“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

Friday, November 29, 2013

Ack! ANOTHER "capture the energy of walking/driving" system

I really don't want to turn this blog into a debunking site but some things just must be said. Here I described a completely impractical system for "capturing energy from pedestrians." And now we find an article from Science Daily about Mexican entrepreneur Héctor Ricardo Macías Hernández, pictured at left, who's developed yet another system for capturing energy from passing traffic - vehicular or pedestrian.

It apparently consists of a traffic wearing surface that sits five centimeters above street or sidewalk level. Passing traffic squeezes a bellows, compressing air into a tank (the linked article says "...where it is compressed..." but I don't imagine that that's accurate) from which it is expanded into a turbine to generate electricity.

Think about it. Your engine (either that of your vehicle or of your metabolism) is squeezing air into a tank. This work will reduce your gas mileage (or use your food energy) as your vehicle or your feet do the work of compression. There is no free lunch here. I'm surprised to see it in Science Daily which, although it is sometimes prone to exaggeration, usually doesn't publish nonsense.

There are no figures given, either in the Science Daily article or the articles linked from there, so I don't know what kind of traffic would be claimed to generate what kind of power. But I do know that, whatever the amount generated, it would be more efficient to burn natural gas in a turbine. Both vehicular internal combustion engines and human metabolisms are inefficient and compressing air is a lossy process. I'd love to see figures for this but it's yet another candidate for my prospective Greenwashing Hall of Fame. Yes, I know that the term "greenwashing" is typically applied to deceptive ad campaigns but I think it's equally applicable to deceptive products.

Update: In thinking about it, I suppose that one could concoct a scenario wherein a developing country with few energy resources would rather have the "rich" who own cars spend some of their energy (i.e., gasoline or diesel) purchase on providing energy for township than purchase natural gas, oil, or coal and then charge the poor residents for the electricity or pay for the fuel with taxes. But even there, better a gasoline tax with the proceeds used to pay for more efficient energy generation.

Solar panels on a truck?

I took my family to the LA Auto Show yesterday. Despite studies and articles contending that young people today are not so attached to automobiles, my son is absolutely captivated by them. He knows the makes and models, what he'd like, how he'd modify it, etc. I knew he'd have a great time and he did. I wanted to see developments in electric vehicles, plug-in hybrids (PHEV), etc., both production and concept.

I noted a pickup truck with a tonneau cover consisting of a solar panel and wondered about its practicality. Neither the Via Vtrux pickup (a series PHEV) nor the SolTrux panel option are in production, which is anticipated for 2014. It's a nice looking truck.

But is the solar panel practical? I have a Jeep pickup into which I've installed a 32 gallon water tank and other items designed to let me be self-sustaining in the Mojave, Sonoran, and Great Basin deserts of the Southwest. Where better to capture the sun?

So what are the appropriate numbers? We'd like to have battery capacity, dimensions and efficiency of the solar panels, and the claimed output. Here we find that the battery pack is 22 kWh. The dimensions of the panel array aren't given. but the standard bed is 78.7" long. The width isn't given but might be 65". The larger panel is stated to be 800 watts.

I see here that, in March (about average) I can expect on the order of 5 kWh/(m^-2*day) (kilowatt hours per square meter per day) for a panel mounted horizontally as it would be on a tonneau cover or roof rack. If I assume that the panels are 72" X 60", or 2.8 m^2 they should intercept 2.8*5 14 kWh per day. At 20% efficiency, I should get (surprise) 2.8 kWh/day. Assuming that I'd never let the battery pack below 20% charge, it would take 17.6/2.8 or a bit over 6 days to fully charge the battery. And the 22 kWh is represented to be good for 35 miles (though my desert miles are VERY hard on energy use). At that ratio, a day's worth of sunshine would take me (2.8/17.6)*35 or about 6 miles and probably a lot less in the rugged terrain where I'd be operating.

I suppose that, were I (through incredible stupidity or possibly a punctured fuel tank) out of gas and stranded, I could drive six miles per day for however many days it took to get to civilization (a very long way from the places I go). The fact of the matter is that it simply takes a lot of square meters to provide significant power. Verdict? NOT worth the estimated $3,000 price for the panels.

Update: Here's a clickable link to the article cited in the comments by Anonymous.

Saturday, November 23, 2013

Embarrassed to be conservative - a (sadly) continuing series

And yet, within MY definition and one that I will defend, I still am.

This Does Not in Any Way Imply That All Climate Deniers Are Obnoxious Blowhards | Climate Denial Crock of the Week:

'via Blog this'

A digression - should interest in sci fi be a qualifier for gifted programs?

Since my blog muse has, hopefully temporarily, abandoned me and my calculations regarding the energetic plausibility of carbon dioxide sequestration via carbonate minerals is taking much more time and effort than I'd anticipated, I'm going to go completely outside any subject space I've dealt with.

As a youngster, I read a LOT of Isaac Asimov's writing. While Asimov is very well known for his science fiction, I read none of it. What I read were his essays, which covered such an amazing breadth of topics that it's hard to believe that a single individual could do it. However, one that I read rankled.

Asimov was clearly a prodigy and, back in my youth, some regarded me as such. All that ever interested me was science and math and I was fortunate enough to attend a progressive (in the academic rather than the political sense) school. I was accelerated, I was offered training in scientific investigation, and I was offered the opportunity to choose what I studied, at least to an extent (I managed to squander most of this advantage upon reaching college but that's a story for another time).

But Asimov wrote an essay (I can't find it but remember it distinctly) suggesting that school children be assessed for accelerated learning or "gifted" (a label sometimes applied to me) programs based on their level of interest in science fiction. I found it then and find it now to have been pretty self-serving and self-aggrandizing for such an otherwise objective thinker.

I started both Asimov's "I, Robot" and his "Foundation" series and finished none of the stories, finding them much less interesting than reading and studying science and mathematics. I could likely count the science fiction stories I've read on the fingers of a hand (and I wouldn't need the thumb). I read "The Hobbit" and found it quite boring, and made it through two and a half of the "Lord of the Rings" trilogy (at Northwestern University in the early '70s, at least in my circles, it was a scarlet letter offense not to have read these - I had a fraternity friend who prided himself on reading the entire trilogy every year). Halfway through the third novel, I concluded that "this sucks, I'm reading it only because I'm supposed to" and put it down, never to complete it. Yes, I realize that Tolkien's works are fantasy rather than science fiction but I'm sticking with the point.

What point is that? It's not really clear, but it's a rant I've kept inside for decades. The trailers for "The Hobbit - The Desolation of Smaug" are popping up and brought it to mind. I've not seen any of the previous Tolkien adaptations (for the matter of that, I saw the original "Star Wars" in 1977 and have seen none of the prequels or sequels). I did watch all of "Star Trek" and some "Star Trek TNG" so I guess I'm not completely immune, but these shows could almost as well have been done as westerns!

In any case, I'm not at all sure that Asimov's razor (as I'll call it) would be the appropriate metric for determining the suitability of elementary school students for gifted programs (assuming such programs still exist in this day of No Child Left Behind-based teaching to the test). I'm sure it's a reflection of both my ego and my ability to hold a grudge that an essay I read, probably, over 40 years ago still causes resentment but perhaps this post will allow me to finally let it go!


Thursday, October 17, 2013

Blog host ethics

Certainly there are no laws on the ethics of hosting/publishing a blog and there are all manner of blogs out there. Some thrive on flame wars, insult hurling, etc. and do no moderation. Others are moderated strictly and say so up front. Still others, though, represent that they welcome open dialogue but moderate comments that disagree with the host's point of view. In my opinion, this is or should be in violation of what I'd consider to be a "blog publisher code of ethics."

The case in point involved a blog to which I linked from mine up until yesterday. It's published by Mark Chu-Carroll ("MarkCC") who publishes "Good Math Bad Math." This blog covers quite a few things that are of interest to me, among which are computer science, math and physics crackpottery, (lately) probability, and others. MarkCC also discusses recipes, music, and other eclectica.

But MarkCC will also delve into social issues and clearly comes from an extremely liberal viewpoint. That's all well and good and I certainly respect his right to hold, promote, and publish his point of view, though I frequently disagree.

Yesterday, MarkCC published a post entitled "It's easy not to harass women." And while I agreed with some of what he wrote and with some of the comments, I hold a contrary point of view on a few of the things. In particular, it's my opinion that the legal, legislative and administrative machinery make it all too easy for opportunists to hold employers, institutions, etc. hostage with the threat of lawsuits over things that may rightly be considered offensive or not even that. Careers, families, etc. are ruined in response to perceived slights using a regulatory schema that rightly seeks to protect (most commonly but certainly not exclusively) women from reprehensible conduct such as the "casting couch," offer of career advancement or employment in return for sexual favors, and other such clearly actionable conduct.

This happens despite the fact that no harassment or sexual innuendo was intended. I do not speak hypothetically. And, frankly, unwelcome sexual innuendo should be handled without lawsuits and without destroying people. And, let there be no doubt, this is neither to condone such behavior nor to suggest that there are no behaviors that merit the full legal arsenal.

On MarkCC's site, I left several comments. None were vulgar, extreme, or confrontational. None were of an ad hominem nature. But, after the first couple of comments and literally in the middle of discussion threads, my comments disappeared without notice or explanation. In fact, a reply to one my purged comments was left so that the subsequent comment was replying to a comment that was no longer there.

Now, can MarkCC do this? Obviously, since he did, he can. Should he be able to? Absolutely and unequivocally, yes. Do I think it's ethical or right? I do not. My respect for Mark has declined precipitously.

Am I writing this in "revenge?" Heavens no, I doubt that MarkCC will ever know that I wrote it and I doubt that his commenters and readers will ever see it, his readership is much larger than mine. But I did want to "get it on the table" and assure my readership that, if it's not spam and it doesn't make a threat, all comments at my site will stay. Even if they insult me personally (which some have).

Sunday, September 29, 2013

Farewell to The Oil Drum

Graphic credit: TheOilDrum.com
For those interested in a holistic understanding of our energy predicament from an educated and technically savvy point of view, there are a variety of sources of data (BP supplies two of them, the U.S. Energy Information Agency, EIA, is another), there are many blogs devoted almost entirely to energy (some are linked in the blog roll to the right of this post), and many more that touch on the topic.

But occupying a unique place among those who study energy and especially fossil fuels was The Oil Drum. The last post in this amazing resource was made on September 22, 2013, and the site is now an archive of the incredibly deep, varied, and informed discussion that has comprised the site's content since April, 2005. It will be a valuable resource for years to come.

The Oil Drum's demise has been described by its editors as being due to "a dwindling number of contributors" and high costs (both in terms of time and money). Unsurprisingly, those who believe in the fairy tale that the free market can create an infinite supply of a finite resource trumpeted this development as indicative of the capitulation of the "peak oil fanatics" to the technological and financial developments that will always and inevitably overcome resource scarcity.

Without getting into a deep discussion of what "peak oil" really means, suffice it to say that it predicts a plateau and then a decline in the rate (yes, rate) at which oil can be extracted as we exhaust the easiest and cheapest sources first and then the progressively more difficult and expensive sources. All this transpires in the face of increasing world wide demand and massive growth in demand from developing nations. The free market "true believers" (and I lean in this direction but am willing to be flexible in the face of data) believe that price will solve all problems of both source and rate. The chart below indicates otherwise (data from the BP site linked above). While oil prices have multiplied ten-fold since 1976 (albeit in nominal $, but see below), production has risen by a bit under 30% in the face of ever growing demand in the developing nations, especially China.


Update: Dan took me to task in a comment for only showing nominal crude price. I've added an inflation adjusted price using CPI-U data. The inflation adjusted price has risen 116% while production has risen 30%.

Learned discussion by knowledgeable experts at The Oil Drum of the technical, economic, and political aspects of energy availability (not at all limited to crude oil) will be sorely missed. While the thoughts and writings of many of the regular contributors to The Oil Drum can be found elsewhere (and links to many of their blogs and web sites are available at the final post of The Oil Drum) and the articles and comments archived for use, the lively discussions are irreplaceable.

Farewell to the site and to its participants!

Saturday, September 21, 2013

Looking into the CT200H mileage trends

What with work and family, sometimes I don't have as much time as I'd like to devote to authoring posts. And some of them take a significant amount of time. In this case, I've made a couple of posts regarding the the possibility of sequestering CO2 from power plants in carbonate rocks, pavers, bricks, etc. I still owe my audience an analysis of this process in terms of energetics and economics. Those are taking some time.


In the mean time, I want to take a look at some of the data from my records of mileage in the Lexus CT200h that's my daily driver. To the left is a plot of the mileage at each fill-up since my acquisition of the car. It raises some questions.

Of course, the very low and very high numbers are related to the profile of driving done during the applicable tank. The lowest, for example, involved climbing into the mountains above Los Angeles for an outing with my son.

But I noted a trend, beginning at the end of the third quarter of 2012 and extending to the end of the first quarter of 2013, of declining mileage. I took the vehicle in for scheduled service in mid-March and told the service crew about the declining fuel economy. When they returned the car, they said they'd checked all applicable parameters in the fuel delivery system, the engine control unit, etc. and found no anomalies and adjusted nothing. But the mileage increased noticeably and is still appearing to be on that upward trend.

Now, to the best of my ability, I always drive in the same way (much to the frustration of my passengers - those who will still ride with me anyway - and the vehicles that share that road with me). And, to the extent possible, I try to always purchase gasoline from the same station. Assuming that it's not related to my route or driving techniques, what could explain it?

One possibility is "winter blend" vs. "summer blend" gasoline. In summer, particularly in California, refiners must use gasoline blends with lower vapor pressure to minimize vaporization due to warmer temperatures (and more driving). In winter, refiners add butane to blends because it's cheaper (thereby partially explaining winter's lower gas prices) and the higher vapor pressure of butane containing blends isn't as harmful due to the lower temperatures and lesser total vehicle miles driven. And butane has a lower specific energy content, thus possibly explaining my reduced fuel economy.

Is there such an annual "signal" in my fuel economy data? I've got 90 data points, and so ran a Fast Fourier Transform of the data. Such a process is used to transform data from the "time domain" (as in a time series) to the frequency domain (showing periodic components in the data). If the winter/summer blend switch, which happens annually, is a significant part of the fuel economy changes I've noted, my theory is that such periodicity should appear in the frequency domain. If you squint, you can even convince yourself that it's there - lower in winter and higher in summer.


Alas, there's no such peak apparent in the Fourier Transform. It's back to the drawing board. I can't imagine that the dealer fixed  or adjusted something and didn't charge me for it!

Saturday, September 07, 2013

Can we use the carbonate "rocks" from carbon sequestration?

Photo credit: Construction Consulting and Testing
In my previous post, I discussed the launch of a pilot plant by a group of entities with the goal of sequestering COin manufactured carbonates that would subsequently be used in construction. These uses may include bricks, aggregates, pavers, etc. Of course, even were the CO2 not used, it's better to have it in an inert mineral material than contributing to radiative forcing in the atmosphere. I suppose that any unsold inventory could simply be dumped. But what about a market?

The claim I mentioned in the previous post was that 50 plants could sequester a gigatonne of CO2. The veracity of the claim aside, what would this mean? For a start, how much rock is represented by converting a gigatonne of carbon dioxide to calcium carbonate (CO2 + CaO  CaCO3), or possibly magnesium carbonate (CO2 + MgO → MgCO3)?  As an aside, it should be noted that these are EXTREMELY simplistic versions of the actual production reactions. A paper giving technical details is available here. Anyway, the molar weight of COis 44 grams, the molar weight of CaCOis 100 grams. Thus, converting a gigatonne of carbon dioxide would produce (100/44)*1 billion tonnes, or 2.27 gigatonnes. The same calculation for MgCOyields 1.92 gigatonnes. Let's call it 2 gigatonnes. Of course, it wouldn't make a lot of sense to convert this to cement (!) so what's the demand for bricks and aggregate worldwide?

What is typically thought of when "brick" is mentioned is the iconic red clay brick. These are usually formed by an extrusion process of pulverized clay materials mixed with water. The most common result is a brick of length 4", height 2 1/4", and depth of 4" weighing 2.7 kg. A similar volume of calcium carbonate weighs 3.20 kg, and of magnesium carbonate, 3.49 kg.  A gigatonne is 1000 kilograms, so 2 gigatonnes is 2 trillion (~2*10^{12}~) kg. I'll use 3.3 kg to determine that 606 billion bricks could be manufactured. The best information I was able to find says that around "seven to nine billion" bricks per year are used.

OK, can't use it all in brick, what about aggregate? This site estimates that demand for construction aggregate worldwide is on the order of 26 gigatonnes. Clearly, this is where the manufactured carbonates are best used. And, it would seem, there is sufficient demand. In fact, working backward, 26 gigatonnes of calcium carbonate aggregate would absorb 13 gigatonnes of CO2, about 40% of our annual emission. And, one would assume, as emissions rise with a growing developing nations economy, so would aggregate demand. If it works, I like it!

There are two further considerations: energetics and economics. After all, if the energy required to manufacture the carbonates is excessive, particularly if it involves fossil fuel energy, there's a problem. And if the cost is too high, it won't matter about demand because it won't be purchased (unless, of course, carbon is taxed or credited in such a way as to balance the price).

I may or may not be able to get a handle on the economics but I should be able to nail down the energetics. I'll do that in my next post.

Monday, September 02, 2013

A home for CO2?

Photo credit: MIT
A hybrid group comprised of The University of Newcastle (through it's commercial entity, Newcastle Innovation), Orica (a chemical company), and GreenMag Group (appears to be an ecologically oriented innovation facilitator) has launched a pilot plant that converts carbon dioxide into bricks, pavers, aggregate, and other construction products. The idea is to capture CO2 from power plants and other large industrial emitters and turn it into such products. It's seemingly plausible. After all, cement is made, in large part, by cooking the CO2 out of limestone, which is CaCO3, i.e., calcium carbonate, to form CaO, lime. The Mineral Carbonation International facility, in a simplistic view, reverses this.

In the inhabitat.com article that alerted me to this concept, it's stated that "fifty carbon capture plants around the world could potentially sequester over a billion tons of CO2 annually." Now, our species emits on the order of 31.6 gigatonnes (Gt) annually, so this potential, if it's real, represents maybe 3.2% of our emissions (I'm assuming that metric tons or "tonnes" is the unit, if not, then it's 2.9%). I'm assuming that the sequestration plant would be collocated with the carbon dioxide emitter. I wouldn't think compressing and shipping the CO2 would be feasible. There are some 50,000 coal fired power plants worldwide. So, if they all had such capability, we could sequester some 1,000 billion tonnes of CO2, 32 times our actual total annual emissions! Woo hoo, let's get started!

But how do we reconcile these numbers? A "typical coal fired power plant," per the Union of Concerned Scientists, emits 3.5 million tons of carbon dioxide annually. If I assume they're utilizing short tons, it fits fairly well with an estimate calculated from Wikipedia that yields 2.4 megatonnes, using a one gigawatt power plant at 80% capacity factor. OK, so 50,000 plants times 3.5 million tons per plant yields 175 billion tonnes, or over five times worldwide emissions. Nothing sensible there either, clearly none of that makes sense unless the average coal fired plant is much smaller than a gigawatt plant. The Union of Concerned Scientists must be referring to a very large, gigawatt scale coal fired power plant.

OK, finally, looking through the EIA site, I can estimate that about 14 gigatonnes of COare emitted worldwide via coal combustion for energy. So the average annual emission of a plant would be 14 billion/50,000 or 280,000 tonnes per plant per year.  Does THIS make sense? The estimate in the previous paragraph of 2.4 megatonnes came from my plugging in a 1 gigawatt nameplate capacity plant at 80% capacity factor. That would mean that the "average" plant operates at (280,000/2,400,000)*800 megawatts or 93 megawatts. I don't find this to be unrealistic, there may very well be many thousands of relatively small coal fired power plants around the world.

But back to the claim that 50 pilot plants can sequester a gigatonne. That would be 20 megatonnes per plant, FAR more than the 2.4 megatonnes emitted by a large (gigawatt size) power plant. The only way for the claim to make sense is if, in contradiction to my speculation above, carbon dioxide is compressed and transported to a sequestration facility. Sorry, I doubt it. Next post: how much carbonate will be produced and what can be done with it? After that, energetics and economics.

Saturday, August 24, 2013

The (probably) last post on regenerative braking

I've posted a couple of times on regenerative braking in my CT200h. This will, I expect, be the last. In the previous post I estimated that regenerative braking on a trip saved me about 5.9% of the gasoline I'd have used without it. I decided that a better test would be a full tank, so I monitored all of the regenerated watt hours for my most recent tank. Since it's kind of a pain in the rear, I'm not going to keep it up.

Calculating in a more efficient way than the very detailed way in the previous post, the results are as follows:

  • The measured economy by miles divided by gallons at fill-up: 50.60
  • The calculated economy without regenerative braking: 47.55
  • Gallons per 100 miles: 1.976
  • Gallons per 100 miles without regenerative braking: 2.103
  • Per cent fuel savings: 6.04%
Not much different, so I think that it's safe to say that regenerative braking saves about 6% of the fuel I'd otherwise use.

I'm a bit surprised that the number is that low. In this post I discussed some of the factors that make hybrids so much more fuel efficient than their non-hybrid cousins and the regenerative braking was one of the factors I considered most important.

There is no non-hybrid CT with which to compare the fuel economy. I went to the DOE fuel economy site for the Camry (the four cylinder version)  and for the Camry hybrid. Using the combined highway and city estimates for each (28 m.p.g. and 41 m.p.g. respectively) it looks like the hybrid, per the government's test protocol, will use about 31.7% less fuel over any distance. It's reasonable to infer that, while the regenerative braking is a significant fuel saver, other factors (operating more frequently on more efficient areas of the engine map, capturing energy while coasting, automatic engine shut-off where appropriate, etc.) are at least as important.

Sunday, August 18, 2013

A response to "it's not hurting you, what do you care?"

Along with shaking my head at homeopathy, faith healing, etc., another guilty pleasure of mine is reading the amazing developments chronicled at the free energy site "Pure Energy Systems News." The site is primarily devoted to various manifestations of energy from (the vacuum, cavitation, magnetic dipoles, zero point, etc. ad infinitum), though its publishers are also hugely invested in pretty much any conspiracy theory out there.

Without going into a lot of detail, the site got excited over a supposed live demonstration of a "self-looped motor generator" developed by one Charles Pierce, who claims a Ph.D. from Bethany University (which never offered either doctorate or science degrees and is now defunct) in "Thermonuclear Reactors." Self powered energy devices (and their their pre-electricity ilk) have been around a long time and the idea here, as usual, is that you use batteries to start a motor that spins a flywheel that runs a generator that turns the motor that spins the flywheel that runs the generator that .... you get the idea. Such schemes have been around for centuries (overbalanced wheel gravity engines are pre-electronic examples) but now they typically come dressed up in jargon involving "quantum tunneling," "resonance with ambient energy," etc. You can make people believe in some pretty bizarre contraptions by throwing the word "quantum" into your explanation (albeit, quantum mechanics is, in fact, quite bizarre in any case).

Anyway, the live demonstration was to have taken place August 8, and Sterling Allan, the site's proprietor, blogged the failure to launch. I (along with others) made a sarcastic comment. The moderator responded with the usual "what harm does it do?" The following was my reply (as of this writing, it's still in moderation):
Your contention that "there's nothing to lose" is, in my opinion, very much false. If I want to have the hobby, for example, of throwing the i-ching or drawing tarot cards, or whatever, that's my business and it's no more harmful than collecting baseball cards or birdwatching. If I choose to guide my life by such activities, that's also my business. But when I try to convince the naive that i-ching or tarot really can foretell the future and then I motivative them to make life decisions based on the chance arrangement of printed cardboard or yarrow stalks, I've crossed the line. When I solicit money to inflict such nonsense on the gullible, I've crossed the line. 
So-called "free energy," given the available evidence (that is, none), is of a kind with i-ching and tarot. People want it to work, I want it to work. But I'd also like it if I could rely on yarrow stalks to assist me in making the best decision at each stage of my life. Sadly, neither has been shown to work and there is excellent rationale and mountains of evidence, dating back hundreds of years, to show that neither can work. Yes, people can make their own decisions on what to do with their lives, their intellectual, physical, emotional, spiritual, and financial resources but, for all Sterling's, Hank's, your belief you are doing actual harm when you lead them down these paths. 
This doesn't even address the many people who have been taken in and lost financially on such schemes (though there are many, as you well know) and I don't (at this point anyway) accuse Mr. Pierce (I will NOT use the honorific "Dr." as it's clear that that's made up B.S.) of running a financial con. Whether or not Mr. Pierce actually believes in his system is an open question for me. People who truly think they've succeeded in producing a free energy device are the most mysterious to me. Con men and hustlers I get. Those who brilliantly design within the constructs of ever-evolving known physical theories, I get. Those who occupy the middle ground (assuming there are such people - not being psychic, of course, I don't know) I don't get. 
Finally, to quote myself, "I've frequently seen (at PESN, on my blog, and elsewhere) a troubling retort to physics based debunking of alleged miracle fuel saving devices, miracle cures, etc. The retort is along the lines of 'I'm sure glad I never took physics so that my view isn't limited by the dogma of traditional physics. I can be open to new ideas.' It's sad, so very much is possible within what we know and, though we certainly don't know everything, we know a lot more than nothing. And knowing what is and is not possible, the 'man will never fly' and 'aerodynamics says bumblebees can't fly, yet they do' tropes aside, enables efforts to be directed at things that have, at least, the possibility of paying off.
Update: A somewhat edited version of my comment made it out of moderation.

Monday, August 12, 2013

More on fuel saved by regenerative braking

I published a post regarding how much energy is captured in the regenerative braking system in my Lexus CT200h hybrid. After some discussion with commenter Gabriel Grosskopf, I estimated that about 59% of the energy available (after subtracting the energy used to overcome aerodynamic drag, rolling resistance, and internal friction) was recaptured and used to charge the battery.

Since I (and others) have represented that the regenerative braking system is among the key reasons that hybrids achieve superior fuel economy, I decided to check the actual impact.

My round trip commute, generally downhill in the morning and uphill in the evening, is 62.46 miles and, for the last 10 fill ups, my average m.p.g. has been 52.47. So, to make my commute, I use, on average 62.46/52.47=1.190 gallons of gasoline. My display showed me today that my regenerative braking system added 700 watt hours or 2,520,000 joules to my battery that I could use for accelerating, hill climbing, etc. If I assume my electric motor is 90% efficient, I put 2,268,000 of these joules to work.

A gallon of gasoline (reformulated blend in this case) has an energy upon oxidation of 111,836 btu or 117,993,000 joules. I estimate that my internal combustion engine is about 25% efficient, so I put about 29,498,000 of these joules to work. My 1.19 gallons thus provide 35,103,000 joules that propel my vehicle (the remainder being lost as waste heat in myriad ways).

If I assume that I used all of the energy my brakes provided, then 35,103,000 + 2,268,000 = 37,371,000 joules of work were done to propel my car. Then, dividing by 0.25, I can estimate that 149,484,000 joules of oxidized gasoline would have been necessary to do this work. This is the energy in 1.267 gallons. Dividing this into 62.46, I find that the fuel economy without the regenerative braking would have been about 49.30 m.p.g. The regenerative braking thus upped my m.p.g. by 3.17.

As I've often said, it's much more intuitively informative to discuss gallons per mile, or gallons per 100 miles. So, the regenerative braking took me from 2.03 gallons per 100 miles to 1.91 gallons per 100 miles. So it takes me 5.9% less fuel to go a given distance, ceteris parabus.

There's no question that I'm carrying a lot more significant figures (apologies to John Denker) than are warranted by the precision of my data, but I think that the figure I've determined is probably in the ballpark.

Saturday, August 10, 2013

Greenwashing Hall of Fame nominee

The Greenwashing Hall of Fame doesn't exist (to my knowledge) but it ought to. I've posted on a potential candidate or two myself. I may set it up and solicit nominees through my blog. The one I have in mind today was brought to my attention by BBC World Service on Sirius XM in my car. It was, seemingly, an advertisement for Pavegen Systems thinly disguised as a news feature (though I'm sure BBC doesn't think so).

Pavegen manufactures tiles that use piezoelectricity (I think it's safe to assume, though the site doesn't say) to "harvest" electricity from motion. They have a variety of posts for tiles installed in offices, at rail stations, schools and colleges, etc.

Specifications are given nowhere on the site, so I've had to use information from secondary sources (though I should be able to take a look at real-time generation at an office during regular hours by going here).

Looking at a couple of videos it looks like a tile deflects maybe a quarter of an inch (call it 0.006 meters) under the weight of a normal size adult male, say 76 kilograms and a weight of 750 newtons (round numbers here, they're just rough estimates). So the work done by 750 newtons through 0.006 meters is 4.5 joules. I'll assume that the tiles are 67% efficient at turning this work into electricity, making 3 joules available per step.

The source linked in the previous paragraph says that, at the West Ham Station installation, each tile got about 5 steps per minute and that a tile will produce about 75 watt hours of electricity "on a good day."  The information is confusing because it says that 50 steps per minute yields 6 watts which, in 24 hours, would yield 144 watt hours. But never mind. OK, back to the calculations. 3 joules times 5 steps per minute/60 second per minute is 0.25 watts. So, each hour would deliver 0.25 watt hours. Doing this for 24 hours would yield 6 watt hours. 50 steps per minute would yield 60 watt hours, close to the 75 cited above.

Anyway, the 6 watt hours would cost me 0.006 kilowatt hours * $0.16/kilowatt hour, or $0.00096 (96 thousandths of a penny). Though the price of a tile isn't given, it's pretty certain to take a very long time to pay off financially at a penny every 10 days or so.

I take something like 5000 steps per day, and would generate 5000*3=15,000 joules, or 3.6 kilocalories (that is, food type calories) were every step on a Pavegen tile. I step about 2.5 feet per step, so 5000 steps is 12,500 feet or about 2.4 miles. Here, we read that a 180 pound man burns about 100 kilocalories per mile as he walks, so I'd burn about 240 kilocalories (in other words, 240 kilocalories of food would be eaten) to walk this distance. I'm sure it's not exact, but here we read that, in order to feed me with 240 kilocalories, 2,400 kilocalories of fossil fuel is used.

So, putting it together, if the Pavegen system harvested the energy from every step of my walking, 2,400 kilocalories would go to produce 3.6 kilocalories of electrical energy. Of course, this isn't fair to Pavegen since I'd also, presumably, have gotten where I was going. On the other hand, I paid for the food to do that walking.

In the end, generating electricity through human effort is just not very efficient in comparison with other methods. If we're using muscle power for exercise and the effort would otherwise simply heat the environment, there may be a place for it (though I doubt it would ever pay off financially) but as a green power source, sorry, it's no sale.

Sunday, August 04, 2013

Gadgetman Groove update

Back in February of 2011, I wrote a post on the Gadgetman Groove, a modification purported to provide spectacular gains in fuel economy and power. And when I say "spectacular," I'm talking about double the m.p.g. and more. As it happens, my Groove page turns up on the most visited statistic fairly frequently. I suspect the visitors may not read what they'd hoped to but, as the Apostle Paul wrote in his first letter to the Corinthians, the time comes when we must "put the ways of childhood behind" (New International Version 1 Corinthians 13:11).

In any case, seeing that post come up as one of my most frequently visited piqued my curiosity and I paid Ron Hatton's (the inventor of the Groove) web site another visit, where I found the following quote: "The EPA tells us more than 60% of the power in your fuel is wasted in the exhaust." Does the EPA actually say such a thing? Well, sort of...

The EPA (and anyone else with a degree of knowledge of engineering thermodynamics) will
tell you that much of the chemical potential energy released in the burning of fuel in the cylinders of an internal combustions engine exits the engine as low grade waste heat in the exhaust, through the radiator, radiantly from the engine, and elsewhere, and 60% is really a very low number for that "waste" in an otto cycle engine. Such losses in a heat engine (or any engine) are an inevitable consequence of the second law of thermodynamics.

Ron Hatton, though, implies that this waste is fuel that isn't burned in the engine. Or, perhaps is burned in such a way as to not produce motive power - I'm not really sure. He has a fourteen minute explanation of its working principles (as he understands them) here. At one point, he mentions that the "ball" of high pressure air created by the groove is a million times more dense than ambient air. That would be ~1.22*10^6kg/m^3~. Yes, the air is so dense that a cubic centimeter of it weighs (ok, has a mass of) 1.22 kilograms or weighs (here at the Earth's surface) 2.7 pounds. This is about 90 times as much as a cubic centimeter of mercury weighs! If it's an ideal gas (it's not, but we're talking order of magnitude here) its pressure is on the order of ~3*10^{13} Pa~ or ~4*10^9 pounds/inch^2~ (where I've speculated that the temperature is around 470 K).

I actually watched an online "talk show" called "Talk For Food" wherein Adam Abraham holds forth on a variety of rather outré subjects. In the subject episode, Abraham interviewed Gadgetman Ron Hatton and had the groove installed in his 1993 Lexus. In the course of the interview, Hatton claimed as much as 90% of the fuel going into a typical internal combustion engine is not burned in the cylinders to produce motive power. Rather, it's burned in the catalytic converter or exhausted unburnt.

This is irrational. A gallon of gasoline releases about 132 MJ (megajoules)/US gallon upon complete oxidation. Let's assume that 13.2 (10%) of those potential MJ are actually released in consuming a gallon, and the vehicle goes, say, 18 miles on that gallon at 55 m.p.h. Let's further, generously, assume that the internal combustion engine (ICE) can utilize 30% of these 13.2 MJ (i.e., the ICE is thermodynamically 30% efficient) then we can calculate that abut 4.5 horsepower is what's required to push this vehicle down the road. Sorry, that dog don't hunt.

Hatton had an analyzer hooked to Abraham's exhaust for a before and after test. The footage showed somewhere around 3,900 ppm (parts per million) for hydrocarbons in the exhaust before installation of the groove and 0 (yes, zero) after. Now, I've not seen any independent testing of the exhaust stream, so I can't say that these results have been replicated (nor that replication has been attempted and failed).

I don't claim that the Groove doesn't work, or that it provides no benefits. I simply state that all the "I think I'm getting about 28 m.p.g. and I used to get 12 m.p.g. and it sure does run smooth now" anecdotes on youtube provide no evidence that it does provide benefits.

But, at a broader level, I ask you: If this simple modification could be so effective, why aren't all the vehicle manufacturers beating a path to Hatton's door to license the (patented) technology? Can the oil companies really afford to pay them off? Imagine that Chevy could announce a Chevy Cruze that achieved 45 m.p.g. or even 60 m.p.g. and that car cost not a penny more to manufacture (the groove would, after all, not be installed by auto workers with Dremel tools as Hatton does it).

Anyway, I'll answer a question that comes up when I write about such matters and then make a comment on a comment I've seen on my blog posts and elsewhere. The question: "why do I care? The customers are satisfied, Ron Hatton seems like a nice guy." I care for a couple of reasons. First, the rising (worldwide, if not in the US) demand for petroleum based transportation fuel coupled with our stagnant ability to provide it makes critical analysis of possible efficiencies crucial and the discounting of pixie dust pivotal. Second, the gullibility and inability to think critically of the US public is disturbing and each example troubles me.

As to the comments, I've frequently seen (at PESN, on my blog, and elsewhere) a troubling retort to physics based debunking of alleged miracle fuel saving devices, miracle cures, etc. The retort is along the lines of "I'm sure glad I never took physics so that my view isn't limited by the dogma of traditional physics. I can be open to new ideas." You'll see such a comment on my original Gadgetman post. It's sad, so very much is possible within what we know and, though we certainly don't know everything, we know a lot more than nothing. And knowing what is and is not possible, the "man will never fly" and "aerodynamics says bumblebees can't fly, yet they do" tropes aside, enables efforts to be directed at things that have, at least, the possibility of paying off.

Tuesday, July 30, 2013

A quick note on the eGallon

Screen shot of my results from DOE eGallon site
In a previous post I mentioned the eGallon concept from a Department of Energy (DOE) web site. It purports to tell a visitor how much he or she would pay to drive as far in an electric vehicle as a gallon of gas takes them in an "average vehicle." It breaks down only as far as by state (or U.S. average). So, for example, if I use California, it tells me that a gallon of regular gasoline costs $3.99 and that my eGallon costs $1.53.

But my average mileage over the life of my vehicle is 50.86 m.p.g. At my most recent fill up I paid $4.059/gallon. I'll use the Nissan Leaf for a comparison, the vehicles are broadly similar in important ways. Each has a Cd (drag coefficient) of 0.29 and, while the frontal area of the CT200h is a bit larger, the Leaf weighs more. The Leaf is rated by the EPA to consume 29 kWh/100 miles for the 2013 model year.

So, on a gallon of fuel, I go 50.86 miles. The Leaf would need (50.86/100)*29 kWh = 14.75 kWh to go that distance. If I assume that the charging system is 85% efficient, I'd pay for 14.75/.85=17.35 kWh. On my most recent electric bill I paid $0.1611/kWh for electricity above the "basic lifeline" rate, so these 17.35 kWh would cost me $2.80 and that's the price of my eGallon. Quite a difference between that number and $1.53, the "true" number is 83% higher whereas the number for my gasoline cost is not far away from what I actually pay. The computed eGallon price would be even further from ReGallon cost ("Rob's eGallon") if DOE had used the 2013 model year numbers for the Leaf in lieu of previous years' 34kWh/100 miles. If I use the 2013 model year number for the Leaf and the EPA combined estimate (42 m.p.g.) for the Lexus CT200h that I drive, an eGallon would cost $2.31, only 51% higher than the site's number.

You can read about their methodology here. The confounding factors are the actual cost of electricity and the fuel economy utilized for the ICE (internal combustion engine) vehicle. For reference, the plot below (you can click it to enlarge and be able to read the numbers) shows an AeGallon ("actual eGallon") for a range of actual fuel economies from 12 m.p.g. (the driver currently in a vehicle getting less than that is not a likely candidate for an EV) to 70 m.p.g. (a hypermiler in a Prius). For this plot, I'll use the same electricity consumption as the DOE site uses, i.e., 35 kWh/100 miles, a blended rate from 5 top selling EVs. Electricity prices on the plot range from $0.09 to $0.20 per kWh. You can calculate your number yourself, it's as simple as 0.4118*(m.p.g.)*(electricity cost per kWh). You'll note that, for combinations of high mileage vehicles and expensive electricity, the eGallon may be more expensive than a gGallon (i.e., a gallon of gasoline).

On the plot, the "front" axis is m.p.g. for the vehicle being replaced with an EV, the rearward extending axis is the price of a kilowatt hour of electricity, and the vertical axis is the price of an eGallon in dollars. You can see that, for low mileage vehicles being replaced, the eGallon is quite inexpensive, regardless of electricity costs. But as replaced vehicle fuel economy climbs, the eGallon becomes much more expensive. The DOE site simply uses a single fleet average fuel economy (28.2 m.p.g.) and does not correct for the 85% charging efficiency I estimated.

Monday, July 29, 2013

Commentary: Is Peak Oil Dead?

Commentary: Is Peak Oil Dead?: A little rain on the parade of the new era of easy oil availability and "American Energy Independence" from an oilfield veteran.

'via Blog this'

Sunday, July 28, 2013

How are we doing on EV adoption?

In November, 2009, I published a post that used the logistic function along with a couple of guesses (one by Nissan CEO Carlos Ghosn, one by me) and assuming that, in the next few decades, essentially all light duty vehicles on the road would be electric, to estimate the additional electrical load needed annually. I speculated (estimated is WAY too strong) that at the peak, sometime around 2039, we'd add 12,000,000 electric vehicles to the fleet requiring 6.6 gigawatts of generating capacity (assuming no smart grid utilization of the vehicles as storage, or other load leveling techniques).

Now, almost four years later, I thought it would be interesting to take a look at how the adoption of EVs ( combining PHEVs or plug-in hybrid electric vehicles such as the Chevy Volt and AEVs or all-electric vehicles such as the Nissan Leaf) is progressing in comparison to the very rudimentary model.


I used Ghosn's response to President Obama's call for one million EVs on the road by 2015, i.e., that that number would be "easily surpassed." I assumed two million in 2015 and 230 million in 2050 and used those points as input to the logistic function. I used Wolfram Alpha to plot the data (if you click the link, the assumptions will be built into the input and you can change them to suit). Of course, the plot starts in 2015 and EVs and PHEVs started to be on the road in 2010 and it's now 2013. But nothing stops me from plugging negative numbers into the plot range to go from 2010 to 2015 (or numerically evaluating the function). Doing so predicts (here I assume January 1, 2010 is -5.0 years, January 1, 2015 is 0 years, and here, about 7/12 of the way through 2013, we're at -1.42 years) just over 1.5 million EVs and PHEVs on the road.


What is the actual number? The best data I've found is at the Electric Drive Transportation Association's site. They've compiled it here and the pertinent graph is to the left (click to enbiggen). The astute reader will note that the actual number is about 112,000, less than 10% of my speculative number. With a year and a half to reach 2015, and two and a half to reach the end of 2015, Ghosn's prediction is looking precarious. Let's speculate some more.

What if I plug actual data into a logistic curve (the curve form EDTA certainly doesn't preclude such a model)? I'll use 112,000 in 2013.5 and 230 million for the ultimate number and see what growth rate yields 6,669 (from the graph using GraphClick) in June of 2011. The rate turns out to be 141% annual growth (initially). I doubt that this growth can be sustained indefinitely as early adopters complete adoption and the curve flattens. Such a rate would result in a 230 million EV fleet in around 2022. It's unimaginable that this could take place. Still, if the growth rate continues, we'll have two million EVs on the road sometime in mid 2015.

Sunday, July 21, 2013

SCMs

My firm is what would, in general, be viewed as one of the larger closely held, locally based construction inspection, materials testing, and geotechnical engineering firms in California. Barriers to entry for, at least, several material segments of our business are very minimal, though to provide the full spectrum of services that we offer they are significantly greater. Unfortunately for us, the "meat and potatoes" of our service line can be served (with arguable effectiveness but very low price) by those who select to provide only those services with the aforementioned low barriers.

Thus, we're constantly looking for areas where the investment we've made in people and equipment of very high capability can provide value that will be recognized by a client base willing to pay for these. In this effort, we've engaged in significant research and development, led by Dr. Boris Stein. Much of this R&D work has been related to various sustainability issues regarding concrete and its use in the built environment.

 Concrete is a construction material composed of cement (typically portland cement and thus referred to as "portland cement concrete"), coarse and fine aggregates, water, and, possibly, various admixtures to customize the concrete's properties in various ways.

The manufacture of portland cement involves (at a very simplistic level) charging a kiln with limestone (calcium carbonate, Ca CO3) and various other constituents (chiefly clay as a source of alumino-silicate), and heating the charge to around 1450°C. This results in the emission of CO2 as CaCO3 is changed to CaO in the so-called "clinker." This process is called "calcining." This clinker is then ground to an extremely fine powder in a grinding mill, and a small amount of gypsum (CaSO4) is added.

The heat may be supplied, in some instances, by the burning of manufactured materials (discarded tires, for example) but is usually accomplished by the burning of fossil fuels. Thus, the production of portland cement is a twofold emitter - the combustion product of the fuel used to heat the kiln and the "cooked off" CO2 from the calcium carbonate. Though estimates vary, for each tonne of cement produced, approximately 750 kg of CO2 is emitted. It's estimated that somewhere around 5% of the CO2 emissions worldwide are a result of the manufacture of cement (I've seen estimates as high as 7%).

Thus, finding substitutes for portland cement in concrete is an active pursuit in the academic and industrial arenas. Some of these pursuits involve replacement of calcium carbonate with a different raw material that either is a non-carbonate, requires much lower temperatures for processing, or both.
Electrotatic precipitator for collecting fly ash


Another approach is partial replacement of portland cement in a concrete mix with various industrial byproducts, "supplementary cementitious materials" or "SCMs." Chief among these are fly ash (a product of coal combustion) and ground granulated blast furnace slag ("GGBFS" or just "slag," a product of the refining of iron and of steel making). It's also possible to use "natural pozzolans" literally mined (typically from Southern California desert locations for use here).

As much as 50% or even 70% of the portland cement in concrete can be replaced with these SCMs, and the resulting concrete mixes can, with suitable attention to proportions and admixtures, result in concrete with much lower carbon footprint and characteristics as good as, or even better than, mixes utilizing only portland cement.

Books can be (and have been) written on the various methodologies of designing mixes with desired properties and I'm not going to go into that here. But let me (as is typical) use some back of the envelope calculations to see what kind of CO2 emission reductions are possible.

In 2011, 3.6 billion tonnes of cement were produced worldwide and this resulted in the emission of over 2 billion tonnes (metric ton, 1,000 kilograms - about 10% larger than a U.S. "short ton" of 2,000 pounds) of CO2. Certainly, some of that cement went into mixes already utilizing SCMs but the fraction worldwide, would be fairly small. Typical U.S. mixes at this time might utilize 15% to 25% fly ash, and many mixes don't use any. If we assume that 10% fly ash might be typical for a worldwide average and that we could ultimately get to mixes with 70% SCMs (entirely possible from a technical point of view). If so, we could reduce the 3.6 billion tonnes to 1.2 billion tonnes (to the great despair of the cement manufacturers who would fight this tooth and nail) and save the emission of something like 1.8 billion tonnes of CO2 annually.

Ah, but what about the availability of the SCMs?  We certainly don't want to burn more coal or refine more iron for the purpose of providing the concrete industry with SCMs. In 2010, 777.1 Mtonnes (megatonnes - a million tonnes or a billion kilograms) of CCPs (coal combustion products, most of which is fly ash) were produced and 415.5 Mtonnes were utilized. While much of the utilized fly ash went into concrete, there are many other uses competing for it. Let's say that, by more effective harvesting and economically incentivizing use in concrete, we could use 500 Mtonnes/year.  We're currently using about 190 Mtonnes in concrete, so we could possibly increase our use by 310 Mtonnes.


As for GGBFS, the latest year for which I could find data was 2005, in which the world produced 110 Mtonne of slag, of which 60 Mtonne went to slag cement. Suppose that we could use 100 Mtonne (assuming both an increase in production and an increase in utilization), a 40 Mtonne increase.

Totaling, and assuming that appropriate mix designs enabled all of the 310 Mtonnes of fly ash and 40 Mtonnes of slag to be used, we could replace something like 350 Mtonnes of portland cement. Thus, rather than the 2.4 billion tonnes feasible with technological implementation of mix designs, supply constrains us to the replacement of 0.31 billion tonnes and the elimination of something like 230 Mtonnes of CO2, on the order of 0.7% of worldwide emissions.

Sadly, SCMs won't save the world, but we are certainly heavily engaged in pursuing them. They have benefits in the final concrete product, they reduce the industrial waste stream and, to a limited extent, can reduce industrial CO2 emissions.


Wednesday, July 17, 2013

Regenerative braking in the Lexus CT 200h

I've been driving my Lexus CT 200h for about two years and about 39,000 miles. In that time, I've learned a lot about driving techniques to minimize specific fuel consumption (g.p.m., gallons per mile). I've also given some thought to what it is about a hybrid that makes it more fuel efficient. One of those items is regenerative braking, where some of the kinetic energy in the moving vehicle is used to charge the battery rather than to heat the brake rotors. This is done by having the energy of the moving vehicle turn the electric motor backwards, thus making it a generator and thereby charging the battery. Of course, friction brakes are also used.


I've wondered just how much of the braking energy goes into the battery and have been hard pressed to find data for this. However, the CT 200h has a display option for "Consumption" (see photo at left). It's difficult to see (click to enlarge) but there are small boxes in the vertical bars that indicate mileage by the minute. Each complete box, according to the legend, represents 50 watt hours of energy (180,000 joules). At the top of a hill, I applied sufficient braking to keep my speed at approximately 35 m.p.h. At the bottom of the hill, a stoplight brought me to a stop.


I can calculate the energy difference from 35 m.p.h. at the top of the hill to 35 m.p.h. at the bottom of the hill by using Google Earth to find the elevation change. I determined it to be 103 meters. Because my speed didn't change, neither did my kinetic energy, therefore the reduction in my potential energy went to some combination of heating my brake rotors and charging my battery.

My best estimate of the mass of the vehicle with the 1/4 tank of gasoline and myself and my baggage is 1,600 kg. Therefore, the potential energy lost in the descent is ~E=mgh=1600kg*9.8\frac m{s^2}*103 m=1.62*10^6joules~. The display shows "E" boxes and fractions of "E" boxes and my best estimate, assuming that 3.5 "E" boxes are shown is that ~3.5*50Wh=175Wh~ or ~630,000joules~ were sent to the battery. I don't think it could be lower than ~585,000joules~ or higher than ~675,000 joules~.

Assuming that I'm interpreting the cryptic display correctly (and that Ed Davies doesn't haul me up short!), about ~630000/1620000=38.9\%~ of the potential energy went to charge the battery. The rest was dissipated as thermal energy in the disc brake rotors and, ultimately to the atmosphere. The battery pack in the CT 200h is a 1.3 kWh Ni metal hydride battery. The 630,000 joules equal 0.175 kWh or 13.5% of a full charge for the battery. Per the owners' manual, I'm able to drive in "EV mode" (battery only) for two miles, but I'd best accelerate slowly even by my standards, and not exceed about 20 m.p.h.

As an aside, this is the energy in about 18 cm^3 of gasoline. Figure I'd have to burn about four times that, or 72 cm^3 to charge the battery with the engine at 25% efficiency. And, of course, the regenerative braking isn't effective when the battery is fully charged, isn't used (much) in hard stops, etc. Still, it does increase overall fuel efficiency.

Finally all of these figures have large "error bars," the regenerated energy on the display, the elevations from Google Earth, the mass of the vehicle, and the ability to stay at precisely 35 m.p.h. (although really, all I need is to be going at the same speed when I stop logging as when I start so that the kinetic energy is unchanged). Still, it's enough for me to have a good idea of what the regenerative braking can give me.

Update: Based on a comment by Gabriel Grosskopf, I measured the distance over which I descended. It was 1,530 meters, thus the slope is 3.86 degrees (0.0673 rad). The typical instrument landing system glideslope is 3 degrees though a few, such as VNY - Van Nuys - at 3.9 degrees, are steeper. Assuming that I drove the 1530 meters at 35 m.p.h. or 15.6 m/s, it took me 98 seconds to put 630,000 joules into the battery. This is a charging rate of 6,440 watts or 6.4 kW. As mentioned in a previous post, when I put fuel in my gasoline tank, I'm adding energy at a minimum rate of 11 mW, about 1,700 times as fast. To be fair, we'll divide that by four since IC engines are much less efficient than electric motors. So we're adding useful energy at 2.75 Mw or 430 times as fast. Coincidentally, the Nissan Leaf touts a 6.6 kW charger to charge its 24 kWh battery.