The hydraulic hybrid may not be grabbing headlines, but it’s a solid technology with a potential future in heavy-duty vehicles. Vehicle manufacturers are considering it for next-generation garbage trucks, school buses, and delivery vans. Caterpillar has already unveiled it in an excavator and PSA Peugeot Citroen is working on a hydraulic hybrid automobile that could hit the streets by 2016. Chrysler Corp. and Ford Motor Co. have talked about it, as well.
To be sure, makers of electric hybrids, such as the Prius and Volt, aren’t looking for it in their rearview mirrors yet. But the technology offers advantages in fuel efficiency and cost, which is why many engineers are keeping it on their radars.
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PSA Peugeot Citroen has filed for 80 patents on its “Hybrid Air” system, which combines hydraulic power, compressed air energy storage, and a gasoline-burning engine. The company says the vehicle will get 45 percent fuel savings in urban driving and 35 percent overall. (Source: PSA Peugeot Citroen)
Bob, that is a good question, what would they make them out of. The ones that I am familiar with are made out of a quite tough grade of steel, and they are thicker than SCUBA tanks by a good bit. Mostly the fill gas is dry nitrogen, so heat conduction would be better than air. The certainly would need to be protected from that six month bath in saturated salt solution, though. But where the hydraulic hybrid system would work best would be in the vehicles that do the most stop-start driving, rather than passenger cars, and those types of vehicles would have more room for the accumulator away from the salt.
I've seen 200PSI air split a welded pipe in dramatic fashion and felt the heat generated when 4000PSI SCBA tanks are refilled. Cycling an accumulator from a few hundred PSI to over 4K PSI a few tens of thousands of times would seem to induce some fairly significant stresses. The accumulator must be made as light as possible, yet able to function for the lifetime of the vehicle - this would seem to be a fairly significant engineering challenge. Considering even a well-built automobile more or less disolves after 15 or so years driving over salted roads, I wonder what they would make a hudraulic accumulator out of.
Bob, hydraulic accumulators, the devices used to store the power during decelleration, are probably some of the safest energy storage devices around. I am not aware of any of them ever having burst, which would be quite a mess. The norma failure mode of an accumulator is leaking out of the high pressure gas relatively slowly, or else a hole in the separator between fluid and gas, which results in poor performance by the hydraulic devices being powered. So the catastophic failure headline is one that you may never see.
I would describe a hydraulic hybrid along the same line as an electronic device using a super-capacitor to provide short bursts of high-energy for very brief periods, thus supplementing a smaller-lighter battery that is capable of significantly lower sustained current. So for instance, Chrysler's 2.4L IC van could provide the same 0-30 performance as a 3.6L or larger IC engine without the MPG penalty at sustained highway speeds. Storage of high-pressure gas has some hazards and any catastrophic release would cause headlines around the world - as witnessed by Boeing and Tesla's recent adventures. I hope the technology can be made to work and look forward to more articles.
In the 1950's diesel-hydraulic was tested as a an alternative to the diesel-electric power in freight locomotives. With the technology of the day, the hydraulic systems were not able to displace the diesel-electric in the US or in Europe. All the locomotives used in the US (about 10) were retired after a very few years. Worldwide, less than a half dozen of the diesel-hydraulic locomotives were saved from the scrapper's torch.
There is a downside to the hydraulic hybrid, which is that the hydraulic fluid does need to be kept very clean. BUT that is not a huge challenge, more of a warning that failing to keep the hydraulics clean inside will lead to wear and reduced efficiency. But that is nothing new. All of the hydraulics needed have been around for many years. Another recent post verifies that in more detail.
This was a decent article, and was sent to me by a friend I mentioned the development, and either suppression or ignoring of petrol hydraulic hybrids. What The article does not mention is the ORIGIN of this tech. The whole auto industry seems pretty stagnant as a whole since it is so heavily determined by government regulations, cooperation with government in the picking of winners and losers via vehicle fleet purchases, etc. The fact is petrol hydraulic hybrids are NOT just for trucks, and are not 2000 plus inventions. google "Ernie Parker mother earth news" and ditto "Vince carman mother earth news" and hydraulic as well for both. In the mid 1970s, from two different tech angles, each of them designed functioning petrol hydraulic hybrid conversions (Vince Carman as his own for sale patent oriented project, Ernie Parker was a technical instructor at a technical community college in Minnesota, did it with his automotive students as a class project).
In short, both of them had systems using off the shelf parts that could convert an existing vehicle to a petrol hydraulic hybrid and double it's file efficiency while maintaining practical traits such as acceleration, etc. It was noted that an optimised designed vehicle, removing parts not needed for the hydraulic hybrid drive train, etc could likely achieve mileage up to 140 miles per gallon, presuming nothing else changed (weight, materials advance, etc). In the 1990s the EPA converted a mid size sedan and achieved more than 70 mpg, using petrol hydraulic systems, and this too could have been put into public manufacturing.
What we are now looking at is nearly 40 year old tech, as implemented effectively and off the shelf by amateurs that has been ignored for these decades, and for another 2 years since a major govern,ent agency of the USA itself replicated and tested it. Rather than the fuel additive mandates (often ineffectivel expensivel and in the case of MBTE very polluting ) and various CAFE demands, which make vehicle weights decrease, and to censure safety, then jack up costs by having to add myriad safety features, crumple components, etc, the entire automotive industry could have gone in a new direction, converting existing vehicles, and redesigning the new models for optimisation.
This tech would be better than the expensive and toxic electric battery driven vehicles. It could be combined with the similarly spiked turbine engines and thus hemp biodiesel could be used, or ANY fuel (even perfume) as the turbine burns clean and efficiently. Look up the informative article at fuel-efficient-vehicles.org on the Chrysler turbine, and the fact that one of the chief concerns that led to it's abandonment was the concern over what would happen to the government revenues due to the fuel taxes that might not be paid when people could use anything as fuel, not just gasoline an diesel. There is also the fact that circa 1940 Ford motor car company revealed a vehicle with a tubular steel frame and the body largely composed of hemp plastic...far lighter than steel with ten times the impact resistance. It was ignored post war with the continuation of the banning of hemp production (allowed during the war as a critical necessity, suppressed immediately afterwards).
I might sound like a radical, but let me mention something about myself. I am a former soldier with special forces experience, self trAined into engineering, and I worked in a capacity for major multi nationals as a design engineer in several fields. I ended up invited, as an engineer for various reasons to the DARPA petroleum free military conferences, where both officially and unofficially I had my eyes opened to some amazing tech, programs, and developments. I also was, at the time, a judge for the IEEE future cities competition, but when I dug into what I had learned via DARPA and other conference attendees It was like falling down the rabbit hole. I also used to work counter drug ops when I was in the military, and what I learned first hand turned me from an ardent believer in the drug war to a rabid opponent.
America could and should legalise cannabis and hemp production. The myriad incredible uses of hemp, biodiesel made from it,particle board, paper, cloth, hempcrete and hemp plastics could ecologically totally revamp numerous industries, and long could have. For those heavily into the whole carbon footprint, hemp tech is an amazing way to sequester carbon. Our vehicles could be lighter, safer, stronger, recyclable, and made from sustainable materials to a Large degree. The computerised fuel injection systems and other complex computerised systems could be abandoned in many models to simplify the production and lower the costs. By combining the technologies, using modular designs, and features, variety on models and capabilities could return to an increasingly homogenised auto industry (the vehicles increasingly all look like each other from a layman point of view because all designs and models have to converge to an increasingly dictated set of government design features). A vehicle designed from th ground up as a petrol hydraulic hybrid, with weight savings from the parts and components not needed (u joint, etc), further weight savings and safety increases could be implemented by having the body made from hemp plastic.
I will nt go so far as to say it is a big conspiracy, but it is clear there have been interests Nd bureaucracy stifling many innovations. Black shelving of patents does occur, and both the government and industry now finally seem to be considering the petrol hydraulic hybrids but I hVe a lot of questions about the sudden appearance f the peugot and where the idea, designs, patents come from, and also what their mileage and such is. Will it be an expensive modest improvement over current standards, or will it be a major mileage improvement over the 1970s designs as it should be since manufacturing tech, ground up design, lighter cars, and forty years of refinements should certainly see a major improvement in the performance and specs compared to 40 year old, non computerised and optimised designs done by garage mechanics and automotive students achieved. They achieved 70mpg plus from off the shelf conversions, so the new hydraulic hybrids should be far better, or it is another planned obsolescence con on the public where revolutionary change, which has long been possible via various tech avenues, has again been stymied for special interests. I used to think this could not be the case, but what I learned via DARPA and the other conference members was just how inter related, how inter dependent manynindustries and government arel. The oil industry has huge stake in, and influence over the auto industries, just as the drug, insurance, and medical industries are cross invested and linked...not for the benefit of the public, but each other, where money from one arm shifts into the accounts of the other.
Hydraulic hybrids are the an extremely good choice for vehicles doing stop-start service, such as garbage trucks, busses, and delivery vehicles. The beauty is that the hydraulic system can recover energy all the way down to zero speed, and it can recover energy very rapidly, limited only by the flow capacity of the piping. The other quite huge advantage is the life of the hydraulic system, which can be tens of years with only minimal maintenance. Keeping the system clean and dry are the major requirements, and while cooling is important, a bit of overheating will not cause a catastrophic decomposition. A typical massive accumulator failure leads to a large drop in performance, not a fire or smoke. And a correctly functioning accumulator can store a full charge for years, with no loss. So the hydraulic system does have a whole lot going for it.
I designed a hydraulic car 20 years ago, using a free-piston engine pump and a Vickers hydraulic motor. Practicality reared its head when calculations revealed the need for an 188gpm fluid flow to move the weight at an acceptable speed. The accumulator became too enormous to be practical. The calculated efficiency was great.
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