<html> <head> <style> .hmmessage P { margin:0px; padding:0px } body.hmmessage { FONT-SIZE: 10pt; FONT-FAMILY:Tahoma } </style> </head> <body class='hmmessage'> Thanks very much, Nick.  I finally got it working. I have a follow-up question; this goes to anyone.  I've been analyzing the results and there's a bit of an inconsistency on a monthly basis.  In the summer months, the average efficiency (electrical output divided by incident radiation) that I calculated is several percentage points higher than the panels specs.  But in the winter months, it's very low (around 2%, vs. the 7% expected).  Looking closely, this seems to be caused by some arbitrary threshold of solar radiation (around 260 W/m^2), below which the PV produces no electricity.  So my horizontal PV panel produces little electricity even on a sunny winter day (lat=44N).   Any idea what might be causing this?  I'm using the Amorphous Watsun model.  Interestingly, the annual performance matches what I would expect; just not the monthly breakdown.   This could be a coincidence.  The same building model but with the simple PV model behaves exactly as expected. Thanks. Liam > Date: Wed, 27 Aug 2008 09:09:12 +0100 > From: nick@esru.strath.ac.uk > To: obrien_liam@hotmail.com; esp-r@lists.strath.ac.uk > Subject: [esp-r] Re: PV modeling > > Liam, > > To get round this problem you will need to have a fixed voltage node somewhere in your electrical network - without this the network cannot be solved. The simplest network I use for this type of problem is two node: > > 1. fixed voltage node (i.e. the grid) > > 2. pv node > > Connect both nodes together with a very low resitance cable and couple the PV panel or panels to the pv node - this should work OK. > > Regards, > > Nick Kelly on behalf of ESRU > > ________________________________ > > From: esp-r-bounces@lists.strath.ac.uk on behalf of Liam O'Brien > Sent: Wed 27/08/2008 04:48 > To: esp-r@lists.strath.ac.uk > Subject: [esp-r] PV modeling > > > Hello all, > > I'm interested in modeling a PV panel only without the effects of network losses, an inverter, etc. Ideally I would have liked to merely have a single node "network" that the PV panel is connected to. However, ESP-r is not allowing me to do so, stating that "Error: Node 1 PV_node is not connected to the network." > > Is there any way around this? While I could model a more detailed network, the configurations I have tried consistently give me errors. (Even if the "check network for errors" passed, bps quits without warning when I try to initiate a simulation. > > Are there any good sources of information for modeling electrical networks? > > Any advice would be greatly appreciated. Thanks. > > Liam > > > ________________________________ > > > _______________________________________________ > esp-r mailing list > esp-r@lists.strath.ac.uk > http://lists.strath.ac.uk/mailman/listinfo/esp-r <hr /> <a href='' target='_new'></a></body> </html>