Add Muneer transposition model

[BernatNicolau]

• Closes to Add Hofierka 2002 model #2117 (this comment)
• I am familiar with the contributing guidelines
• Tests added
• Updates entries in docs/sphinx/source/reference for API changes.
• Adds description and name entries in the appropriate "what's new" file in docs/sphinx/source/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
• New code is fully documented. Includes numpydoc compliant docstrings, examples, and comments where necessary.
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels (including remote-data) and Milestone are assigned to the Pull Request and linked Issue.

[AdamRJensen]

An initial review

[AdamRJensen]

These two sources follow different citation convention.

Also, could you add a DOI?

[BernatNicolau]

Resolved in 8b13595 . First time I do it, @AdamRJensen can you check if it is alright?

[RDaxini]

@BernatNicolau both look typed out correctly, but I don't think the second DOI value is correct (review comment)

[echedey-ls]

Looks really good! Some minor documentation comments down below.

Since this is a new feature, we have to do some additional changes to the code:

1. Docs. I suppose you have tried to find your function at the built readthedocs page, but had no luck. That happens because each function we want to publicity show in the API needs to be listed in some index pages. The appropriate list for this function is in docs/sphinx/source/reference/irradiance/transposition.rst
2. Tests. We want to ensure this function works as expected in the future, so tests is a must-have. Look for test_irradiance.py and try to add a test. You can just mimic current code or read more about pytest. If you need some help with that let us know. By the way, the best way I have found to make test data is by using a spreadsheet, so you can double check you implementation.

At some point a whatsnew entry will need to be made. Best is to defer that for a bit so we can have more reviews till then.

[echedey-ls]

Suggested change

	Surfacetiltangleindecimaldegrees. Tiltmustbe>=0and
	<=180.Thetiltangleisdefinedasdegreesfromhorizontal
	(e.g. surfacefacingup=0, surfacefacinghorizon=90)
	Surfacetiltanglefromhorizontal. E.g.,
	facingup=0°, facinghorizon=90°.
	Indegrees [°].

[BernatNicolau]

Got the wording from perez. For consistency, should other functions also be updated or shall I keep the one that currently is (from perez)?

[cwhanse]

echedey-ls edits are an improvement but I'm not in favor of changing documentation for other functions. You can change it here, but I think it's not a big deal if we use the old language.

[BernatNicolau]

It is quite hard to do the testing of the code since PVGIS directly provides the transposed data, without providing GHI, DHI and DNI (if I am wrong please tell me). I wanted to cross check if I obtained the same results by downloading the transposed signal and by applying it with the function, but I think I am reaching a dead end here...

[echedey-ls]

I think I am reaching a dead end here

Not really! Most of the time we don't have original data to work with. It's a good enough test if you can make up some data by using a spreadsheet like Excel and implementing the model there. Just rewriting the equations and making input data up for DHI and b values, then typing both the inputs and expected output in the test should be fine. That way we can confirm this new code complies with the expected behaviour.

[kandersolar]

since PVGIS directly provides the transposed data, without providing GHI, DHI and DNI (if I am wrong please tell me)

It may be possible to recover the original GHI/DHI/DNI components by specifying surface_tilt=0. Of course the poa_direct would need to be corrected for zenith angle to get back to DNI.

[BernatNicolau]

I have come to realize that the Muneer transposition is not as straightforward as I thought. At the beginning I was following this paper which I understand is the original Muneer transposition. However, I have found this article that describes a Muneer model, referencing this book from 2004 which is more complex, but can surely be implemented.

To be able to code the 2004 Muneer model, a inverse_square_spencer71() function needs to be added in pvlib.solarposition, providing the inverse square described in the linked Fourier paper:

$$\frac{1}{r^2} = 1.000110 + 0.034221 \cos(T) + 0.001280 \sin(T) + 0.000719 \cos(2T) + 0.000077 \sin(2T)$$

I am not sure which model should pvlib offer (1990 or 2004). I would gladly accept some guidance here :)

[adriesse]

I am not sure which model should pvlib offer (1990 or 2004). I would gladly accept some guidance here :)

I suggest implementing the version from the book.

PS. Somewhere I have a floppy disk containing the software from the book, in case it is needed.
PPS. And somewhere, I also have a floppy disk drive!

[BernatNicolau]

since PVGIS directly provides the transposed data, without providing GHI, DHI and DNI (if I am wrong please tell me)

It may be possible to recover the original GHI/DHI/DNI components by specifying surface_tilt=0. Of course the poa_direct would need to be corrected for zenith angle to get back to DNI.

This could be a good standalone feature to be included!

[cwhanse]

@BernatNicolau I would choose one (my preference is also 2004) and name it muneer2004 or something similar.

[BernatNicolau]

@BernatNicolau I would choose one (my preference is also 2004) and name it muneer2004 or something similar.

After having read the book section, I finally understood that the model is the same as 1990 but explained with greater detail and with some examples that compare different transposition models. So as far as I understand, there is no need to name it muneer2004 and can be kept muneer.

Note that I still need to do testing and add better documentation.

[kandersolar]

After looking into this some more, it seems to me that we have to regard the PVGIS/Hofierka model as being related to but distinct from the Muneer 1990 model. Compared with Muneer, Hofierka uses different equations for different conditions (aoi < 0, solar_elevation < 5.7) and does away entirely with the b parameter. I don't see how we could have one function that cleanly implements both models.

So, we need to decide which of the two models we are aiming to implement here. If we want to implement Muneer, we cannot use PVGIS to produce validation data for the tests. @AdamRJensen, this was your feature request -- any thoughts on how we should proceed?

[BernatNicolau]

I agree with you @kandersolar . However, either way I don't think we can use PVGIS for validation, I was recently doing more testing and I am obtaining very spurious results while analyzing poa from PVGIS.

I modified your testing code to produce the 12 months of the TMY for that example location:

Click to show code

importpvlibimportpandasaspdimportmatplotlib.pyplotaspltimportnumpyasnpimportpvlib.toolsastoolssurface_tilt=20surface_azimuth=180latitude=40longitude=-80# get PVGIS GHI, DHI for one month by requesting the TMY dataset:pvgis_tmy, months, _, meta=pvlib.iotools.get_pvgis_tmy(latitude, longitude)
pvgis_all=pd.DataFrame()
foryinrange(1, 13):
print(y)
pvgis_tmy_year=pvgis_tmy.loc[pvgis_tmy.index.month==y]
# now get PVGIS POA for the same year/month:year=months[y-1]['year'] # the year for the TMY januarypvgis_poa, _, meta=pvlib.iotools.get_pvgis_hourly(
latitude, longitude, start=year, end=year, surface_tilt=surface_tilt, surface_azimuth=surface_azimuth, usehorizon=False)
pvgis_poa=pvgis_poa.loc[pvgis_poa.index.month==y] # keep only january# transpose GHI, DHI to POA:sp=pvlib.solarposition.get_solarposition(
pvgis_poa.index, latitude, longitude)
sp.index=pvgis_poa.indexdni_extra=pvlib.irradiance.get_extra_radiation(pvgis_poa.index)
poa_diffuse_muneer=pvlib.irradiance.muneer(
surface_tilt, surface_azimuth, pvgis_tmy_year['dhi'], pvgis_tmy_year['ghi'], dni_extra, solar_azimuth=sp['azimuth'], solar_zenith=sp['zenith'], b=0)
poa_muneer=pvlib.irradiance.get_total_irradiance(
surface_tilt=surface_tilt,
surface_azimuth=surface_azimuth,
solar_zenith=sp['zenith'],
solar_azimuth=sp['azimuth'],
dni=pvgis_tmy_year['dni'],
ghi=pvgis_tmy_year['ghi'],
dhi=pvgis_tmy_year['dhi'],
dni_extra=dni_extra,
model="muneer",
)
aux=pd.DataFrame({
'sky_diff-PVGIS': pvgis_poa['poa_sky_diffuse'],
'sky_diff-muneer': poa_diffuse_muneer,
'poa-PVGIS': pvgis_poa.iloc[:, 0:2].sum(axis=1),
'poa-muneer': poa_muneer['poa_global']
})
out=pd.concat([aux, pvgis_tmy_year, sp, dni_extra], axis=1)
pvgis_all=pd.concat([pvgis_all, out])
pvgis_all.to_csv('comparison_allyear.csv')

There are some months of the TMY where the poa value seems correct, but there are other months that the poa doesn't make any sense to me. Let me illustrate:

On this day, the poa has a lower value than the ghi, and it seems to be a non-cloudy day.

This day doesn't make sense to me either...

[adriesse]

I thought I had commented on the b parameter earlier, but maybe my comment got lost. In this FORTRAN code that accompanied the 2004 edition of his book, the b parameter is already gone. I suggest implementing this since it is well-defined and documented, but of course if PVGIS does use something different, then that should be implemented as well.

C PROG4-2.FOR
C PROGRAM FOR SLOPE IRRADIANCE - OUTPUT FOR SEVEN MODELS Character*1 Anum
1 format(A1)
DOUBLE PRECISION EPSBINS(7)
DOUBLE PRECISION F11R(8), F12R(8), F13R(8)
DOUBLE PRECISION F21R(8), F22R(8), F23R(8)
DOUBLE PRECISION B2 DOUBLE PRECISION Z,ZH
PI=3.14159
DTOR=3.14159/180.0
WRITE(*,*)'SLOPE IRRADIANCE - OUTPUT FOR SEVEN MODELS'
WRITE(*,*)' '
WRITE(*,*) 'SELECT THE SYSTEM USED FOR TIME LOG'
WRITE(*,*) 'INPUT "1" FOR SOLAR, OR "2" FOR LOCAL CLOCK TIME'
READ(*,*) NTIMES
IF(NTIMES.EQ.2) THEN
WRITE(*,*) 'INPUT LAT, LONG, STD. TIME MERIDIAN (real values)'
WRITE(*,*) 'NORTH = +, WEST = + '
READ(*,*) YLAT,YLONG,YRLONG
ELSE WRITE(*,*) 'INPUT LATITUDE (real value)'
WRITE(*,*) 'NORTH = +'
READ(*,*) YLAT
YRLONG=0.0
YLONG=0.0
ENDIF
WRITE(*,*) 'INPUT SURFACE AZIMUTH AND TILT (real values)'
WRITE(*,*)'AZIMUTH - NORTH=0, EAST=90, SOUTH=180, WEST=270 DEG'
WRITE(*,*) 'SURFACE TILT - VERTICAL = 90 DEG'
READ(*,*) AZI,TLT WRITE(*,*)'INPUT YEAR (YYYY),MONTH,DAY,HOUR(0-23),MINUTE'
write(*,*)'only integers to be used' READ(*,*) IYR,IMT,IDY,IHR,IME WRITE(*,*)'ALL IRRADIANCE VALUES ARE TO BE EXPRESSED IN W/m2'
WRITE(*,*)'NOTE: 1 Wh/m2 = 0.0036 MJ/m2'
WRITE(*,*)'INPUT HORIZONTAL GLOBAL,DIFFUSE IRRADIANCE , ALBEDO'
READ(*,*) GRAD,DRAD,RHO
C Calculate GHA360, DEC XLCT=(1.0*IHR)+(1.0*IME/60.0)
UT=XLCT+(YRLONG/15.0) IF (IMT.GT.2) THEN
IYR1=IYR
IMT1=IMT-3
ELSE
IYR1=IYR-1
IMT1=IMT+9
ENDIF
INTT1=INT(30.6*IMT1+0.5)
INTT2=INT(365.25*(IYR1-1976))
SMLT=((UT/24.0)+IDY+INTT1+INTT2-8707.5)/36525.0
EPSILN=23.4393-0.013*SMLT
CAPG=357.528+35999.050*SMLT
IF(CAPG.GT.360.0) THEN
G360=CAPG-INT(CAPG/360.0)*360.0
ELSE
G360=CAPG
ENDIF
CAPC=1.915*SIN(G360*DTOR)+0.020*SIN(2*G360*DTOR)
CAPL=280.460+36000.770*SMLT+CAPC
IF(CAPL.GT.360.0) THEN
XL360=CAPL-INT(CAPL/360.0)*360.0
ELSE
XL360=CAPL
ENDIF
ALPHA=XL360-2.466*SIN(2*XL360*DTOR)+0.053*SIN(4*XL360*DTOR)
GHA=15.0*UT-180.0-CAPC+XL360-ALPHA
IF(GHA.GT.360.0) THEN
GHA360=GHA-INT(GHA/360.0)*360.0
ELSE
GHA360=GHA
ENDIF
DEC=ATAN(TAN(EPSILN*DTOR)*SIN(ALPHA*DTOR))/DTOR
C Calculate Solar Hour Angle IF(NTIMES.EQ.2) THEN
SHA=GHA360-(YLONG)
ELSE SHA=GHA360
ENDIF C Calculate Apparent Solar Time
IF(NTIMES.EQ.2) THEN
AST=12.0+(SHA/15.0)
ELSE
AST=XLCT
ENDIF
C Calculate SOLar ALTitude TRM111=SIN(YLAT*DTOR)*SIN(DEC*DTOR)
TRM112=COS(YLAT*DTOR)*COS(DEC*DTOR)*COS((SHA+180.0)*DTOR)
TRM11=TRM111-TRM112
SOLALT=ASIN(TRM11)/DTOR C Calculate SOLar AZiMuth TRM121=COS(YLAT*DTOR)*TAN(DEC*DTOR)
TRM122=SIN(YLAT*DTOR)*COS((SHA+180.0)*DTOR)
TRM12=TRM121+TRM122
TRM14=TRM12*COS(DEC*DTOR)/COS(SOLALT*DTOR)
SOLAZM=ACOS(TRM14)/DTOR
IF(SHA.GT.0.0) THEN
SOLAZM=360.0-SOLAZM
ENDIF
C Calculate SOLar INCidence angle
TRM15=COS(TLT*DTOR)*SIN(SOLALT*DTOR)+SIN(TLT*DTOR)*COS(SOLALT
1*DTOR)*COS((SOLAZM-AZI)*DTOR)
SOLINC=ACOS(TRM15)/DTOR C Calculate Day Number
DN1=(IDY+INTT1+INTT2)
IMTX=1
IYR1=IYR-1
IMT1=IMTX+9
INTT1=INT(30.6*IMT1+0.5)
INTT2=INT(365.25*(IYR1-1976))
DN2=(INTT1+INTT2)
DN=DN1-DN2
C Calculate horizontal Extraterrestrial irRADiance & kt
ERAD=1353.0*(1.+0.033*COS(0.0172024*DN))*SIN(SOLALT*DTOR) TKT=GRAD/ERAD
C BEAM IRRADIATION IF(SOLINC.LT.90.0) THEN
BSRAD=(GRAD-DRAD)*COS(SOLINC*DTOR)/SIN(SOLALT*DTOR)
ELSE
BSRAD=0.0
ENDIF
C GROUND REFLECTED RADIATION
RSRAD=RHO*GRAD*SIN(TLT*DTOR/2.0)**2
C SKY IRRADIANCE - ISOTROPIC MODEL
TLTISO=(COS(TLT*DTOR/2.)**2)
SISO=TLTISO*DRAD
C SKY IRRADIANCE - HAY'S MODEL CLRFRA=(GRAD-DRAD)/ERAD
TLTFAC=(1.0-CLRFRA)*(COS(TLT*DTOR/2.)**2) IF(SOLINC.LT.90.0) THEN
TLTFAC=(CLRFRA*TRM15/TRM11)+TLTFAC
ENDIF SHAY=TLTFAC*DRAD C SKY IRRADIANCE - REINDL'S MODEL
CLRFRA=(GRAD-DRAD)/ERAD REINDF=SQRT((GRAD-DRAD)/GRAD)
TLTFAC=(1.0-CLRFRA)*(COS(TLT*DTOR/2.)**2)*
1(1.+REINDF*SIN(TLT*DTOR/2)**3)
IF(SOLINC.LT.90.0) THEN TLTFAC=(CLRFRA*TRM15/TRM11)+TLTFAC
ENDIF SREIND=TLTFAC*DRAD C SKY IRRADIANCE - SKARTVEIT-OLSETH'S MODEL CLRFRA=(GRAD-DRAD)/ERAD BKB=MIN(CLRFRA,1.0)
BRB=MAX((TRM15/TRM11),0.0)
CAPBSO=MAX((0.3-2.*BKB),0.0) SSKOL=DRAD*(BKB*BRB+(CAPBSO*COS(TLT*DTOR))+(1.-BKB-CAPBSO)*TLTISO)
C SKY IRRADIANCE - GUEYMARD'S MODEL H01=SOLALT*0.01
GA0=-0.897-3.364*H01+(3.96*H01**2)-1.909*H01**3
GA1=4.448-12.962*H01+(34.601*H01**2)-48.784*H01**3+(27.511*H01**4)
GA2=-2.77+9.164*H01-(18.876*H01**2)+23.776*H01**3-(13.014*H01**4)
GA3=0.312-0.217*H01-(0.805*H01**2)+0.318*H01**3
CFS=(1.0-(0.2249*SIN(TLT*DTOR)**2)+(0.1231*SIN(2.0*TLT*DTOR))
1-0.0342*SIN(4.0*TLT*DTOR))/(1.0-0.2249)
CGH=0.408-0.323*H01+(0.384*H01**2)-0.17*H01**3
CRD0=EXP(GA0+GA1*TRM15+(GA2*TRM15**2)+GA3*TRM15**3)
CRD0=CRD0+CFS*CGH IF((DRAD/GRAD).LE.0.227) THEN CAPY=6.6667*(DRAD/GRAD)-1.4167
ELSE
CAPY=1.2121*(DRAD/GRAD)-0.1758
ENDIF
CNPT=MAX(MIN(CAPY,1.0),0.0)
SMLB=0.5+CNPT CAPBG=2.*SMLB/(PI*(3.+2.*SMLB))
CRD1=(COS(TLT*DTOR/2.)**2)+CAPBG*(SIN(TLT*DTOR)-(TLT*DTOR)
1*COS(TLT*DTOR)-PI*SIN(TLT*DTOR/2.)**2)
SGUEYM=DRAD*((1.0-CNPT)*CRD0+CNPT*CRD1)
C SKY IRRADIANCE - MUNEER'S MODEL
CLRFRA=(GRAD-DRAD)/ERAD IF(SOLINC.GE.90.0) THEN
CAPB=0.252
CLRFRA=0.0
ELSE
c The user may select one of the following four models:
c CAPB= 0.003 33 -0.415 F -0.698 7 F**2 [for Northern Europe]
c CAPB= 0.002 63 -0.712 F -0.688 3 F**2 [for Southern Europe]
c CAPB= 0.080 00 -1.050 F -2.840 0 F**2 [for Japan]
c CAPB= 0.040 00 -0.820 F -2.026 0 F**2 [for the globe]
c Model for Northern Europe CAPB=0.00333-0.415*CLRFRA-0.6987*CLRFRA**2 c End of model for Northern Europe ENDIF TLTFAC=(COS(TLT*DTOR/2.)**2)+CAPB*(SIN(TLT*DTOR)-(TLT*DTOR)
1*COS(TLT*DTOR)-PI*SIN(TLT*DTOR/2.)**2) DSRAD=TLTFAC*(1.-CLRFRA)+CLRFRA*COS(SOLINC*DTOR)/SIN(SOLALT*DTOR)
SMUN=DSRAD*DRAD C SKY IRRADIANCE - PEREZ MODEL
DATA F11R / -0.0083117, 0.1299457, 0.3296958, 0.5682053,
10.8730280, 1.1326077, 1.0601591, 0.6777470 /
DATA F12R / 0.5877285, 0.6825954, 0.4868735, 0.1874525,
1-0.3920403, -1.2367284, -1.5999137, -0.3272588 /
DATA F13R / -0.0620636, -0.1513752, -0.2210958, -0.2951290,
1-0.3616149, -0.4118494, -0.3589221, -0.2504286 /
DATA F21R / -0.0596012, -0.0189325, 0.0554140, 0.1088631,
10.2255647, 0.2877813, 0.2642124, 0.1561313 /
DATA F22R / 0.0721249, 0.0659650, -0.0639588, -0.1519229,
1-0.4620442, -0.8230357, -1.1272340, -1.3765031 /
DATA F23R / -0.0220216, -0.0288748, -0.0260542, -0.0139754,
10.0012448, 0.0558651, 0.1310694, 0.2506212 /
DATA EPSBINS / 1.065, 1.23, 1.5, 1.95, 2.8, 4.5, 6.2 /
B2 = 5.534D-6 G=GRAD
B=(GRAD-DRAD)/TRM11
Z=(90.0-SOLALT)*DTOR
SLOPE=TLT*DTOR
XPINC=SOLINC*DTOR ZENITH =Z/DTOR
ZH = MAX(TRM11, 0.0871557)
AIRMASS = 1.0 / (TRM11 + 0.15 * (93.9 - ZENITH)** (-1.253))
DELTA = DRAD * AIRMASS / 1367.0
T = ZENITH**3.0
EPS = (B + DRAD) / DRAD
EPS = (EPS + T * B2) / (1.0 + T * B2) DO 70001 I = 1,8
IF ( (I .EQ. 8) .OR. (EPS .LE. EPSBINS(I)) ) GOTO 70002
70001 CONTINUE
70002 F1 = MAX1(0.0, F11R(I) + F12R(I) * DELTA + F13R(I) * Z)
F2 = F21R(I) + F22R(I) * DELTA + F23R(I) * Z
A = (1.0-F1)*( 1.0 + COS(SLOPE)) / 2.0
B1 = F1*MAX(TRM15,0.0)/ZH
C=F2*SIN(SLOPE)
SPER = DRAD*(A+B1+C) C print results
WRITE(*,*) '-------------------------------------------------' WRITE(*,*)'ALL IRRADIANCE VALUES ARE EXPRESSED IN W/m2'
WRITE(*,*) 'EXTRATERRESTRIAL IRRADIANCE =',ERAD
WRITE(*,*) 'HOURLY CLEARNESS INDEX, KT =', TKT WRITE(*,*) 'SLOPE BEAM IRRADIANCE =',BSRAD WRITE(*,*) 'SLOPE REFLECTED IRRADIANCE =',RSRAD
WRITE(*,*) '-------------------------------------------------' WRITE(*,*) 'ISOTROPIC SKY-DIFFUSE IRRADIANCE =',SISO WRITE(*,*) 'HAY SKY-DIFFUSE IRRADIANCE =',SHAY WRITE(*,*) 'SKARTVEIT-OLSETH SKY-DIFFUSE IRRADIANCE =',SSKOL
WRITE(*,*) 'REINDL SKY-DIFFUSE IRRADIANCE =',SREIND WRITE(*,*) 'GUEYMARD SKY-DIFFUSE IRRADIANCE=', SGUEYM WRITE(*,*) 'MUNEER SKY-DIFFUSE IRRADIANCE=',SMUN WRITE(*,*) 'PEREZ SKY-DIFFUSE IRRADIANCE=',SPER
write(*,*) 'Key-in any alphanumeric key to exit'
read(*,1) Anum
END 

[cwhanse]

Just a comment, this discussion illustrates the original motivation for pvlib - to clarify what each is in each model. Hang in there @BernatNicolau

[BernatNicolau]

I have created the function based on the 2004 book, but I have not pushed it to this PR because I don't know how to proceed:

• Should I push it in this PR?
• Shall we have two muneer functions muneer1990 and muneer2004, or the Muneer from 1990 can be considered as deprecated and only implement the one from 2004?

This article 10.2790/91554 explains the transposition model used in PVGIS which basically is the one from the book with an improvement for low solar elevations. The function I have created is based on this article.

[adriesse]

I would say the more models, the merrier. There may be some overhead in making them all available in the model chain(s), but that is neither obligatory nor urgent. Having a single muneer function with a selector argument (1990, 2004, 'pvgis') might make sense, but I would be equally happy with three separate functions. Or perhaps two of them call the third to reuse some code.

[AdamRJensen]

• Should I push it in this PR?
• Shall we have two muneer functions muneer1990 and muneer2004, or the Muneer from 1990 can be considered as deprecated and only implement the one from 2004?

Outside of PVGIS I have never heard of the Muneer transposition model, nor have I seen studies where it has an outstanding performance. Given that there are so many transposition models, I think we best only include the more recent Muneer model that is used by PVGIS.

How well does it match PVGIS btw? I have made my own implementation and can get it to match quite well for most times. I'd be happy to collaborate on investigating how well it matches pvgis.

[BernatNicolau]

• Should I push it in this PR?
• Shall we have two muneer functions muneer1990 and muneer2004, or the Muneer from 1990 can be considered as deprecated and only implement the one from 2004?

Outside of PVGIS I have never heard of the Muneer transposition model, nor have I seen studies where it has an outstanding performance. Given that there are so many transposition models, I think we best only include the more recent Muneer model that is used by PVGIS.

How well does it match PVGIS btw? I have made my own implementation and can get it to match quite well for most times. I'd be happy to collaborate on investigating how well it matches pvgis.

I have commited the muneer function from the book (muneer2004), note that the documentation is not updated. Can you replicate the results I obtain from the following code (comparison_allyear.csv) with your own version of the function so that we can compare differences? If you find a better way to collaborate please tell me :)

importpvlibimportpandasaspdsurface_tilt=20surface_azimuth=180latitude=37longitude=-4# get PVGIS GHI, DHI for one month by requesting the TMY dataset:pvgis_tmy, months, _, meta=pvlib.iotools.get_pvgis_tmy(
latitude, longitude, usehorizon=False)
pvgis_all=pd.DataFrame()
foryinrange(1, 13):
print(y)
pvgis_tmy_year=pvgis_tmy.loc[pvgis_tmy.index.month==y]
# now get PVGIS POA for the same year/month:year=months[y-1]['year'] # the year for the TMY januarypvgis_poa, _, meta=pvlib.iotools.get_pvgis_hourly(
latitude, longitude, start=year, end=year, surface_tilt=surface_tilt, surface_azimuth=surface_azimuth, usehorizon=False)
pvgis_poa=pvgis_poa.resample('H').mean()
pvgis_poa=pvgis_poa.loc[pvgis_poa.index.month==y] # keep only january# transpose GHI, DHI to POA:sp=pvlib.solarposition.get_solarposition(
pvgis_poa.index, latitude, longitude)
sp.index=pvgis_poa.indexdni_extra=pvlib.irradiance.get_extra_radiation(pvgis_poa.index)
poa_diffuse_muneer=pvlib.irradiance.muneer2004(
surface_tilt, surface_azimuth, pvgis_tmy_year['dhi'], pvgis_tmy_year['ghi'], dni_extra, solar_azimuth=sp['azimuth'], solar_zenith=sp['zenith'])
poa_muneer=pvlib.irradiance.get_total_irradiance(
surface_tilt=surface_tilt,
surface_azimuth=surface_azimuth,
solar_zenith=sp['zenith'],
solar_azimuth=sp['azimuth'],
dni=pvgis_tmy_year['dni'],
ghi=pvgis_tmy_year['ghi'],
dhi=pvgis_tmy_year['dhi'],
dni_extra=dni_extra,
model="muneer",
)
aux=pd.DataFrame({
'sky_diff-PVGIS': pvgis_poa['poa_sky_diffuse'],
'sky_diff-muneer': poa_diffuse_muneer,
'poa-PVGIS': pvgis_poa.iloc[:, 0:2].sum(axis=1),
'poa-muneer': poa_muneer['poa_global']
})
out=pd.concat([aux, pvgis_tmy_year, sp, dni_extra], axis=1)
pvgis_all=pd.concat([pvgis_all, out])
pvgis_all.to_csv('comparison_allyear.csv')

[adriesse]

Just wondering what might be the next step on this...?

[RDaxini]

Moving to 11.3 (comment), hopefully we can get this merged in the next release:)

[BernatNicolau]

Hi folks! I have been quite disconnected from contributing these days due to overload of tasks but I am willing to keep working on this :) Which do you think is the best way forward with this topic? @AdamRJensen Can you share your implementations/comparisons with PVGIS so we can collaborate on this?