Sunday, December 29, 2013

Are People the Problem or the Solution?

Probably both.  At any rate, that is the title of an introductory lecture on demographics from Joel Cohen of Rockefeller and Columbia universities (which I learned of from the Dot Earth blog at the New York Times).  Here's a video
And here is a link to the transcript of the lecture (for those who, like me, prefer to read rather than to watch videos).

I've referred before to the command in Genesis to "fill the earth".  Looking at a graph like this, it seems that this at least is one command that humanity has succeeded in carrying out.

So what next? Professor Cohen makes his case for studying demography as follows:

I’d encourage any freshman, sophomore, junior, senior, adult, high school student—I’m not age prejudiced—anybody who wants to do three things to consider demography.  It’s not the only field that offers these attractions but it does offer them in spades.  It’s really very attractive.  First of all, demography gives you tools and analytical perspectives to understand better the world around you.  That’s understanding.  

Secondly, it gives you equipment to solve problems mentally.  It’s mentally exciting; you really have to use your noggin, and if you’ve got one use it or lose it.  So it’s use it.  And third, it is the means to intervene more wisely and more effectively in the real world to improve the wellbeing, not only of yourself—important as that may be—but of people around you and of other species with whom we share the planet.  

So it prepares you to go out and do something that’s worth doing for a larger good than only yourself.  So there’s an old saying, “If I am not for myself who will be; but if I am only for myself what am I; and if not now, when”?  So now is the time.  Pull up your pants and get to work.

Friday, December 27, 2013


Things run out.  The oil in the ground; the food we can grow; the days of our lives.  The nature of this blog (or maybe of its author) is to focus attention on such limits.  To live wisely is to live within bounds.  "So teach us to number our days", says the psalm attributed to Moses, "that we may gain a heart of wisdom". (Psalm 90:12)

Not just our physical resources run out.  Our emotional strength, our ability to forgive, even to pity.  There are limits to all of these, perhaps closer to the surface than we realize.  In Chesterton's story The Chief Mourner of Marne, the characters claim to "forgive" a crime whose nature they do not understand.  When realization dawns on them, they swing over to the opposite side like a door slamming. "There is a limit to human charity" cries the most sympathetic of them, 'trembling all over'.

Christians (in Chesterton's story represented by Father Brown) make the outrageous claim that there is one inexhaustible force at work in the world: the love of God.  Unlike "human charity",  Love never ends. (I Cor 13:8)  Christmas is the sign and token and proclamation that this love - electing, purifying, creative - has come among us and will persist - patiently, and at great cost - in bringing to fulfillment human beings and the world in which they share.  This love will not let go.  This love will not give up.  This love will not run out.  This love will win.

So, if I speak in the tongues of scientists and activists, but have not love, I am a noisy gong or a clanging cymbal.

And if I have prophetic powers, and my climate model is more accurate than any other; and if I have faith enough for geoengineering, but have not love, I am nothing.

And if I give away all that I have, and live off the grid an an ecovillage, and return my body to the cycle of nature through cremation, but have not love, I gain nothing.

For natural resources may be exhausted; tongues will cease; as for knowledge, it too will pass away.

But love never ends. 

Photo by Flickr user Fiona Shields, licensed under Creative Commons

Saturday, December 14, 2013

Recycling Heat

A lot of water flows to waste each day from the average American home. (Over 300 gallons per day according to the EPA.)  What's more, quite a bit of that water is hot. To heat a gallon of water (from domestic cold to hot temperatures) takes about 750 kilojoules of energy so 100 gallons a day of hot water represents 75 megajoules -  something like 800 watts of energy, all day, every day.

Even if cleaning and reusing the water itself might not be economic in a domestic context (and by the way, that is not so clear - especially as regards using "grey" water to flush toilets) it still makes sense to try to recover some of that heat before it goes down the drain. The most effective, but somewhat high-tech, way to do that would be to store the warm "grey" water somewhere and use it as the source for a heat pump.  However, simpler devices can be effective too. 

For instance, one can fit a shower drain with a heat exchanger like the one illustrated from ReTherm.  The idea is that the cold water supply to the shower exchanges heat with the waste water running down the drain.  The cold supply therefore arrives at the showerhead somewhat pre-warmed, and this reduces the demand on the hot water heater.

It is pretty easy to do an idealized mathematical analysis of the performance of this system.   What one finds is the following.  If a denotes the setting of the shower temperature mixer, then with the usual plumbing arrangement the showerhead temperature is
ah + (1-a)c
where h is the hot supply temperature and c the cold.  With the (idealized) heat exchanger in play this changes to
(2a-a2)h + (1-a)2c
If you know a little calculus you'll see immediately that this means the shower temperature control becomes "twice as effective" when it is at the lower end of its range.  Towards the upper end (i.e. if your shower is as hot as your hot water supply) recycling heat becomes less effective because the relative amount of cold water used is less.
Note  The ReTherm device illustrated is installed in a slightly different way than described above - it preheats the cold water supply to the hot water heater rather than the cold water supply to the shower.  Although this changes some of the details of the above analysis, the overall energy savings are the same. 

Saturday, December 7, 2013

Prius report

With both our kids reaching college age, the time came this spring for an important life transition: we sold our mini-van.  To replace it, we wanted to invest in a hybrid car and after thinking about it for a while it seemed that the standard in that class is still the Toyota Prius, which (amazingly to me) has now been on sale for well over a decade. 

Here's some thoughts after six months.
  • Without trying too hard, it seems easy enough to average 50 mpg in the summer (I've definitely noticed the mileage going down as the cold weather approaches - partly this is because winter gas blends are less energy dense, partly I suspect because the system doesn't have time to reach its optimum operating temperature on a short trip). That would represent a saving of maybe 150 gallons of gasoline per year.  Each gallon of gas is responsible for about 9kg of carbon dioxide emissions (source: EPA) so that means our switch reduces our family's annual emissions by about a ton and a half. Not bad.  But, as I posted before, it pales in comparison with air travel: one round-trip to Europe will release roughly as much carbon dioxide as our Prius-driving will save us in a year.
  • I do think the car has an "educational" effect (at least on me).  Having instant feedback about fuel consumption and whether I am running on electric or gasoline power encourages me to drive more economically.  Moreover, acceleration is kinda leisurely and I find myself adopting a more relaxed driving style that goes with that.  All to the good I suppose.  On the other hand, a negative educational effect is possible too.  Perhaps, driving a car that carries the social "message" of the Prius can insulate the operator inside a bubble of passive-aggressive moral smugness.  A study reported in the New York Times suggests that drivers of "high status" vehicles are less likely to behave courteously towards others, and Prius drivers are up there with BMW drivers in terms of discourtesy.
  • Finally, the obvious point: in the end it is another consumption item (despite my perhaps disingenuous use of the word "invest" earlier). I referred just a moment ago to the "social message" of the Prius, thus providing an excellent example of the prevailing ethos of consumerism: the car we drive is not just a metal box on wheels, the stuff we buy is not just stuff, it is a way of conveying who we are.  Raising consciousness about the environment is all very well: but will it simply be co-opted to generate another niche market sector, which can increase overall sales still further?  This is the "business case for environmentalism".  Who shall deliver us?
Photo from Top Speed review of Toyota Prius Persona,