Jim Kelley wrote:
The peak intensity of a standing wave will always be greater than the
simple sum of the two waves.

No reference to peaks here, Jim. Everything is average values.
The average value of the energy in the standing waves *always*
equals the average values of the energy components of the
forward and reflected waves added together. If there are X joules
in the standing waves, there will be X joules in the sum of the
forward and reflected waves.

But I think
nature will somehow conspire against you if you try to make use of more
than the 100 watts input. ;-)

It was a rhetorical question for people who say, "Just do
a vector analysis and the energy will take care of itself."
Understanding exactly how the energy takes care of itself
is the point of this thread. Hint: 171 joules/sec from two
50 joules/sec waves requires an additional source of energy.
In the case of this example, the 71 joules/sec of constructive
interference requires 71 joules/sec of destructive interference
energy occurring somewhere else.
--
73, Cecil http://www.w5dxp.com