Today’s installation of this 24 sq ft AET solar hot water collector adds a roof to our outdoor shower area and completes our hybrid solar and wood-fired hot water system.
This is a miniaturized version of a larger system that I lived with for 10 years off the grid. It uses a water jacketed stove pipe and a flat plate collector to passively thermosiphon hot water to a 28 gallon hot water heater tank that sits above our bathroom at the end of the house. The geometry of this setup takes careful planning, solid plumbing skills, and direct sun for at least half of the day, but with those requirements met it provides a huge amount of free hot water after the initial investment.
I decided to incorporate some selective shading on this one, using an oversized collector but also placing the collector slightly below the porch shade so it doesn’t produce hot water early in the day which should help to keep the house from overheating (from the hot tank inside) in the middle of summer.
To keep things simple and also due to a lack of availability of certain products, this is an open loop system so draining the panel on cold nights and a freeze protection valve as a back up protects the panel.
The feed and return lines are left deliberately uninsulated so they will bleed off heat if the system gets too hot. This is important when using ordinary water heaters as solar collector tanks because they aren’t designed for the high temperatures that can occur in a well insulated solar loop.
You would think that a system like this would leave you pissed off in the shower from time to time, but at least in the larger version this happened so rarely that we never even bothered to install an electric back up. It will be interesting to see how well it works in the tiny house. I’m on the edge of my seat waiting for a sunny afternoon to watch it work!
-Brian
