Growing your system

[soyer38301]

I have been reading conflicting reports on whether you can expand your system, be it wind or solar, after the fact.

I understand that if you are going to change voltages then there would be some major changes.

I guess my question is this -- if you start with a 12v system are you able to just add batteries if/when (and as you can afford more  ;-)) you need them or would you have to change fusing etc? Should one consider the "top" end of where you want to go when you design the system for fusing and disconnects?

Thanks.

Scott

[pvale]

Yep, my philosophy is to start small, make my mistakes when it won't be a large cost and go on from there. Even if I eventually have a large 24 or 48 volt system, I'm going to need some 12VDC for amateur radio equipment and small loads that have no business connected to an inverter. Whether I keep my small 12VDC system I've got now as a standalone system, or supply 12VDC with a DC-DC converter from 24 or 48 volts is not quite clear yet. It depends upon the price of DC-DC converters in the future when I build a larger system.

From a lot of reading on this site and others on the net, it seems that at around 1000 watts, it becomes uneconomical to continue at 12V, as the copper cost is so high. It may very well be the building of a Axial type generator as shown on this site that determines my uprating to a higher voltage. The wire needing to be run from any 12V wind generator will be much more than what's needed at higher voltages.

There is some point where it ceases to be a hobby thing and becomes a real power producing machine. I'm not to that point yet, but will be someday. So keep looking and building upwards.

P

[Flux]

This is always a problem. Few systems stay the way they started out. If it is going to stay small then there may be some merit in starting at 12v but if you know that it is going to grow then 24v makes a lot of sense.

The big snag with upgrading is the problem of inverters and wind turbines, you can always add more solar panels or batteries.

Fusegear and switches used for 12v will be fine at 24v. If you think of going up to 48v then they MAY be ok and I suspect most people use the same stuff. At 48v dc you are in a questionable region where you are pushing your luck with ac switches and some of the low voltage fuses can't be guaranteed to clear the fault current of a 48v battery. True dc switchgear and breakers cost a small fortune if you can get them. You are within the range of Forklift equipment so that should be an option for fuses and possibly breakers.

If you are going to try to be self sufficient or go in for large power then 48v is the way to go, but I think it ought to be planned from the start. Upgrade from 12 to 24 is not a big leap but going from 12 to 48 will probably mean a fresh start unless you start out with equipment that is over the top for 12v use.

Fortunately in this day and age nearly every load is run from inverters so the problem of dc switchgear doesn't arise much. If the inverter is fused safely then you should only need an isolator switch and this can be ac rating if you never ask it to break load.

Flux

[SparWeb]

I started out last year with all 12V equipment so that parts and supplies were easy to find and simple to install - not to mention cheap.  I would rather blow up a 200$ inverter than suffer the meltdown of a 1000$ unit.  Since I'm doing this for fun, as a hobby, there's no pressure to go all-out.

During the winter, I bought a 24V inverter, and started collecting other items I would need for the upgrade.  Since July, the windmill has been shut down a lot for the conversion process to take place, but I don't see any worthwhile wind in the summer, anyway.  It is finally starting to prove an improvement, mostly due to increase efficiency, but there is still more to be done.  I'm really enjoying the process of adding and improving components, every week something new goes in and I look back and think "even better, now".

You can't predict the future, and if the goal is not to immediately have an off-grid house, then you don't need to make expensive choices right now.