"Oz" wrote in message
...
David Hare-Scott writes

Both the air lift pump and hammer pump lift a proportion of water
from a
body of water that has a head over its destination without input of
energy from the outside by using some of the energy in the head. You
say both types are very inefficient.

They are in that only a small proportion of the available energy is
used
for useful work.


I don't know the proportion but I will take your word for it that it is
small.

Whether that matters or not depends on the situation.


That is what I was saying. If you get what you want for no input energy
cost it matters not if the system is only low efficiency. You are
harvesting a small proportion of what cost you nothing, that's still
cheap.

I come back to my previous point. What type of pump that needs no
external energy source is efficient by
your standards?

Certainly neither can be considered as 'new' or 'not described
scientifically'.


So what? Do they work? Are they cheap? Are they suitable for some
situations? Whether those who are publishing this stuff now are right
about the origins of such ideas has nothing to do with the usefullness
of what they are publishing.

David