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I have been reading a bit about these here Stirling engines and they
have fascinated me..
i wondered how big they can be scaled up?.
see..i believe they work on temperature difference between
cylinders...?
..now if these were used in colder countries, with one cylinder
placed underground, and the cold one above ground..this could provide
a constant source of temperature difference..more at night than
during the day which is what household power consumption patterns
are...so any feedback is welcome...thanks..a curious d.

Scaling up a low temperature to a size where it would have the power to light up a houshold is not a theoretical but practical problem. And then, not because of financial or metalurgical reasons (low temperature and working presure would permit the use of inexpensive materials such as wood and styrofoam) but because of its sheer size. My humble opinion is that an engine runnig off such a low temperature diference would be unpracticaly large.

In a previous post someone mentioned mirrors focused on a Stirling to run an ac compressor... Consider, refrigerating two brine tanks, one for heat, the other for cold. Store up a big enough potential difference to either do a very big job for a short time or run through the long winter night.

Please, how big would have to be an engine that would produce 2HP (1500 Watts mechanical output) on a temp difference of 40 degrees Celsius? (70V hot and 30 C cold). Of course, it would be big, but how big? Considering that such thing would be purely stacionary power generating station in a remote off-grid settlement, it can be really big and still be considered perfectly practical. If the only alternative is bringing extremely expensive diesel fuel to run a generator, bringing it in 10+ days of journey by riverboat, even very big fuel-free generator is very, very practical. This is not a theoretical excercice, this is a real-life scenario in hundreds of settlements in the Amazon (Brazil). My idea is to use conventional solar collectors (good and cheap ones available here) to heat water in a large thermo-isolated water tank (like 15000 litres, we regularly use these), acting as a thermal battery, allowing the engine run at night). Then, the hot water (70 degrees C) wold be pumped to the hot side of the big, simple engine by small continuously running pump. The cold side would be cooled by water from nearby river (there's always one in the Amazon), keeping the cold side at 30 degrees Celsius. The engine can be really huge, absolutely no problem with that. Maximum size that would be considered practical is 12x2,5 metres, 3 metres high. This is a size of an object transportable by a standard flatbed truck (brazilian flatbed truck). It's dry weight can be up to 30000 kg (yes - 30 metric tonnes). Do someone thing such a ting can be built? If the answer is yes, I'm going to do it for real!

I've been thinking about this recently also. A week ago I was talking to some old electricians who told me about a guy who made a greenhouse, and then a Stirling engine that used freon gas. Freon has a much lower boiling point than water, and therefore, was more sensitive to daytime/nightime temperatures. Supposedly, this engine was able to run around the clock, assuming there was no breakdown. The green house would also serve to hold heat during the night. One might also think that it would be even more effective during the winter, in the intermountain west, with snow on the ground.

Or why not build these big engines out in the nevada/new mexico desserts or wherever...

i think that

Oops, sorry, didn't really mean to post that.

the practical problem which our brazilian friend told is really true i am in the business of diesel engines & the practical difficulty to operate a diesel engine for power generation is true but this is the same concept on which i am studing anybody can help me in the comparison of the diametre of the power piston & expansion chamber would be appreciable also if somebody has a toy model he can measure the dimensions & mail me on ottosaloon@gmail.com