Heavy Load Motor-Generator (Dynamotor) Questions

[TRBob]

The motor-generator will be used to pull a load up a mountain side/steep incline on a rail system, the load is between 10 and 300 tonnes, its for a gravitational potential energy storage system. Excess electricity pulls the load up the incline, when there is demand for electricity the load is released driving the generator. Obviously a good gearing system is required.

Is this technically possible? How much do you estimate one would cost? What would be the device's efficiency?

 

[russ_watters]

The motor-generator will be used to pull a load up a mountain side/steep incline on a rail system, the load is between 10 and 300 tonnes, its for a gravitational potential energy storage system. Excess electricity pulls the load up the incline, when there is demand for electricity the load is released driving the generator. Obviously a good gearing system is required.

Is this technically possible?

Welcome to PF! Absolutely, it is technically possible. It's a relatively straightforward means of storing energy.

How much do you estimate one would cost?

There's a big difference between 10 and 300 tonnes and a bunch of different ways of doing it, so it's pretty hard to just pull a cost estimate out of the air. Expensive, though, since you have to build a structure that can support your chosen mass.

What would be the device's efficiency?

Motors and generators are both pretty efficient, so depending on how serious of an estimate you need, start with 95% each, off the top of my head. Then take another 20% off for drive losses. So you might be able to see around an overall 70-75% efficiency.

I'm not sure where you're going with your question, but if you're trying to think if this would be a viable means of energy storage either for a home or on an industrial scale - probably not. The main reason is that lifting a big weight stores less energy than most people realize, which means that storing a useful amount of energy costs a lot more than people realize. That's why pumped water is more often used - if the geology is right, you don't even have to build a tank for it!

 

[TRBob]

I've been searching for a suitable motor-generator (Dynamotor), but the largest I have found is a mere 2 HP! Does anyone know of any manufacturers that produce larger ones?

The system would be used in a small remote community (with suitable topography) to store energy generated by an intermittant renewable source.

 

[russ_watters]

Did you calculate how big of a mass you need and how far you need to lift it to store the capacity you want?

 

[TRBob]

Initially 300 tonnes, raised through 500 metres, not accounting for transmission losses I got 409 kWh, which is quite alot, so the load could be reduced some what. I'm more interested in the motor-generator though, whether ones exist that could be applied to this problem and if so how much they cost.

 

[russ_watters]

Initially 300 tonnes, raised through 500 metres, not accounting for transmission losses I got 409 kWh, which is quite alot, so the load could be reduced some what. I'm more interested in the motor-generator though, whether ones exist that could be applied to this problem and if so how much they cost.

Wow, that's quite a mass and quite a height.

So are you looking for a motor/generator more on the order of 100 kW? I think you may need to find a manufacturer for a dedicated product, but it is my understanding that an ac induction motor can be used as a generator.