commercially. batteries are being developed with high output, rechargeablity and long lasting. Probably in that order. I have been reading about "crystal cells" which are very different, they are long lasting first. One person has set up a bank of these cells that has been powering a small motor continuously for over two years now with no outside charging. He expects it to continue for his lifetime. I did some reading on the effect and there are lots of amazing claims... which I don't believe however, these could be a great part of an off grid (or even on grid) setup. My guess is that these are just batteries and all the stuff about grabbing this or that energy is out there stuff, but really, it doesn't matter. If I can draw current from these easy to make cells even for two years, I would be willing to make them that often if I don't have to worry about more complex stuff. If I can get enough power to keep "safety lighting" going regardless of any inverter/battery/genset/grid power/lack of sun problems, this would be worth while.
One of the problems I have seen with power systems is the "one source does everything" idea. It works fine on the grid most of the time and even most battery systems are quite reliable too. But both systems waste power and both systems have weak spots that the whole system relies on. If that one thing breaks, there is no power at all. Or, even during maintenance there may be no power. I think it is good to build in redundancy.
Lighting is a good place to start. Light comes in from the sun, we convert it to electricity at 20% or so and use that to charge batteries. Batteries leak (self discharge) and so we have to save more than we need, then we convert that to AC so that the LED lamp can convert it back down to low voltage DC to make light... all so we can standardize our power. We use dual inverters so we can switch between high low power models depending on load. Lots of stuff that maybe isn't needed for all applications.
What do people think? is standardization really important? (so we are willing to give up efficiency?) or is it worth while using matched power and load where possible?
I am thinking that it may be possible to make a self contained lamp about the size of the standard emergency lamps found in public buildings (my first target size) that would last as long as the LED without maintenance. That it would give enough light to get around in a messy home without tripping in the dark (first target brightness). I think it may be able to do things smaller or brighter.
So if lighting is taken out of the solar/battery/inverter chain, what does that do for battery life? It would seem that the inverter could spend a lot more time totally off. Maybe this could be spread to entertainment things too... my TV has a wall wart it could run on low volt DC, computer same thing.
Ok what is left for the solar panel to power then?
- washing machine
- computer's printer
- well pump - etc.
Most of these things should be able to be configured for use when the sun shines. That is to direct draw from the solar source. It is called working when the sun shines. The result is that the battery pack (most expensive, needs most maintenance, fails soonest) can be down sized and maybe even at least partly be replaced with a capacitor bank for motor surge that the solar panels can't handle. Maybe you are looking at that list and thinking some of those things need to work all the time... like the freezer for example... maybe not. If the fridge is used only as a cooler and not also as a freezer, the freezer box can be filled with mass. This will keep the fridge cool enough even with no power over night... maybe even a few days. A freezer with two thermostats can keep the food really cold when the sun is out and when batteries are in use use a backup thermostat set to -10C during the night or cloudy periods. The mass of the food will keep the freezer from warming to that point for a long time and that thermostat may never trip at all. Well pump... maybe think in terms of a mini-water tower, kept full when the sun is out but allowed to almost empty before pumping at night.
This is my thoughts on bringing "permaculture ideas" to power generation. Call it poly-power if you want.