We will be building a large wind system in the near future.  We are an engineering/mfg firm so would look to design and build our own system.  Our first gennie would likely be in the 15-25KW size area and eventually build a 75kw unit.  The design goal was to use direct power from the generator when running as well as charge a battery bank.  One of the largest costs and most complex things for us in the battery system.  To get enough capacity, we are looking at a HUGE investment in batteries or DIY a system.  We have built lead-acid batteries before but this would be on a large scale. 

Even in building Lead-acids though, the life of a battery bank for this application is VERY minimal.  Estimations are only in the 1000 cycles area so maybe only 4-5yr life.  Our first design goal was to support our facility in part or in full for 1 week.  Doing the math for that proved ridiculous in terms of battery needs.  Lead-acid seems cheap but with a limited DOD and life cycles, that might be a large waste. 

Does anyone know of other promising technologies or other DIY stratigies?  Lead-acid just is not that complex.  OTOH, Li-ion just is not a DIY technology.  There are other batteries such as the VRB which have significantly higher life cycles and DOD but I am not familiar with it much.