On 10 July 2014 05:53, Vitaliy M wrote: > Russell: > So the sterling engine puck will deliver well under 5 mA under the best > conditions. Is that correct, or did I lose too many zeroes? > > It's complex. And mA is not the best measure (unless you mean into a 5V "USB" load. And I'd hope to get more than that. But it would not be good. I thought about what it would take to model it. A major issue is that for the very small delta-T, and temperature drop across the hot end inlet and cold end thermal exhaust must be minimised if it is not to eat your breakfast dinner and tea. Atsay 90 C hot and 20C cold. Delta T 70C. Thot =3D 273 + 70 =3D 343. Z_arnot =3D Delts_T/Thot =3D 70/343 =3D 20.4%. Imagine you can achieve half that =3D 10% - which would be a magnificent achievement. If you want say 1 Watt out then as Z=3D10% you must have 9 Watts of energy = to exit the cool end and 10 Watts cominhg into the hot end. A 1C/Watt heatsink is usually a fairly impressive affair. Imagine you can achieve 1C/Watt at hot and cold ends - ghow is inobvious given smooth surfaces and small size. That give a 10C drop at the hot end and a 9C rise at thje cold end so the delta T is 51C (down from 70C and carnot =3D 51/(273+51) =3D 15.7%. If we a= gain get half this output efficiency is 7.9%, down from 10%, and that's just due tpo using seriously large heatsinks or heat exchange units at hot and cold end. You cannot afford this sort of input & output drop and 1C/W is hard to do. In reality you need much better than that - so you'll need some mix of fins, forced air and heat pipes. Thermal content of water is ~ 4 J/cc/k. If you cool a 250cc cup of 100C water to 80C you liberate about 250cc x 20 C x 4 =3D 20 kJ. IF we get 10% efficiency we get 2 kJ output. If we had a 5V 500 mA =3D 2.5 W output load = it would notionally operate for 2000/2.5 =3D 400 seconds. =3D 0.111 hour. In t= hat time you'd 200,000 mAs or about 138 mAh. At 5% that would be ~=3D 70 mAh. As temperature falls Carnot efficiency drops and the portion of it that can be achieved also drops. Overall you'd probably be doing very well indeed if you could get 200 mAh all up - and how you get the <