[ExI] gas prices

[spike at rainier66.com]

From: extropy-chat <extropy-chat-bounces at lists.extropy.org> On Behalf Of Rafal Smigrodzki via extropy-chat
Sent: Saturday, 19 March, 2022 10:08 PM
To: ExI chat list <extropy-chat at lists.extropy.org>
Cc: Rafal Smigrodzki <rafal.smigrodzki at gmail.com>
Subject: Re: [ExI] gas prices

 

 

 

On Sat, Mar 19, 2022 at 1:23 AM <spike at rainier66.com <mailto:spike at rainier66.com> > wrote:

### What about a drop-in range extender fitting into the trunk or frunk? Rafal

 

 

Hi Rafal, thanks for posting.  I thought of that and worked on it for a while but eventually calculated that there is not a practical way to dump the excess heat. Which is about 60 kW.  

 

I am finding plenty of solutions where the whole rig comes in under 600 pounds without fuel, about a thousand pounds with fuel.  That is easily handled by one person.

 

>…### You do have a point. A drop-in generator would have to be comparably wimpy and would still be hard to handle.... but the range-extended Tesla does not need to drive fast. All it needs is the peace of mind as you trundle to the nearest megacharger at a steady 50 mph…

 

Hi Rafal, 

 

I sized the generator at 20 kW.  The excess heat you need to dump is about triple the output of the IC/generator combination, after you account for the heat generated by the gasoline motor and generator.  That is where the 60 kW number came from.  A steady 75 on the freeway with AC or heater, accounting for the extra drag by the trailer gets you to about 20 kW power requirement which gets you to about 60 kW heat rejection requirement.

 

>…How many kW is that for a Model 3 running on flat road in windless conditions with no AC?

 

No Model 3, we are talking S here.  The S is a bit more sincere in the power department, a lot more, but of course it is also heavier.  As an engineering exercise, we assume worst case conditions likely to be encountered in use, so we are talking S.

 

>… Quora says about 4.5 kW. 60kW and 1000 lb worth of generator sounds like an enormous overkill. My 13 kW house generator weighs 400 lb as a stationary device that's intended to be too heavy to vibrate…

 

You would be surprised at how much your 13 vibrates if you have a means to measure it.  But you can’t run that (or any other small generator) in any small enclosed space.  It needs room to breathe.  The closest you will find is a generator they use for RVs, but those also need to breathe and they don’t generate enough power.  The 1000 pound estimate accounts for the trailer, the air-cooled IC, additional sound suppression, the generator, the rectifier and about 60-70 gallons of fuel needed to run a good coupla days under worst-case conditions, three under more ideal conditions.

 

>… so a much smaller car generator should weigh a fraction. And it's OK to refill out of a Jerry-Can every 50 miles or so…

 

It does.  But it doesn’t make enough power.  Those Teslas don’t have enough cargo room (they aren’t designed to be cross country runners.)  So if I were building a generator trailer, I would leave enough room to tie on a coupla suit cases, or four good sized ones probably, or a cooler and a coupla good sizes cases.  I wouldn’t build something like this to be inadequate for a high-speed cross country run.  Teslas cost a lotta money and are kinda overkilly in many areas, so… in keeping with that attitude, model S with all the trimmings, towed generator coming in at about 1000 pounds.

 

>… Sure, going uphill in winter at night upwind might be a bit of a problem...

 

Ja, heating in the Tesla is all electric resistance, which is a huge power eater compared to the heating in a gasoline car, which is free: it uses the waste heat from the cooling system.  The Tesla is one to one: every kW you dump in the passenger compartment comes off of the battery.

 

>…but think about how much of the planet you would avoid killing!

 

I do!  Recall the way the Tesla is used: you only go on cross country trips once in a long while for most of us.  The rest of the time you are whirring around town, not burning gasoline at all.  Tesla drivers burn only coal and natural gas, with about 14% wind and solar.

 

>…Plus, the drop in generator would be hidden with only an innocuous-looking gas vent to betray your wickedness…

 

Eh, no.  If you are going to run that generator, you need a lot of air circulation with probably an external radiator, which is why you never see a gasoline car without one.  They all have those ugly aerodynamically dirty radiators up front, something the Tesla doesn’t have.

 

>… How would you live down the shame if the modern Mrs Grundy saw you pulling a planet-killer behind your car?

 

Rafal

 

Ah glad you asked.  If one is a clever designer, it wouldn’t be obvious that you were hauling a dinosaur burner back there.  I included some weight for a sincere sound-suppression system, which would be about 40 pounds.  Since the rig would only run while you are underway (air-cooled engine would have inadequate cooling for stationary use) the tire noise would cover the suppressed racket.  If one wanted to take it to a kind of silly extreme, a fuel tank could be dressed up to look like a two really big suitcases or a toolbox.  Even the filler could be stealth-ized if you wanted to, but I am good at living down shame.  The other Tesla-ers would know what you are doing and understand.  I don’t want to spend 100k on a car that isn’t practical for cross country runs.

 

spike

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