Some argue that concentrating people into cities will solve the energy woes of our civilization. Let’s see. According to a researcher, city densities in Toronto are up to 63,765 people in the one square kilometre of the St James Town neighbourhood. People in Toronto are one of the top energy users in the world; consuming at the rate of 309.94 GJ per person per annum. This means that the consumption is 1.97e16 J per annum for this one square kiloemetre. That’s a lot.

Energy gets deposited from the Sun. To be sustainable, we should aim to only use energy that we can collect from the Sun. Assuming we have a perfect energy capture device then we could collect 21.4e12 J per annum for this same square kilometre. Wow, this is only about 0.1 % of the consumption. If we were to rely upon plants to capture the energy and then use the plants then we could expect at best 10% efficiency thus we could only expect 0.01 % collection efficiency if we relied upon second hand energy from plants. The sun can’t meet our demands.

Let’s look closer. Given this collection efficiency then for the one square kilometre of St James Town to sustain its energy needs, it would need to collect energy from about 10,000 sq km or about half the area of Lake Ontario. Let’s expand the area to all of Toronto. Its population is 5,583,064. Given the calculations of above then it would need 59,050,000 km2 of land set aside to sustainably collect energy for their needs. This area is about 6 times to total area of Canada. How sustainable do you think that this is? Do you think that concentrating people into cities will solve our problems?