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Comments

I'm confused. I don't mean to be picky, but I thought the major jet streams flowed west to east, thus aiding easterly flights.

No, I'm confused. I can never remember which way I gain time. :) Thanks for the correction.

The Prius certainly seems to be the best production hybrid car ever, but I was primed by the following comment, from a BBC News story today about an experimental hybrid sports car, at http://news.bbc.co.uk/2/hi/technology/7265267.stm, "Hybrid cars already use regenerative braking - normally it restores about 10% of the energy, ... Lifecar is aiming for 50%." to question your claim that the Prius has a "braking system that recovers as much wasted heat energy as possible" (my emphasis). Googling "Prius braking energy" got a few interesting sites (the first two, "http://privatenrg.com/" and "http://thuledingles.com/?p=163" seemed worth a look to me; I particularly liked the latter's account of "prius rage" against drivers who drive very conservatively), but not immediately any info on the efficiency of the Prius's restoration of braking energy.

On buildings, the 1920s Condo I live in has been working on our steam heating, to little avail on efficiency. I believe we would have to convert the existing system to hot water instead of steam, at a cost of over $100K and considerable disruption that none of the owners want to undertake. Getting real savings without knocking down all the old buildings in the country seems very difficult.

No worries, mate about the time confusion. maybe you were remembering that you actually span 4 time zones from NY to LA (or any west coast locale)

"As much energy as possible" for the design of the Prius, was my point. Obviously the technology is still improving. I would HOPE that the Prius braking system, as well as its other features, are continuously being improved upon, both by Toyota and other manufacturers. "Prius rage" is a behavioral problem that is not limited to the Prius... it annoys me that I can be going 75 MPH in a 65 MPH zone -- hardly driving conservatively -- and STILL have drivers tailgating me impatiently because I'm too damned slow for them. Clearly, "speed limit" does not mean what I think it means. :) At any rate, traffic in LA is so bad, that this is only an issue on road trips. Generally, I hit an LA freeway and find traffic moving at a steady 45 MPH or thereabouts. If it slows down to a steady 35 MPH, I get KILLER gas mileage (around 70 MPG if I time things right). Let the road ragers vent their spleen; I get the last laugh. Like I said, I used to be one of those drivers. The Prius has made me much more aware of the raw energy costs of locomotion. Maybe road ragers should be forced to drive a Prius for a month or two. :)

As for very old buildings -- I owned a 1918 condo myself when I lived in DC, so I hear you on the cost of retrofitting. The point I was trying to make is not that any one person needs to realize "considerable" savings, but that tiny improvements, changes in behavior, and so forth can add up rather quickly. If everyone in the world unplugged their vampire appliances when they weren't using them, that would have a significant impact on carbon emissions into the atmosphere.

ALthough at some point, the situation could become serious enough where that $100K investment (and more) might be well justified, even key to survival. In the meantime, why not try to squeeze out as much efficiency as we can, weighing the cost and inconvenience against the very real gains to be made? A recurring theme at the conference was that there is no "silver bullet" -- rather, it's more like "silver buckshot." :)

"In general, the faster you go, the more energy it takes to maintain that speed, so driving just at (or slightly under) the speed limit can also result in energy savings."

The faster you drive the more power (energy per unit time) is required to maintain your speed. Of course it also takes you less time to get from A to B.

There is a trade off between power required and distanced covered. Beyond a certain point slowing down will actually reduce overall fuel efficiency as the increased time required to travel a given distance will outweigh the reduced rate of fuel burn. In other words, an hour at 60mph will probably burn less fuel than two hours at 30mph.

The optimum travel speed will vary from car to car. Fancy cars, like say a Prius, have fuel flow meters that allow the driver to determine by experiment the speed that yields the best gas mileage. Less fancy cars sometimes have their most efficient speed printed in the handbook.

For the rest of us, 60mph or maybe a little bit less is probably not a bad guess. The important thing is that we don't want those hippie types out there getting the idea that cruising the freeway at 30mph will save the planet. Not only is it annoying, it's probably counterproductive.

The important thing is that we don't want those hippie types out there getting the idea that cruising the freeway at 30mph will save the planet.

Not to worry: their kind is suffering attrition proportional to the attrition of 1960s-era VW vans. Sadly, the cell-phone talkers are picking up their slack.

It was wonderful getting together, Jennifer. With Sean next time!

I think mileage readouts should be required to be standard on all cars, and there should be a tax credit for having one installed on late model cars.

Having that display of instantaneous and average MPG really does increase your awareness of how driving style and mileage are connected. Totalling up your mileage when you refill the tank just doesn't cut it.

I think this would really help people reduce their gas usage.

"There is a trade off between power required and distanced covered. Beyond a certain point slowing down will actually reduce overall fuel efficiency as the increased time required to travel a given distance will outweigh the reduced rate of fuel burn."

I think a lot of wasted gas happens when people gun their engines when the light turns green, or when they keep on the gas and then brake at the last minute rather than gradually slowing to a stop.

A mileage readout really makes this obvious.

"Based on Hafemeister's calculations, this means that no furnace heating is needed to maintain an indoor temp of around 65 degrees F until the outside temp hits 35 degrees F." I give up. This 'free heat' is supposed to result in a 3 degree difference between indoor and outdoor temperatures, according to the sentence that precedes this one, but this example represents a 30 degree difference. 3 degrees is an insignificant amount of temperature difference, really - it probably represents some primitive level of insulation, but 30 degrees seems in violation of the second law of thermodynamics. What is the story here?

Honestly, the calculations were difficult to follow, with lots of variables, and I'm not entirely convinced about this "free heat' thing anyway. Ergo, the lack of details. Mostly, I liked the fact that Hafemeister had bothered to run so many calculations on heat transfer in his house. Should he post his slides somewhere in the near future, containing the gory details, I'll link to it with an update....

As an automotive engineer, historic vehicle racer, and an avid "car guy" I will say this:

There will be no signifigant improvement in the total efficiency of automobiles until ...

the elimination of testosterone.

There, I said it. Doubleplusthink carbon offset credits to me.

-steve

Steve, your comment is amusing, and no one denies the influence of testosterone, but I've never bought into the notion that testosterone excuses aggressive behavior -- any more than I buy into the notion that PMS excuses bad behavior by women. We are influenced, not RULED, by our hormones. We are still responsible for our choices and actions.

There. I said it. TRIPLEplusthink carbon offset credits to ME. :)

"We no longer teach such practical things in physics."

Aaah, but the principles are still taught. Further, somewhat north of the Physics Department, in Etcheverry Hall, the Mechanical Engineering Department spends a fair amount of time worrying about it...

I am very confused.

"Take your standard heat pump technology, designed to transfer warm air to cooler air. There are some fundamental physical limits to how efficiency the heat pump can be; thermodynamics is a harsh mistress. But Harvey found that by cutting the flow rate through ducts or pipes in half, he could reduce the electricity needed by a factor of 6 or 7. There's always a trade-off, of course, in this case, a slight loss in efficiency -- otherwise, there might be a reduction by a factor of 8."

If I didn't know that was written by a physicist, I'd figure it was the product of erious ignorance. (Cf. Jane Harman: she who celebrated a law that will get rid of those notoriously inefficient [her words, at least in essence] 100-watt bulbs. Perhaps she should find out what "efficient" means, and read some labels and learn to do division and compare the output per unit input for different sizes of incandescent bulb. Bah! But I digress.)

OK, so it uses 6 to 7 times less electricity, and it's less efficient? That means it produces 8 (or more) times less output??? Not necessarily a desirable result. No, that can't be it.

So what does it mean? Efficiency here is computed as what over what? And does either "what" relate to the massively reduced electrical input?

I know there's a good answer to this, just can't figure it out.

Regarding your comment on LED lighting, as used in street lights or traffic lights, there is a serious reliability issue here.
In two local cities, all the stop lights have been replaced with LED lights.
Over the last 4 years or so I have observed really huge failure rates of LEDs going dark. That is, of the 100 or so LEDs making up one red light, one to
1/3 of the total LEDs will just go dark, kind of randomly.
Over the course of 12 months after an install, I guesstimate that any
given intersection has at least one red light with significant burnouts.

The burned out lights look quite dilapidated. It is like looking at a building
with broken windows. You notice it is basically working, but why all the
dark lines and spots? It looks broken down.

Now I doubt the LEDs themselves are failing at this rate. More likely
an environmental factor, such as the physical mounting and electrical contact
of the LEDs, perhaps.

I would say the LED lights must really be expensive with such failure rates.
Further the mfg should be providing free replacements for every burnout,
so that increases costs too.

FYI, Rich

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    Physics Cocktails

    • Heavy G
      The perfect pick-me-up when gravity gets you down.
      2 oz Tequila
      2 oz Triple sec
      2 oz Rose's sweetened lime juice
      7-Up or Sprite
      Mix tequila, triple sec and lime juice in a shaker and pour into a margarita glass. (Salted rim and ice are optional.) Top off with 7-Up/Sprite and let the weight of the world lift off your shoulders.
    • Listening to the Drums of Feynman
      The perfect nightcap after a long day struggling with QED equations.
      1 oz dark rum
      1/2 oz light rum
      1 oz Tia Maria
      2 oz light cream
      Crushed ice
      1/8 tsp ground nutmeg
      In a shaker half-filled with ice, combine the dark and light rum, Tia Maria, and cream. Shake well. Strain into an old fashioned glass almost filled with crushed ice. Dust with the nutmeg, and serve. Bongos optional.
    • Combustible Edison
      Electrify your friends with amazing pyrotechnics!
      2 oz brandy
      1 oz Campari
      1 oz fresh lemon juice
      Combine Campari and lemon juice in shaker filled with cracked ice. Shake and strain into chilled cocktail glass. Heat brandy in chafing dish, then ignite and pour into glass. Cocktail Go BOOM! Plus, Fire = Pretty!
    • Hiroshima Bomber
      Dr. Strangelove's drink of choice.
      3/4 Triple sec
      1/4 oz Bailey's Irish Cream
      2-3 drops Grenadine
      Fill shot glass 3/4 with Triple Sec. Layer Bailey's on top. Drop Grenadine in center of shot; it should billow up like a mushroom cloud. Remember to "duck and cover."
    • Mad Scientist
      Any mad scientist will tell you that flames make drinking more fun. What good is science if no one gets hurt?
      1 oz Midori melon liqueur
      1-1/2 oz sour mix
      1 splash soda water
      151 proof rum
      Mix melon liqueur, sour mix and soda water with ice in shaker. Shake and strain into martini glass. Top with rum and ignite. Try to take over the world.
    • Laser Beam
      Warning: may result in amplified stimulated emission.
      1 oz Southern Comfort
      1/2 oz Amaretto
      1/2 oz sloe gin
      1/2 oz vodka
      1/2 oz Triple sec
      7 oz orange juice
      Combine all liquor in a full glass of ice. Shake well. Garnish with orange and cherry. Serve to attractive target of choice.
    • Quantum Theory
      Guaranteed to collapse your wave function:
      3/4 oz Rum
      1/2 oz Strega
      1/4 oz Grand Marnier
      2 oz Pineapple juice
      Fill with Sweet and sour
      Pour rum, strega and Grand Marnier into a collins glass. Add pineapple and fill with sweet and sour. Sip until all the day's super-positioned states disappear.
    • The Black Hole
      So called because after one of these, you have already passed the event horizon of inebriation.
      1 oz. Kahlua
      1 oz. vodka
      .5 oz. Cointreau or Triple Sec
      .5 oz. dark rum
      .5 oz. Amaretto
      Pour into an old-fashioned glass over (scant) ice. Stir gently. Watch time slow.