openLCA archived user forum

Hello again;

When I attempt to quick analyze for LCA results, I receive the error message:
"Linear equation cannot be solved because the matrix is singular."

I assume I forgot to include something that the program needs. I can't think of what. Any advice?

Hi Linza,
this is not a software but a modelling issue - it is caused by a singular technology matrix, which in turn can be caused by a process that has a quantitative reference of 0 but is input in another process, or also by an internal loop (production of 1 kg product in process a as input to another process b that delivers 1 kg to process a). You can create the same error e.g. in SimaPro.
If you want, you can send us the model and we'll check.
Best wishes,
Andreas

I'll figure it out! Thanks. :)

EDIT: Great success! Sorry. I guess I had been staring at the computer screen too long. It seems really obvious now. -_-' Thanks very much. :)

Keep getting Null Pointer Exceptions. Previous discussions on the topic indicate the inclusion of a deleted or failed upload process or flow. Looked through everything-- everything seems to be here. :-/

Ok, it isn't me. or, just me. I built the product system without connecting anything to it, then afterwards selected each box and built the supply chain. No problems if I do it that way, but if I try to connect everything when I first build the product system, it returns a null pointer exception.

"My name is Java and I'm pointing at nothing like a boob." :P

Do you have an intermediate flow that is used by multiple processes? Maybe that could be messing up a connection somewhere in the model, which is why it works fine when you connect everything manually. Or it could be trying to pull a process that outputs that flow but is messed up somehow.

Well, shoot. Lots of flows are used by multiple processes. This is going to take forever to track down.

I'm not an expert in using the software so it is just a guess.

Out of curiosity, how do you know that the software is building the product system graph correctly if you use the same product flow as an output of multiple processes?

By expanding the boxes and looking. :) I have modeled a couple of different versions of a solar product (using different types of PV, for example, but outputting the same product flow to be used as input for the packaging phase, transit phase, et cetera). If you go to the processes that use that and select the appropriate source process from the 'default provider' drop-down list, and save, then the auto-build will use whatever is the default provider. Then you can go back and change it when building the same product system but with a different type of PV.

This saved me from having to build 5 copies of the same transit, use, and EoL phases.

Thanks, that's helpful. Somehow I've never noticed the Default Provider column in a process before. Did you ever figure out the null pointer issue?