The MIT Senseable City Lab recently asked: How does urban morphology affect the solar potential of cities? If you assume that transparent photovoltaic cells are on the way and that building facades are soon going to become a place where we generate solar energy, then this is actually a pretty interesting question. Are some built environments naturally better suited than others?

To answer this question, they looked at the "urban surfaces" of ten cities, including New York, Singapore, Toronto (pictured above), Hong Kong, Paris, as well as others. These surfaces included roofs, facades, and ground planes.

What they, not surprisingly, discovered is that you need a lot of exposed facades to get the numbers up. And so the cities that come out on top in terms of annual solar irradiation are cities like New York and Singapore. They have a lot of tall buildings, but they also fluctuate in height, giving greater exposure to the facades.

All of this is potentially relevant because -- if building facades become a big deal for solar -- it could start to inform how we plan our cities. In fact, I would go so far as to bet that, over the long-term, solar energy will have a greater impact on urban morphologies than this current pandemic.

Image: MIT Senseable City Lab

The Financial Times published the following chart last night. It shows the cumulative number of COVID-19 cases around the world, across the number of days since the 100th case in that particular country. The message here is that most western countries appear to be on a similar trajectory. (The grey dotted line represents a 33% daily increase.) Whereas in Asia, and in particular Hong Kong and Singapore, they have seemingly managed to slow the spread.

Now, there are a number of possible explanations for the outliers; everything from stricter quarantine rules to more rigorous testing. There's also an argument that Hong Kong and Singapore were better prepared as a result of the SARS outbreak in 2002. (More on these explanations, here.) But the other factor at play seems to be climate.

A recent study (by Jingyuan Wang, Ke Tang, Kai Feng, and Weifeng Lv) has concluded that, like the flu, the transmission of COVID-19 appears to be significantly impacted by both air temperature and relative humidity. In their research, they looked at the reproductive number (R), or the severity of infectiousness, for all Chinese cities with more than 40 cases between January 21 to 23, 2020. (Large-scale government interventions began on January 24, 2020 and would have therefore skewed the numbers.)

What they found was that for every one degree Celsius increase in temperature and every one degree Celsius increase in relative humidity, the reproductive numbers drop by 0.0383 and 0.0224, respectively. Air temperature, in other words, has more of a positive impact on containing spread than relative humidity -- which feels right. That is also apparent when you look at the above charts. Take note of Korea, Iran, and Italy near the top left corner of the temperature chart.

If you'd like to download a full copy of the research paper, click here.

At the beginning of this year, Singapore expanded its preschool subsidies and improved its support for assisted reproduction and fertility treatments. The goal: more Singaporean children. According to the World Bank (via the Wall Street Journal), Singapore has one of the lowest fertility rates in the world at about 1.14 children per woman as of 2018. This is down from about 3 in 1970, when the government was actually worried about the opposite problem -- too many children.

Of course, this trend is not unique to Singapore. This is generally the way the winds are blowing in the developed world. Young people are spending more time on education, career, and travel. And they're delaying marriage (or not getting married). On top of this, family-sized housing has become fairly expensive in most big cities. The fastest solution is to ramp up immigration, but many countries, including Singapore, have concerns about what this does to the "national identity."

So there seems to be a preference for throwing money at the problem and promotional material with slogans like this one: "Have three, or more if you can afford it."

Chart: WSJ