Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Cameron D]

That is part of it, but some of the early morning examples are up to 500% 
different, although with very small values.  In those cases I still suspect 
there is extra scattered radiation from the surroundings, whether it be 
trees or buildings.
I wonder also if the sensor type may change results slightly.
There may also be a calibration error, due to the different spectral energy 
distribution comparing dawn and midday, or perhaps even simple nonlinearity 
near zero output. These are not research-grade instruments that most of us 
are using.
If you add all that in with ozone, water vapour and particulates of 
different sizes, all of which change seasonally and daily, you will never 
expect precise agreement.

Here's another example - I left the RS and Bras models with the same values 
as previous, and changed the BH model to ignore just ozone, water vapour 
and particulates.
That gave the solid line. Then I set albedo for the full snow cover and the 
result was  the dashed line.

So, the "theoretical curve" for around Boston is anywhere in that range of 
curves, or it could be even lower in moderately polluted skies.
On Wednesday, 23 December 2020 at 10:51:08 pm UTC+10 tke...@gmail.com wrote:

> Very useful, Cameron.
>
> It looks like the R-S curve is quite a bit lower, maybe as much as 20% 
> lower, at dawn and dusk, which seems to be when people are experiencing 
> values higher than maxSolarRad.
>
> On Wed, Dec 23, 2020 at 1:19 AM Cameron D  wrote:
>
>> And then I forgot the attachment!
>>
>>
>> On Wednesday, 23 December 2020 at 7:18:31 pm UTC+10 Cameron D wrote:
>>
>>> 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  writes: 
>>>
>>> > Can someone share how to add maxSolarRad (when 

Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Tom Keffer]

Very useful, Cameron.

It looks like the R-S curve is quite a bit lower, maybe as much as 20%
lower, at dawn and dusk, which seems to be when people are experiencing
values higher than maxSolarRad.

On Wed, Dec 23, 2020 at 1:19 AM Cameron D  wrote:

> And then I forgot the attachment!
>
>
> On Wednesday, 23 December 2020 at 7:18:31 pm UTC+10 Cameron D wrote:
>
>> 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  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
>>
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> 
> .
>

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Cameron D]

And then I forgot the attachment!


On Wednesday, 23 December 2020 at 7:18:31 pm UTC+10 Cameron D wrote:

> 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  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 
>


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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Cameron D]

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  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 

>>>

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Cameron D]

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  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 
>>>
>>

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Greg Troxel]

"t...@tom.org"  writes:

> 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 have added maxSolarRad to my db and am now looking at it.  This
morning, I saw values that exceeded theory right at dawn, then going
under theory after a while.  Two thoughts from this:

  Instruments are typically specified at something like 5% of full
  scale.  I just looked up the VP2 and that is exactly what it says.
  So that's 5% of 1800 W/m^2, or 90 W/m^2.  That's huge compared to
  morning levels.

  The theory is presumably for a sensor that is somewhat off the ground
  in an open area with not only no trees but no buildings.  A
  light-colored building nearby might reflect light from direct sun.

> 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

Thanks.  That seems to refer to fairly old work (which doesn't mean it's
wrong, but it seems there has been a lot more attention paid to this
more recently).

With any luck someone can go over the various theory papers and
implement a few more algorithms.

This looks like the state of the art:
  
https://pvpmc.sandia.gov/modeling-steps/1-weather-design-inputs/irradiance-and-insolation-2/irradiance-data-sources-for-performance-modeling/national-solar-radiation-database/

but my guess is that using the Wikipedia article is going to be easier.

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Description: PGP signature

Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[moth...@gmail.com]

These are the mine measurements in the Netherlands today 21-12-2020.
Ton

Op maandag 21 december 2020 om 20:24:13 UTC+1 schreef kk44...@gmail.com:

> http://www.michler-fischer.privat.t-online.de/Bulletin68_83_94.pdf
> (from Switzerland, unfortunately in german)
>
> tke...@gmail.com schrieb am Montag, 21. Dezember 2020 um 19:53:14 UTC+1:
>
>> Selection of the algorithm is in there --- just not documented. (I often 
>> do that with configurations that are not quite settled.)
>>
>> Here's the default. It will be documented in V4.3.
>>
>> [StdWXCalculate]
>>   [[WXXTypes]]
>> [[[maxSolarRad]]]
>>   algorithm = rs
>>   atc = 0.8
>>   nfac = 2
>>
>> Adjust as you please.
>>
>> -tk
>>
>> On Mon, Dec 21, 2020 at 10:47 AM Karen K  wrote:
>>
>>> First, I see 2 different formulas in WeeWX. Additionally there is a 
>>> factor that can be between 0.7 and 0.91. It may be an idea to adjust those 
>>> values. (But in the moment I found no place to put "atc" and 
>>> "maxSolarRad_algo" into weewx.conf.
>>>
>>> tke...@gmail.com schrieb am Montag, 21. Dezember 2020 um 19:38:30 UTC+1:
>>>
 Well, if someone has a better source for calculating maximum solar 
 radiation, that matches the radiation spectrum of popular sensors, I'm all 
 ears.

 On Mon, Dec 21, 2020 at 8:19 AM 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  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 
>>>
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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Karen K]

http://www.michler-fischer.privat.t-online.de/Bulletin68_83_94.pdf
(from Switzerland, unfortunately in german)

tke...@gmail.com schrieb am Montag, 21. Dezember 2020 um 19:53:14 UTC+1:

> Selection of the algorithm is in there --- just not documented. (I often 
> do that with configurations that are not quite settled.)
>
> Here's the default. It will be documented in V4.3.
>
> [StdWXCalculate]
>   [[WXXTypes]]
> [[[maxSolarRad]]]
>   algorithm = rs
>   atc = 0.8
>   nfac = 2
>
> Adjust as you please.
>
> -tk
>
> On Mon, Dec 21, 2020 at 10:47 AM Karen K  wrote:
>
>> First, I see 2 different formulas in WeeWX. Additionally there is a 
>> factor that can be between 0.7 and 0.91. It may be an idea to adjust those 
>> values. (But in the moment I found no place to put "atc" and 
>> "maxSolarRad_algo" into weewx.conf.
>>
>> tke...@gmail.com schrieb am Montag, 21. Dezember 2020 um 19:38:30 UTC+1:
>>
>>> Well, if someone has a better source for calculating maximum solar 
>>> radiation, that matches the radiation spectrum of popular sensors, I'm all 
>>> ears.
>>>
>>> On Mon, Dec 21, 2020 at 8:19 AM 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  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 
>>
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>> .
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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Tom Keffer]

Selection of the algorithm is in there --- just not documented. (I often do
that with configurations that are not quite settled.)

Here's the default. It will be documented in V4.3.

[StdWXCalculate]
  [[WXXTypes]]
[[[maxSolarRad]]]
  algorithm = rs
  atc = 0.8
  nfac = 2

Adjust as you please.

-tk

On Mon, Dec 21, 2020 at 10:47 AM Karen K  wrote:

> First, I see 2 different formulas in WeeWX. Additionally there is a factor
> that can be between 0.7 and 0.91. It may be an idea to adjust those values.
> (But in the moment I found no place to put "atc" and "maxSolarRad_algo"
> into weewx.conf.
>
> tke...@gmail.com schrieb am Montag, 21. Dezember 2020 um 19:38:30 UTC+1:
>
>> Well, if someone has a better source for calculating maximum solar
>> radiation, that matches the radiation spectrum of popular sensors, I'm all
>> ears.
>>
>> On Mon, Dec 21, 2020 at 8:19 AM 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  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
>
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>>> .
>>>
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> 
> .
>

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Karen K]

First, I see 2 different formulas in WeeWX. Additionally there is a factor 
that can be between 0.7 and 0.91. It may be an idea to adjust those values. 
(But in the moment I found no place to put "atc" and "maxSolarRad_algo" 
into weewx.conf.

tke...@gmail.com schrieb am Montag, 21. Dezember 2020 um 19:38:30 UTC+1:

> Well, if someone has a better source for calculating maximum solar 
> radiation, that matches the radiation spectrum of popular sensors, I'm all 
> ears.
>
> On Mon, Dec 21, 2020 at 8:19 AM 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  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 

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>>  
>> 
>> .
>>
>

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Tom Keffer]

Well, if someone has a better source for calculating maximum solar
radiation, that matches the radiation spectrum of popular sensors, I'm all
ears.

On Mon, Dec 21, 2020 at 8:19 AM 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  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
>>>
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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[t...@tom.org]

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  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
>>
>

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Karen K]

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  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
>

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Greg Troxel]

Greg Troxel  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

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Greg Troxel]

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?

I think the answer is the same for seasons and traditional.

I only just today updated to 4.2.0 (well, git master from this morning),
and it is running fine (NetBSD 9, RPI3, python 2.7).  I also changed my
db to the extended schema following the really great documentation at:
  https://github.com/weewx/weewx/wiki/Switching-to-the-new-wview_extended-schema

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Re: [weewx-user] Re: Solar Radiation > Theoretical Max

[Greg Troxel]

I had a thought about this last night.

There are two entirely separable questions.  One is whether the
maxSolarRad value is correct, and the other is what your sensor is
measuring.  I think the "is the max correct" can be answered (and should
be) without considering your data at all.

First, I think we're talking about radiation incident on a horizontal
surface.  I didn't level my sensor carefully, but it's within a few
degrees.


I see in the defautl config file that maxSolarRad is set to
prefer_hardware, but I am guessing VP2 does not actually output that.


For theory, there seem to be multiple approaches, and notions include
not only the in-space radiation of 1353 W/m^2, but some contribution
from diffusion as well as air-mass attenuation and pollution (but
northeast air quality is pretty good)

https://en.wikipedia.org/wiki/Air_mass_(solar_energy)

{The rest of the specific numbers I mention in this post assume 42.5
latitude, which is more or less where Tom and I are.)

At 42.5 degrees and the winter solstice, the sun elevation is 20.  In
the summer, it's 65.  So that's 70 and 25 in terms of zenith angle.

Interpolating by guessing from the table, that leads to

   1017 W/m^w summer solstice
   710 W/m^2 winter solstice

but as I understand it, that is radiation at the arrival angle, not
radiation horizontally.  It just does not make sense to me that there
would be 710 W/m^2 on horizontal panel when the sun is 20 degrees up -
but my intuition has not been working well so far on this subject.

Tom's graph shows 461 for yesterday's peak theoretical
and I'd expect 243 horizontal for 710 at 20 degrees.   Except that the
diffuse component would not be reduced, just the direct, from the angle.

For 1017 incident , basically discounting air mass and keeping the 10%
gain, I'd expect 347.

So I have no idea where that 461 is coming from.

Looking back near the solstice at a cloud-free day (June 17), I see a nice
sine-ish curve over the day peaking at about 941 W/m^2.
If I take 1017 and multiple by sin(65deg) I get 922.


So I guess the big point is that this is much harder than I thought it
was going to be when I started looking it up!



This may be useful, but it seems to be about daily energy
  https://naldc.nal.usda.gov/download/34980/PDF

This might have some data from calibrated instruments:
  
https://www.ncdc.noaa.gov/data-access/land-based-station-data/land-based-datasets/solar-radiation

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[weewx-user] Re: Solar Radiation > Theoretical Max

[Cameron D]

The main cause of higher than expected insolation is scattered light being 
added to direct light.

Thin clouds are a good source of scattered light, but if you have nearby 
structures, such as walls, above the sensor then they can also contribute.

Your very high ratio early morning is almost certainly indirect light, and 
it might be that the "theoretical" calculation only gives a direct light 
value (I haven't looked at the code).

Finally, theoretical calculations still have to take into account 
atmospheric absorption by minor gases and particles that are not known 
locally. If the calculations assume a moderate level of pollution but you 
have very clear air then you will see higher than expected insolation, but 
your readings look too high to be explained by just that.

On Sunday, 20 December 2020 at 11:36:19 pm UTC+10 t...@tom.org wrote:

> OK, update on this..
>
> I made sure the consoles and weewx had the exact same lat/long. They were 
> very close but not exact.
>
> I'll just use one station for this today, which is the one in MA at 42.5 
> latitude.
>
> It is completely overcast today, at least so far.
>
> I ran this query against my archive table:
>
> SELECT datetime, convert_tz(from_unixtime(datetime),'GMT', 'US/Eastern') 
> as Date, radiation, round(maxSolarRad,0) as maxRad, round(radiation - 
> maxSolarRad, 0) as delta FROM weewx_ma.archive where radiation > 0 order by 
> datetime desc limit 288;
>
> Here are the results as of now:
>
> '1608471000','2020-12-20 08:30:00','38','82','-44'
> '1608470700','2020-12-20 08:25:00','39','72','-33'
> '1608470400','2020-12-20 08:20:00','47','63','-16'
> '1608470100','2020-12-20 08:15:00','44','53','-9'
> '1608469800','2020-12-20 08:10:00','38','44','-6'
> '1608469500','2020-12-20 08:05:00','32','36','-4'
> '1608469200','2020-12-20 08:00:00','29','28','1'
> '1608468900','2020-12-20 07:55:00','26','21','5'
> '1608468600','2020-12-20 07:50:00','26','15','11'
> '1608468300','2020-12-20 07:45:00','20','10','10'
> '1608468000','2020-12-20 07:40:00','16','6','10'
> '1608467700','2020-12-20 07:35:00','12','3','9'
> '1608467400','2020-12-20 07:30:00','10','1','9'
> '1608467100','2020-12-20 07:25:00','5','0','5'
> '1608466800','2020-12-20 07:20:00','4','0','4'
>
> So I am having this issue on a cloudy day with lat and long aligned.
>
> Is anyone else seeing this in their environment??
>
> On Saturday, December 19, 2020 at 4:48:52 PM UTC-5 t...@tom.org wrote:
>
>> Double-checked on both counts.
>>
>> On Saturday, December 19, 2020 at 2:34:50 PM UTC-5 vince wrote:
>>
>>> On Saturday, December 19, 2020 at 10:18:43 AM UTC-8 t...@tom.org wrote:
>>>
 Looks like I might have unlocked some secret of the universe because my 
 solar radiation numbers are regularly above the "theoretical max" as shown 
 in the Belchertown skin.


>>> Many stations emit readings like this (WeatherFlow to name one).
>>>
>>> I guess I'd suggest making sure you have pyephem installed and that your 
>>> lat/lon in weewx.conf is correct.
>>>  
>>>
>>

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[weewx-user] Re: Solar Radiation > Theoretical Max

[t...@tom.org]

OK, update on this..

I made sure the consoles and weewx had the exact same lat/long. They were 
very close but not exact.

I'll just use one station for this today, which is the one in MA at 42.5 
latitude.

It is completely overcast today, at least so far.

I ran this query against my archive table:

SELECT datetime, convert_tz(from_unixtime(datetime),'GMT', 'US/Eastern') as 
Date, radiation, round(maxSolarRad,0) as maxRad, round(radiation - 
maxSolarRad, 0) as delta FROM weewx_ma.archive where radiation > 0 order by 
datetime desc limit 288;

Here are the results as of now:

'1608471000','2020-12-20 08:30:00','38','82','-44'
'1608470700','2020-12-20 08:25:00','39','72','-33'
'1608470400','2020-12-20 08:20:00','47','63','-16'
'1608470100','2020-12-20 08:15:00','44','53','-9'
'1608469800','2020-12-20 08:10:00','38','44','-6'
'1608469500','2020-12-20 08:05:00','32','36','-4'
'1608469200','2020-12-20 08:00:00','29','28','1'
'1608468900','2020-12-20 07:55:00','26','21','5'
'1608468600','2020-12-20 07:50:00','26','15','11'
'1608468300','2020-12-20 07:45:00','20','10','10'
'1608468000','2020-12-20 07:40:00','16','6','10'
'1608467700','2020-12-20 07:35:00','12','3','9'
'1608467400','2020-12-20 07:30:00','10','1','9'
'1608467100','2020-12-20 07:25:00','5','0','5'
'1608466800','2020-12-20 07:20:00','4','0','4'

So I am having this issue on a cloudy day with lat and long aligned.

Is anyone else seeing this in their environment??

On Saturday, December 19, 2020 at 4:48:52 PM UTC-5 t...@tom.org wrote:

> Double-checked on both counts.
>
> On Saturday, December 19, 2020 at 2:34:50 PM UTC-5 vince wrote:
>
>> On Saturday, December 19, 2020 at 10:18:43 AM UTC-8 t...@tom.org wrote:
>>
>>> Looks like I might have unlocked some secret of the universe because my 
>>> solar radiation numbers are regularly above the "theoretical max" as shown 
>>> in the Belchertown skin.
>>>
>>>
>> Many stations emit readings like this (WeatherFlow to name one).
>>
>> I guess I'd suggest making sure you have pyephem installed and that your 
>> lat/lon in weewx.conf is correct.
>>  
>>
>

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[weewx-user] Re: Solar Radiation > Theoretical Max

[t...@tom.org]

Double-checked on both counts.

On Saturday, December 19, 2020 at 2:34:50 PM UTC-5 vince wrote:

> On Saturday, December 19, 2020 at 10:18:43 AM UTC-8 t...@tom.org wrote:
>
>> Looks like I might have unlocked some secret of the universe because my 
>> solar radiation numbers are regularly above the "theoretical max" as shown 
>> in the Belchertown skin.
>>
>>
> Many stations emit readings like this (WeatherFlow to name one).
>
> I guess I'd suggest making sure you have pyephem installed and that your 
> lat/lon in weewx.conf is correct.
>  
>

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[weewx-user] Re: Solar Radiation > Theoretical Max

[vince]

On Saturday, December 19, 2020 at 10:18:43 AM UTC-8 t...@tom.org wrote:

> Looks like I might have unlocked some secret of the universe because my 
> solar radiation numbers are regularly above the "theoretical max" as shown 
> in the Belchertown skin.
>
>
Many stations emit readings like this (WeatherFlow to name one).

I guess I'd suggest making sure you have pyephem installed and that your 
lat/lon in weewx.conf is correct.
 

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[weewx-user] Re: Solar Radiation > Theoretical Max

[t...@tom.org]

By the way:

http://www.tom.org/
http://vtwx.tom.org/

On Saturday, December 19, 2020 at 1:18:43 PM UTC-5 t...@tom.org wrote:

> Looks like I might have unlocked some secret of the universe because my 
> solar radiation numbers are regularly above the "theoretical max" as shown 
> in the Belchertown skin.
>
> I see this on two different stations in two different places, so I doubt 
> it is my station.
>
> Does anyone know how to adjust this max or have another recommendation?
>
> Or have I unlocked the secrets of the universe?
>
> Thanks in advance.
>

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