
Ultracapacitor Bus Recharges at Each Stop - naish
http://www.technologyreview.com/energy/23754/
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asciilifeform
A capacitor can _discharge_ at least as fast as it can charge. Let's see what
remains after the first wreck.

The ultracapacitors store 5.9 KWH. (From the manufacturer's specs:
<http://www.sinautecus.com/products.html>)

5.9 kilowatt-hour = (5.9 kW)(1 hour) = (5900 J/s)(3600 s) = 21.24 MJ.

A stick of dynamite contains roughly 2.1 MJ.

Welcome aboard!

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proee
Maybe you could create something similar to an airbag sensor, but instead of
having it deploy an airbag it could dump all the charge in the caps into a
resistive load (or maybe a one-time discharge load of some kind). It's
certainly an easier problem to contain then say a tank of hydrogen.

~~~
padmapper
Which would cause all of the energy to be dissipated as heat in an instant...
perhaps you could put it into some non-volatile heat sink, but unless it's a
really big heatsink, you wouldn't want to be anywhere near that thing when it
went into resistor mode, especially if the energy density/storage of these
caps increases. Maybe put it into a heatsink that's within a big vacuum
thermos... :-)

Regardless, it's definitely easier to deal with than a tank of hydrogen, but
I'd say that tech is a non-starter anyway. If we can make electricity alone
work via advances in charging time over batteries and energy density over
existing caps, there's really no reason to transport energy around in an
intermediary, let alone an extremely inefficient and volatile one like
hydrogen. Power mains are a much better solution, relatively lossless by
comparison to an intermediary transform.

On the other hand, for action movies of the future, hydrogen tanker trucks
would provide great explosion fodder :-)

~~~
jbert
> perhaps you could put it into some non-volatile heat sink, but unless it's a
> really big heatsink, you wouldn't want to be anywhere near that thing when
> it went into resistor mode

Specific heat capacity of water ~= 4(KJ per Kg per Kelvin)

so, assuming we can safely take water from 20 degC to 90decC, we'd need 21MJ /
4KJ/K/degC / 70degC == 75Kg of water as a heatsink.

Or about the weight of one passenger.

Double or triple up for safety factors (avoid steam) and you're still OK. Have
some insulation and drive some A/C to chill the water further and you're also
OK.

So yes, dump it into a resistive load immersed in a tank of water?

(Edit, that said I do think that The Right Way to do transport+energy etc is
for us to find our correct "limitless" source of energy (fusion or orbital
solar, I guess) and turn that into synthetic hydrocarbons as a convenient,
relatively safe, energy dense fuel. i.e. we don't build massive supergrids for
pushing that power to people over wires. We pump the power into a
CO2+H2O=>petrol converter which we then ship around the world using the
existing infrastructure. We also don't need to retool the whole world's
transport infrastructure. Obviously all carbon-neutral too. (Carbon -ve if
you've got the spare power.))

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dmv
How would systems running on petrol be carbon-neutral? Granted, you reduce one
form of carbon emissions by presuming a clean form of energy and petrol
generation. Use of the petrol, however, should still result in carbon
emissions. Have I missed something?

~~~
jbert
If you're making the hydrocarbons from CO2 and H2O, you're taking as much CO2
from the air as burning the hydrocarbons will liberate.

Obviously, you need to put in the energy too. But I think synthetic
hydrocarbons are a great way to carry around useful energy. They're very
energy-dense, should be cleaner than oil from the ground and the whole world
is tooled up to use them.

However, they're not useful until we also have:

\- loads of power

\- an efficient way of turning that power + CO2 + H2O into hydrocarbons

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chasingsparks
It is an elegant idea, but I am not sure it could reach wide adoption.
Basically, the pitch is that over its lifetime, it will be cost efficient when
compared to _current_ alternatives. However, everyone thinks that near-term
alternatives -- including those that include advanced ultra-capacitors -- will
be even better so they wait.

I did really like the article saying _The buses can also capture energy from
braking, and the company says that recharging stations can be equipped with
solar panels (although this is mainly to further the perception that the
vehicles have a lower carbon footprint)._ It always bothers me that green
concepts try to create an amalgamation of 50 different green sources. Carry
over the Unix philosophy, please.

~~~
sophacles
Um, doesn't having 50 different devices to convert X into electricity, then
piping all of them to a storage device actually match the Unix philosophy
perfectly?

~~~
chasingsparks
I should have been more precise. I was referring to the solar panels at bus
stops, not the regenerative breaking technologies.

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jacquesm
That's a really clever idea. Ultra-capacitors are by themselves a very neat
technology, this kind of ingenuity in the transportation industry is a small
step in the direction of letting go of the oil addiction, sooner is better in
my opinion.

The way the system is described it has clearly been engineered to maximize
cost savings, but I don't think the passenger will be too happy with a bus
that stops for several minutes every couple of stops. Better to do that
charging in smaller gulps at every stop, it will cost more (because you need
more charging stations) but the public will be much more accepting of a
technology that does not right away contain a very visible drawback.

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nathanb
So what you're saying is that if my bus is stuck in stop-and-go traffic for
too long I will have to get out and push?

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yread
Hmm so I'll be going on a bus and it will every couple of miles stop for _a
few minutes_ to charge? I guess I will stick with trams and trolleybuses.

~~~
gbookman
What they're trying to do is have it recharge a little bit at every bus stop,
and from braking.

Basically the exact same ride experience as you have now.

