Keith Dysart wrote:
. . .
Well it is pretty clear to me that if the net current is always 0,
then
no current is ever flowing and the power must be zero.

It seems to be a bit of a common fallacy to assign meaning to the
intermediate currents computed for the superposition solution to
a problem. Connect two equivalent batteries in parallel. The only
sensible answer is that no current is flowing since the voltages
are the same. (In another post you seem to accept this), though
if you use superposition to solve the problem, you get a very large
current flowing in one direction and an equally large current flowing
in the other. Only the resultant current is in any sense real. Same
for those waves on a transmission line. Just superposition. Just a
convenience to help reach the final solution. Don't over extend
and assign them meaning (or energy). In the end it will cause
deep conceptual difficulties.

I think you've put your finger right on Cecil's conceptual problem. When
we solve the battery example by superposition, we get the right answer,
zero current. But now let's put a resistor between the two batteries and
repeat the solution. When we "turn off" the left hand battery, we have a
lot of power being dissipated in that resistor. Using Cecil's view, we
would assign this to be the power associated with the current flowing to
the left. Then we "turn on" the left hand battery and "turn off" the
right hand battery. Again we have a lot of power being dissipated. This
would be the power associated with the current flowing to the right. The
problem comes in having to somehow manipulate these powers to get zero,
which is what we actually see. The mistake, as you continually point
out, is attributing a power to each current -- or each wave -- in the
first place.

Roy Lewallen, W7EL