The ideal direction to maximize the electricity production of a solar panel in Copenhagen is south and 3° degrees east (read more in my previous blog post). Solar panels in the northern hemisphere should get the most sun when facing due south, so now I am wondering what factors cause that 3° difference.
I use NREL’s SAM model to simulate solar production under different climate conditions.
Temperature
Most electronics operate more efficiently in cold temperatures and solar panels are no different. The outdoor temperature is cooler in the morning before the sun warms up the ground and air. This pushes the ideal angle of a solar panel east so it can get more sun when it can produce electricity more efficiently.
Copenhagen has a mild climate without large temperature variations:
The average temperature between 6AM and noon is 10.56°C and the average temperature between noon and 6PM is 10.95°C. The same solar panel produces 0.14% more electricity at 10.56°C than at 10.95°C (as simulated by NREL’s SAM). Even that small temperature increase can make an impact on solar panel production, so temperature is a contributing factor pushing the ideal solar angle east.
Wind Speed
Wind can cool off solar panels through more efficient heat transfer with air. Wind is caused by the sun heating up land faster than water, so I would expect to see hourly trends in wind speed.
The mornings are windy in Copenhagen. The average wind speed between 6AM and noon is 4.66m/s and the average wind speed between noon and 6PM is 4.36m/s. The same solar panel produces 0.18% more electricity with wind blowing at 4.66m/s than at 4.36m/s. Copenhagen’s wind increases solar panel production efficiency in the morning and pushes the ideal solar panel angle east.
Cloud Cover
Clouds can block sunlight before it reaches solar panels. Clouds are caused by the sun evaporating water, so I would expect to see hourly trends in cloud cover.
The mornings are cloudy in Copenhagen. The average Direct Normal Irradiation (DNI) between 6AM and noon is 190.18W/m2 and the DNI between noon and 6PM is 190.38W/m2. The same solar panel produces 0.06% more electricity at 190.38W/m2 than at 190.18W/m2. Copenhagen’s clouds decrease solar panel efficiency more in the morning, but this effect is not significant.
As a side note it is much cloudier in the winter, so the complaints about dark winters are justified:
Conclusions
There ARE a lot of factors that are not discussed here because they do not have hourly trends. One interesting factor I did not consider that does have an hourly trend is wind direction. The model I used (NREL’s SAM) to simulate solar panel production does not take into account wind direction. But I would expect better panel cooling when blowing over the face of the panel than the sides.
The dominant factors causing the ideal solar panel angle to be shifted east in Copenhagen are temperature and wind. Cloud cover pushes the ideal angle west, but it is not as strong.
I hope you learned something about the impact of climate on solar production!
Very cool!