David:
48 volts is a "forced" standard by many in the industry, because a relationship of watt hours storage time, and cost of the multiple battery banks, as well as, the concept that higher voltage is EXTREMELY dangerous.
Most of the forum grows out of people "crying" for help that many times have electrical power knowledge limitations, I have not searched for other forums to see if there are some for 24 / 48 / higher volts, there is one for 12 volts that I visit more or less periodically to see what is going on, 12VDC_Power@yahoogroups.com .
Higher voltage is ideal to get higher efficiencies, better inverters, over all reduction of the wire sizing, specially now days that the copper has increased its value due to the the great demand of it.
You really scared me with the dollars you input -- and for some time, I said WHAT is going on with that power source, then I discovered you were in Hon Kong, and a very heavy weight came Off -- then I was able to move my body.!!
I do not know the relationship of energy and income there, to see what would be a good way to develop a system with a good ROI (return on investment).
Energy reduction is the issue here and if You have a place for a wind mill and/or Solar Panels, then a solution for the battery voltage depends on the distance between the sources and the battery banks as well as where the loads are and how the energy requirements are.
I have, always, assumed that 12 Volts is for emergency use, of course there are the die hards that say 12 Volts period .. !!!!! and the system is a total compromise with constant miseries ( many times ) for those that really do not have a good electrical know how.
- volts is, for me, still a compromise that came from the 1890's with the wind mills in USA that run 24, or 36 volts and a few 48 volts, as well as, the small 24, 36 or 48 volts gas generators --- which have permeate up to this these present 2006+ years.
- volts,from my point of view, would be the minimum to use -- though I have made 120 volts battery banks, because in the countries that use 120 AC GRID power there are too many electrical products that can use 120 Volts DC, in case the inverter fails.
I have designed a very in-expensive MSW inverter using 120 volts battery bank, capable of many Kilo Watts that is very easy to build, and my circuit has protection included, (there is one that does not have such protection, that the plans are sold in Ebay for around USA 40-50 dollars -- I have been unable to find it in Ebay).
Maybe, You could include some other parameters You may have, like the place where you can install your Mill and/or the panels, the distance to the battery bank and loads, and what type of loads you have, and their use.
Regards
Nando