Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

BEopt PV generation difference between site and source outputs

asked 2020-04-08 00:42:49 -0500

updated 2020-04-08 06:58:55 -0500

The simulation outputs for PV electricity generation are different between source and site energy use. I see that the same conversion factor for electricity (i.e., 3.150) is applied to PV generation. Are we assuming that the PV output is fed to the grid and then fed back to the building? Even in that case, I think only the portion related to the transmission loss should be applied as opposed to the whole 3.150, which includes other factors such as inefficiencies in burning the fossil fuels.

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted

answered 2020-04-08 08:57:54 -0500

The on-site PV generation offsets imported electricity, thus the same factor is used. This follows the guidelines of ASHRAE Standard 105-2013, Table J2-A.

edit flag offensive delete link more


Thanks, Eric! That makes sense. So, that black line in BEopt's outputs for source energy use shows an equivalent/virtual energy. I would suggest changing it to a dashed line to show this is an equivalent source energy that can be offset by PV generation as opposed to an actual energy generation. Btw, I don't have access to ASHRAE 105 and cannot review Table J2-A. I couldn't find a preview of this standard on the web, either. Any thoughts where I can find this table?

Ehsank's avatar Ehsank  ( 2020-04-10 23:06:19 -0500 )edit

I think Standard 105 is available for purchase from ASHRAE.

Eric Wilson's avatar Eric Wilson  ( 2020-04-13 08:55:17 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Question Tools



Asked: 2020-04-08 00:42:49 -0500

Seen: 136 times

Last updated: Apr 08 '20