Comments on: Corn stover collection project

By: Engineer-Poet

Engineer-Poet — Sat, 12 Jan 2008 00:20:15 +0000

There’s plenty in the pipeline but I can’t seem to get anything finished.

This is partly because I’m swamped for time. I won’t bore you with the details, but I don’t have any prospects this weekend or the next.

By: Justin

Justin — Fri, 11 Jan 2008 00:30:53 +0000

Are we ever going to get another blog post?

By: BBM

BBM — Mon, 21 May 2007 21:47:21 +0000

You’ve probably seen this:

http://www.businessweek.com/autos/content/mar2007/bw20070319_949435.htm?campaign_id=rss_topDiscussed

Probably a very small light wt vehicle, but interesting. Doesn’t say if there is any regenerative braking, though. If there is not, then there’s even room for improvement.

By: Engineer-Poet

Engineer-Poet — Wed, 02 May 2007 02:11:56 +0000

There have been several compressed-air cars, including one now being promoted in India. The problem with using air for regenerative braking is that it’s hard to package all the filtration, intercooling, drying and such gear that stationary high-pressure compressors have, and the tanks for low-pressure would be mighty big.

By: BBM

BBM — Wed, 02 May 2007 01:29:19 +0000

I wonder how much energy could be stored in a compressed air tank of reasonable size. Those tanks are pretty heavy, though as you point out. Perhaps a carbonfiber tank? Crash protection would also be a worry.

By: Engineer-Poet

Engineer-Poet — Wed, 02 May 2007 00:46:57 +0000

The hydraulic systems have high efficiency but a relatively low specific energy. This makes them very good for short start-stop cycles (e.g. garbage trucks) but not so good for typical passenger car cycles; you would need a very large and heavy accumulator (relative to the vehicle) to absorb all the braking energy.

I went searching for the 30% figure, because I was wondering about the methodology and the split with the friction brakes. The one hit I found was a pointer to a page which is now 404. Regardless, larger batteries (e.g. PHEV-class) will have a higher regeneration efficiency because they can absorb more power.

By: BBM

BBM — Wed, 02 May 2007 00:25:26 +0000

EP,

I’d like to get your opinion on something.

What do you think about constructing a hybrid car that consists of a hydraulic accumulator, connected to a pneumatic drive motor, with an energy battery electric motor keeping the accumulator charged?

I was thinking about that because apparently current electrical regenerative braking tech is only 30% efficient, but the pneumatic recapture is about 70% efficient.

The accumulator could act sort of like a cheap ultracapacitor, allowing the batteries to be optimized for energy storage rather than power burst AND storage. And this would not interfere with the eventual electrification of transportation, as other types of pneumatic hybrids might.