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Category — energy

Twenty megawatts in your hands

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 []

November 13, 2008   4 Comments

Bringing Streetcars back to DC, part 2

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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November 9, 2008   1 Comment

Heat

To be fair, it did cool to 77 degrees Fahrenheit. But that was at 6 in the morning, at the very minimum of temperature, after a whole night of radiative cooling into the night sky and before the sun has had a chance to warm things up again. And with 84% humidity, there was no relief to be had stepping into air during this moment of relative cool. By the time I leave the house, just before 8, it’s already 80 degrees. By 11am, it has hit 90, a mark it won’t drop below until the sun sets. The weather’s been at this for a few days now, and with each successive afternoon bake, the overnight relief becomes more meager. 

To keep the house habitable–which has meant keeping the (upstairs) bedrooms at or below about 81 degrees, I have to keep the downstairs at about 76. Such is life when your house is under-insulated, and your central air system is grafted on to early 1940s ductwork that was put in place presuming the house would only be heated.

This evening brings a chance of thundershowers: if they’re big enough, we will get cooling, but if they’re too small, then all we get is an increase in humidity.

To do this summer: install ceiling fans, and upgrade the insulation.

June 10, 2008   No Comments

Hear the hoofbeats

One horseman of the apocalypse is global warming, another is peak oil, and the hoofbeats of each are now loud enough that we can’t really pretend we don’t hear anything. The story of global warming is fairly well known, thanks in large part to Al Gore. The story of peak oil, on the other hand, although gaining in prominence, is largely overlooked, even as crude oil pushes past $130/barrel and gasoline tops $4/gallon. Perhaps this is because Americans can imagine living in a world in which the global warming catastrophe has happened (hey, just turn the AC up!) but can’t imagine a world in which we can’t each consume more than a gallon a day of gasoline.

A succinct summary of the peak oil story has been (re-)posted at The Oil Drum, which is perhaps the leading site for oil news and peak oil discussion.

May 24, 2008   No Comments

Scale in the media

I lamented in an earlier post that questions of scale are all too often left out of discussions of environmental solutions. To recent pieces that bring the issue up:

Michael Pollan’s Why Bother?, from last Sunday’s New York Times Magazine, opens by recounting what for Pollan was the “most upsetting moment” of An Inconvenient Truth: the “immense disproportion between the magnitude of the problem Gore had described and the puniness of what he was asking us to do about it.” Pollan defends notions of virtue and the steps, particularly gardening, that individuals might take to reduce their individual carbon footprints, vis-à-vis other responses to the climate crisis such as hopingfor some future technology. He writes: “Cheap energy, which gives us climate change, fosters precisely the mentality that makes dealing with climate change in our own lives seem impossibly difficult…. Al Gore asks us to change the light bulbs because he probably can’t imagine us doing anything much more challenging, like, say, growing some portion of our own food.”

Second, the April 12th Sierra Club Radio podcast has a segment with Bob Schildgen—Mr. Green—promoting his new book, which compiles questions and answers from his column in Sierra magazine. On the question of paper vs plastic (his answer–neither; bring your own bag), he encourages listeners to put things into perspective by mentioning that you likely burn as much petroleum in one trip to the grocery store as it takes to make all the plastic bags you’d use in a whole year. I can’t find his numbers online, but using the figures I wrote about earlier: 330 bags per American per year, 200 bags per gallon, so just over one and a half gallons of oil per American devoted to plastic bags. At 20 miles per gallon, you could make a round trip to a supermarket 15 miles away. Right order of magnitude, but I think you could travel a bit farther on that amount of gas.

This exercise in scale is then thrown out the window later in the interview, when host Orli Cotel asks the heavily loaded question: “For our listners who do own cars or need cars for whatever reason, what tips can you give us, as Mr. Green, to help reduce the amount of gas that we’re using,  besides of course cutting back on car travel?” (As if there’s some secret, magic way to drive without using gas that only the hardcore enviros know about.) Mr. Green goes on to mention that Americans lose about 4 million gallons of gasoline per day because of underinflated tires. Of course, he doesn’t put this into perspective: that’s about 1% of our daily gasoline consumption; we burn through 4 million gallons of gasoline in about 15 minutes.

April 25, 2008   No Comments

The scale of green solutions

For someone who’s long identified himself as an environmentalist, the rise in recent years of the profile of environmental issues, particularly climate change, is heartening. Much of this attention is the result of Al Gore’s An Inconvenient Truth, which concludes, as much of the more optimistic reporting on the subject does, with solutions and steps to avert the prospect of catastrophic global climate change.  An often overlooked but absolutely critical aspect of any of these “greener” ways of doing things is an investigation of the way they scale. Two questions that need to be asked of any proposed solution:

  1. Is the idea feasible on a large scale?
  2. If implemented on a large scale, how does the overall benefit compare with the magnitude of the problem that the solution purports to address?

We do need to constantly look for ways to lower energy use, to create less waste, to reduce the release of toxics to the environment. An abiding quest to green and re-green our lives should become a universal American value, in much the same fashion that thriftiness was admired during the depression, or that discount shopping was admired in the 1990s. But at the same time, we must be careful not to fool ourselves: there is a real prospect that, if we do not consider the scale of the problems and potential solutions, we’ll stop short, that metaphorically we’ll change a lightbulb and recycle a soda can and think we’re done.

Consumption of energy is the biggest part of greenhouse gas emissions, which is the biggest environmental problem facing us today. Almost universally, in the popular press, there is a widespread lack of awareness of scale involved, which is both understandable and frustrating. It is frustrating because figures on overall energy consumption are unambiguous and readily available from the Department of Energy, yet understandable because the numbers involved are so huge. Large scale energy consumption is measured in quads, or quadrillion BTUs. The United States consumes roughly 100 quads, or 100,000,000,000,000,000 BTUs, of energy per year. The outline of the flow of this energy is brilliantly presented in this graph from the DOE. On average, this amount of energy consumption is equivalent to a power consumption of 3.3 trillion watts.

As a very crude1 (but illuminating) approximation, suppose that every American, all 300 million of us, turns off a lightbulb and reduces our power consumption by 100 watts. In this approximation, we imagine a bulb which had been on 24/7/365 to now be off. All total, we’d save 30 billion watts. Sounds like a large number, doesn’t it? It’s the output of 30 Gigawatt-sized power plants. Certainly admirable. But it’s just 1% of our overall 3 Terawatt power consumption.

Petroleum constitutes roughly 40% of our energy consumption, to the tune of 865 million gallons per day.23 This turns out to be 10000 gallons per second;  it takes our country about a minute and 40 seconds to burn through a million gallons of oil. Keep this scale in mind the next time you hear about a great way for our country to save a million gallons of oil: wonderful, but hardly the whole solution.

Of this oil, each day we burn 388 million gallons of gasoline and 175 million gallons of diesel fuel.45 It is contemplating these figures that lead us into question 1 above: how feasible are any of the alternate fuels touted as replacements for gasoline?

For the moment, I will just address biodiesel. To make biodiesel, vegetable oil is combined with an alcohol and a strong base to produce a liquid that is similar to petroleum-based diesel fuel. There are serious questions as to the energy efficiency of this whole process, which I will not address in this post. As a reasonable approximation, suppose one gallon of vegetable oil can be turned into one gallon of biodiesel.

The entire annual US production of vegetable oil is about 2.9 billion gallons.6  If all the vegetable oil produced over the course of a whole year were converted into biodiesel, it would displace about 5 days of gasoline and petro-diesel use.

I’ve seen (but can’t find at the moment) a figure that roughly 10% of our vegetable oil production ends up as waste vegetable oil. So if we converted an entire year’s supply of  used french-fry oil, etc., to biodiesel, we’d keep our country motoring for about 12 hours and 22 minutes.

This is why I’m more than a little skeptical when conversion to bio-diesel is taken as evidence that someone or some organization has “gone green.”  To replace all our motoring fuel with bio-diesel, we’d have to scale up production by a factor of 70. Even if we set a more modest target of replacing a quarter of our motor fuel with biodiesel, we’d need to produce 18 times as much vegetable oil as we do today. In this context, discussion about whether one method of producing biodiesel is, say, 20% more efficient than another method, or whether one type of biodiesel-burning engine is, say, 30% more efficient than another is really irrelevant. What’s relevant is the scale.

I’ll close with one final calculation that puts the scale in perspective. Just looking at gasoline, 388 million gallons per day is equivalent to 1.3 gallons per person per day. We can see that it makes sense: it’s what you get if everyone drives 30 miles per day. We tend not to think of the volume of gasoline that we consume because we don’t see it: it goes from a tank underground through a hose to a tank under our car. But aside from water, there’s nothing for which each and every one of us consumes that’s on that scale. For a family of four, 1.3 gallons per day is 36 gallons per week: imagine this volume of vegetable oil, every week. Sound absurd? That’s what the bio-diesel solution would be.

  1. Crude because it mixes primary energy–like coal and gas–with electricity, which is good for order of magnitude, but keep in mind that only a third of the heat value of the primary energy makes it into electricity. []
  2. 1 barrel is 42 gallons []
  3. Equivalent to the volume of Lipsette Lake every two days. []
  4. distillate fuel oil=diesel []
  5. plus 68 million gallons of jet fuel []
  6. See Table 6 of any of the reports. Note that production of oilseed and production of vegetable oil are different things; only part of the weight of the oilseed is oil. Here I use a specific gravity of 0.9 to convert from metric tons to gallons, so about 7 pounds per gallon. []

April 3, 2008   1 Comment

Kunstlercast

There are three books that form the foundation for my urban Weltanschauung, and I hope to write of each. The first of these, for me, was James Howard Kunstler’s The Geography of Nowhere, a polemic examination of the state of our built environment. Written before global warming or peak oil commanded the attention they do today, Kunstler focused on the dehumanizing aesthetics of postwar development, particularly suburbia.

I’d long felt an uneasiness about the suburbs: I’d had a general notion that total reliance on cars must be bad for the environment, and I also knew that the suburbs appeared dull and boring at best, but I could never quite put a finger on precisely what was wrong with them. Kunstler’s book was a clarion illumination of the problems of suburbia; he put into amusingly acerbic words precisely what I had felt.

Kunstler wrote two more books about the built form: Home from Nowhere, and The City in Mind, and he maintains a curmudgeonly website, with his delightful eyesore of the month. Kunstler is, by trade, a writer, and so his work is generally very well crafted. In the past few years he has mostly been concerned with Peak Oil and the complete catastrophe it could be for the American Way of Life, and his book on the subject, The Long Emergency, isn’t quite as captivating as his other works: in large part because the depth of research and analysis that went into his other books just isn’t there.

As someone who listens to several podcasts, I was excited to learn that he is now doing a weekly podcast of his own: Kunstlercast. The first episode concerns (chain) drugstores, and their proliferation. It’s worth listening to.

February 25, 2008   1 Comment

VMT and MPG

Perhaps the best reason to listen to Sierra Club Radio is to hear the fascinating guests that come on the show, who often manage to say something insightful despite host Orli Cotel’s bubbly demeanor and loaded questions. But one theme has come up in two recent programs–indeed, you hear it often from the Sierra Club–that really gets to me: the notion that the answer to the problem of our nation’s oil consumption is to “go farther on a gallon of gas” by raising fuel economy standards. Since raising fuel economy standards is just about the only progressive thing left in the energy bill that made it through Congress, much has been made of this phrase of late.

It seems simple enough: increase the fuel economy, and our fuel use goes down. But there’s a really big if here: that’s if the number of miles driven doesn’t go up. I will argue in this post that there’s no evidence to support the notion that the amount of driving will stay fixed. This is the problem with the phrase: “going farther” implies more driving, by using the same amount, “a gallon,” of gas.

From the standpoint of an individual, many environmentally-minded folks buy high fuel economy cars in order to achieve “guilt-free” driving. When faced with a transportation decision: whether to travel, and if so, which mode to choose, the fact that one has a car with higher than average fuel economy certainly makes it easier to choose to drive. This is actually a well-known phenomenon known as the Jevons paradox: improvements in efficiency of consumption of some good leads to a larger overall rate of consumption of that good, because use of that good becomes feasible for more uses as the efficiency grows. It’s the same reason you spend more time online when you have a faster Internet connection. Overall, America’s gasoline consumption is analogous to a (faltering) dieter who eats a whole box of fat-free cookies because they’re “healthy.”

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December 19, 2007   9 Comments

Happy Buy Nothing Day

It’s 6am; I’ve overslept! I should have been in line at the mall three hours ago!


Buy Nothing Day Visa Poster

I’m not a strict BND observer, but considering how you can’t separate the environmental damage caused by manufacturing, by mining and refining raw materials for manufacture, by transportation of goods and materials, and by disposal of packaging and worn-out junk from the purchase of new goods, BND does seem to be one of the more useful spiritual holidays around. There’s a reason that “reduce” is the first keyword in the “reduce, reuse, repair, recycle” mantra.

Many argue that stuff not bought today will be bought some other day, so it’s understood that BND is not a cure for consumerism, but rather a time to reflect on the future of a consumer society in the age of global warming and Peak Oil. We should question the underlying assumption of that argument, though, that there’s some fixed amount of stuff that we’re going to buy. Rather, we need to keep the Jevons paradox in mind, and consider whether the ease with which we can purchase something plays a role in our decision to purchase it in the first place.

If you’re going to make any observation of BND today, I’d say the first priority is to avoid products that are explicitly marketed as “green.” One of the softer, and IMHO more unreasonably optimistic environmental notions out there is that we can save the world simply buy buying the right stuff. A much larger fraction of the Green Living blog and its companion piece on Sierra Club Radio are devoted to buying less damaging products, instead of reducing, reusing or repairing. So today, instead of buying a shirt made from organic cotton, ask yourself instead whether you really need another shirt in the first place.

I did look through all the sale flyers that came with Yesterday’s Washington Post. Among the things advertised, without which I think that that, on balance, the world would be a better place: electric martini makers, “Latte” makers (ironically, from a company called “Back to Basics”), and Margarita makers. And scented candles.

November 23, 2007   2 Comments

Plastic bags

Americans throw out 100,000,000,000 plastic shopping bags each year. This is the figure given in Katharine Mieszkowski’s article about plastic bags in Salon.com, which I first heard about when Sierra Club Radio Interviewed her.

I won’t repeat what’s in the article: that’s what links are for. Suffice it to say that plastic bags wreak havoc on the environment. But let’s explore the numbers.

As I write this, the Census bureau estimates the US population at 303,384,903: that means that, on average, each American throws away about 330 plastic bags each year, or just one bag per day most days of the year. Five bags of groceries plus two other purchases a week would do it; this tells us there’s no reason to doubt the 100 billion figure. In fact, thinking about all the double-bagging that goes on at supermarkets, and not to mention all the other shopping that’s going on all the time, the figure seems a bit low. And unfortunately, there isn’t one evil industrial polluter to which we can assign the blame: what seems like a normal number of plastic bags times a whole lot of us means a whole lot of bags.

Producing the 100,000,000,000 plastic bags apparently takes 12 million barrels of oil. One barrel of oil is 42 gallons, so you can make about 200 bags from a gallon of oil, or about 2/3 fluid ounce of oil per bag.

According to the US Department of Energy, the US uses 20.7 million barrels of oil per day, or 7.6 billion barrels of oil per year. Of this, roughly 3/4 goes to transportation fuels. So if we took all the oil that presently goes into plastic-bag production, and used it instead for moving around, it would last about 19 hours.

Which means: plastic bags are awful for wildlife, and very ugly when they’re littered around, but they’re not really a significant part of our dependence on foreign oil. If someone comes up with a scheme to recycle plastic bags into an alternative fuel for cars, then perhaps it will be clever, but it won’t really be anything like a solution.

November 16, 2007   2 Comments