Connection of modules with different azimuths or inclinations.

[Georgy PM]

Dear PVSYST team. First of all, my thanks for the latest software updates, the improvements are very welcome. Now based in South Korea, I have very particular cases of systems with modules in series having different orientations and/or inclinations.  I insisted a lot to my colleagues that this would result in very high mismatch losses, due to the difference in current produced by each module. However, I was asked a very good question (which I think is perfectly valid): how far apart in orientation can you connect modules in series without incurring significant losses (less than 1%, for example)? Would it be 1 degree apart? or 2? 

Is PVSYST able to simulate a string of modules with 2 different orientations? I've been trying to do it for a while, unfortunately without success, so I'd be very grateful for your help. Thank you very much in advance. Bon début d'aneee ! 

[Muhammed Sarikaya]

Dear Georgy,

 

I can't answer you because it depends on multiple variables.

 

In PVsyst, you can't set different orientations within a series of modules.

 

I suggest increasing the detailed losses for mismatch in your simulation. The idea is to simulate the worst-case scenario. That way, when you install your PV modules, the actual electrical production will likely be higher than the simulation.

 

Regards,

 

Muhammed Sarikaya

[Georgy PM]

Dear Muhammed, 

Thank you for your previous response,

I tried to convince everyone of avoiding mixing orientations, but more interesting cases are appearing. For instance, some clients are requiring more “stylish” solar carports, things like this:

Hence, it is harder to match module’s orientations and strings (like if solar installer’s life wasn’t already hard enough 🙄). Since in cases like this one we have to absolutely mix two different orientations, the big question that arises now is : how much appart the orientaiton can be ? Lacking availibility to think about complex formulas of irradiation and photo current, I tried to get the mismatching losses directly from PVSYST results. First, I made a simple simulation with 4 panels with 15degrees of inclination, then other 2 four modules systems with 5 and 10 degrees (same azimuths). Then, I exported the hourly results and “mixed” the Array’s outputs (for a maximum of 8 modules, only 2 orientations at time), follwing two simple rules: voltage of each group of 4 modules are added, and the current of the string is the smallest produced by any of the 2 groups of 4 modules. For instance, the results of the Array current for each group and the mixed results are shown below (Iarray5g and the mixed are the same):

Finally, in order to estimate the loss produced by the mismatching, I did: 

I mean, the loss would be the ratio between the he total energy that one would get by having each group connected to independents MPPT divided by the mixed E_Array. Since the almost linearity of the inverter’s output, the E_Grid should have a similar reduction. By mixing 5 and 10° orientations I got -1,98%, 10 and 15° -1,64% and 5-15° -3,54%. They seem big to me as expected, so I will try smaller orientation variations in order to get less than -1 or -0,5% of losses. Economically this would be acceptable since it is much more expensive not doing the installation 😊.

Before continuing, I wanted to have your opinion about this approach. Do you think that we can reproduce this procedure for calculating the mismatch losses for much more complex systems? For instance, having 1 module with one orientation and 7 with another, or varying the Azimuths (which will start to shift the output’s curves). Below I send you two links where you can download the project and the excel file.

Many thanks in advance for your feedback.

원주공항 Project v2.zip

원주공항 Project_VC5 Az0, 15 vs 10 g, 4PV.xlsx

Best regards

[Michele Oliosi]

Dear Gregory,

This seems like a very good approach, I see no inconvenient in applying it to other subdivisions. Of course, keep in mind that this is an approximation, but that will give you a good estimate of orientation mismatch within a string.