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Vienna would need about 150 km² of solar panels to produce enough electricity
(discuss.tchncs.de)
Yes, i did think about this in the shower.
Just to put things into proportion:
This is vienna. Vienna has an area of around 400 km².
And the blue area is the area that would have to be covered by solar panels to produce enough energy for the whole city:
Source: I did the maths myself. I assumed that per person around 30 MWh of energy/year are needed. Data for this: our world in data, energy usage per person. It's well known that 1 m² of solar panel produces around 200 Wp and that's 200 kWh/year. So you need about 150 m² of solar cells per person. Vienna has about a million inhabitants, so that makes 150 km² of solar panels approximately.
Its not super wrong to include external costs as well, but it definitely explains the crazy estimate they got to.
The most misleading part is that this is cherry picking a dense city, and implying all power generation needs to be within city limits. 3 out 11 thermal power stations in Austria are in Vienna, the rest are outside of the main city.
it was more a size comparison, i didn't really mean to say that it has to be within city borders. cables can cross political borders, of course.