I should have looked a bit more closely before posting! I used the solrad excel code from Uni Washington. I had adjusted my B&H parameters to represent quite clean air but forgot to match the Bras and RS code from default. If I:
1. reset the BH turbidity params to default, 2. adjust the Bras param down to 1.6 and 3. adjust the RS param to 0.84, then the curves are close to normalised at peak. The RS curve is still a somewhat poor representation at dawn and dusk, while Bras is probably close enough to BH that it's not worth the extra effort. The main advantage with B&H is the atmospheric moisture, which I think contributes significantly, but differently from the atmospheric turbidity parameters and changes the shape of the curve. So a single parameter cannot account for all variables. The safest bet might be to adjust the parameter for clear skies and then say that is an upper limit. On Wednesday, 23 December 2020 at 6:31:47 pm UTC+10 Cameron D wrote: > So the weewx python code says it is using the Ryan and Stolzenbach model, > which has a few approximations that don't work well in some cases, and it > looks like this is one of them. > > I've attached a plot comparing 3 insolation models predicting global > horizontal irradiation. > Bird and Hulstrom 1991 > Bras 1992 > and Ryan and Stolzenbach 1972 > > B&H has a lot more parameters to account for, but I have just thrown in > the date/location for Boston, using whatever parameters were in the > spreadsheet, and come up with the following comparison. > I used the B&H predictions for modelling my solar PV system and found it > gives very close results - or at least it did before my system got a bit > older. However R&S also gives results that aren't too bad in my location. > > I have the code in php, but no spare time at the moment to convert to > python. > > On Tuesday, 22 December 2020 at 2:19:29 am UTC+10 t...@tom.org wrote: > >> kk, glad you corroborated my observations. I am no expert in this for >> sure. I am just tired of all of the comments I get from visitors to the >> website about how my readings exceed theoretical max. I could remove the >> max, but that doesn't seem fun. >> >> I do not have the expertise to validate the way weewx calculates it nor >> am I even competent in Python, but for those who may, here is a link to the >> code: >> >> >> https://github.com/weewx/weewx/blob/d91635f3bc429f906d1f084c6a6bc8ee09fa1a27/bin/weewx/wxformulas.py#L332 >> >> >> >> On Sunday, December 20, 2020 at 1:26:31 PM UTC-5 kk44...@gmail.com wrote: >> >>> I found that thread interesting, so I added the column "maxSolarRad", >>> too. >>> >>> [image: dayradiation.png] >>> Readings of the console and the WeatherLinkLive device are quite the >>> same. And the readings of "radiation" are higher than "maxSolarRad". The >>> values I upload to the local weather network are well in the range of other >>> stations nearby. >>> >>> >>> Greg Troxel schrieb am Sonntag, 20. Dezember 2020 um 17:58:01 UTC+1: >>> >>>> >>>> Greg Troxel <g...@lexort.com> writes: >>>> >>>> > Can someone share how to add maxSolarRad (when it is in the db) to >>>> the >>>> > graphs for the traditional skin? Can I graph radiation, max >>>> (observed), >>>> > and theory all at once, having three? >>>> >>>> The answer is to just add it and label it; it comes out in green after >>>> radiation in blue and max in red. Pro Tip: add it after radiation_max, >>>> which is the max of local observations, and don't stick the line after >>>> the radiation_max header and the 4 lines defining how max should be. >>>> >>>> >>>> [[[dayradiation]]] >>>> [[[[radiation]]]] >>>> [[[[radiation_max]]]] >>>> data_type = radiation >>>> aggregate_type = max >>>> aggregate_interval = 3600 >>>> label = max >>>> [[[[maxSolarRad]]]] >>>> label = theory >>>> >>> -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to weewx-user+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/0d468847-eed9-4d9d-9649-4937a5e61901n%40googlegroups.com.
