hydraulic hybrid vehicles (HHV)

[serpretetsky]

Most hybrids on the road are a combination of gasoline/diesel engine and an electric motor and battery. However, hydraulic hybrids vehicles (HHV) exchange the electrical motor and battery for a pump and tank that compress and store some fluid (I think usually it's just air).

Everything I'm reading about HHV's suggest that they are generally cheaper and more efficient at recovering energy. Why are electrical hybrids so common in passenger vehicles and why is HHV non existent in passenger vehicles?

Do you think there should be a bigger push for HHV's?

 

[Ben90]

That's why.

 

[serpretetsky]

I wonder if, in the current state of research, it would be any more expensive or cheaper to mass produce such a system in a passenger vehicle.

http://www.youtube.com/watch?v=9AB7yp40fQg
http://www.youtube.com/watch?v=6uzFfWEiDB8
http://www.youtube.com/watch?v=BuERSmGL8BE

 

[dkozloski]

I remember reading years ago that a very efficient and lightweight method of storing and releasing energy was to use a wound up rubber band. I know it worked very well in model airplanes. Maybe we need to be looking at a system based on bungee cord.

 

[Wall Street]

The energy density of compressed gas is quite a bit lower than a battery and much much lower than hydrocarbons. A cubic foot of gas can get you 250 miles. A one cubic foot battery can get you at least 25 miles. I would be surprised if a one cubic foot hydraulic compression chamber would get you more than a few miles.

 

[serpretetsky]

The energy density of compressed gas is quite a bit lower than a battery and much much lower than hydrocarbons. A cubic foot of gas can get you 250 miles. A one cubic foot battery can get you at least 25 miles. I would be surprised if a one cubic foot hydraulic compression chamber would get you more than a few miles.

For stop and go traffic on relativily flat ground does it matter? That's actually the other thing I don't understand; why do all of these new hybrids have giant batteries packs? Why don't they have a series of ultra capacitors? They last longer and are more eifficient. Do hybrids really need all of that energy capacity? I mean... they use gasoline anyways.

I figure as long as they can soak up the energy from the slow down from 60mph to 0 (and let's say we double it just in case) then any added capacity after that probably doesn't do much. yay nay?

 

[serpretetsky]

Heh, just answered my question on why they dont' use ultra capacitors:

60mph = 27m/s
3000lb car = 1361 kg

Energy of car moving at 60mph
= 1/2 mv^2 = 1/2 (1361 kg)(27m/s)^2 = 496 084. 5 Joules

Energy capacity of 500F 12V ultra capacitor 630$
= 1/2 CV^2 = 1/2 (500 F)( 12V)^2 = 36 000 Joules

would need more than 10 of those to store the energy of deceleration from 60mph which would be roughly 6000$. I think the battery packs in the totyota prius are only 2500$

Assuming using the following ultra capacitor and charging it only 12V of its 16V maximum
http://www.mouser.com/Passive-Compo...z0x565&Keyword=167816066&FS=True&Ntk=P_MarCom

 

[John Connor]

I seen on the Today I show I think it was years ago UPS having a truck that used regenerative breaking. I have always thought why don't garbage trucks have this?

 

[Scarpozzi]

Manufacturing and materials costs is such a buzz-kill. When you consider what even gas/electric hybrids save in annual fuel costs, cars in the same class are cheap enough that the justification of buying a hybrid is a hard sell for me. I just don't drive enough miles to take a risk on battery technology unless gas prices increase 50%.

 

[serpretetsky]

Manufacturing and materials costs is such a buzz-kill. When you consider what even gas/electric hybrids save in annual fuel costs, cars in the same class are cheap enough that the justification of buying a hybrid is a hard sell for me. I just don't drive enough miles to take a risk on battery technology unless gas prices increase 50%.

Yeah, in terms of pure price it definitely is a hard sell. While hybrid manufacturers do try to market their vehicles as saving on fuel, I think ultimately the buyer they are targeting is someone who wants to save resources(globally) and/or cause less pollution.