You gotta sit up and take notice when a new technology claims a 40 to 50 percent increase in fuel economy. Either that or hide your checkbook. Personally, professionally, I’ve never heard of a hydraulic hybrid vehicle (HHV), never mind a diesel hydraulic hybrid vehicle (DHHV?). But IndustryWeek has, as well as the United Parcel Service, which plans to deploy a fleet of two (count ’em two) HHVs in Minneapolis early next year. The only explanation for the taxpayer-funded technology involved is, to say the least, literally, marginal. “The technology, originally developed in a federal laboratory of the Environmental Protection Agency, stores energy by compressing hydraulic fluid under pressure in a large chamber.” Does one of our Best and Brightest care to elaborate? Meanwhile, it’s kinda weird to hear our government officials talk about the hybrid premium: “The EPA estimates that when manufactured in high volume, the added costs of the hybrid components can be recouped in less than three years through lower fuel and brake maintenance costs.” [thanks to nutbags for the link]
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UPS will deliver packages via steam locomotive? Guess by “hybrid” they mean it will burn either coal or wood.
This isn’t so new. I have (at home) a 1975 (or possibly 1976) Popular Science (or) Popular Mechanics (or) Mechanix Illustrated (they were as interchangeable as GM, Ford and Chrysler back then) with an article about an “inventor” who came up with a hydraulic hybrid, and installed it in a (US) Ford Granada six.
He went from 17 mpg to 34 mpg with the 200 cubic inch 78hp engine. Mostly in city driving, I think.
The transmission and driveshaft went away, a Volvo hydraulic elevator pump was put on the back of the engine and obviously some hoses and tanks, and another hydraulic elevator pump attached to the (back) drive axle. Needless to say, you could push the “go” pedal and get all oars in the water so to speak – the pressurized tank backed by the engine ramping up in power would provide plenty of giddy-up. Presumably, more than the standard pathetic 78hp six. (Crude emission controls on 1960 tech engines sucked).
Without modern electronics, it was a tad out of the ordinary to drive since if you wanted to regenerate (recoup energy) when slowing down, you used the two-way “gas” pedal which pivoted in the middle. Push the toes – go fast, push the ankle, slow down. Need brakes? Hit the left pedal.
For full sized cars, SUVs, pickups, vans and delivery vehicles, hydraulic hybrid actually may make more sense than electric hybrids. Tank size constraints probably make the system not workable for many cars, and especially mid sized and smaller cars.
http://en.wikipedia.org/wiki/Hydraulic_Launch_Assist
When normal vehicles stop, all that kinetic energy is lost through the brakes as heat (although not so in hybrid cars that have regenerative braking). This systems turns some of that kinetic energy into potential energy which can then be released again when the vehicle accelerates from a stop. The way it stores this kinetic energy is to use the motion of the vehicle, transferred through hydraulic fluid, to compress air in a chamber. When the vehicle moves again, the air in the chamber expands, pushing on the hydraulic fluid, and providing some force to reduce the use of fuel.
Think of it like a vehicle using a giant spring to stop instead of brakes, and then releasing that spring when the vehicle wants to move again.
The biggest benefit of this technology would be vehicles that start and stop a lot, such as delivery trucks, buses, etc.
Eaton has been working on this for about a decade now, but it requires an accumulator as mentioned above. See link.
Hydraulic Assist
PS Good analogy GeeDashOff.
There are a ton of articles on greencarcongress.com on this topic. Type “hydraulic hybrid” in the search–too many to link in this comment. Seems like a cool idea to my non engineer brain. Especially for things like garbage trucks and delivery vans.
http://auto.howstuffworks.com/hydraulic-hybrid2.htm
GeeDashoff –
The biggest benefit of this technology would be vehicles that start and stop a lot, such as delivery trucks, buses, etc.
Agreed. Hydraulic drives (in series) aren’t very good for moving a vehicle at high speed. You’re wasting perfectly good energy in a hydraulic pump that you could’ve transferred directly to the wheels.
https://www.thetruthaboutcars.com/high-efficiency-digital-displacement-tranny-to-double-mileage-maybe/
Asked and answered? Maybe…
I think Saab/Scania has already done this or will be releasing it soon
The 1970’s Ford converted by the genius (mentioned in my prior post) to hybrid drive was a series hybrid, yes.
But a lot of the savings were from the gasoline engine cycling on and off and obviously shutting down at stop lights, too. Forgot to mention that.
Obviously on the highway, this cycling would probably cease, or be severely limited (as it is on my Prius – pretty much down-hill only).
As with electric hybrids, most savings would be on the city cycle. Some savings on the highway cycle (not nearly as much as city cycle) could be derived from using a smaller gasoline or diesel engine than the corresponding non-hybrid (with the “needed power” made up for by the instant access to stored power).
I saw this at the Eaton labs several years ago.
The best application is for refuse trucks – the lab guys told me that refuse trucks go through brakes very fast due to their constant stop/go duty cycle.
The system would pay for itself in brake replacement savings alone, so the fuel savings is on top of that.
Their test mule was a one ton pickup and the components took up most of the under chassis real estate. Of course in production many components would be reduced in size (and cost), but the tanks need to maintain their size for the energy storage (hydraulic fluid is not compressible).
Wasn’t Ford trotting this about as an eventual option for their larger trucks?
Working for a company that specializes in hydraulic equipment (in Minneapolis no less), this makes sense – especially for stop-and-go city driving like UPS and FedEx trucks. Richard Chen’s howstuffworks.com article is dead on.
Hydraulic systems and electrical systems are very much similar. Capacitors = accumulators, current = flow volume, voltage = pressure.
For a big heavy truck in stop/go traffic, a hydro-pneumatic system can be much more efficient than electricity for the workload demand.
I just want to see one of those slammed, flamed UPS rigs roll up to my front door!
“…stores energy by compressing hydraulic fluid under pressure in a large chamber.” No way. Hydraulic fluid is virtually incompressible. If it weren’t, it wouldn’t be able to transmit forces as it does. Perhaps Ms. Selko is referring to hydraulic accumulators, as noted above, which have been around for oh, about 80 years.
There’s already a fleet of dump trucks testing this technology. Huge fuel and maintenance savings. Also a big plus for those of us with houses nearer to the street. Those squeeling brakes are really annoying!
What a mess if a fully compressed tank got ruptured in an accident. On the plus side, if the fluid could double as a fire retardant…
I’m interested in seeing if this idea goes anywhere.
It would actually be the air (or whatever gas they’re using) in the accumulator that would be compressed. Technically, the hydraulic fluid would be compressed too, but by an extremely insignificant amount.
There’s a lot of potential (ahem) for this tech, though repairs would have to be handled by the local Caterpillar dealer.