Something I have wondered about for a while and finally getting around to start investigating...

Would it be possible to lift giant boulders (rocks) and use them as a type of battery?

Like say you have a solar panel array that runs a DC motor connected to a very geared down pully system that slowly but surely lifts an incredible amount of weight (say 5 tons). Then at night time (or whenever) you release the motor lifting the weight and then connect an alternator and release the 5 tons so that it slowly drops running the alternator.

Is that even feasible?

I just started looking up the calculations for this. Please check my math.

For an example I take my laptop

It says 4.74 amps at 19V.

That would be 90 watt hours. right?

If I ran my laptop 10 hours a day that's 900 watt hours.

using google 900 watt hours = 663 foot pounds per second (663 pounds moving 1 foot every second?)

5 tons = 10,000 pounds

10,000/663 = 15

Does that mean I would need 5 tons moving 1 foot every 15 seconds to generate enough power to power my laptop for 10 hours? This is the point I am at.

How do I calculate this?

Would I go

90 watts per hour to power my laptop/60 minutes / 60 seconds = .025 watts per second

.025 watts = .02 foot pounds per second

would that be .3 inch pounds per second?

How do I get to something that makes sense?

Is it 0.02 feet * 1 lbs / seconds? or is it 0.02 lbs * 1 foot / seconds? I'm a little confused here.