This is far too vague to answer.
Is it for wind or solar and what sort of power level are we looking at?
There is no particular advantage with using ac unless you increase the voltage in the link. If it is wind then you start with ac anyway. For solar you have a slightly different problem.
For a small installation 50ft is not very far and to use transformers to raise voltage would cost a fortune and the overall efficiency would be worse than even modest cable.
If you are looking at kilowatts then the cable cost for modest loss does get a bit heavy at 12v.
With wind if you start out with the right ideas the cable run needn't be a problem at all, you need some losses to avoid stall and you can save a lot on the cost of cable if you start with a more efficient alternator. The increase in magnet and copper cost of the alternator can be largely offset by savings in cable and you have an alternator that will stand more overload.
For solar the loss is more of a problem but 50 yards is still not beyond reason.
12v has lots of limitations and is best left to small systems but as long as you keep things small the volt drop can be managed. If cable loss is a serious issue then better to avoid 12v rather than use fancy schemes. The only exception may be a high voltage mill with transformer and rectifier at the battery. Stepping up from a low voltage mill and transforming down again is hardly ever justified.
For solar at 12v on long cable runs then use something like a MX60 if the system is large ( not worth it below about 500W).
Probably not much help, shouldn't have guessed your question in the first place.
flux
