Hydrualic prime mover - the accumulator

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SUMMARY

The discussion centers on the feasibility of using a hydraulic accumulator for energy storage in a mid-sized vehicle, specifically targeting an energy storage capacity of approximately 10 MJ. The initial calculations suggest that a robust accumulator would require a tank size of around 80 gallons and operate at pressures of 4-5k psi, yielding only a few MJ of usable energy. Historical examples indicate that while hydraulic accumulators have been utilized in heavy mobile equipment, their size and weight make them impractical for standard vehicles. The consensus is that achieving the desired energy storage in a compact form is challenging and may not be the optimal solution.

PREREQUISITES
  • Understanding of hydraulic systems and their components
  • Knowledge of energy storage calculations and requirements
  • Familiarity with accumulator types and their applications
  • Experience with vehicle dynamics and performance metrics
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  • Research the design and specifications of hydraulic accumulators in heavy machinery
  • Explore alternative energy storage solutions such as flywheels or batteries
  • Investigate the principles of hydraulic motors and their integration in automotive applications
  • Learn about energy recovery systems during deceleration in hydraulic systems
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This discussion is beneficial for automotive engineers, hydraulic system designers, and anyone involved in the development of energy-efficient vehicle technologies.

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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: