MAY 22, 2018 POSTED BY: ANDREW COOK CHARGING WITH NATURE

The Disadvantages of Solar Panels - They're Not As Bright As They Seem

Solar panels are a great solution for generating energy in permanent deployments, where sunlight is something that you can depend on.

However for campers and hikers looking to capture energy in the wild, solar panels may not be the best choice. There are many disadvantages of solar panels that can affect the performance. Let's take a look!

The Angle of The Sun

Solar panels work the best when pointed directly at the sun. Unfortunately, this optimal angle is changing throughout the day as the earth rotates around the sun. If you had your panels perfectly set up at 1:00pm, by just 1:30pm your charge rate would be falling. This can be a huge disadvantage for solar panels.

This means that for hikers who carry panels on their backpacks, achieving peak charge rates is an impossible task. Alternatively, nobody wants to stay at camp to realign their solar panels during the day’s brightest hours! Check out this video from Linus Tech Tips to learn more.

Peak Efficiency

A solar panel can really only operate for about 4-6 hours per day around “solar noon”. During the winter months this window gets reduced further. This is because as the sun gets lower in the sky, there is more atmosphere for the suns rays to pass through (and more air particles to bounce the rays around) reducing the amount of solar energy that reaches the panel.   This time-frame shrinks the window where you could be actually using the devices you brought with you. Instead of exploring with your GPS and camera during the brightest hours of the day, you could be stuck charging them.

Weather

Weather is another major factor that can be a huge disadvantage for solar panel users. Clouds, rain, snow - essentially any conditions aside from blue skies dramatically reduce the efficiency of panels. Even objects on the ground can affect charge rates such as dust and dirt, or shade from tree-cover. We’ve spoken with outdoor enthusiasts who have had their trips dangerously extended, because bad weather has inhibited their ability to charge their satellite phones. For trips of any length, a dependable power source may be a better alternative.

Solar panel ratings can also be misleading. Solar panels are rated according to Standard Test Conditions (STC). This is done in a very controlled environment in the lab so that it is easier for comparison.

The amount of light hitting the panel is measured in watts/meter^2 and for STC the panel is subjected to 1000 Watts/meter^2. A value that is difficult to achieve on the surface of the earth. As well it assumes that the light is directly overhead, with one atmosphere of air above and the temperature is controlled at 25 degrees Celsius.

Conclusions

So what does this all mean? With all of the variables described above (sun angle, clouds, time of year, temperature) it means that a panel will probably never reach its rated wattage in real world conditions. Typically you should expect 60-70% of the panels rated power output during optimal periods of the day (sun higher in the air, no clouds) - which is about 4-6 hours / day depending on time of year. Outside of that range, performance drops dramatically!