Urbanist dreams and urban realities

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The argument that increased urban density has very significant climate benefits has been well made by Edward Glaeser, David Owen and others. The US writer Alex Steffen has joined the ranks of those with books out arguing for promoting density, with the view that we simply cannot reduce emissions enough through low carbon energy alone. Urban density will do the trick. He appears to believe that cities can reduce energy use by 90%, but only seems to provide hand waving explanations of how this is possible.

However, a statement he made in a recent interview to The Atlantic is reflective of a common problem with solutions to climate change: the unwillingness to do basic arithmetic.

for example if you have a more distributed energy system, you can have the energy system in one neighborhood go down, and energy systems in other neighborhoods remain unaffected. By distributing things, you make it possible for disaster to strike, and not have everything go down if something fails.

Now, presumably Steffen doesn’t have neighbourhoods being powered by small modular reactors or gas plants with CCS in mind. So, he must somehow believe that neighbourhoods can be powered entirely by local renewables, with perhaps some yet to be invented storage technology providing back up. A fundamental problem however is that his vision of high urban density and localised energy production are in conflict.

Consider New York City. This city certainly fits the category of high urban density. However, think about what would happen if New York tried to power itself entirely from renewables within city limits: constant blackouts. This is a simple consequence of its high population density and the laws of physics. An author such as Steffen who claims to have thought deeply about climate change, urbanisation and energy really ought to be aware of this. So, why can New York not power itself from local renewables?

A little back of the envelope arithmetic.  Now, from memory,  I know that UK energy use works out at about 1.25 Watts per square meter. The United States as a whole has about double the per capita energy use of the UK, however New York is about 30% of the US average. Factoring in the difference between UK and New York population densities would give us a ball park figure of something like 30 Watts per square meter in New York.

That’s the demand side. Can we possibly get this from renewables? Wind power is clearly off the cards in New York. But, what if we covered every inch of New York in solar panels. We need 33 Watts per square meter. This is about double the energy density you could get from solar thermal in the North African desert. New York is clearly not getting this. A ball park maximum (and someone correct me, if I am wrong here) for ideally placed New York solar panels would be 10 Watts per square meter, already just one third of total demand. Now, how much of New York could you actually cover in solar panels. Let’s go with one third as a rather optimistic top estimate. All of a sudden you are down to around 10% of energy needs coming from solar, with the real figure likely to be a great deal lower.

So, it seems impossible to argue that a dense urban area could power itself from distributed power, and Steffen’s imagined urban areas of the future are nothing but the imaginings of a wishful thinker.

Densely populated cities will have to be powered largely by energy pumped in from outside, be it from windfarms or nuclear power plants. This much ought to be axiomatic. Yet, here I am writing this.


4 thoughts on “Urbanist dreams and urban realities

    John Russell said:
    December 3, 2012 at 10:10 am

    Some of the arguments for dense urban living seem to me to come very close to the arguments for rearing animals in battery cages. While city living can be fun for the gregarious, young and affluent (the typical proponent of these arguments, in my experience), it’s the idea of hell for — a guess — a significant proportion of the population. Personally, living in a city would destroy me psychologically.

    All these ideas miss the point that a highly-insulated, low-energy, environmentally-sensitive house can be built just as easily on its own as it can cheek-by-jowl in a city high rise (and without any use of concrete). OK, transport is an issue, but then that presupposes that people commute distances from where they live to where they work. The key to reducing energy use is to develop workplaces and living places very close together; and to make both places so attractive that people don’t feel the need to travel for their entertainment or enjoyment. I can go for weeks without moving more than a mile (on foot) from the place I live. If that place was in a city, I’d top myself.

    As we’re talking long-term systemic change here, a major initiative to limit population growth would be much more acceptable, and cheaper, in my opinion. Of course that would completely screw the economists who rely on constantly growing populations to make their ideas work. There lies your problem.


    Adam said:
    December 5, 2012 at 2:13 pm

    Ok, so as I mentioned on Twitter, I’d agree that these excerpts and interviews could use more data and calculations, though that could always be editors given we’re not talking about the book itself. It does seem like you’re talking past each other almost to the point of being a strawman though.

    Eg, energy efficiency improvements would surely be part of any radical energy usage cut, with some work in NYC already underway. 

    Increasing density must have a negative correlation with distributed potential production per capita beyond a certain point. Basically each person has less land to install generators on. It’s not true for the whole land per person axis though. Eg in a city under construction a typical suburban lot may be reduced in size by removing the garage, and density increased, with some proportion of the land dedicated to generation.

    That threshold is pretty much passed at central New York densities. Another storey on an apartment block doesn’t add any more power generation. But even for New York, the effective megalopolis spans far beyond current political boundaries, even across state lines. And much of that space is not so densely populated. It does raise the interesting possibility of climate-based optima. Maybe temperate New York gets more benefit from density due to heat efficiencies and lack of on site capacity, but Phoenix can support more of a yeoman homeowner solar generator model.

    Lastly on ruggedization and distribution. It seems an extreme reading of that quote that every borough has to be self-sufficient. Surely some extra grid and generation redundancy would allow any single borough to lose power / generation without impacting all others?

    Feeling less guilt about the lack of numbers in this comment as neither of us have seemingly read the book yet …


    neil21 (@neil21) said:
    January 30, 2013 at 7:48 pm

    Following up from twitter, and agreeing with Adam here. Sounds like two exaggerated straw men:
    1. NYC as the sole definition of density, when instead walkability (i.e. daily needs don’t require emissions; also some insulation benefits from building proximity) can be achieved at less intense levels. Mostly anywhere built before 1950, and almost certainly before 1850 would fit this. Obviously lots of European and Asian examples. Kitsilano in Vancouver isn’t perfect, but is well-liked and would work for me.
    2. Every borough must be self-sufficient: a bit extreme. Instead, ensure policies allow islandable microgrids to be quickly and easily built and approved. There’s no getting rid of the grid, and your renewables penetration concerns are valid (although isn’t there some aggregation smoothing that might help?).


    Robert Wilson said:
    January 30, 2013 at 8:47 pm


    You don’t really seem to be responding to my post at all. The post is in response to the opinions Alex Steffan appears to hold. Though when I pressed him on Twitter he denied holding the views he seems to express.

    Also my opening sentence makes it clear I accept the argument that urban density is good for climate change. (and I have said this elsewhere https://carboncounter.wordpress.com/2012/11/18/switzerlands-green-immigration-referendum/) I am only saying that Steffan is vastly exaggerating its potential.

    Your point about New York does not seem valid. Many European cities are much denser, e.g. Paris and Barcelona. Kitsilano also appears to only be about 30% less dense than NY.


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