Author: chogan@directresearch.com

Post #1613: How the Prius does its thing.

 

Introduction:  The U.S. market for gas-powered cars in 2005.

Source:  Analysis of US EPA gas mileage and vehicle specification data, 2005 model year.

Back in 2005, my wife needed a car.  And by that I mean, we were interested in a gasoline-powered passenger car.  Not a truck, crossover, van, SUV or the like.   And not a diesel.   We’d done that, and didn’t much like the drawbacks of the diesels of that era. A passenger sedan, in the parlance of the era.  Fueled by gasoline.

I was interested in buying something that was efficient.  But the raw MPG numbers were a jumble, driven largely by the size of the vehicle.  I didn’t really want to try to squeeze into some tiny econobox just because it got better mileage than a bigger car.  I was interested in identifying something that was efficient at converting gasoline into movement of passengers and luggage.  Not just the tiniest car I could fit into.

I took data from the EPA and calculated fuel efficiency in a way that put large and small cars on more-or-less equal footing.  Instead of looking at miles per gallon, I calculated cubic-foot-miles per gallon.  Where “cubic foot” is combined interior passenger and luggage room, measured in cubic feet.  Under this approach, a car that was twice as big, but got half the gas mileage, would count the same as a car that was half as big, but got twice the gas mileage.  They both used the same amount of gas to move a given volume of passengers and luggage.

My “cubic-foot-miles per gallon” for passenger cars is similar to the concept of ton-miles per gallon for freight vehicles.  For the simple reason that miles-per-gallon doesn’t tell you how much you were able to haul.  Trains, after all, burn a lot of diesel fuel per mile.  But they also move a lot of tonnage with that fuel.  In some sense, what matters isn’t the amount of fuel burned, it’s the usable carrying capacity that the fuel consumption provides.

The idea was to make this a two-step process.  First, I would separate out the vehicles that were efficient, regardless of size.  Then, from the lineup of vehicles that rose to the top of that listing, we could try to make an informed choice about what size of car we wanted to buy.  Given the choice of efficient vehicles on the market at that time.

Things did not quite turn out as planned.  I figured I’d get a “spectrum” of efficiencies, with a few dozen cars to choose from at the high end of the spectrum.

When I did that calculation– and so removed the variation that was driven merely by the size of the car — the data resolved into the amazingly simple picture, shown above.  For gasoline passenger cars, the 2005 American market consisted of three pieces:

  • The Prius
  • The Honda Civic Hybrid
  • Everything else.

The real eye-opener, to me, was the extent to which “everything else” was just that.   Basically, all non-hybrid cars were roughly equally inefficient.(!)  Sure, you had some muscle cars come in at the bottom of the heap.  But the point is that there wasn’t some nice, smooth distribution of cars in terms of their efficiency.  There was crowded mass of vehicles with little to distinguish one from another.  There was the Honda Civic Hybrid, poking up above that mass.  And there was the Prius, running about three times as efficiently as the average. 

The upshot is that if you wanted an efficient gas car in 2005, the decision was a no-brainer.   You bought a Prius.  The only other gas car that came close to it was the Honda Civic Hybrid, and that was just a bit too small for me.

The best way I know of to illustrate how different the Prius was from other offerings at the time is to ask this simple question:  In the 2005 car market, what was the most efficient gas-powered vehicle capable of moving six people?  The answer?  Two Priuses.  Every six-passenger sedan, van, or SUV got less than half the gas mileage of the Prius.  It was that far ahead of its time.

(As a footnote, I never put pickups, vans, or other special purpose vehicles (SUVs, etc.) on this graph because I couldn’t get the interior volume information.  The EPA showed the MPG for those vehicles, but in 2005, the EPA only tracked interior volumes of passenger cars.  And, as it turns out, that’s still the case.  They only note the interior volume of traditional passenger cars.)

Redo:  The U.S. market for gas-powered cars in 2022.

Now fast-forward to the 2022 model year, and ask the same question.  If you were interested in buying an efficient gas-powered car, what would your options be?  (I use 2022, not 2023, because the 2023 model year data from the U.S. EPA are not yet complete).

First, you have to acknowledge how much the market has changed.

In 2005, there were no electric vehicles (EVs) or plug-in hybrid electric vehicles (PHEVs).  For passenger cars, 99% of the offerings were straight-up gas vehicles.  There were a couple of hybrids, and a couple of diesels.  Roughly speaking, 99% of the models offered were standard gas cars.

In 2022, here’s how the U.S. passenger car market shaped up.  (Recall, this is just cars, not pickups, vans, SUVs, and the like.)  In 2022, three-quarters of the offerings are still standard gas vehicles.  But more than one-quarter are  alternatives — hybrids, plug-in hybrids, or EVs.

Now let me ask the gas-car-efficiency question, for 2022.  I’m ignoring EVs, and for the PHEVs, I’m using just their gas-only mileage.  How do gas-powered cars shape up, in terms of my efficiency measure (cubic-foot-miles per gallon)?

 Source:  Analysis of US EPA gas mileage and vehicle specification data, 2022 model year.

Unlike 2005, the Prius now has quite a bit of company.  The 2022 Prius is slightly more efficient than the 2005 model, but now there are a couple of gas-powered cars that top it, and many that are nearly as efficient.

Unsurprisingly, everything at the top of the efficiency charts, for gas-powered cars, is a hybrid of some sort.  The entire cluster of gas sedans at the top consists of hybrids and PHEVs (where only the gas portion of the PHEV mileage has been counted.)

For the record, the two Prius-beaters on that graph are the Hyundai Ioniq and Ioniq Blue.  For reasons that must make sense to Hyundai, those are no longer being made as gas hybrid versions.   Hyundai discontinued those cars as of June 2022 (reference).

So, by the time we get to the 2024 model year, the Prius will be back at the top of the heap.  As it should be.  But now, at least, it has some close company.

Finally, I have to emphasize that this was for gas-powered vehicles.  On paper at least, there are many fully-electric (EV) and partially-electric (PHEV) cars that get MPG-equivalents in excess of the 54 MPG for the Prius Eco (highlighted in the chart above).  But here, I wanted to look at gas-powered cars, for comparison to my 2005 analysis. And I don’t want to get into what those MPGe numbers actually mean.  It’s not straightfoward.

How does the Prius achieve such efficiency?

You see a lot of bad information about how the Prius achieves its high efficiency, for a gas-powered car.  Some is just plain confused, some gets the orders-of-magnitude wrong.  Some explanations appear to violate basic physics, such as the law of conservation of energy.

To be clear, Toyota did optimize many aspects of the operation of that car.  If you look at a list of where energy gets dissipated in a typical car, the Prius addresses every area.

Source:  Energy.gov

Take wind resistance, for example.  Once you actually manage to get energy to the wheels of the car (Power to wheels line, above), about half of that energy gets dissipated as wind resistance.  If you want decent mileage, you need to keep that to a minimum.  The Prius has a “coefficient of drag” of 0.24, among the best ever measured for a mainstream U.S. passenger car (see the extensive list in Wikipedia.) By contrast, your basic brick-on-wheels design  — a Jeep Wrangler — has a coefficient of drag of about 0.45.  What people perceived in 2005 as the somewhat odd shape of the Prius was all about providing interior volume while minimizing air resistance.

There are other minor contributors.  The Prius comes with low-rolling-resistance tires.  It minimizes losses from braking by using regenerative (electrical) braking where possible.  It reduced the parasitic losses from (e.g.) air conditioning by employing a more efficient compressor design.  And so on.

But as you can see from the chart above, most of the energy wasted by a standard gas car is wasted by the engine.  As I understand it, the single largest driver of Prius efficiency — and the reason it had to be made as a hybrid in the first place — is that it uses a different type of gasoline engine.  It’s an Atkinson-cycle (or maybe Miller-cycle) engine, instead of a standard car Otto-cycle engine.

Why do I think the use of an Atkinson engine is key?  Well, here’s a list of the top 20 most-efficient gas cars offered in the U.S. in 2022, listing their specs and the type of engine they use.

Notice anything?

What was unique to the Prius in 2005 is now the standard way to achieve good fuel efficiency in a gas-powered car.  But, as explained below, in most cases, you have to add some secondary propulsion (electric motors) to get adequate on-road acceleration.

Here’s the explanation in brief.

The chemistry of gasoline dictates that you need a fairly “rich” gas-air mixture in an internal combustion engine.  If you make the mix too lean — too little gasoline relative to the air — the spark plug can’t ignite it and/or it burns poorly and/or it generates a lot of nitrous oxides.  To get reliable ignition and a clean burn, you more-or-less need to mix gas and oxygen in the ratio needed for complete combustion of the gas.  Too little gas in the mix and the engine stumbles and dies, or runs dirty.

But if you fill the engine cylinder with that relatively rich gas mix, you end up with more chemical energy in that cylinder than you can use.  Sure, you can compress it and ignite it.  But there’s so much energy that you’ve still got quite a bit of usable gas pressure left when the piston gets to the bottom of the cylinder.  (The number I see cited most often is that, under load, the gas pressure in the cylinder is still at five atmospheres when the piston hits the bottom of its range of motion.)  At that point — once the piston bottoms out — all you can do is open the exhaust valves and let all that potentially usable energy — that still-usable gas pressure — escape out the exhaust.

And that’s exactly what a standard Otto-cycle car engine does.  The intake stroke and power stroke are the same length, the valves open and close within a few degrees of the piston being at bottom dead center/top dead center.  At the end of each power stroke, there’s plenty of pressure left in the gas inside the cylinder.  And with each cycle, that energy gets tossed out the exhaust port.

This has been known for decades, i.e., that gas engines would run more efficiently if you could put a much leaner mixture into the cylinder.  The problem was getting that leaner mix to ignite and burn well.  Back in the 1970s, Honda tried to address this with its stratified-charge engine (reference).  That used two carburetors — one rich, one lean — and two intake valves.  It filled the top of the cylinder with a richer mixture that the spark plug could ignite.  And the rest of the cylinder with a leaner mixture that would itself be ignited by the rich mix at the top.  It was moderately successful, and I recall that the Honda CVCC with that engine was among the most fuel-efficient cars of its generation.

A better way to put less gasoline into the cylinder, and yet have it burn well, is to fill only part of the cylinder on the intake stroke.  Where I need to define “the cylinder” as the full length of the resulting power stroke.  That way, the air-to-fuel mix is correct for consistent ignition and clean burn.  You simply have less total fuel in the cylinder before you ignite it.

And that’s exactly what the modern Atkinson (or Miller) cycle engine does.  And it does that by closing the intake valve well after the piston hits bottom dead center.  This allows the piston to push out maybe 30% of the total air-fuel mix, then compress and explode what’s left.  As a result, you get both the right chemistry (the right air-to-fuel ratio) and the right amount of fuel to allow the resulting energy to be used efficiently.

In the Prius engine, more-or-less, the intake valve closes when the piston is 30% of the way up the bore.  (The engine has variable valve timing, so, well, that varies).  That works out to be, in effect, about a 10.5:1 compression ratio, and a 13.5:1 expansion (power stroke) ratio.

And so, while the standard Otto-cycle engine has nearly-identical compression and expansion (power stroke) ratios, the Atkinson-cycle engine has a much lower compression ratio, compared to its expansion (power stroke) ratio.  The whole point of which is to allow you to put the right fuel-air mix into the cylinder, just less of it.

But this comes at a cost.  With less fuel, and a longer expansion stroke, there’s less power with each power stroke.  And part of that power stroke now occurs at pressures much lower than you would get in an Otto-cycle engine.

As a result, the Atkinson engine is efficient, but it has a relatively poor power-to-weight ratio.  In the case of the Prius, the older 1.6 liter engine might have produced maybe 140 horsepower configured as run as a standard Otto-cycle engine.  But as an Atkinson-cycle engine, I think it barely broke 90 horsepower.

The result would have been a car with unacceptable on-road performance.  (Yeah, even for Prius drivers.)  So, the engineers at Toyota (and Ford) added electric motors, a big battery to run the motors, and so on.  And the hybrid was born.

To be clear, the electrical side of the modern hybrid is more-or-less a necessary evil.  It was something tacked on after the fact, to allow the engineers to replace the inefficient Otto-cycle engine with a more efficient, but less powerful, Atkinson-cycle engine.

So, now you know the primary source of Prius efficiency.  And you know why the 20 most efficient gas-powered cars offered in the U.S. all use Atkinson-cycle engines.

 

Post #1612: CO2 emissions from gas versus electric leaf blowers.

Source: Xerces Society for Invertebrate Conservation

To be clear, I think the right thing to do with your fallen leaves is to leave them alone, to the extent that you can (Post G22-034).  But if you’re going to use a leaf blower, how do gas-powered ones compare to electrics, in terms of generating C02 emissions?

Bottom line:  7-to-1.  At Virginia’s current electrical generation mix, a gas-powered leaf blower produces about seven times as much C02 emissions as an electric leaf blower.  I show the calculation below.

In part, that’s because the grid just keeps getting cleaner.  A couple of decades ago, the difference would have been more like three-to-one.  But mostly that’s because small two-stroke engines, as used on leaf blowers, are inefficient.

Note that this 7-to-1 ratio is just for C02.  In terms of total air pollution, gas powered leaf blowers stack up far, far worse compared to electrics.  In particular, smoky two-stroke gas engines produce huge volumes of unburned hydrocarbons, as anyone who has ever seen and smelled the exhaust from a two-stroke can attest.

To be clear, leaf blowers don’t use enough gasoline to matter, in terms of our annual C02 emissions.  They are a drop in the bucket.  And not that there aren’t a lot of other reasons to skip leaf blowers entirely, let alone gas-powered ones.  But this is a statistic that I wanted to pin down.  So here is the calculation, with citations as to source.

Background

My wife asked me a simple question today regarding gas-powered versus battery-powered leaf blowers.  How do they compare in terms of C02 emissions?  I did a quick back-of-the-envelope and got numbers that didn’t appear credible.  So I decided to do a more formal calculation, with the metric being pounds of C02 produced per 100,000 cubic feet of air moved.

It’s already well-established that gas-powered leaf blowers produced a tremendous amount of air pollution, per amount of work performed.  That owes mainly to the use of small two-stroke engines.

No shock there — these are the engines where you mix the oil with the gas, and burn that mixture to produce a smoky blue exhaust.  That exhaust is every bit as dirty as it looks.  You can look that up anywhere, and as far as I know there’s more-or-less zero disagreement about that.  Here’s what appears to be a fairly sophisticated test (reference Edmunds).

In terms of pollutants (e.g., unburnt hydrocarbons) and such, that’s the pretty much the end of the story.  Except to note that a part of the resulting air pollution is black carbon, which is increasingly being recognized as a major contributor to global warming (See Post G22-058).  So, these two-stroke gas engines contribute to global warming beyond their emissions of C02 alone.

But my question was in terms of C02 emissions.

In absolute terms, obviously, the gas consumed in lawn care is a drop in the bucket, compared to the gas consumed by cars and trucks.  (So, priding yourself on using an electric mower, while you drive an inefficient car, is straight-up greenwashing, in terms of impact on C02 emissions.  It might ease your conscience, but in the grand scheme of things, your lawn mower is rounding error in your household carbon budget.)

That said, just exactly how do the C02 emissions compare, between gas and electric leaf blowers?  My first rough cut seemed to say that gas leaf blowers produced vastly more C02, compared to electrics, than gas cars did compared to electric cars.  (Which, for a Prius, is about 2.5:1.  Gas miles in our Prius Prime produce about 2.5x as much C02 as do electric miles.).  So I decided to do a more careful and better-documented calculation.

A virtual trip to Home Depot, and a surprise.

I went to the Home Depot website and began with the first gas-powered leaf blower that showed up.  This is an ECHO gas-powered backpack leaf blower.  I downloaded the manual to see what I could find out.

My first shock was in finding that this can be fitted with air pollution controls.  For example, this model has a catalytic converter and a gasoline evaporation control system, at least in some areas.  This, apparently, is required by law, and has been required, in at least some areas, since the mid-2010s.

Source:  Manual for the ECHO backpack leaf blower referenced above.

I then looked at a similar Ryobi model, and it too has a catalytic converter as an option.  That said, the owners’ manual says that it must be replaced every 50 hours.(!)  Hard to find it labeled as catalytic, but it appears that the muffler assembly is a $50 part.  I’m guessing the average user will not bother to replace that after 50 hours of use.

Source:  Manual for the Ryobi backpack leaf blower cited above.

The important implication of this is that older comparisons — such as the 2010 testing done by Edmunds, cited above — may (or may not) be vastly out-of-date.  Those older studies predate catalytic-converter-equipped units.  It’s not clear to me whether all units are now equipped with catalytic converters, or whether the typical owner bothers to maintain those catalytic converters.  But this does make me wonder just how much all of the often-cited literature on the dirtiness of these engines is out-of-date.  I certainly see recent articles that still cite the remarkable findings of that Edmunds comparison.

It also appears that most of the advocacy articles focus on the high levels of unburned hydrocarbons.  That’s where the blue-smoke-spewing two-strokes do the worst.  All of them also seem to add in a huge amount of spilled gasoline, though how they could possibly know the average spill rate for the average consumer is beyond me.

Anyway, catalytic converters on two-stroke leaf blowers — that was news to me.  (Though if you Google it, you can find many examples.).  Maybe I’ll investigate further at some point.

For now, I’m looking for fuel consumption (which will dictate C02 output) and work produced, probably measured as cubic foot of air moved per minute.

Moving on.

After looking at a few more gas-powered leaf blowers, it’s clear that they use so little fuel that homeowners don’t care what the fuel consumption is.  The issue of fuel consumption per hour, or typical run time on a tank of gas, is simply not addressed in any of the consumer literature for these devices.

You really have to dig to get it.  Luckily, Stihl introduced some fuel-efficient models about a decade ago, and as part of that, they produced statistics on typical gasoline consumption per hour.  These were aimed at demonstrating cost savings to professional users such as landscape maintenance companies.

With that in hand, it’s just a question of comparing some off-the-shelf plug-in electric models to a couple of efficient Stihl gas models.  Here’s the calculation.

Discussion

The bottom-line figure seems completely credible to me. 

For a Prius, the equivalent number would be 2.5 to 1.  That’s my best estimate (presented in long-ago prior posts), based on our experience with a 2021 Prius Prime.

It’s no surprise that the ratio would be not quite 7 to 1 when comparing small two-stroke engines to electric motors.  In general, engine efficient drops with size, due to proportionately larger heat losses in small engines.  And two-stroke engines are designed for a good power-to-weight ratio, not for fuel efficiency.  Meanwhile, electric motor efficiency — at least at this size — varies only modestly by size.  And as a result, what was a 2.5 to 1 advantage for electric cars becomes a 7 to 1 advantage for electric leaf blowers.

That said, the global warming impact of these devices is almost negligible, at least in terms of C02 emissions.  Note, from the table above, that you’d have to run those leaf blowers for about three hours to use up one gallon of gasoline.  Compare that to the U.S. average of about 650 gallons of gasoline per licensed driver per year, and it’s obvious that leaf blowing really doesn’t much matter, in the overall U.S. carbon budget.

That said, this is just another illustration of something that I hope is becoming increasingly clear to most Americans:  The future is electric.  The rapid de-carbonization of the grid means that more and more frequently, the low-carbon option is going to be the electric option.  Whether that’s for transportation, heating with heat pumps (Post G22-058), or for moving your leaves from place to place.

On the smugness of raking, or, TANSTAAFL

I’m sure that at least some readers have thought to themselves, “Why use a leaf blower at all?  I rake my leaves, therefore I don’t use any fossil fuels to collect my leaves.”. 

Well, it just ain’t that simple. 

  • Raking consumes energy.
  • We supply that energy with fuel.
  • That fuel is a highly refined substance called “food”.
  • Food production and distribution consumes enormous amounts of fossil fuel.

One way or the other, everybody wants to think that there’s a free lunch.  In this case, the free lunch is the illusion that if you don’t consume fossil fuels directly, then you can ignore the fact that you’re consuming them indirectly.

And I’m the guy who gets to tell you that nope, there ain’t no such thing as a free lunch.  The facts are that:

  • it took a lot of fossil fuels to make your lunch, and
  • if more exercise means you eat a bigger lunch, then
  • more exercise means you consume more fossil fuels.

The only trick is that you consume those fossil fuels indirectly, via increased food consumption, not directly, by gassing up your power tools.

I was introduced to this concept in an article entitled “Bicycling Wastes Gas?“.  I can do no better than suggest that you read it.

Here’s the story of how I finally came to understand this.  In my youth, for two years, I biked to work about three times a week, during the warm weather.  Work, in this case, was downtown Washington DC.  The round-trip distance was about 32 miles.  For a guy my size, that burns about 1600 calories.

Lo and behold, I found myself eating a lot more.  Conservation of energy, and all that.  Those 1600 calories of daily exercise had to come from somewhere.  And if my weight remained stable, they had to come from an additional 1600 calories of food.

The kicker is that, for the standard American diet, it takes about 10 fossil-fuel calories to make and deliver one edible calorie.  Estimates vary, but that’s a nice round credible number.  So, while 1600 calories doesn’t sound like much energy (for comparison, a gallon of gas contains about 31,000 (kilo) calories of energy in it), once you factor in how the fossil fuel energy required for one edible calorie, suddenly, you realize that your 1600 calories of typical-American-diet embodies as much fossil fuel as … roughly half-a-gallon of gasoline.

Here’s a reference that, at the end, comes to the same conclusion that I’m about to state.  Bottom line:  As a bicyclist, eating the average American diet, I get about 63 MPG equivalent.  That is, when you divide the additional fossil fuels required, to produce the additional food I consumed, when I biked 32 miles a day, at the standard U.S. diet, by the total miles traveled, that worked out to be 63 MPGe.  (Where the “e” means that it’s compared the total fossil fuel energy to the amount of energy in a gallon of gasoline.)

(You have to be careful when you do such a calculation, because exercise calories-per-hour data are always the gross calories, including your basal metabolism.  Nobody cites the additional calories consumed by the exericise, over and above basal metabolism — the amount you would burn in any case.  You have to derive that before doing the calculation.)

Your mileage will, of course, depend on what you eat.  Potatoes embody very little fossil fuel.  Beef embodies an almost unbelievably large amount.  And many have pointed out that typical ovo-lacto-vegetarian diets embody about half as much fossil fuel as typical carnivorous diets (reference, Pimental, Cornell U.).

But to make this clear, assuming 10 fossil fuel calories per edible calorie, if my wife and I bike together, and maintain a stable weight, we actually consume more fossil fuel than if we drove together in a gas Prius.  And me, by myself, bicycling (while eating the average American diet) consumes more fossil fuel per mile than traveling on electricity in a Prius.

In other words, if I parked my electric Prius and did all my travel by bike — while eating the standard American diet — if my travel miles were held constant, I would increase my fossil fuel consumption.

Weird, huh?  And saying that inevitably makes bicycling advocates angry.  Nevertheless, it’s just math.  And a belief in basic physics, i.e., conservation of energy.

Arguably, the biggest fossil fuel savings from committing to using a bike rather than a car comes from total miles traveled.  Because, in fact, if I have to power them myself, my total miles traveled will not remain constant.  Not even when considering local transport only.  A short jaunt to the hardware store by car becomes a major investment in time and effort by bike.  Consequently, if my only option were biking, I’d be making a lot fewer trips to the hardware store.

What about leaf raking?  With that as preamble, at my weight, this calculator says I’d burn a gross total of 481 calories per hour, raking my lawn, from which I need to net out about 135 an hour for basal metabolism (e.g., just sitting and reading).  For me, then, leaf raking is a net ~350 calories per hour.  Supplying an additional 350 calories, with the average American diet, requires 3500 (kilo) calories of fossil fuel energy.  Or about as much as you’d get in 0.11 gallons of gas.  Inverting that, by raking leaves (and replacing those calories with the average American diet), I consume gasoline-equivalents at the rate of about one gallon every nine hours.

Compare that to the gallon-every-three-hours of the smaller gas-powered leaf blower above.

Conclusion:  Once you factor in the “fuel” for your leaf raking, you consume about one-third as much fossil fuel as you would using a small leaf blower.  That’s per hour.

How that stacks up per cubic yard of leaves is anybody’s guess.  But my guess is that, as with my example of bicycling above, your fossil fuel consumption from food-powered leaf raking is not hugely different from gas-powered leaf blowing.  All due to the fossil fuels embodied in the extra food required to replace the calories burned in raking.

And, as with the bicycling example above, it’s a pretty good bet that electrically-powered leaf collection — your electric leaf blower — beats hand raking, in terms of total fossil fuel impact.

There are plenty of good reasons to rake leaves by hand.  Less noise.  Great exercise.  Commune with nature.

And, as with bike-versus-car, if you are powering the operation with your own muscles, you’re probably going to do a lot less.  You’ll likely to be motivated to move the leaves less, and maybe be motivated to #leavetheleaves.  All of those are positives.

But in terms of the implications of that for fossil fuel use, that’s far from clear.  Raking requires energy.  That comes from food.  If your weight is stable, more energy output requires more food input.  And food production in the U.S. requires large amounts of fossil fuels.  Bottom line is that there ain’t no such thing as a free lunch.

Post #1611, COVID-19, still stuck at 12 new cases per 100K per day

 

The U.S. still stands at 12 new COVID-19 cases per 100K population per day.  We’ve been at this level for just about two weeks.  So, maybe we’re about to enter the long-awaited winter wave of COVID.  That said, judging from the recent European experience, if we have a winter wave this year, it’s not likely to be much of a wave.

Graphs follow.

Continue reading Post #1611, COVID-19, still stuck at 12 new cases per 100K per day

Post #1610: For every idiot-proof system, …

 

… there’s always a bigger idiot.

The idiot-proof system in this instance is the tire pressure monitoring system (TPMS) in my wife’s car.  And the bigger idiot was, of course, me.

To cut to the chase:  Happy ending.  No lasting damage.  Just a cheap and timely tire repair.

But only after a couple of days of pondering why the idiot light on the dashboard had malfunctioned.  And whether or not I should just fix it 70s-style (by taping over it), or take it to the dealer.

Not for one moment did it occur to me that this car idiot light might actually be flagging a problem that needed to be fixed.

In this post, for benefit of younger readers, I’m going to explain why old people routinely ignore idiot lights.  (Hint:  It’s how we were brought up.)  Because unless you live through the nadir of U.S. auto engineering — the 1970s — you have no idea just how good modern cars are.  And just how much of a joke dashboard warning lights were, to my generation.

1970s auto engineering and the advent of idiot lights.

Source:  Vega, left:  Motor Trend Magazine.  Pinto, right:  Ford Division Public Relations, Dearborn, Mich.. Ford Pinto Runabout – 1977. [Photographic Prints]. Retrieved from https://libwww.freelibrary.org/digital/item/53235;

Look at any list of the worst cars ever sold in America, and you will find a whole lot of mainstream 1970s vehicles.   The Chevrolet Vega, where the only question was whether body rust or astoundingly excess oil consumption would kill the car first.  The Ford Pinto, under-powered and famous for exploding if rear-ended.  The Chevy Shove-It, a.k.a., Chevette, with back seats that required you to be a contortionist to access.  The AMC Gremlin, arguably the ugliest car ever sold in America.

I could go on.

The decade of the 1970s was a perfect storm of problems for the U.S. auto industry.  The first was the Arab Oil Embargo, and the resulting energy crises and shortages of gasoline.  This left car makers scrambling to produce smaller, higher-MPG vehicles.  The second was the introduction of the catalytic converter, which forced manufacturers to more-or-less completely re-engineer their engines to deal with unleaded gas and with the added complexity of the catalytic converter itself.  The third was the string of recessions (or economic malaise) that was the direct result of the oil embargoes and energy crises of the 1970s.  Which meant that in order to be sold, cars had to be built as cheaply as possible.

The result was a string of small, cheap, poorly-built cars for which every possible expense had been spared.

And one of the expenses that was cut was the cost of dashboard gauges.

Historically, in addition to a speedometer and gas gauge, cars had gauges for oil pressure, engine water temperature, battery charge or ammeter, and so on.  You had gauges for items that were critical to the operation of the engine.  You could look at the gauges and check the health of the engine.  And if (e.g.) the coolant temperature was climbing, you had advance warning before the engine actually overheated.

The 1970s was the generation of cars in which those expensive gauges were replaced wholesale with cheap warning lights.  So now, instead of getting information on (say) engine coolant temperature, when the engine overheated, a red light would come up on the dash.  And tell you that your engine had overheated.

These were universally termed “idiot lights”, but there is some controversy over the exact derivation of that term.

The story I learned is that the idiot in question was the typical driver.  People were incapable of (or unwilling to) pay attention to standard gauges.  And so, warning lights were introduced because, unlike gauges, they were harder to ignore.  In effect, the data provided by an oil pressure gauge was replaced with a much simpler message, “hey, idiot, you’re out of oil”.  In other words, the lights were introduced because people were too stupid to pay attention to gauges.

In theory, idiot lights would illuminate when there was a serious problem.

In practice, idiot lights would come on for no reason at all.  And they were impossible for the average driver to turn off.  In all the years that I and my friends drove those cars, I never heard of an idiot light actually coming on at the right time and preventing damage to the vehicle.

Instead, it was common knowledge that when your idiot light came up, that signaled that the idiot light was broken.  (Or, on rare occasions, it actually functioned correctly and told you that you had just damaged your engine beyond repair.)

And literally the only fix for a broken idiot light, available to the average U.S. driver, was to block the idiot light so that you couldn’t see it.  Black electrician’s tape being the product of choice for that purpose.  But Magic Marker or Sharpie would do for an ultra-low-effort fix.

You had an entire generation of Americans, driving crappy little cars, with little pieces of tape covering the universally-useless dashboard idiot lights.   I couldn’t make stuff like that up.

And for that generation, the absolute and immediate gut reaction to any idiot light on the dash is, oh, the idiot light must be broken.  Because that’s literally all we ever saw in our youth.  Only after considerable reflection might it occur to one of us that maybe the idiot light is signalling a problem.

Fast-forward to the modern check engine light.

Unless you lived through that era, you just can’t appreciate how much better cars are now.  Materials, rustproofing, engine life, gas mileage, safety, convenience, reliability.  All of that is vastly better now than in the 1970s.

In particular, the US EPA-mandated On-Board Diagnostics (OBD) system really changed the game for car maintenance, including idiot lights.  That was introduced in the late 1980s in California, and the modern (OBD-II) system was mandated for all U.S. vehicles starting in 1996.

That’s had two implications.

First, if you want old-style gauges, instead of simple idiot lights, you can easily add them via devices that plug into your car’s OBD-II port.  For years, I drove with a ScanGauge plugged in, so that I could see things like engine temperature, engine load, and instantaneous gas mileage.

Second, in general, idiot lights are mostly reliable now.  If your check engine light comes on, that pretty much guarantees that something is actually wrong with your engine.  And not with your idiot light.  Sure, sensors can fail, and so on.  But I’d say that on the typical modern car, when an idiot light comes on, the odds are overwhelming that it’s flagging a true problem with the car.

But the tire pressure monitoring system light is an exception.  In some (but not all, see below) cars, those monitoring devices are battery powered, and sit inside the tires.  As cars age, the batteries die, turning on the TPMS warning light.  Replacing them required dismounting the tire from the rim.  So a lot of people end up simply ignoring the TPMS light, and instead check their tire pressure manually from time to time.

As a result, the TPMS indicator is the last of a proud tradition in U.S. auto engineering.  It’s an idiot light that typically tells you that the idiot light is broken.  That’s going to be true mostly on older cars, where it’s just not worth the expense of replacing the worn-out tire pressure sensors.

But on a new car, you can’t blithely dismiss the TPMS idiot light.  Eventually, this dawned on me, I checked the tire pressures, and sure enough, I had picked up a nail in one tire, leading to a slow leak.  And then to a quick and cheap repair at my local tire shop.

TPMS:  You still have to check your tire pressure. 

Just to up the intellectual content here, note that TPMSs work in various ways.

One system is an “indirect” TPMS.  It uses the car’s wheel speed sensors to estimate the diameter of each tire.  An under-inflated tire will have smaller diameter and so will spin slightly faster.  If the wheel speeds differ enough, that will eventually trigger the TPMS warning light.   These indirect systems have no hardware that requires periodic replacement. but they may require (e.g.) re-calibration each time you rotate, change, or inflate your tires.

The other approach is a “direct” TPMS.  These literally include battery-powered air pressure sensors in each tire.  Our car (Toyota Prius) uses direct sensors.  As with the indirect system, if the car senses low air pressure in a tire, it turns on the warning light.  For direct TPMS, you have to replace the battery-powered sensors when the batteries die.

But in either case, your tires can get pretty low before that TPMS light will turn on. 

With a direct TPMS, any tire that is more than 25% under-inflated will trigger the light.  For a typical 35 PSI passenger tire, that means you have to be under-inflated by 9 PSI or more to trigger the light.  That degree of under-inflation will cut your gas mileage and induce excess tire heating and wear.

Worse, many indirect TPMSs will not notice a problem, at all, if all the tires gradually go flat at the same rate.  If you never check your tire pressure, you can end up with four grossly under-inflated tires.  As long as they are all under-inflated by about the same amount, your TPMS light can remain dark.

The moral of the story is that the TPMS does not fully relieve you of the burden of checking the air in your tires.  Every so often, you still need to pull out a gauge and check them the old-fashioned way.

The icon-challenged generation and the snowflake trapezoid of doom.

Today, the proliferation of idiot lights, coupled with manufacturers’ unwillingness to use text labels, results in what I can only describe as icon overload.  Instead of idiot lights for a handful of key functions, with text labels like “oil”, you now have a dashboard populated with dozens of itty-bitty unlabeled icons.

As the driver, a) you have to notice when one of those little lights comes on, and b) you have to be able to interpret what the icon means.  Preferably without having to pull out the owner’s manual.

And sometimes, I have a hard time figuring out what the little icon is supposed to represent.

I am not alone in this.

One of my brothers drives a Prius.  The first year he owned it, he thought it was periodically malfunctioning.  A yellow warning light would appear on the dashboard.  The icon was an elongated trapezoid, with some sort of star-shaped symbol at one end.

But the car seemed to run fine.  So, as is typical for persons of my generation, he dealt with it by ignoring the idiot light.  He dubbed it the snowflake trapezoid of doom, and kept on driving.

Turns out, that was the Prius frost warning indicator.  It’s supposed to represent snow on a roadway, and comes on any time the outside temperatures are below 37 F.  To hear him tell it, my brother owned that car for several months before he finally figured out what that icon was supposed to represent.

And, really, I can’t blame him.  Even now, I look at the array of icons apparently standard on modern Toyotas, and some of them still leave me shaking my head.

Source:  Brent Toyota.

I’m sure those are all completely obvious to some of you, but I have a hard time even guessing what the (e.g.) car-on-a-lift one is for, or the P ! icon.  What’s the gear with an exclamation point for?  And so on.  All of these must have made sense to some Toyota engineer somewhere.  But I’d still need to consult the user’s manual to know what some of them are supposed to be telling me.

Post #1609, COVID-19, stuck at 12 new cases per 100K per day

 

The U.S. still stands at 12 new COVID-19 cases per 100K population per day, same as it was at the end of last week.  At this point, we now have a little flat spot on the end of the graph of daily new cases.  It’s too soon to say whether or not that means we’re about to enter our long-awaited winter wave of COVID-19.

Continue reading Post #1609, COVID-19, stuck at 12 new cases per 100K per day

Post #1608, COVID-19, still falling

 

The U.S. stands at 12 new COVID-19 cases per 100K population per day, same as it was at the end of last week.  That said, the new case rate continues a steady decline — it has just reached the point where it takes several days to reduce the (rounded) count by one.

You should probably take today’s numbers with a grain of salt.  Many states did not report new data today, owing to yesterday’s Federal holiday.  A few days from now, we should have a better idea of whether or not the U.S. Omicron wave is continuing to fade.

Continue reading Post #1608, COVID-19, still falling

Post #1607, Hating Maple Avenue

Today, as I was driving home after a trip to one of our local parks, I got honked at on Maple Avenue, in the Town of Vienna, where I live. 

My offense?  Failing to cause an accident on Maple Avenue.  Apparently the Tesla driver behind me wanted me to clear the roadway by running into the car that was blocking the lane ahead.  Instead, I stopped.  (It’s not as if I had a choice, because I literally couldn’t get around the lunkhead blocking the lane.).  In any case, after a three second delay, the lane cleared, and we all proceeded merrily down the road.

Despite the stupidity of honking at me for failing to run into somebody, maybe that impatient driver can be forgiven.  Because, unless you’ve bothered to look at the data, you probably don’t realize just how many car accidents occur on that innocent-looking two-mile stretch of road we refer to as Maple Avenue.

So in this post, I’m going to dig up a few pieces of data on reportable accidents along Maple Avenue in Vienna.  Just to remind myself that on this stretch of road, the occasional bit of defensive driving is no sin.

Saturday afternoon is the pits.

The main commercial district of the Town of Vienna, VA lies along an arterial highway, Virginia Route 123.  Although here in the TOV that stretch of Rt. 123 is called Maple Avenue.

It’s a congested urban arterial highway that sees about 30,000 vehicles per day.  With all that implies.

In the past, I outlined the fundamental reason why traffic is so consistently awful on this piece of road.  The Washington and Old Dominion railroad was here before the roads.  There’s roughly a five mile stretch of the old W&OD rail bed  that acts like a fence.  For that stretch, the only gate in the fence — the only road that crosses that old railroad bed — is Maple Avenue (and a couple of nearby side streets). As a result, anyone who wants to move north-south in this area, or east-west in this area, and doesn’t want to use the interstate, ends up driving on Maple Avenue in Vienna.  Either that, or do an end-run around that old railroad bed.

 

This road is congested during the AM and PM rush hours every business day.  But at least during rush hour, the traffic flow is predictable.  Almost everybody is just passing through.

For my money, the absolute worst time to drive on Maple Avenue is Saturday afternoon.  In addition to having the road packed and the traffic slow, traffic is chaotic.  Cars are moving in all types of unpredictable ways.  It’s jumbled mix of people running errands locally, and people just trying to get from one side of Vienna to the other.

Traffic crawls.

To add to the fun, in order to squeeze five lanes into the road bed, the lanes are about as narrow as they can possibly be.  The travel lanes are about 10′ wide.

But the real killer is is that the center turning lane is just 9 feet wide.  Which, if you drive a small car, is OK.  But if you drive a large SUV, crossover, or truck, you need some real skills to get your vehicle fully out of the travel lane, and fully into the turn lane, on-the-fly.  And, since many people lack those skills, but still drive those vehicles, the result is that people making left turns consistently block the adjacent travel lane, because they haven’t pulled their vehicle fully into the allotted 9′ space.

Which is why I got honked at today.  I couldn’t move forward, because the rear bumper of the left-turning SUV in front of me stuck out about two feet into the travel lane.

I’ve lived here long enough that I’m completely used to this.  I expect it.  If it’s Saturday afternoon, you aren’t going anywhere very fast on Maple Avenue.  And you’ll be dodging a lot of bad driving along the way.  That’s just the way it is, as we all try to negotiate this narrow urban arterial highway.

Nor is that ever going to get any better.  The Town, in its Wisdom, ensured that some new, large, and very expensive buildings were going to get put up right next to the road.  (They made it a condition of the zoning that the face of the building could be no more than 15′ from the road.)   So, short of Armageddon, there will never be any way to widen that roadway.  There’s a roughly 49′ curb-to-curb distance now, and that’s the way it’s going to be.

If that’s not enough, we’re now in the middle of changing the zoning in order to pack in some high-density housing directly on Maple Avenue.  Because, apparently, what we think we need here in Vienna is thousands of additional residents, all living directly on Maple Avenue.

Congestion has predictable consequences.

Here’s a map of reportable accidents that occurred in 2021, on or around Maple Avenue in Vienna.  As you can see, there were 100 car accidents involving significant property damage, injury, or both.

But 2021 was a good year, as traffic was down due to the pandemic.  If you look at the last pre-pandemic year, the count was 134 accidents.  More-or-less an accident every three days, along Maple and vicinity.

Source for both maps:  VA TREDS system

I guess I’ll stop there.

Fact is, every year, a whole lot of people damage a whole lot of expensive hardware, doing stupid things in Maple Avenue traffic.

And so, if some yoyo is partially blocking the travel lane, yeah, I think I’ll stop.  Honk at me if it makes you feel better.  Because it’s probably smarter to stop, than to roll the dice and see if I can squeeze by without doing any damage.

I am not, in general, a patient or polite person.  But on Maple Avenue, on a Saturday afternoon, I purposefully strive to be both.

At the end of the day, I guess I pity the folks who still can’t manage to figure out that no matter how much you honk your horn, if you’ve chosen to drive in that traffic, you aren’t going to go anywhere very fast.  It’s just the way it is.

 

Post #1605, candles versus batteries.

 

I continued the process of Getting Rid of Stuff.

Today I started in on my lifetime accumulation of camping equipment.  I was an avid backpacker as a teenager, and continued hiking and camping well into adulthood.  The resulting equipment runs the gamut from ancient to merely old.

I stopped when I ran across a couple of packages of nine-hour candles.  These are made to be burned in a backpacker’s candle lantern.  That’s a cheesy,  lightweight, spring-loaded contraption that pushes the candle up as it burns, keeping the flame in the same place as the candle is consumed.

I couldn’t put my hands on my old candle lantern, so I looked on-line to see what was available now.  To my surprise, candle lanterns have all but disappeared from the camping/hiking market, even in stores catering to backpackers (e.g., REI, Campmor).  The sole option is one high-end candle lantern from one manufacturer — the same one who made my candles.

After about a minute of thought, it finally dawned on my why nobody uses candle lanterns any more.

Once upon a time, this was a reasonable way to have a bit of light when you were backpacking.  If your only electrical alternative was a flashlight with carbon-zinc batteries and an incandescent bulb, candles arguably provided more light per unit of weight than a standard flashlight could.

But as technology changed –– first with alkaline batteries, then with LEDs — candles became obsolete as a lightweight source of light.  A quick internet query shows that the inefficiency of candles as a light source is common knowledge in the backpacking community.

But just how obsolete are they, really?  That is, what’s the illumination-to-weight ratio for candles, compared to AA batteries running an LED flashlight?  Does electricity now have a slight edge, or is it more the case that you’d have to be an idiot to take a candle lantern backpacking these days?

Inquiring minds want to know.

Candles:  Not so great, as a source of light.

The first hurdle is getting an estimate of the light output of a nine-hour candle.  Virtually everyone assumes that, well, it’s a candle, so it must produce one candlepower.  But candles vary widely in terms of combustible material, wick size, and the resulting light output.

The original definition of one candlepower was based on a candle that burned at a rate of 7.8 grams of combustible material per hour.  (Reference).  The actual material used to define candlepower was wax from a sperm whale.  That said, it’s likely that the energy density of that animal-based hydrocarbon is similar to the energy density of modern petroleum-based hydrocarbons, including paraffin wax.

Effectively, then, one candlepower is what you’d see from a candle that burns 7.8 grams of wax per hour.  The definition changed somewhat over time, but not enough to matter for this rough calculation.

Unsurprisingly, these candles — meant to burn as slowly as possible — produce less than one candlepower.  These nine-hour candles weigh almost exactly 50 grams, meaning that they burn at a rate of just 5.6 grams per hour.   Based on the standard definition above, we’d expect these slow-burning nine-hour candles to produce (5.6  / 7.8 =) about 0.7 candlepower.

But how does that compare to the light output of a flashlight?  When applied to candles, candlepower really is a measure of total light output.  By contrast, when that term is applied to flashlights, by convention, candlepower is used to describe only the brightest part of the beam.  If you want total light output, for a flashlight, you need to get it in lumens.

And, just as a matter of faith, I see several internet sources that all derive the same conversion factor.  One candlepower = 12.57 lumens (reference).

And so, 50 gram nine-hour candles will produce a total of (0.7 candlepower x 12.57 lumens per candlepower x 9 hours) about 80 lumen-hours of light.

Coincidentally, two alkaline AA batteries or four AAA batteries weigh just about exactly the same as one nine-hour candle.  Two AAs weigh just shy of 50 grams (reference).  Or, four alkaline AAAs would weigh in at around 46 grams (reference). Close enough.

So, how many lumen-hours can I get out of two AA or four AAA alkaline cells?

West Marine advertises one nautical safety light getting 11 hours’ run time, at 25 lumens, using a single AAA cell (reference).  They advertise another with 30 hours’ run time, at 20 lumens, from two AA cells (reference).

Respectively, four of the AAA lights would provide (11 hours x 25 lumens x 4 =) 1100 lumen-hours.  One of the AAA lights would provide (20 x 30 =) 600 lumen-hours.

And I haven’t even tried to look for the most efficient flashlight available.  These are just off-the-shelf marine safety products.

In short, candles aren’t even close to competitive with flashlights these days, on an illumination-to-weight basis. An off-the-shelf LED flashlight, with standard alkaline batteries, provides roughly 10 times as much light as a candle, per unit of weight.

Sure, I’ve ignored the weight of the devices themselves, and only concentrated on the fuel (or batteries) consumed.  And, in theory, you might have to carry some dead batteries around for a while, if you were backpacking with them.  And so on.

But it’s no wonder backpacking candle lanterns have all but disappeared.  They’re a really dumb idea in the era of alkaline batteries and LEDs.

Candles:  Much better as a heater.

That said, the actual energy density of candle wax is far higher than the energy density of alkaline batteries.  In the same way that (say) ten gallons of gasoline stores vastly more energy than the equivalent weight of charged lithium batteries.  It’s really merely the case that candles are incredibly inefficient at converting that energy to light.  For that efficiency, you see estimates that are all over the map, but if I had to guess, I’d guess that vastly less than 1 percent of the energy of the burning candle is actually released as light.  The rest is released as heat.

So, as as heat source, candles stack up pretty well against any battery-powered device. But just how well?

A typical high-end AA alkaline cell holds about 4 watt-hours of energy (reference).  So two of them would be able to release about 8 watt-hours.

Candle wax contains about 46 kilojoules per gram (reference), and a watt-hour equals 3600 Joules (reference).  Together, all of that means that one 50-gram candle contains about (50 grams x 46,000 Joules/gram / 3600 Joules/watt-hour =) 640 watt-hours of energy.  Restated, one nine-hour candle contains about 80 times as much total energy as two AA alkaline cells.

This shouldn’t be a surprise.  In fact, it’s probably conservative, given that gasoline is cited as being somewhere between 50 and 100 times as energy-dense as lithium batteries, depending on the metric and the source of the comparison.

So, candles as heaters, great concept.  Candles as a light source, not so much.

Finally, we can roughly infer just how inefficient candles are at converting chemical energy into light.   A typical figure for modern LED efficiency is 30%.  That is, 30% of the electrical energy ends up as light, the rest ends up as heat.  All told, that nine-hour candle has 80 times as much energy, and produces one-tenth the light.  Which means that if an LED is 30% efficient, then a candle is about 0.04% efficient.  Which, surprisingly, is quite close to a quoted figure of 0.05% (reference). In other words, 99.9+% of the energy in the candle wax is converted to heat, not light.

That said, per unit of weight, as a heat source, candles are no better than any other hydrocarbon.  Other than an ability to burn them quite slowly, there doesn’t seem to be any advantage to using candles as a heat source rather than (e.g.) gasoline, kerosene, propane, butane, etc.

Addendum:  Can’t I just add a mantle?

Source:  Amazon

Traditional kerosene lanterns are also incredibly inefficient at converting fuel to light.

But more than a century ago, the dismal inefficiency of a traditional flat-wick kerosene lamp was improved by the addition of an incandescent mantle.  A modern kerosene lamp works not by producing light directly, but by heating the mantle until it glows.  Aladdin kerosene lamps, for example, are unpressurized kerosene lamps that use a mantle.  They produce about four times as much light as traditional flat-wick kerosene lamps, per gallon of fuel (reference).

The use of an incandescent mantle is standard for all modern lights powered by burning hydrocarbons.  Next time you see a decorative natural gas light, look closely, and you’ll see a mantle over the flame.  Burning natural gas, by itself, produces almost no light.  The light you see from a gas lamp is the light of the glowing mantle, heated by the burning natural gas.

So, why not stick a mantle in a candle lantern?  Near as I can tell, the flame from burning wax is just as hot as the flame from burning kerosene.

I’m pretty sure that the issue isn’t so much the temperature of the flame, as it is the total amount of heat produced.  Both Coleman (pressurized) and Aladdin (unpressurized) lamps burn about three ounces of fuel, per burner, per hour.  That works out to roughly 65 grams of hydrocarbons burned, per hour, or roughly 10 times the burn rate for my nine-hour candles.  Plausibly, if I put a Coleman lantern mantle over my candle, I could get a little spot to glow.  But there’s no way I’m going to get that entire mantle to glow with just the energy input of a nine-hour candle.

Addendum to addendum: Well, I couldn’t just leave it like that, so I bought a Coleman lantern mantle and tried it.  Turns out that the only part of the candle flame hot enough to make the mantle glow is a tiny bit of it, right in the heart of the flame.  With that, you can get a piece of the mantle about the size of a match head to glow. 

The upshot is that a mantle is totally impractical for a candle lantern.  You have to suspend a tiny piece of the fragile burnt mantle literally inside the candle flame.  And then, you get a modest increase in light output.  Even if you could set that up and make it work, that fragile piece of mantle would never survive even the slightest bump.