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.
I wonder how much rooftop space in Vienna could be cannibalized for solar panels.
This is a very good point. Also parking garages
yeeah, i had that thought too. thing is, it’s significantly easier to build solar parks on flat ground than on rooftops, simply because of installment cost.
i remember seeing a plot that says that installing rooftop solar is about twice as expensive than flat area solar (for the same kWp), but i can’t find the diagram anymore, after looking for it on the internet for 5 minutes.
Vienna has around 68km² of roof surface.
But there are two nice facts that make the whole calculation easier:
- Resources used in a city don’t need to be produced inside the city. Imagine we had to grow all the crops and lifestock consumed in a city also inside of the city borders. Or gas, oil, coal, water or any other resource. Cities can only exist by importing resources from the outside. And luckily power cables are a thing, so it’s quite easy to import electricity from outside of the city.
- Solar isn’t the only kind of renewable energy. The area north east of Vienna is dotted with wind turbines. There’s a huge amount of hydropower all over Austria. In fact, 87.5% of the electricity generated in Austria is generated by renewable energy, and the remaining 12.5% are pretty much only to cover the times when renewables don’t output enough power.
So the whole point is kinda moot. If we would put solar on all rooftops in Vienna, it would be enough to cover for the entire remaining fossil-based electricity generation in Austria if we had the means to store that excess energy.
I think your calculations are off. I think that you’re including the number for everything including manufacturing etc.
If you’re just powering a home, the average American household averages around 11 megawatt.
Megawatt-hours hopefully, because if it was 11 MW no wonder we have global warming :D
It’s 11 MWh per month, a more reasonable 0.01507 MW.
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.
within city limits
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.
yeah i included manufacturing because i was like “most big factories are in or close to big cities, because that’s where the workforce lives, so it makes sense to build factories there. and factories need energy.”
ofc small variations in power are a given, because you have things like electricity being more efficient than oil, so you need fewer kWh, and such.
So combine it with other renewable energy, you know, how it’s usually done.
Imagine how far down they would have to drill to find oil in Vienna, though.
Imagine how deep the mine would have to be to find coal under Vienna.
Vienna isn’t even the worst place for solar power. Consider places like Ireland, Scotland or Sweden for example. No wonder why wind, hydro or even tidal power suddenly begins to make a lot more sense. IMO, solar really begins to make sense in Spain, Italy, Greece and Turkey. Those places actually get some decent sunshine. Using solar power in Austria should be ok, but it’s not great by any means.
Nearby mountains probably get in the way of building large solar facilities. Maybe you could combine solar power with farming. The panels can provide some shade to more sensitive plants.
See also: Solar Atlas
Sidenote: Iceland and the northern half of Norway, Sweden and Finland aren’t even on the map. I guess Solar Atlas is trying to tell you that you don’t need a fancy map to know that building solar in places like that is a waste of money.It depends on the size and geography of your installation. Everywhere short of the arctic circle, solar is more dependable than wind for a single home size or smaller installation. Wind and tidal power come in when you can throw up a bunch of 300m windmills to power a town. Wind in particular needs a very large area, and multiple disbursed areas are even better.
Does it need to be in the city, though?
Also for reference from Google ai: For global electricity needs: An area of approximately 40,000 to 55,000 square kilometers (about 15,000 to 21,000 square miles) could theoretically generate the world’s total electricity consumption. This is less than 1% of the total land area of the United States. For total global energy needs: The estimated area is around 497,000 square kilometers (about 192,000 square miles), roughly the size of Spain. This covers the total projected energy demands, including converting non-electric needs (like transport fuel) to solar-generated power.
The thing is it doesn’t need to be produced in the city. Cities are notoriously population dense. If you take into account the energy usage of the surrounding rural areas and the land area that they have, it starts to be a tiny proportion of all of the land area of a country, rather than a city.
yeah it’s sth like 1% of humanity’s total land area usage (i did that math last week). 97% of humanity’s land area usage go to agriculture
And the nice thing: mixing solar panels and agricultural land use can increase crop yields depending on the plant!
