I'm not so sure about the "no water needed" as batteries require cooling (and sometimes heating). And perhaps batteries are not risky like nuclear waste, but by volume there would me much more battery material than nuclear material, and there is fire risk that must be mitigated. You can't just wire up a big stack of batteries, they need carefully designed separation and fire suppression so that if one battery goes into a thermal runaway it doesn't take out the entire installation.

I imagine it wouldn't be nearly in the same ballpark, since one side does not perform the classic mechanical generation from temperature difference, and deal with the associated waste heat.