Research of the hydrostatic transmission for deep-sea current energy converter.

• Dual-pump confluence achieves easily the power aggregation. • Dual-pump confluence reduces operating pressure while motor speed is kept constant. • The operating pressure depends not only on load but on the turbine shaft speed. • Distributed HST system can be applied to deep-sea by aggregating dispersed energy. It is well known that generating electricity in the deep-sea has always been a very challenging problem. Aiming at the power demand of the underwater observation system, this paper presents a novel distributed ocean current energy hydrostatic transmission (HST) power generation solution, which can generate electricity efficiently and continuously in large depth and low flow velocity environment. The proposed solution adopts a dual-pump confluence design. According to this, the working pressure of the HST is reduced to avoid overflow compared to the single pump design, and therefore the dispersed micro-energy in deep-sea can be aggregated together to convert continuously to active power rather than to the heat. Furthermore, the solution employs an energy-saving strategy involving constant pressure pump and seawater cooling and improves effectively the efficiency to some extent. Besides, it was found that the working pressure of the system depends not only on load torques but also on turbine speeds reversely, while the speed of hydraulic variable displacement motor maintains constant. Therefore, dual-pump confluence implies power aggregation and plays a key role in generating electricity in deep-sea. Simulation results and the tests based on the 5 kW prototype verifies the feasibility of the proposed distributed HST solution. Accordingly, at the current status, the distributed HST power generation is the most probable solution applied to the deep ocean. [ABSTRACT FROM AUTHOR]