Hydraulic accumulator is used as energy storage element and static pressure transmission technology is used to drive walking, rotary and other action equipment. There are three main types of hydraulic hybrid power system, series type, parallel type, hybrid type, and are in the development.
1.Comparison of energy storage devices
The performance of energy storage devices such as battery, hydraulic accumulator, energy storage flywheel and super capacitor is compared. The power density of hydraulic accumulator is the largest and that of battery is the smallest. The energy density of battery and energy storage flywheel is large, and the hydraulic accumulator and super capacitor are small. Compared with several other energy storage components, the efficiency, discharge and life of the battery are the lowest. When the hydraulic accumulator and energy storage flywheel are abandoned, the chemical pollution to the environment is less, and the environmental protection performance is the best. Super-capacitors have the advantages of high safety and discharge energy, but because of the low maturity of technology.
2.Advantages of Hydraulic Accumulator Technology
(1).High power density
Energy density and power density are the two most important parameters of energy storage elements. From the point of view of energy density, fuel cells, batteries, energy storage flywheels and super capacitors can provide energy for a long time because of hydraulic accumulators. From the point of view of power density, hydraulic accumulator is superior to other energy storage methods. Only high power density systems can keep up with the energy conversion and storage requirements when braking in a short time. Therefore, hydraulic accumulators are more suitable for medium and heavy urban public transport and construction machinery than other energy storage methods.
(2).Lightweight energy storage device
Electric hybrid vehicles use batteries or super capacitors as energy storage units, and batteries usually use nickel hydrogen batteries and sodium nickel chloride batteries. The hydrostatic transmission hybrid power system uses hydraulic accumulators to store energy. For the same class of hybrid vehicles, the weight of the Ni-MH battery and the sodium nickel chloride battery energy storage system is nearly twice that of the hydraulic energy storage system, and the weight of the super capacitor system is also 40% higher than that of the hydraulic accumulator. lighter energy storage systems can maximize the payload and fuel economy of hydraulic hybrid vehicles.
(3).High cycle efficiency
The cycle efficiency of the energy storage system refers to the efficiency of the braking energy from the drive shaft to the energy recovery system and the recovered energy to the drive shaft again. Compared the energy cycle efficiency of different energy storage systems, the cycle efficiency of hydraulic energy storage system is higher than that of battery and super capacitor system. The new composite accumulator and hydraulic pump hydraulic motor technology are improved, which further improves the energy cycle efficiency of hydraulic energy storage system, and the cycle efficiency can reach 82%.
(4).Value, safe and reliable
Compared with other types of energy storage systems, hydraulic energy storage systems are cheaper, mature technology and high reliability. The hydraulic accumulator shell is strong and can withstand the limit pressure from the inside many times. Long service life, suitable for multiple, fast, large energy flow energy storage, to avoid spontaneous combustion, explosion and other hazards.
(5).Low pollution to environment, easy maintenance
Battery contains a large number of toxic raw materials, whether it is production or waste components treatment, will cause great pollution to the environment. However, the waste components of hydraulic accumulators can be recycled and reused without causing pollution to the environment. Hydraulic energy storage system can work in harsh environment, which is obviously less affected by high temperature, cold and humidity than electric hybrid power system. Hydraulic accumulator has been widely used in industry and mature technology, so hydraulic energy storage system is easy to integrate and equipment maintenance is simple.