Hydrualic prime mover - the accumulator

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The discussion centers on the challenges of using hydraulic accumulators for energy storage in a vehicle, particularly for acceleration needs. A proposed system requires substantial energy storage, estimated at around 10 MJ, but initial calculations suggest impractically large accumulator sizes, such as an 80-gallon tank at 4-5k psi. Participants note that while hydraulic accumulators can provide high torque and performance, they tend to be large and heavy, making them unsuitable for mid-sized cars. Historical attempts at similar systems have faced significant limitations, including the need for extensive fluid reservoirs for cooling. Overall, the feasibility of using hydraulic accumulators in this context remains questionable due to size and weight constraints.
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I am working on a hydraulic system for a vehicle of nominal weight. Of course, the hp required to keep it at reasonable highway speeds is reasonably in the 30-40 hp range.

My issue is energy storage for acceleration (s). This of course is substantial (like 150hp, over 8-10 seconds).

My first instinct is to consider a robust accumulator. But when I jump into the most basic of napkin approaches, I end up with a tank in the order of 80 gallons, 4-5kpsi, with the resulting storage capacity of only a few MJ of energy storage. Enough only to accelerate ~ 2 x. (I will address later (as others have) regeneration energy storage during deacceleration)

Am I heading down the wrong path here in considering a hydraulic accumulator (s), in a mid-sized car, to provide ~ 10 MJoules of energy storage?

Thanks in advance. Mike
 
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It has been done before, and yes you will end up with a large and heavy accumulator system. The one I saw had three cylinders a little larger than a K-bottle on a 3000 psi system. This is more often used on large and specially design moble heavy equipment. Accumulators are never small and light weight.
 
I have no expertise in this matter, but did have the brilliant (:rolleyes:) idea about 30 years ago of using hydraulic motors on a homemade sports car. I figured that it would provide ridiculous torque and eliminate the need for differentials. I wanted it to exceed the performance of my Roadrunner, which was 12-second quarter-mile times and a top speed of 160 mph, with 4-wheel drive. It was based upon the best equipment available from the Rucker catalogue at the time.
Jeez, but did that not work out! I can't even remember what sort of accumulator arrangement I had, if any. The pump was to be driven by a 1,500 hp diesel engine. The main killer, though, was that it would have required something on the order of a 1,000 gallon reservoir in order to allow for decent cooling of the fluid. That would have been bigger than the rest of the car. :frown:
 

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