> Ask the designer/author why if it is such a wonderful
> machine that he has not built one to demonstrate its viability.

It is a design project, not a working machine. Do you doubt it would
work given a larger deltaT? (just curious about where your objections
lie).

> Advocacy talk is cheap, a genuine working example is hard to refute.

This is not advocacy. This is scientific curiosity and imagination. Why
can't a machine use the available temperature differences? Are you
really sure one can't be designed that works? There is no fundamental
principle preventing it. A typical design (no doubt including this one)
fails because of _avoidable_ losses, not theoretically unavoidable effects.

The trick is to figure out a way to avoid the losses without incurring other
losses in exchange.

> The bubble pump air compressor described in posts 41 & 42 incorporate
> some of the ideas of the hydraulic air compressor at Ragged Chutes but
> is an entirely different beast supposed to run on diurnal fluctuations
> of ambient air temperature. It will never go!
>

The diurnal fluctuations are a _design goal_, not a statement that this design
actually works. Nowhere is it stated that the design works such low delta T.
So your news is no news at all.

The goal is to think about various machines and learn where they go wrong.
In the case of the bubble pump / trompe, the problem is that the bubbles need
to be very tiny so that they move with the water. But such tiny bubbles take a
long time to separate from the water when this is needed.

If you use larger bubbles, a larger delta T is needed because of losses due to
bubbles lagging behing the water in the trompe and leading the water in the
bubble pump.