LarryC, after my hasty last post, I did a few calcs on 'flywheel' energy storage, with some interesting and positively 'hat-eating' results.

Let's look at a plain steel-disc flywheel.
For ease of calculation, let diameter be 24" and thickness 1".
Weight 131 lb. Mean diameter, [c. of gyration, all forces assumed to act at ], = 17".
Let rpm = 24000.

Mean V; 24000/60[secs] x 2pi x 17"/12 = 3560ft/sec.

Kinetic energy; 131x3560x3560/64.4[2g] = 25780149ft.lb. giving 582.6 kWh

In a plain disc flywheel, stress is at maximum at the center, reducing toward the rim. But a flywheel can be contoured progressively, [thinning rimward], to show equal hoop and radial stresses at every point while rotating. This contouring also increases the energy stored per pound of weight. The above flywheel, same approx weight and centre of gyration diameter, but contoured, would have hoop and radial stress of about 50 tons/sq. inch throughout.
Alloy steels can be made to achieve the above as working stresses, but not in large 'ruling sections'*, [ and here I am thinking of big ship-mounted flywheels transporting hydro-power].
[* This is for practical heat-treatment reasons ].
Large wheels could, however, be laminated from thin plates and / or by the use of composite materials such as carbon fibre. There are technical manufacturing difficulties here, not least the need for perfect balance and getting big wheels to run and stay true for a long useful life.

OK, let's build a machine round our shiny new 24" contoured flywheel. If the shaft, casing etc. weigh 70 lb. = 201 lb total, [ and I'm assuming here we go gaga with someone else's money [Linked Image] and build a 'vaccuum casing' and special low-friction bearings to reduce our drag losses]. Our machine performs 582/201 = 2.9kWh/lb.
Only 43% that of gasoline but more than 3 times Europositron's claims. And this is today's technology for the investors to risk their capital on, no 'ifs' or 'buts'. Our machine, properly built and maintained, could do much better than 3000 cycles, and with no pollution. However, note that our losses will be time dependant- eventually friction will dissipate all the stored energy, so rapid transport and use is necessary for a viable scheme.

Now, although 'shaft' or 'electrical power' is often expressed or compared with 'heat units', they are not the same! Heat energy in a gas is chaotic, the motion of the molecules is in all directions. The primary purpose of a heat-engine, [ turbine, piston engine, etc.], is to [ what I like to call ] "tidy up the energy and arrange it in straight lines". In doing so a heat-engine incurs unavoidable thermodynamic losses- [ Google; Carnot's Cycle ]. 75% loss in a gasoline engine, 60% in a diesel. But flywheel energy is already 'straightened', [ as is electrical energy, BTW ]. Gasoline may have 2.3 times the kWh of our flywheel per pound, but put it through a piston engine to get shaft power and it only gives 60% as much!

So, the Big Ship sails on the Allyally-oo on the 1st day of September, and on board are a bunch of flywheels humming expectantly with stored energy. On arrival in NY or Liverpool, we couple and run generators to extract the power and run it to the Grid.
One design possibility might be to have a motor-generator permanently in-line with each flywheel, simplifying layout and charge/discharge to the operation of a simple clutch once speeds are synchronised. Electrical output will vary with the gradual loss of speed on discharge of course, but this is not a problem with solid-state devices creating the sinusoidal power output to the grid.

Larry, this shows some promise!

Now, where's my Fedora sandwich?

Alan

Wood work but can't!