I think that even a run of 600 feet would be fine if it was in a trench, even a shallow one. I mean, it would cool the trench itself for a bit, but if it ran continuously, that would be a fairly minor thing, as there'd be no more, or relatively little more, heat
energy left in the soil surrounding the trench to warm it.
That's pretty awesome, William. I like the piped spring
water idea for cooling, and I think it might even apply, to some extent, to purpose-built dual-mode hydronic systems, where it's conventional
hot water in the cold season, but circulates cold spring water in the hot season. That would need to then go into a holding tank or something for irrigation, so as to not be wasted, but still, it's a damn sight better than sticking a noisy box in a window and generating more heat than is being removed from your dwelling and pumping it into the atmosphere.
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein