Re: [weewx-development] Where does the crt extension get the value for SolarMax?

'John Kline' via weewx-development Mon, 01 Dec 2025 20:38:12 -0800

maxSolarRad defaults to hardware preferred. Assuming it is not supplied by the driver, it is calculated in wxxtypes.py

The function is below. Note that the default for maxSolarRad_algo is ‘rs’.

def calc_maxSolarRad(self, key, data, db_manager):

altitude_m = weewx.units.convert(self.altitude_vt, 'meter')[0]

if self.maxSolarRad_algo == 'bras':

val = weewx.wxformulas.solar_rad_Bras(self.latitude_f, self.longitude_f, altitude_m,

data['dateTime'], self.nfac)

elif self.maxSolarRad_algo == 'rs':

val = weewx.wxformulas.solar_rad_RS(self.latitude_f, self.longitude_f, altitude_m,

data['dateTime'], self.atc)

else:

raise weewx.ViolatedPrecondition("Unknown solar algorithm '%s'"

% self.maxSolarRad_algo)

return ValueTuple(val, 'watt_per_meter_squared', 'group_radiation')

wxformulas.py: solar_rad_RS:

from weewx.almanac import Almanac

if atc < 0.7 or atc > 0.91:

atc = 0.8

if ts is None:

ts = time.time()

sr = 0.0

try:

alm = Almanac(ts, lat, lon, altitude_m)

el = alm.sun.alt # solar elevation degrees from horizon

R = alm.sun.earth_distance

z = altitude_m

nrel = 1367.0 # NREL solar constant, W/m^2

sinal = math.sin(math.radians(el))

if sinal >= 0: # sun must be above horizon

rm = math.pow((288.0 - 0.0065 * z) / 288.0, 5.256) \

/ (sinal + 0.15 * math.pow(el + 3.885, -1.253))

toa = nrel * sinal / (R * R)

sr = toa * math.pow(atc, rm)

except (AttributeError, ValueError, OverflowError):

sr = None

return sr

On Dec 1, 2025, at 8:19 PM, John Smith <[email protected]> wrote:

On Tue, 2 Dec 2025 at 14:14, 'Peter Fletcher' via weewx-development <[email protected]> wrote:
No. The logic of the crt code implies that it is a theoretical max value, and the actual values reported in realtime.txt are consistent with this.

What's it based on, latitude?

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Re: [weewx-development] Where does the crt extension get the value for SolarMax?

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