In Henry Moray's work, there are also indications toward electric potential, such as "in night time the power is a bit less than during daytime".
Well, that can be also due at night the temperature was a bit lower than during daytime in that desert.
I think, it may be possible to harvest atmospheric electricity somehow. But I think Moray's device had too much power output for such a small antenna in such small altitude difference relative to it's grounding.
Note: The thermoelectric effect does not require a temperature differential (think thermocouples) -- it just works better with one.
That is not true. If you connect two different kind of metals, there is a junction voltage between them. But when you close the circuit on the other side, you get the same junction voltage, but opposite polarity, if both junctions are at the same temperature. Current only flows, if there is a temperature difference between the junctions. Please check: http://en.wikipedia.org/wiki/Thermoelectric_effect
This thermal noise is very broad frequency.
And the distribution of that frequency range is dependent on the temperature. AFAIK it is almost the same as the black body radiation frequency distribution: http://upload.wikimedia.org/wikipedia/c ... dpi_en.png
That diagram shows wavelength instead of frequency, but you can calculate the frequency using vacuum light speed. Inside the metal the wavelength will be different, but the frequency remains the same.
I'm not sure if I described my idea clearly enough. What I wanted to tell about is a circuit, where in every cycle I charge up a piece of metal slowly, and discharge quickly. It have to be charged to a very high negative voltage, and the discharge should be very quick to get usable power. It should work at almost near to absolute zero degrees too.
Robert, what you described with the different shaped cathode and anode, that works too. I heard about some Chinese gentlemen who created a diode like that: http://www.google.com/patents/US6768177
I don't know why didn't they make a commercial product yet.