Full wave rectifier capacitance calculation
Here's the circuit I believe you refer to: -



And here's the formula: -



It's an approximate formula because it assumes the discharge of the capacitor between recharges is linear (it's actually exponential) but is reasonable for ripples up to 10%.

So for 100 amps with a ripple voltage of (say) 5Vp-p at 60Hz, the capacitance is 0.333 farads.

However, given your power requirement (5kW) I'd be strongly considering a 3 phase transformer and 3-ph bridge rectifier to make life easier.