A New Electrohydraulic Hybrid Energy-Saving System Used on the Reversible Rolling Mills

Table 1

Performance parameters of different energy storage elements [3–10].

Parameters	Mechanical energy storage	Electrical energy storage				Hydraulic energy storage
Energy storage unit	Flywheel	Lead-acid battery	Nickel metal hydride battery	Lithium battery	Supercapacitor	Hydraulic accumulator
Energy density per unit mass (W·h/kg)	5∼200	30∼65	30∼110	100∼250	10∼30	2.4∼6.5
Power density (W/kg)	5000∼10000	90∼500	250∼1200	3550∼4000	500∼5000	2000∼19000
Number of cycles	∼107	300∼800	2500	2000∼10000	105	3–5 years
Efficiency	≈96	≈80	≈90	≈95	≈95	≈90
Impact on the environment	Hardly	Large	Large	Large	Small	Small