Facility Total Surplus Electricity Energy" not match the annual "Surplus Electricity Going To Utility"? Make sure it does before moving on. Repeat the exercise (on an hourly basis), for a month where the home is actually drawing electricity from the grid (NOT June, maybe e.g. December?). For the hours when the house is drawing from the utility, compare demand vs PV VAC generation vs storage discharge vs utility - they should add up.

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-12-02 06:58:34 -0500 )edit

yes you are right, I fixed my problem. I have another question regarding which variables in E+ can be used to show "monthly heating and cooling demands"?

sheida's avatar sheida  ( 2023-12-15 14:23:46 -0500 )edit

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Asked: 2023-11-26 20:53:36 -0500

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Last updated: Nov 30 '23