I'm a student from the KULeuven in Belgium and I'm doing some research on developing a hydraulic energy recovery system. I've already modelled in Matlab/Simulink (mathematic program) a hydro-pneumatic system that recovers braking energy. But now I want to model a system that recovers energy from lowering a load.
I'm using two one-way cilinders.
The pump must be driven by an ICE (internal combustion engine). The energy that is recovered doesn't have to be stored in a battery but in accumulators so I can use the recovered energy for lifting a load.

I'm looking for a hydraulic scheme for this energy recovery system and maybe some formulas. Any help would be most welcome!!!