My dear friend and Elmer Bonnie replied to a question on one of my posts. I thought it would be incredibly useful to share with any of you considering deploying portable solar panels out in the field.
Why is this important? One of the questions I see most often is, “why does Julian use/need a 120 watt solar panel in the field?”. Bonnie does a great job of answering this question. She also included some supporting information and illustrations from a NASA study.
Enjoy the read
Solar energy versus location
Considering Julian’s arctic circle location, he needs roughly twice the solar panel rated capacity than we do in continental USA.
It also depends a lot on cloud cover and sun exposure time (length of day).
When I was operating on expeditions close to the equator (Borneo and Peru) I was amazed at the “improved output” of my solar panel, compared to California.
Using the same solar panel, in the arctic circle it would have about 40% of the solar power we would get compared to the equator.
The greater thickness of the atmosphere at higher latitudes, due to lower angle of sun, attenuates the sun’s rays.
The peak energy received at different latitudes changes throughout the year. This graph shows how the solar energy received at local noon each day of the year changes with latitude. At the equator (gray line), the peak energy changes very little throughout the year. At high northern (blue lines) and southern (green) latitudes, the seasonal change is extreme. (NASA illustration by Robert Simmon.)
The total energy received each day at the top of the atmosphere depends on latitude. The highest daily amounts of incoming energy (pale pink) occur at high latitudes in summer, when days are long, rather than at the equator. In winter, some polar latitudes receive no light at all (black). The Southern Hemisphere receives more energy during December (southern summer) than the Northern Hemisphere does in June (northern summer) because Earth’s orbit is not a perfect circle and Earth is slightly closer to the Sun during that part of its orbit. Total energy received ranges from 0 (during polar winter) to about 50 (during polar summer) megajoules per square meter per day.