# From weatherstation data to solar irradiation on specific surface

• BM99
In summary, the author is trying to calculate the irradiance on a window in a particular orientation using solar energy conversion factors.
BM99
So, at home I have a weatherstation which measures solar irradiation in the east, south and west in lux. I can read in these measured sensordata. From these measurements, I would like to calculate the solar irradiance on my windows. The solar energy formulas could help me with that. The work of Soteris A. Kalogirou explains these phenomens in Chapter two (see http://1.droppdf.com/files/AvIdq/solar-energy-engineering-processes-and-systems-2nd-ed-2014-.pdf).

So for example, I have a window which (which has a slope of 90°, vertical) is oriented 20° from the south (clockwise is positive). I know what the incidence angle is and I know that I should use the formule for 'Total radiation on tilted surfaces' which is explained on page 100-101 in the pdf. Starting from the total irradiation in the east, south and west known from my weatherstation, does someone know how to use these measurements to calculate the total irradiance on my window in W/m²?

I hope this explanation is clear enough!

Converting from lux to illuminance is not obvious here due to the large amount of (spectrally) non-visible sunlight. Fortunately, sunlight is important enough that conversion factors have been developed: the solar constant is, on the Earth's surface, approximately 1 kW/m^2 and also 128 klx. That conversion factor definitely won't work if the sky is overcast and is also less accurate as the sun moves off zenith.

For fun, you may be able to pseudo-calibrate your weatherstation by sending 'direct sunlight' into one of the ports and then use it on clear days; I'd be curious what your results are. Check the user guide- don't damage the optical detector by doing this.

For example- use a mirror to send noontime sunlight into a port, and the weatherstation tells you that it's receiving (say) 100 klx so you have a 'weatherstation calibration factor' of 1.28. Then, the next day (or whenever), your station pointed in the direction of your window gives a reading of 50 klx, which means your window actually receives 64 klx = 0.5 kW/m^2.

good luck!

Andy Resnick said:
Converting from lux to illuminance is not obvious here due to the large amount of (spectrally) non-visible sunlight. Fortunately, sunlight is important enough that conversion factors have been developed: the solar constant is, on the Earth's surface, approximately 1 kW/m^2 and also 128 klx. That conversion factor definitely won't work if the sky is overcast and is also less accurate as the sun moves off zenith.

For fun, you may be able to pseudo-calibrate your weatherstation by sending 'direct sunlight' into one of the ports and then use it on clear days; I'd be curious what your results are. Check the user guide- don't damage the optical detector by doing this.

For example- use a mirror to send noontime sunlight into a port, and the weatherstation tells you that it's receiving (say) 100 klx so you have a 'weatherstation calibration factor' of 1.28. Then, the next day (or whenever), your station pointed in the direction of your window gives a reading of 50 klx, which means your window actually receives 64 klx = 0.5 kW/m^2.

good luck!

I will try that as a validation of my estimation. Somehow, I'm convinced that with the measured total radiation in the three orientations, I could convert these to a total radiation on a window in any orientation. Well maybe not the total radiation, but rather the beam radiation as I suppose the diffuse and ground-reflected solar radiation to be zero. The following formulas should do it i think considering I know every concerned angle.

## 1. What is a weather station?

A weather station is a facility equipped with instruments and sensors that collect data on atmospheric conditions such as temperature, humidity, air pressure, wind speed and direction, and precipitation. This data is used to monitor and predict weather patterns.

## 2. How is solar irradiation measured?

Solar irradiation is typically measured using a pyranometer, which is a device that measures the amount of solar radiation reaching a specific surface. The unit of measurement for solar irradiation is watts per square meter (W/m²).

## 3. What is the specific surface in relation to solar irradiation?

The specific surface refers to the area on which solar irradiation is being measured. This could be the surface of a solar panel, a rooftop, or any other designated area. It is important to specify the specific surface when measuring solar irradiation as it can vary depending on the location and purpose of the measurement.

## 4. How does weather station data contribute to calculating solar irradiation?

Weather station data, such as temperature, humidity, and air pressure, are important factors in calculating solar irradiation. This data is used to determine the amount of solar radiation that reaches the specific surface, taking into account any atmospheric conditions that may affect the measurement.

## 5. What are the applications of using weather station data to calculate solar irradiation?

The data collected from weather stations can be used to accurately calculate solar irradiation, which is essential for various applications. This includes predicting solar energy production, assessing potential locations for solar panels, and monitoring the impact of weather on solar energy systems.

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