Monday, July 29, 2013

Driving a Tesla

I got to drive a friend's Tesla this evening.  Actually, it wasn't even his Tesla; his Tesla was in the shop for some buffing / detailing work, so he had a loaner Tesla.  And, of course, they loan the Model S Performance, which will do 0-60 mph in 4.2 seconds.

I have never driven a car with that much power, and frankly, probably never will again.  My current car is a 175 hp 2009 Nissan Altima, and the car before that was a ~110 hp 1998 Subaru Legacy.  The Model S is equivalent to a 416 hp car.  And without gears to shift, the ability to put all that power directly to the wheels -- even from a standstill at 0 RPM -- is mind-bending.  The slight pause that we have all come to expect from traditional engines and transmissions just isn't there, and it keeps dumping torque to the wheels.  The best analogy is that it's like getting launched from an electromagnetic roller coaster.  Except you're driving this one.

I was admittedly a little nervous about driving around the streets in DC for fear of getting cut off or not seeing someone in the slightly-larger-than-I'm-comfortable-with blind spots. (The C-pillar is jagnormous.)  But all worked out okay in the end, and I had a fun drive. 

Three more observations:
   1.  I'm told BMW's are set up the same way, but I kept hitting the cruise control lever instead of the turn signal.  It's very annoying to set the cruise control on HOLYSHITGO!!!! when you're accelerating and trying to merge into the next lane.
   2.  The car is fighting pretty hard to engage regenerative braking.  I know why it's doing it, and I applaud the efforts to eke out every mile possible (as well as to recharge the battery at a voltage that actually does something), but it takes some getting used to.  My Subaru was a stick (yes, I drove a stick for many years in and around DC), and the Tesla slows down as if the car was in 2nd gear the whole time.  This is adjustable, but of course, everyone wants the best mileage and range they can eke out.
   3.  My friend showed a picture of when he was charging at at Supercharger station when the battery was almost empty and "drinking" from the Supercharger as fast as it could: 226 amps at 371 volts.  226 amps at 371 volts is about 84 kilowatts.  That's about 14x more than your average house draws at full power.  Or, to put it another way, if you charge at 84 kilowatts for about 3 hours, that's roughly the same as your average house will drink in a week. 

I bring this up to compare to my previous calculation that about 20 megawatts of power (equivalent) is flowing through your gasoline hose when us ordinary folk fill up at the gas station.  So, there's a tremendous amount of electricity flowing through the wires, and some very talented engineers found a way to safely transfer all that power, but it's still two hundred times less power (equivalent) than is flowing through your gas hose at the gas pump.

[Nerd note on that last item: for any technically minded folks out there, I acknowledge that electric vehicles are about 3x more efficient that gasoline powered vehicles, thus making the "equivalent power" flowing only about a factor of 70 less than the gasoline pump.  But still.  70x.  Wow.  Gasoline is pretty energy dense.]

At this point, I would like to close with a picture of me in front of said Tesla but, alas, no pictures were taken.  You'll just have to take my word for it.

And thanks for the ride, Greg.

Sunday, July 21, 2013

Pandora's Promise - A Critical Review

Like a lot of other nuclear engineers, I went to see Pandora's Promise last night.  It's a documentary about the benefits of nuclear power, and is touted as an "Official Selection" at the 2013 Sundance Film Festival. (I'm not sure what that means.  It doesn't appear on the list of award winners, for instance.  Perhaps it's a fancy name for "participant"?)  There were lots of other fellow geeks and nerds in the audience, and people were glowing about it afterwards.

Unlike a lot of other nuclear engineers, I was disappointed.

Saying such a thing is a bit of heresy in many circles.  I admit, it's a nice, entertaining, and enlightening 86 minute documentary.  But as for its intended purpose?  It misses the mark, guys.

The director, Robert Stone (a previously anti-nuclear environmentalist who changed his mind about nuclear and decided to do something about it), is quoted as saying:
For the past three years I have devoted almost every waking moment to taking these ideas and shaping them into a documentary about what is perhaps the biggest and most unwieldy subjects imaginable: how do we continue to power human civilization without destroying the environmental conditions that has made modern civilization possible?
Look, there was an impressive amount of momentum behind this thing.  Just two years after the Fukushima nuclear accident, here was a movie that potentially could appeal to the masses and change the public opinion on the importance of nuclear power.

This was intended to shape the dialogue.  I don't think it's going to move the needle a bit.
  • Where are the pithy one liners?
  • Where are the memorable moments?
  • Where are the quotes that people will re-use in everyday conversation?
The documentary may sway a few open-minded people who happen to see the show and perhaps question some previously held beliefs.  But its message will not get across to other folks at the water cooler, at the lunch table, at the sidelines of a soccer game as parents are watching their kids play; the documentary provides no entree into those areas.  Those are the elements that will really shape the dialogue today.  And it missed.

The projections of energy use in 2030, 2050, and 2100 were interesting, and the CGI graphics of the earth spinning and lighting up more and more were neat.  The pie charts of fossil fuel use vs. everything else were instructive.  And the pictures of Hyman G. Rickover explaining to the world the basics of how nuclear power propelled a submarine were memorable.

But we've had all those before, and they just don't seem to gain much traction.  The movie was entertaining, but it didn't tell a story that was any more compelling than Lawrence Livermore's Sandkey charts.  
LLNL's Energy Flowchart.  Seriously, take a minute with this one.  The amount of energy we lose is staggering.
(It's also easy for me to be a critic here; I'm not the one who has funded and produced a pro-nuclear documentary.  I should take a lesson from Teddy Roosevelt.)

At the end of the day, each new nuclear power plant will take approximately 10 years to build and $7 billion to construct.  There is no way your "average" utility can sink those kinds of resources into power generation -- and that's $7 billion that has to be sunk before you can pull rods and start generating power.  It's a tough sell to put $7 billion worth of eggs all into one basket, and only then can you begin making money.  It's just an insurmountable up-front cost.

Which is why I'm a little more hopeful about small modular reactors.  As a nuclear engineer, I hope that SMR's can provide a lower up front cost as well as get political support because the entire thing can be made domestically. (Admittedly, it remains very much unclear if the resulting product can generate power at a reasonable cost.)  Pandora's Promise talked about energy executives deciding to build a new nuclear power plant over a golf game; they could do that because the things were so cheap and easy to build in the 1950's and 1960's that many utilities could afford them.  Fossil fuels will continue to be favorable until either the cost of generating CO2 goes way, way up, or the cost of building nuclear goes way, way down.

But, despite all this, go see the movie.  It's at least worth the price of admission.

Wednesday, July 17, 2013

Beat the Heat with a Cheap, Indestructible Water Table

pretty severe heat wave is gripping most of the east coast about now.  With the help of some other internet sites, I modified a design for a kid's water table that makes a great, cheap way to have hours of fun and stay cool at the same time.

Total cost: about $30
Time to assemble: about 2 hours, maybe less with this guide
Tools needed: a jigsaw.  You could probably do it with a hacksaw, but it would take a lot longer.

   - 2 ten-foot lengths of 1" diameter PVC pipe
   - 8 1" T-fittings
   - 8 1" 90-degree elbows
   - A 41 quart Sterilite tub.

Other tubs are certainly usable, but they would change the dimensions from what I'm about to describe. The 41 quart tubs are great for water tables, moon sand, regular sand ... the possibilities are endless.

Unless you own a pickup truck, it's unlikely that ten-foot sections of PVC pipe are going to fit in your car.  Have the store cut each ten-foot section for you at the 54.5" mark.  That way, it'll more easily fit in your car and it saves you a cut at home.  See the below figure for where to make the cuts:

It really helps to make two lines on the PVC pipe as you're marking it for cutting; it gives you a better line to follow when you're cutting.

Here are the pieces, mostly cut:

It helped me to label, with a piece of masking tape, the 11 and 14.5" pieces.  They're close enough that they're easy to confuse.  The 11" pieces make the legs, and the 14.5" pieces make the "ends" that hold up the tub.

Lastly, don't throw away the spare pieces.  We need to cut them into 8 small pieces (total), each 1.5" long.  These will act as little connectors between the T-fittings and the elbows.  You can see some of them jutting out of the T-fittings here, and 6 others stacked on-end:

Theoretically, there's supposed to be 1" of overlap between a fitting (like a T or an elbow) and a pipe, meaning the little connectors could theoretically be 2" long.  But friction really works against you when cramming PVC together, and 1.5" is plenty of overlap.

Assemble everything together, and have fun with your new water table!!!

Some notes:

  • You could glue the PVC together for added stability and permanence.  But as it is, it's rock-solid and I like the possibility of taking it apart someday.
  • The 11" legs are just barely tall enough.  You could go to 12 or 13 inches and it might be better for bigger kids.
  • If you're really fancy, you could cut the 11" legs about 1/3 of the way up and add in another 4 T-fittings, thus giving you some ends that could make a shelf for storing stuff.  Maybe I'll do that as a modification in a few weeks...
  • The setup was sturdy enough to easily support Beth lying in the tub (before we filled it with water), and she weighs about 28 pounds now.

Thursday, July 11, 2013

A Bad Credit Card Deal

I got a notice in my inbox today from one of the credit cards I hold.  It was advertising the special deals they have with some vendors:

Wow, I get 1 point per $1 I spend at Walmart and Lowe's!

Wait a minute ... look at that last paragraph: "And, don't forget you can earn 2 points per $1 spent on your everyday purchases."

Suddenly, this seems a very bad deal.  While I normally get 2 points per dollar spent at other stores, I get HALF that reward at Walmart and Lowe's.  What??!  Why on earth would I want to do that?

Nowhere in the email does it state these are bonus points, or that these rewards are earned above and beyond what you normally earn.  The terms and conditions the email links to are here, and they don't spell anything else out, either.  Thus, I have every reason to believe that this is a disincentive to shop at Walmart and Lowe's.