In 2020 I wondered if I could run my blog on solar power, being inspired by Low-tech Magazine, doing the same thing (but better)1. The answer was ‘yes’, but only through spring and summer.
I live in an apartment complex in The Netherlands and my balcony is facing east. This means it only receives direct sunlight from 16:00 onward during spring and summer. Most of the time, the panels only get indirect sunlight and therefore generate just a tiny fraction of their rated performance. The key issue is not solar, but the east-facing balcony (it should ideally be facing south).
original solar panel
It’s fair to say that my experiment isn’t rational because of the sub-optimal solar conditions. Yet, I’m unreasonably obsessed by solar power and I wanted to make it work, even if it didn’t make sense from an economic or environmental perspective2.
When I wrote my blog about my solar-powered setup, I was already on my second iteration: I started out with just a 60 Watt panel and a cheap $20 solar controller3. That didn’t even come close to being sufficient, so I upgraded the solar controller and bought a second panel rated for 150 Watt, which is pictured above. With the 60 Watt and 150 Watt panels in parallel, it was still not enough to keep the batteries charged in the fall and winter, due to the east-facing balcony.
A Raspberry Pi 4B+ consumes around ~3.5 Watt of power continuously. Although that sounds like a very light load, if you run it for 24 hours, it’s equivalent to using 84 Watts continuously for one hour. That’s like running two 40 Watt fans for one hour, it’s not insignificant and it doesn’t even account for battery charging losses.
So 210 Watt of solar (receiving mostly indirect sunlight) still could not power my Raspberry Pi through the winter under my circumstances. Yet, in the summer, I had plenty of power available and had no problems charging my iPad and other devices.
As my solar setup could not keep the batteries charged from October onward, I decided to do something radical. I bought a 370 Watt4 solar panel (1690 x 1029 mm) and build a frame made of aluminium tubing5. Solar panels have become so cheap that the aluminium frame is more expensive than the panel.
Even this 370 Watt panel was not enough during the gloomy, cloudy winter days. So I bought a second panel and build a second tube frame. Only with a 740 Watt rated solar panel setup was I able to power my Raspberry Pi through the winter6.
I didn’t create this over-powered setup just to power the Raspberry Pi during the winter. I knew that solar performed much better during spring and sum
