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Vienna would need about 150 km² of solar panels to produce enough electricity
(discuss.tchncs.de)
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.
Whats the total surface area of Veinna rooftops? Square footage of balconys in the city? How nearby is 150km of rural land? How windy is the surronding area?
Im betting you can get 30% there with a mix of rooftop and balcony solar. The rest of the renewable influx can be from local wind or large scale solar farms. Worst case, you build long distance, low loss DC power transmission lines to interconnext to another clean grid within 1000 miles.
Clean power is best when its very local, but it doesnt have to be. As an example, Washington state exports hydroelectric power a 1000 miles to Los angeles, California. It can be done.
EDIT:
Looking into Viennas current power, it looks to get around 60% from hydro, 6% from wind, and currently 6% from solar. Yall are at 72% renewable right now. Some random info docs also put Vienna greenspace at 40% of the city, so that means you have 240km of some kind of private or public building. Knock off 100km for errors sake, and yall may even have roughly 150km of solar area availible, right now.
If you use just 18% of it for solar roofs/balconies, you will get to 90+% renewable. At that point smile and have a glass of local wine from one of your city vineyards. You did it.
I'm not a fan of rooftop solar because it's expensive. I remember reading it's about twice as expensive as large-scale flat-area ("utility-scale") solar arrays, in fact.
Source
I would prefer it if the solar panels were installed on large-scale flat-area patches of land, close to the city. Because of cost and simplicity of maintenance. These factors matter because it makes the whole system easy-to-build and easy-to-maintain, which leads to a much faster solar energy transition, IMHO.
You gain plenty of postivies with that expense. Individual energy independence, system resilency, price stabalization, on and on. Lifespan of solar panels is 30+ years, and payback is often in the 4-7 year range. The numbers work out in your favor for a long time.
But okay, leaving out rooftop solar, and just going grid scale. With the renewable mix your city has now, and assuimg your intial power usage numbers are correct, you need 30% of the 150km to have the city running on 100% renewables. Thats 45 kilometers of nearby land. Seems way more doable than 150km, especially if its 10km here, 15km there, etc. Using a mix of agrivoltaics (farm + panels) and distressed land (old mining/industrial/military/etc) should make that even more viable.
This. Leave people their balcony to enjoy, but I don't know why we haven't plastered solar panels on every roof in the city yet. Even if it's not enough to push us to 100%, it's better than nothing or are we using that space for anything else?
Im more talking about german style plugin balcony solar. The panels are normally hung off the side of the balcony and plugged into an outlet directly:
Im 100% with you on rooftop solar.