This is a very often mentioned error. The Wayne industries microwave emitter was basically a weaponized, industrial strength microwave oven! What happens if you put a human in a microwave oven? Nothing good! It's not a plot hole though. Plot holes are inconsistences in the story. The existence of the device was explained by Wayne industries switching to arms manufacturing and export.
Its theft by the League was explained in the film as was the importance of Wayne tower to the city's network. Nolan weaves his stories like a spider does a web; intricately, beautifully, skillfully, so it's rare to find a plot hole, although his films are so ambitious that they're unavoidable.
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Yes, this is an often mentioned error. The Wayne industries microwave emitter was basically a weaponised, industrial strength microwave oven! What happens if you put a human in a microwave oven? Nothing good!
It's not a plot hole though. Plot holes are inconsistences in the story. The existence of the device was explained by Wayne industries switching to arms manufacturing and export. It's theft by the League was explained in the film as was the importance of Wayne tower to the city's network.
Nolan weaves his stories like a spider does a web; intricately, beautifully, skilfully, so it's rare to find a plot hole, although his films are so ambitious that they're unavoidable.

Thanks .. fictional craft it is then

I just chalked it up to being a comic book thing. That it would only work if it was 90% or more water.
Of course, that doesn't explain why there weren't explosions coming out of the buildings which have water and sewer lines, but I still liked the movie.