The discussion centers on the feasibility of coupling a hydraulic motor with an AC generator to produce electric energy efficiently. The proposed setup includes a 100 kW AC generator operating at 100 RPM, paired with a hydraulic motor generating 500 RPM and 2400 Nm torque, utilizing a 5:1 gearbox. Participants concluded that the system would require at least 125 kW of hydraulic power input to achieve a maximum output of 100 kW, indicating that this configuration does not yield high efficiency. The consensus is that energy conversion always incurs losses, making the proposed system inefficient for practical applications.
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Welcome to PF!Vardges said:Hi there. I have an idea which is interesting. Let's suppose, we have AC generator which has capability of 100 KW and 100 RPM. And we have hydraulic motor which produces 500 RPM and 2400 Nm torque. Additionally, I attach 5:1 gearbox for reducing 500 RPM to 100 RPM for Ac generator. Please, share your thoughts, is it possible to produce high efficiency and electric energy with this combination?
125kW input for 100 kW output is not generally considered high efficiency. In practice it would be even less than that.Vardges said:Hi there. I have an idea which is interesting. Let's suppose, we have AC generator which has capability of 100 KW and 100 RPM. And we have hydraulic motor which produces 500 RPM and 2400 Nm torque. Additionally, I attach 5:1 gearbox for reducing 500 RPM to 100 RPM for Ac generator. Please, share your thoughts, is it possible to produce high efficiency and electric energy with this combination?
The hydraulic motor is spun by hydraulic pump. And the hydraulic pump is powered by electric motor.russ_watters said:Welcome to PF!
Depends -- what is making the hydraulic motor spin? And what do you consider "high efficiency"?
Dale said:125kW input for 100 kW output is not generally considered high efficiency. In practice it would be even less than that.
Power density is not relevant to the question of efficiency. For efficiency all that is considered is the input power and the output power. It doesn't matter how dense the power is, just how much goes in and how much comes out.Vardges said:Hydraulic motors have 10 times more power density than electric motors have.
Sure. That is what a hydroelectric power plant does. As @mfb and I have said, the efficiency of such a conversion is strictly less than 1.Vardges said:I want to use hydraulic mechanism to get electric power
Dale said:Power density is not relevant to the question of efficiency. For efficiency all that is considered is the input power and the output power. It doesn't matter how dense the power is, just how much goes in and how much comes out.
Based on your numbers above at least 125 kW hydraulic power goes in and at most 100 kW of electric power comes out. That is not a very high efficiency, but might be acceptable in some scenarios (e.g. If the hydraulic power were very inexpensive so you could sell the smaller amount of electrical power for more)
Sure. That is what a hydroelectric power plant does. As @mfb and I have said, the efficiency of such a conversion is strictly less than 1.
Perperual motion machines do not work and are not discussed on PF. Thread closedVardges said:typical hydraulic press consumes 5-7 KW electricity ... couple them to 100 KW PM generator.