I came here to say exactly what esshup said about building a fluid trap at the compressor. Further, you should plumb in some clear tubing (pressure rated) to use as a "sight glass". You can also plumb in an electrical float switch to turn off the compressor before the fluid build up reaches the equipment.
I think running the airline over the hill will by MUCH less expensive than running electrical line over that distance. Further, you will have significantly lower energy costs not suffering line losses over your long electrical run. You just need to ensure that your pipe run does not have any dips in the line that could also slowly accumulate fluid. Running a line uphill or downhill at a constant slope is NOT a problem.
I am NOT an aeration expert. However, I have designed and operated larger diameter pipelines.
Question for the actual aeration experts: Humidity is generally much greater at ground level than it is higher in the air. Would it make a significant difference to plumb an 8' chimney stack (with a rain vent) into the cooling fan intake? I think that would pull much less humid air through the compressor, especially after heavy rains or all of the times when there is heavy dew on the grass.
