cities. physics. food. environment. fatherhood.

I needed to buy more gasoline for the car today, and I decided to see how long it took to fill the tank. I bought ten and a half gallons of gas, and it took 70 seconds to fill it up. Although filling up a gas tank is something that millions of Americans do every day, it’s really remarkable when you stop and think about the energy transfer going on.

Gasoline has, approximately, 113,000 BTUs per gallon.¹ One BTU is 1055 Joules. So I transferred 1.25 Billion Joules in those 70 seconds, which is a rate of 17.9 megawatts. When you consider that you spend less than two minutes pumping the same amount of energy you burn in four hours of driving, it’s not surprising that you end up with such a high power. What’s more interesting, I think, is to contemplate the rather fundamental limits this puts on plug-in electric cars.

Internal combustion engines, according to Wikipedia, are only about 20% efficient, which is to say, for every 100 BTUs of thermal energy consumed by the engine, you get 20 BTUs of mechanical energy out. This is, in large part, a consequence of fundamental thermodynamics. Although electric motors can be pretty close to perfectly efficient, a similar thermal-to-electric efficiency hit would be taken at the power plant.

Let’s consider, then, that we want a similar car to mine, but electric. Instead of 1.25 gigajoules, we need to have 250 megajoules. Battery charging can be pretty efficient, at 90% or so, which means we’d supply 280 megajoules. If we expect the filling-up time to be comparable to that of gasoline cars–call it 100 seconds for simplicity–then we’d need to supply 2.8 megawatts of power. At 240 Volts, which is the voltage we get in our homes, this would require 11700 amps; if you used 1000 Volts, it would take 2800 amps. Although equipment exists² to handle these voltage and current levels, it is an understatement to say that it cannot be handled as casually as gasoline pumps are handled. Nor is it clear that any battery system would actually be able to accept this much power.

A linear relationship exists between the power requirement for filling, and the vehicle range, the vehicle power, and the time for a filling. If you’re satisfied with half the range of a regular vehicle, for example, you could use half the filling power. Let’s imagine that you’d be happy for the filling to take ten times as long as with gasoline, or 1000 seconds, just under 17 minutes. At this level, you’d need 280 kilowatts of power. If battery charging is 90% efficient, that means 10% of the power is going to be dissipated as heat, which in this case would be 28 kilowatts.

For comparison, a typical energy consumption rate for a home furnace is 100,000 BTU per hour, about 28 BTU per second, or 29.3 kilowatts. Which means that the waste heat dissipated during charging for the example–of a 1000 second fill for a vehicle with similar range and power as a modest gasoline powered sedan, at 90% charging efficiency–is as much as the entire output of a home furnace.

No wonder overnight charges are the standard.

1. Summer and winter blends have slightly more and less, respectively. [↩]
2. think about how large the wires would need to be [↩]

Part 1 of this series looked at the beginnings of the DC government’s effort to expand the transit network. We left off in the Spring of 2005, having been to several meetings and having received several newsletters.

The study finishes

The final project newsletter, Fall 2005, and an “Executive Summary“ of the whole project were presented to the public at a final meeting, held September 29, 2005. For transit enthusiasts following the project, the end results were disappointing and frustrating. Instead of a visionary transformation of mobility in the District, the final recommendations proposed a meager streetcar buildout that, despite its modest size, would take 25 years to build. The report was frustrating because it relied on tortured reasoning that bordered on downright dishonesty, it used self-contradictory and mutually inconsistent reasoning, and offered little more than poorly-defined chimeras wrapped up in wishful thinking.

Added to the project was “Rapid Bus,” as a lower-class technology mode, joining streetcars and “bus rapid transit.” Modes were assigned to routes. The newsletter used separate streetcar and “bus rapid transit” assignments, while the executive summary lumped these together as “premium transit.” In the newsletter, streetcars got a handful of routes: the crosstown Georgtown to Minnesota Avenue route; the north-south Georgia Avenue route, which would end at K street; a Union Station to Anacostia via Eastern Market route; an M Street SE/SW route, and a short Bolling AFB–Pennsylvania Ave route. A bit of “bus rapid transit” was added: mainly Woodley Park to Eastern Market via Florida Avenue, while the rest of the 50-mile route structure developed over the course of the study was designated “rapid bus.”

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A recent post by economist-blogger Brad DeLong, which was also picked up Matthew Yglesias, mused upon the clustering of the Dow Jones Industrial Average clustered near values starting with 1. He showed a chart with the years 1971–1984, and 1996–2008 circled, when the Dow appeared to fluctuate near 1000 and 10000, respectively. Many commenters quickly jumped to point out that this was an example of Benford’s Law, which says, essentially, that if you’re throwing darts at a logarithmically shaped dartboard, you’re going to hit “1″ more often than any other digit. If you pick random values of some phenomenon that is logarithmically distributed, you should get values beginning with “1″ about 30% of the time, which makes sense if you’ve ever looked at log scale graph paper.

It occurred to me that this is an easy thing to investigate with Mathematica, much like my earlier post on the Bailout. Mathematica 6 includes access to a huge library of curated data, including historical values of the Dow Jones Industrial average and other indices (and individual stocks, and so forth). The function here is FinancialData, which Wolfram cautions is experimental: I believe they get the data from the same source as, say, Yahoo! Finance, and just do the conversions to make it automatically importable into Mathematica. That is, it is no more reliable than other web-based archives. The computations are absurdly easy, taking only a few lines of Mathematica code. 

The graph I (eventually) produced shows the relative frequencies of first digits that are calculated by Benford’s Law, together with the relative frequencies of the leading digits from the Dow Jones Industrial Average, the S&P 500, the NASDAQ Composite index, the DAX 30, and the Nikkei 225:

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Prologue

Bringing a 50-mile streetcar network to Washington DC is the top priority for the DC Chapter of the Sierra Club. I have been following this issue with the Sierra Club since 2002, and it was recently suggested to me that I write down a brief history of the effort, to provide context for those new to the subject. Current progress on the issue is blogged at streetcars4dc.org. 

The DC Transit Improvements Alternatives Analysis gets underway.

The last time streetcars ran in DC was the early morning of January 28th, 1962, after which all lines were converted to buses. Such was the state of public transit in the District until March 27, 1976, when Metrorail opened. Metrorail, of course, has been a tremendous success, but it does not serve all areas of DC, and was designed primarily to move suburban commuters to their jobs in downtown DC.

The District government has, in principle, been planning to bring streetcars back to DC for some time now. My involvement began in September 2002, when I testified on behalf of the  at a joint oversight hearing of the DC City Council. A relatively small, two-year study had recently been completed (DC Transit Development Study), and then-DDOT director Dan Tangherlini, and then-DDOT Mass Transit Administrator Alex Eckmann went before the council (read their presentation) to ask that a more expansive study be funded. Plans to expand transit in the District stretch back further than that, and are generally said to have begun with the Barry-era DC Vision Study of 1997, itself 2 years in the making. And after more than ten years of talk and study, there are still no streetcars.

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For those that live on Capitol Hill, this is old news, but the good news is that Peregrine Espresso has opened, in the space that once occupied by Murky Coffee. The better news is that Peregrine is co-owned by a former Murky Coffee employee (and 2005 Southeast Regional Barista Champion [warning:pdf]) Ryan Jensen. Which is to say, Peregine continues, and expands upon, Murky’s pursuit of coffee excellence.

I visited Peregrine for the first time Saturday. The space has been remodeled to look much cleaner–in fact, nothing from the old Murky remains. Their blog has several pictures. The chalkboard menus are gone, the walls are painted, the floors are freshly finished. The menu has been simplified, to the point where each drink comes in only one size. The brewed coffee offerings are given more prominence. 

Peregrine gets its coffee from Counter Culture Coffee, the same supplier that Murky uses. Their milk comes from Trickling Springs Creamery, a relatively local dairy in Pennsylvania that sells milk in re-usable and returnable glass bottles. This is one step beyond Murky, which as far as I know used ordinary supermarket milk. 

I had a cappuccino–regrettably, to go, as there were no free seats. Even in the (appropriately sized) to-go cup, the barista poured a small rosetta. It had been months since I’d had a “third-wave” cappuccino: the way-beyond-starbucks, hand-crafted expression of exactly how amazing coffee can be. Delightful.

Coffee lovers in Washington do owe much to Nick Cho, owner of Murky. That his business skills are sloppy is unfortunate, but he planted the seeds of coffee culture in DC. That a former employee is able to open a cafe that improves upon its predecessor reflects both the technical training and the enthusiasm for coffee that Nick imbued his employees with.

A friend of mine (and regular commenter here) has pointed out that, even if the $700,000,000,000 bailout passes, and adds to our National Debt, we’d still have a Debt-to-GDP ratio that was less than Germany’s.¹ Wikipedia says that the US National Debt is 60.8% of our GDP, that Germany’s is 63.1%, and that our GDP is $13.8 trillion. Well, add $700 billion to 60.8% of $13.8 trillion and the new figure is 65.8%–pretty close; there are different ways of measuring both GDP and the Debt.

But I realized that this sort of comparison is something that Mathematica 6 is supposed to be good at. Mathematica is an amazingly powerful system for doing mathematics on a computer. Its strength, traditionally, has been symbolic manipulation–I most often use it for the Integrate command, which can do most of the integrals that in grad school I’d look up in Gradshteyn and Ryzhik. Version 6 has added, amongst other things, a huge library of curated data, loaded over the Internet, that’s relatively straightforward to use.

The command CountryData gives access to all sorts of country-by-country information, including “GDP” and “GovernmentDebt”. So following one of the examples in the documentation, I produced this graph, plotting the Debt-to-GDP ratio versus GDP for (nearly) all the countries for which Mathematica has data. (Note that the x-axis is a logarithmic scale.) The United States, before and after a $700 billion bailout, are shown in green and red, respectively.

If the xhtml export actually works the way it’s supposed to, you should be able to hover your mouse cursor over each point and have a little ToolTip pop up telling you which country the data are for.

GDP [$US]

Mathematica has a syntax that strikes many as arcane. Since I learned about computers with procedural programming, and haven’t really done any functional programming, I too struggle to get Mathematica to do what I want it to do. But one can often do complicated things, such as the above graph, with a very compact command. To make the main graph–the red and green dots are relatively trivial additions–the command I used is:
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1. He is, nevertheless, against the bailout. [↩]

In Sacramento, where I grew up, we would have the occasional colorful tree in the fall, but there weren’t any really impressive displays of fall color, at least not that I remember. It wasn’t until I was away at grad school, in Ithaca, NY, that I was in an area that could have really impressive displays. I also learned that the peak of fall color really lasts two weeks or so: there must be a mad dash among professional photographers who want to use beautiful fall color as a backdrop. We have this image of the canonical fall day: crisp air, blue sky, reds and oranges and yellows in the trees, but in reality we only get a handful of these days, not a whole season.

There are, for the fall foliage seeker, plenty of online guides: Maine, New Hampshire, Vermont, New York, Pennsylvania, and Virginia all have guides. The Foliage Network maps out reports from a network of 500 correspondents, and Yankee Foliage does the same for New England.¹

There is a whole bunch of data out there, somewhere,² which could probably answer the questions that came to my mind as I was thinking about fall foliage today:

• How much variation is there, geographically and year-to-year, in the duration of the peak color period?
• How fast does the peak color “front” move? Could you hike along with it?
• What is the longest hike you could plan that would keep you in peak color the whole time? Could you stay in peak color along, say, the Appalachian Trail?
• What sort of bike ride could you plan, to stay in peak fall color the whole time?
• Although the timing of the arrival of fall color shifts around from year to year, does all of the Northeast experience the same shift? Could one use the arrival of peak color in northern Maine to predict the arrival of peak color in central Pennsylvania?

And of course the big question, will I see any fall foliage this year?

1. Curiously, the current reports from these two networks seem to disagree with the current reports for the state tourism boards in Maine and New York, but this could be the result of different standards. [↩]
2. The Foliage Network actually has ten years or so of archived, weekly maps [↩]

Sundays May through October we have, in our neighborhood, what could accurately be called a “Farmer Market,” because these days, we’re down to just one farmer, except that I think he’s more of a consolidator for a few mostly-organic farmers and less of a farmer himself. But the produce he sells is good, and I really don’t need more than one vendor of green beans or potatoes.

There are other vendors, too, including Fresh Off the Roast, a local coffee roaster who started as a hobbyist but who has been steadily expanding his business. I’ve been getting my coffee from him for just over a year now. He roasts every Friday, and I pick up just enough for the week on Sunday. It works out very well. He blogs at Cuppa Joel.

There is now, at our Farmer Market, a tea vendor as well. A fellow Brooklander recently bought Pearl Fine Teas, which has mostly, I believe, been a mail-order firm dealing in higher-end loose teas. She had several teas–black, scented, and herbal–on display, which were sold in one-ounce packages. She blogs at TeaLove.

I drink more coffee than tea. Every morning starts with coffee, although I lean towards tea at work because low-effort tea is much better than low-effort coffee, doubly so if there’s nobody else around who would want to share the coffee. My tolerance for caffeine in the evenings isn’t what it used to be, so I tend to favor herbal teas after dinner, although there is no better accompaniment to dessert than coffee.

For our little Farmer market to become a center for high-quality beverages is pretty cool.

The short answer is that my new Brompton has substantially improved my commute. The combination of Brompton and Metrorail is by far the fastest way for me to get to work without a car. It gives me more freedom than the all-Metro commute, in which I was tied to the (unreliable) bus schedule. And it isn’t as grueling as the all-bicycle commute.

The one part of the commute that is longer is the first part, taking my son to his day care. It’s on the way to the Metro, but instead of simply pushing him in his stroller, I have to push his stroller and haul my bike at the same time. I’ve become somewhat adept at the one-handed stroller push, so that I can walk my bike with my other hand. It’s faster than leaving my bike at home and going back for it, but slower than just pushing the stroller.

On the return trip, though (my wife picks up Matthew in the evening), cycling the 3/4 mile between the Metro and our house is much faster than walking, or calling home to get a ride.

As folding bicycles are rather rare, I am frequently asked about it. A friend of mine once observed that Americans, in particular, have a tendency to ask how much you paid for something: this is certainly true of the Brompton. Complete strangers are often most interested in how much it cost me and have no hesitation about asking. I’m also asked where I got it, and I’ll go into a little spiel about going to New York City to buy it, and that College Park bicycles says they carry it but never have any in stock but they do have other, cheaper brands, and a new place in Vienna [Virginia] now carries them. I really should print up a bunch of cards listing the stores to give to others who might be interested in folding bicycles.

Although it’s certainly easier to wrangle than a full sized bicycle, the Brompton is more “luggable” than portable, so it’s as awkward as any other piece of luggage on the Metro. As such, my seat preferences have shifted. On the red line, I used to try to get a window seat with a view of the Amtrak yards; now I prefer to be at the ends of the car. Going home, I’ll try to board last, so I can stand near the doors. The doors open on the right at Gallery Place, and at the next stop (Judiciary Square), which tends to have very light traffic. After that, the doors open on the left all the remaining stops, including Brookland, so I can stay out of everyone’s way near the left-hand door.

The all-bicycle commute is 10.2 miles: at this distance, one really wants to wear separate cycling clothes, and probably shower at the end of the ride. On the way to work, this just shifts the shower to the health club at work, but on the way back it would add to the trip, but in any case even changing clothes adds time. The three and a half miles from Metro to work is short enough so that I don’t feel a change of clothes is necessary.

The steps of my commute are now:

1. unfold bicycle
2. ride to Brookland Metro
3. fold bicycle
4. lug bicycle through faregates to platform
5. wait for train
6. ride to Gallery Place
7. lug bicycle to Green line platform
8. wait for train
9. ride to Congress Heights
10. lug bicycle through faregates outside
11. unfold bicycle
12. ride to work
13. park bicycle

I include many of these steps, which might take a minute or two, to emphasize the fact that they do add up: five steps that take two minutes each means ten minutes. In a sense 10 minutes isn’t a terribly long time, but psychologically the difference between a 45 and a 55 minute commute is huge.

The other point with all the steps is that I don’t have any big contiguous block of time along the trip, so (say) trying to read is really not feasible. When I did Metrorail and Metrobus, I’d usually pick up the Washington Post Express and work the Sudoku, and listen to podcasts on my iPod. No time for the Sudoku now, and I have much less iPod listening time, so I’m down to a handful of podcasts.

Folding or unfolding the bike takes less than a minute, unless someone has asked about the bike and I’m sort of narrating the process and giving a demonstration.

Step 12 above is reliably 20-25 minutes, depending on the wind, traffic lights, how much air is in my tires, how heavy my bag is, and how willing I am to work up a sweat. I’ve done the ride in less than 20 minutes, but during much of the summer I prefer not to. According to WMATA, step 6 above takes 8 minutes, and step 9 takes 12 minutes. 

All total, the whole trip–office to front door–can be done in 50-55 minutes. I think that 45 might be possible, if I have a tailwind and no red lights, and have no waits for trains. But I’ve found, though, that I’ve become a much more relaxed commuter. No longer worried that I might miss a bus by a minute or two, which would mean I’d have an extra 20 minute wait, I don’t feel as compelled to rush for trains as I used to. And especially in the summer, I’ve found that a leisurely pace ensures that I feel comfortable without a change of clothes.