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.
Uhm 30MWh? That can’t be right…
In the past 5 years on average my home has used around 3.5MWh per year. We live here with two persons so that would be around 1.75MWh per person per year. Now let’s say we are very efficient and say the average person would need about 2.5MWh per year, that’s still one order of magnitude off from your number.
I can’t believe the average person in Vienna uses that much energy, especially not those living in apartment buildings.
Edit:
Ah they include everything in that graph, so the entire energy requirements of the nation divided by the population. So this includes agriculture, industry, transportation (including gas for personal vehicles) etc.
This is a pretty unfair comparison, as the people in the city would only need to generate the power for living there. Industry can have its own power sources. And in my experience many farmers have huge solar installations on top of their huge ass barns. They produce so much energy they often have their own energy infra building next to their property.
So if you include all of the energy for stuff that isn’t living, you should also include all of the surface area for stuff that isn’t living. In other words, way more than just the city itself.
And getting 100% of that energy from solar probably isn’t the best idea, it should be a mix of sources to make sure power is always available.
Yeah my reasoning was that big industrial (manufacturing, not agriculture) centers are often close to cities so the energy is consumed close to the city :) So it counts as “city consumption” to me.
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.
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.
That’s definitely a lot of solar panels!
I really don’t understand why fields are used for solar panels, instead of parking lots
Por que no los dos? In the case of germany, 60% of agricultural Land is used for feeding live stock. 10% is used for “energy plants” - With a yield ~50 times lower than an equivalent pv-area. You’d need 5% of all of the agriculturally used Land to be fitted with solar panels to fulfill the electrical energy demand of germany. It’s frankly just stupid that we don’t try to go for that.
Don’t know the numbers for austria, but i assume they are simmilar.
But his question was why not use parking lots first? It’s already dead ground for nature, has the additional advantage to keep the cars cool in the shade and the electricity is produced closer to where it’s needed.
