First a quick note. Psyonyk I just found your blog right before you shut it down, and I wanted send you praise, its one of the best source of info i’ve found for small PV installations. I love the text + picture format, youtube style videos are obnoxious garbage in comparison.
I’ll try to keep background short, keep this at a forums post size not personal blog length.
I live on a few acres with cheap grid connection. I got FOMO that PV panels are as cheap as they’ll ever be thanks to subsidies, found 6x 305W panels on local classifieds as leftovers from a big project that bought by the pallet. Paid just under $0.50/watt.
live in northern cloudy area with an estimated 15% capacity factor for PV, i’ll knock it down to 10% to include a bit of pessimism. On a yearly average, 1800w of solar panels may generate 180w continuosly. Doesn’t come close to satisfying my current ultra wasteful lifestyle but if “TEOTWAWKI Grid Down Prepper Fantasy Scenario” happens i guess i’d probably appreciate it more than 0 watts.
However, what is running through my mind now is actually non-civilization ending scenario and a goal called “not being stupid with your money”. On their own, if those panels could offset power i would otherwise buy, that generates a value of ~$156 / yr at current rates of $0.10/kwhr. Pays for themselves in ~6 years, or a few more if you want to add in a discount rate, IF i can actually use the energy for something i already would use grid electricity for.
Batteries seem to ruin the economics of it, i’m served by a simple utility that offers no Time Of Use rates or peak shaving incentives, so essentially i’d be cycling batteries and wear them out powering a fraction of the house’s electrical loads, just for my own amusement - while the reliable $.10/kwhr grid is sitting there most of the time.
Now, I think I’ve found the holy grail on this quest of efficiently utilizing PV energy, and its not really talked about much, and like all the highest quality info on the internet its wrapped in a primitive looking website.
I present for your consideration: http://waterheatertimer.org/Convert-AC-water-heater-to-DC-water-heater.html
This solution offers:
A huge capacity battery* I already own and regularly charge. It just happens to be thermal battery rather than electro chemical.
Built in over-“charge” circuit (via ECO), and built in automatic load transfer switch to use grid power for demand if needed at night or in low solar times.
A circuit that requires an absolute minimum of additional electronics compared to anything I’ve seen.
I’m really blown away, this seems awesome even too good to be true. Is there a catch i’m overlooking?