What is the equivalent of a "mtHIT" cell type?

[Miguel Sánchez de León Peque]

Hi,

Reading some .PAN files, I can see the "Technol" field may be set to "mtSiMono" or "mtSiPoly". When estimating the CEC parameters of the module, the translation to pvlib's `celltype` for these values, seems trivial: "monoSi" and "polySi", respectively.

However, I see some "mtHIT" too. From the datasheet, I suspect it may be misspelled, and it should be "mtHJT" instead, from HeteroJunction Technology.

Is there an equivalent of "mtHJT" to use as `celltype` in pvlib/SAM? Otherwise, what would be the best match? I am not sure about the implication of choosing one or another when passing that parameter to the simulation.

Thanks a lot and best regards,

Miguel

[Anton Driesse]

There really are HIT modules from Sanyo/Panasonic.

Anton

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[Miguel Sánchez de León Peque]

Thanks Randy for your note and Anton for your comment.

Just in case I did not ask my question clearly (sometimes I do that :-D), I wonder which `celltype` I should be using when calling `pvlib.ivtools.sdm.fit_cec_sam()` to fit parameters for a HIT/HJT module. If there is currently no `celltype` for this technology, which one could I use as a replacement to have the best approximation?

It seems the currently-supported values are: 'monoSi', 'multiSi', 'polySi', 'cis', 'cigs', 'cdte' and 'amorphous'.

Thanks again for your help and best regards,

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[cwh...@sandia.gov]

TL:DR  Within pvlib, I'd suggest using celltype = monosi when working with a HIT module.

HJT = heterojunction technology

HIT = Heterojuction with Intrinsic Thin Layer, this is Sanyo's name

I've no idea which term was earlier in use. The cells are monocrystalline silicon sandwiched between thin amorphous silicon layers. The a-Si layers reduce recombination losses, which increases both Voc and conversion efficiency. That's as much as I understand of the underlying physics. 

pvlib.ivtools.sdm.fit_cec_sam() passes the celltype string through to a SAM function that calculates the CEC model parameters. I don't know exactly what the SAM function does with that value, probably assigns a bandgap energy value and perhaps initial guesses for parameters. In SAM's CEC module file, Sanya HIT modules are assigned celltype 'Mono-c-Si', see any of the "HIP" series modules.

The only other use of 'cell_type' in pvlib is to select parameters for the First Solar spectral modifier model. As an aid to that model, there's a function pvlib.pvsystem._infer_cell_type which can map from the CEC or Sandia module data files (fields Technology or Material, respectively) to a cell_type string expected by the First solar model. In that mapping pvlib assigns HIT == monosi. I don't recall exactly why we made this choice, but it still seems reasonable, since most of the conversion to photocurrent will be done in the mono-Si layer of an HIT cell.

If your objective is to match (as close as pvlib can) Pvsyst behavior, I don't think that Pvsyst applies a spectral modifier to HIT cells - see the Help page titled FirstSolar Spectral Correction.

Cheers,

Cliff

 

[Mark Campanelli]

Along these lines, does anyone know what PVsyst uses for the band gap of the mtHIT Technol?

Furthermore, does PVsyst let one specify a custom value for the band gap?

Thanks,

Mark

[Anton Driesse]

From my imperfect memory: I think there's a list of technologies in the help file or forum, and I think you can change the band gap for each cell type in the hidden parameters, but thereby you change the results of all future simulations of all systems using that cell type so that's probably not a good idea.

Anton

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