Re: Honda H2 FCEV goes 157 miles without refuelling

From: Charles Edmondson (edmondson_at_ieee.org)
Date: 09/29/04 

Date: Wed, 29 Sep 2004 09:07:01 -0700

Dan Bloomquist wrote:

>
>
> John Larkin wrote:
>
>> On Tue, 28 Sep 2004 10:13:35 -0700, Charles Edmondson
>> <edmondson@ieee.org> wrote:
>>
>>
>>> John Larkin wrote:
>>>
>>>> On Mon, 27 Sep 2004 16:17:49 -0400, "G. R. L. Cowan" <gcowan@eagle.ca>
>>>> wrote:
>>>>
>>>>
>>>>
>>>>> I've often said FCEV power is significantly less efficient than
>>>>> ICE, here is some evidence that to some extent is to the contrary:
>>>>> http://msnbc.msn.com/id/6090680/
>>>>>
>>>>>
>>>>> --- Graham Cowan
>>>>> http://www.eagle.ca/~gcowan/Paper_for_11th_CHC.doc --
>>>>> How individual mobility gains nuclear cachet
>>>>
>>>>
>>>>
>>>>
>>>> Can anybody make sense of...
>>>>
>>>> "the fact that while the FCX's capacitor provides energy from
>>>> braking while the car is moving, it doesn't store it while stopped.
>>>> So from a
>>>> stopped position, there's no extra punch to draw on."
>>>>
>>>> John
>>>>
>>>>
>>>>
>>>
>>> John,
>>> One of the problems with ultra-capacitors is that they can have a lot
>>> of leakage current, i.e. they don't hold a charge very long. They
>>> are great for holding a lot of current for a short time, such as a
>>> few seconds, but if you get stopped at a light for 30-60 seconds,
>>> most of that stored energy has leaked out of your capacitor bank.
>>>
>>> Don can probably go into greater detail, as I believe he has
>>> researched them in more depth, but that is the simple answer... 8-)
>>> --
>>> Charlie
>>
>>
>>
>> If a capacitor absorbs horsepower-levels of power during braking, and
>> can't store it long enough to assist the next start, it's not only
>> useless, but it will obviously get hot enough to explode.
>>
>> I suspect the writer, another typical journalism major, just got
>> something confused. Or the engineer was jiving him.
>
>
> I would think he just didn't understand the physics. At 2
> microampers/farad, leakage is just not a real issue.
>
>>
>> John
>
>
> Best, Dan.
>
Sorry, guys, but I haven't researched this in any great detail. Was
just relating a possible mechanism for the low storage time, from some
of the things that I have 'heard'!

These things have also improved a lot since I last even looked at them,
but last I looked the leakage was a couple of orders of magnitude higher
than Dan is quoting.

My masters is in RF, not power electronics! 

-- 
Charlie
--
Edmondson Engineering
Unique Solutions to Unusual Problems
Quantcast