Dave Redvalley wrote:I've been using a set of NiFe (Nickel Iron) coupled with a AGM Lead Acid bank for about a year now, and I will never go back to the LA batteries again. They are able to discharge to a much lower level (70% vs. 20% DOD) so you can get away with a much smaller Amp/Hr battery bank. I was able to utilize my existing (lead acid) charge controllers, and inverters with the new batteries, and I even used my old batteries in a hybrid battery bank (NiFe and AGM). I think with the current availability of technology to integrate with the NiFe battery charging requirements, and their inherent robust nature (rebuildable, durable, high depth of discharge(DOD), and less toxic electrolite) makes them a perfect fit for alternative energy use. There are only a few suppliers here in the states, but they are worth the investment for me. These things are reported to last for generations vs. a decade or two....how could you go wrong with this technology....I love 'em.
Dave Redvalley wrote:It's a little goofy, but I'll see if I can explain it and have it make sense. So here goes...
The banks are coupled parallel, so they draw down to the same voltage. The AGM bank was abused and on its last legs so I don't feel bad running them down as low as I do. The AGM's are there basically to dump amps on a heavy draw (like well kicking on). So here comes the goofy part....the NiFe cells will take and hold voltage at such a high rate (without damage) that the AGM's are setup in three parallel 30 volt banks and the NiFe's are nominally at 24 volts. The NiFe cells are 1.2 volts so I have 20 cells (24 volts). The AGM's are 3 sets of 15 cell strings (5 six volt cans). I know it sounds weird, but it works. We use the back-up generator about half as much as the previous home owners and our family is three times the size, so not bad stats in my view.
bob golding wrote:for long term stationary battery systems there are some interesting things coming down the pipeline. i spent a long time researching vanadium redox flow batteries. the problem with them is the cost of the PEM membranes. until some other that dow starts making them cheap they will stay out of reach.
there seem to a few companies working on rechargeable zinc air batteries. i have asked one of them for some basic information about them. still waiting for a reply. if they survive thier estimated costs are around the same as lead acid, but without knowing a bit more about them i am not holding my breath. the world of battery storage is littered with companies claiming to beat lead acid on price and longevity.
not many survive past the start up stage. the vanadium one i was dealing with is now chinese owned and only dealing with megawatt size units. this seems to be where all the interest is. the problem is the way the wholesale electricity market is set up there is not incentive to invest in storage as they can make a lot of money from selling peak electricy. i did read the USA has spent more in the last year on off peak storage that the rest of the world put together. wheather that down to us mere mortals remains to be seen.
i think the most promising electrical storage system may be thermo electric. one lab is claiming a efficiency of up to 80% once all the bugs are ironed out. that would be a game changer. use your solar and wind to power a heating element and you wouldn't need anything better than lead acid. still waiting for them to get out of the lab.. been waiting about 6 years since they first said they were working on them. check out power chips for the latest updates.
bob golding wrote:the reason i said solar to electric element to power chips was that solar thermal is a lot more complex in that you need a tracker to get the best out of it. you would be losing a fair bit in the conversion but gain with less complexity. using solar pv to heat water and then attaching power chips to the water tank would a good option. i am not holding my breath that they will get out of the lab anytime soon. they do seem to have a few major advancements in the last few months though. the reason zinc air seem like a potential winner is the fact that zinc is a common metal and they is plenty of it. if i can find it there is a very good independent report that has done all the maths for us. will send a link when i remember where i put it!