Considering a mini-tank to supplement batch solar, but is it the best option?
I'm a tenant in a yurt in east San Diego County, elevation ~4,000 ft. Right now the hot water needs are served by a homemade batch solar heater (old tank painted black with reflector), which is plumbed to an outdoor shower about 15 feet away. The yurt lies 30 ft. beyond the shower and has an indoor sink, which is currently cold water only. This system works well April - October, and intermittently through the rest of the year. Propane and 120v electric are available at the site.
The powers at be think it reasonable that I have hot water inside during the winter and the ability to shower during overcast stretches. The question is the best way to make this happen. I personally really enjoy the simplicity of the current setup, and another consideration is that the yurt serves as sort of a demonstration of a simpler type of housing to kids/adults who tour the farm where it's located. I'm not above some personal inconvenience to keep the system simple and low impact, and a (reasonable) higher install cost is acceptable to meet those goals as well.
During winter, 75-80% of the hot water use would be just to fill the indoor sink to wash some dishes. I don't shower long, or particularly often.
I'm leaning toward:
Sprucing up the existing tank (could be repositioned to catch more winter sun and needs to be insulated.)
Adding a 6 gal. mini-tank heater
Re-plumbing the shower so that the batch heater can feed either the cold or hot water line (reasoning that in the summer, incoming hot needs to be mixed with cold, but that during winter, luke-warm mixed with the hot from a the very small tank might give a bit longer shower.)
Issues I've yet to resolve:
The combined ~45 ft. outdoor run from the batch heater->shower->to the yurt
Where to put the HWH along that run (try to squeeze it under the yurt sink? or build a small insulated compartment somewhere near the shower?)
I'm love your thoughts on whether the above plan makes sense, considering my goals, whether I should be considering a gas tankless instead, and any suggestions for dealing with the outdoor run and placement of the heater. Recommendations or good experiences with particular brands of mini-tanks would also be appreciated.