This is an interesting twist in diesel technology that makes me wonder if it would be applicable to railroad motive power, specifically in commuter service. Sounds like an intriguing idea…it’s a hydraulic accumulator, not a transmission aka SP’s ill fated venture…although they had a brutish visual kind of appeal like a armored cab unit…
Hydraulic Hybrid Research
EPA is a research leader in the application of hydraulics in vehicles. Hydraulic hybrid technology uses a hydraulic energy storage and propulsion system in the vehicle. This hydraulic system captures and stores a large fraction of the energy normally wasted in vehicle braking and uses this energy to help propel the vehicle during the next vehicle acceleration. The hydraulic system also enables the engine to operate more efficiently when it is needed.
Hydraulic hybrids draw from two sources of power to operate the vehicle - the diesel or gasoline engine and the hydraulic components. In other words, a typical diesel-powered or gasoline powered vehicle can be fitted with hydraulic components as a secondary energy storage system. The primary hydraulic components are two hydraulic accumulator vessels (a high-pressure accumulator capable of storing hydraulic fluid compressing inert nitrogen gas and a low-pressure accumulator) and one or more hydraulic pump/motor units.
Benefits of Hydraulic Technology. Hydraulic drivetrains are particularly attractive for vehicle applications that entail a significant amount of stop-and-go driving, such as urban delivery trucks or school buses. A major benefit of a hydraulic hybrid vehicle is the ability to capture and use a large percentage of the energy normally lost in vehicle braking. Hydraulic hybrids can quickly and efficiently store and release great amounts of energy due to a higher power density. This is a critical factor in maximizing braking energy recovered and increasing the fuel economy bene
Some laboratory geek with limited to no practical experience in the mud, sludge and grit thinks this is a wonderful idea, and the media, which immediately suck up to anything ‘green,’ put it out as some kind of a panacea.
Until this scheme has a proven track record of near-perfect reliability, any rail executive who suggests using it will be advised to take two aspirin and call his doctor in the morning. NOTHING that might delay commuter traffic will be adopted until some very skeptical managers are convinced that it won’t. Imagine the impact if a crowded big-city commuter train dies - hundreds of people with cell phones (some with speed-dial to their favorite media outlets) and a reason to scream. Now imagine them screaming that the [censored] hydraulic booster system blew a line and soaked the immediate area with hydraulic fluid, as well as blocking the line…
Maybe, after 10-15 years of experimentation on some less-sensitive traffic, they MIGHT come into use on commuter trains. If you’re a betting man, place your wagers elsewhere.
Chuck (modeling Central Japan in September, 1964 - including diesel-hydraulic MU cars)
Most DMUs around to-day have hydraulic transmission ,so this cannot be discounted. This particular development would however need to be tried out on a prototype first.
Some of these DMU trains are also fitted with hydraulic retarders (the hydraulic equivalent of dynamic braking), so it’s a logical development to link the systems and make use of the otherwise waste energy.
Where you find the space underneath the train for the accumulators is another matter…
Tony
Interesting concept. However… (there’s always a however!)
Unless I am missing something really important, this concept will apply well to hydrostatic type power trains, in which a prime mover powers an hydraulic pump which in turn powers hydraulic motors. Such power trains are remarkably common these days, on both small (lawn mowers) and large (construction earth moving) equipment. Where they aren’t common is on large equipment which moves at higher speeds, or where there is a significant weight consideration.
The diesel-hydraulic units (with, as noted, in some cases retarders) found on rail equipment (e.g. many DMUs, the RDCs, and the Krauss-Maffei units, among others) are hydrodynamic drives, not hydrostatic, and there is a critical difference: the hydrostatics operate at relatively low flow rates, through hoses or pipes, at high to very high pressures, while the hydrodynamics operate at very low pressures, no hoses, and very very high flow rates. It is not that hard to create a device called an accumulator for a hydrostatic drive; the amount of energy stored can be remarkably high, and the energy density (which is dependent mostly on system pressure) can also be high, although the point about where do you put the things has a good deal of merit since they can get rather large. I have to admit that I fail quite completely to see how one could store any significant amount of energy from a hydrodynamic drive, since the pressures are, as I noted, very very low.