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Comment by fastbeef | Hacker News Reader

A common misconception. Even in northern Sweden, which is above the arctic circle, you can still generate ~80% of the energy that Southern Europe generates.

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This is fascinating if true. Do you gave any sources, I'd be really interested in reading more on the matter.

This gives a good overview. What people miss is that during the summer the sun is up all the time. (In the winter, not so much.) And average cloud cover is also accounted for.

http://re.jrc.ec.europa.eu/pvgis/countries/europe/EU-Glob_op...

PVGIS is an excellent tool and I have been using it for years!

Thanks! That is quite surprising, and very encouraging.

It seems that solar is a very good overall fit for even most of the world, and once the tech is good enough to be used in huge numbers the differences can probably be compensated with other, local power sources (like hydro in Scandinavia, which is huge there).

Do I understand correctly that the wishful thinking value of 75% photovoltaic conversion efficiency is plotted in the diagram?

It means the conversion factor of yearly yield in kWh to installed PV in kWp. "Yearly sum of solar electricity generated by 1 kWp system". It's not about the physical PV efficiency.

The 75% performance ratio represents system losses not module efficiency. So a system rated at 1kW(peak) which may be 5-6 square meters in size, and which is exposed to annual sunlight of 1200 kWh/m2 might only produce 900 kWh of usable power.

So efficiency has to do with the rated power per surface area and the performance ratio reflects all the system electrical and environmental factors that reduce the amount of usable power below what would be expected based upon module ratings and annual sunlight exposure.

That diagram suggests Northern Sweden to Southern Europe is 50%, not 80%, which sounds more plausible.

> What people miss is that during the summer the sun is up all the time. (In the winter, not so much.)

It sounds like these two effects should cancel each other out. Are you saying that people take winter into account but not summer?

Depends on what you're using it for. A common use-case is cottages that run off the grid, which are only used in the summer half of the year anyway.

But cold panels produce more power.

See the comment from bjelkeman! I don't have any "hard" sources but reserarching solar panels for myself by hanging around Swedish solar forums and noticed people way up north still get a good yield from their panels.

Most of the energy comes from ambient light, direct light is best of course but not strictly needed

Nitpick: Only the northern tip of Sweden is north of the polar circle. But yeah, Sweden is pretty dark anyway.

One factor that helps is that solar cells become less efficient if temperature goes up (https://www.thegreenage.co.uk/article/the-impact-of-temperat...)

This is a good introduction & has excellent maps. http://solarinsolation.org/tag/map/page/2/

Here in Maine your solar panels are going to be covered with snow 5 months of the year, so the power production in the winter can't be very significant.. It's one thing to store energy between night and day and it's another thing to store energy between summer and winter. Don't get me wrong, I think solar is the future, but not sure how to make it work up north.

In curious about this, does it snow so heavily for 5 months there would be no way to clear the panels?

I mean they're installed at an angle to start with so how does the snow build up? Could panels not be designed with inbuilt defrosters?

The snow could be cleared off with a shovel, but then you have to either pay someone to do it in the case of industrial solar, or in the case of home solar, go up on your roof when it's covered with ice and snow, not the safest maneuver. Defrosters might be possible but that might use more power than the panels generate. You'd have to raise the temperature of the panels to above the freezing point of water, which might be a change of 20 or 30 degrees F on really cold days. Some years are worse than others- 2014 was really bad, I didn't see bare ground until late April.

I live in Massachusetts, and have 37 250 watt panels. Snow isn't an issue. The panels generate a little bit of resistive heat, which means snow typically doesn't stick. If it's snowing so heavy, and is so cold that the panels do get covered with snow, the snow melts and slides off within an hour or so.

In July my panels make 1300 kwh and in December and January they make 300 kwh, mostly because of the angle of the sun and the length of the time above the horizon. I also have significant southern tree cover, so my production is not optimal for my area.

It's a combination of the 80% output and the cheap local hydro power which makes it not attractive.

It's true that power here is cheap (~0.1€ per kWh). However, since most electric companies buy back what you overproduce you can get an installation that covers your whole years supply and have it paid of in 7-10 years.

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