Open Source Solar Water Heater

Basics

• A Device that uses Solar Thermal to heat water
• Can be used from cold to near boiling (see Open Source Solar Steam Generator ) for water to Wet Steam, and Open Source Steam Superheater for Wet Steam to Dry Steam
• There are many ways of doing this but this page will focus on pancake coil type designs, see Open Source Thermosyphon for thermosyphon designs
• Pancake works well, a tube with modular screw in ports for long plastic tube runs is better for high flow
• Need to look into if these can be grouped for boiling temperatures (this may lead to Steam Hammer and/or overpressure explosions, but perhaps with the right precautions (Steam traps, overpressure valves. etc)
• Direct systems can be used for pool/utility water, for potable water, indirect may be better
• Hard part seems to be storage systems for the pressurised, potable water
• Some way to make a sort of "on demand hot water" for central hot warer, via indirect heating?
• If not simplest market is pool heating

Industry Standards

Plastic Tube Panel

• A Common Panel Design ~350 USD minimum

Existing Open Source Designs

Plastic Tube Coil

• This Design by the Youtube Channel "Dessertsun02" Uses a copper coil with a metal reflector behind it, and a wood frame

Minimum Viable Product

• Should be able to reach near boiling (~80C is what most existing designs could reach in one stage)
• Should be a small flat square (less than 1m^2 wide, and less than 5 cm deep?)
• Should use standard hose fittings for both the "in" and the "out"
• Optional temperature probes
• perhaps have a thicker and slightly wider model with insulation

Basic Design

Plastic Tube Coil

Box

• A wood or metal box
• Optional insulation

Backplate

• =Sheet metal
• make reflective or dark as well?

Coil

• Standard OTS refrigeration coil, or custom bent tubing
• Has the standard fittings at each end

Insulation

• Foam and/or fiber for the main areas
• Glass and air/vacuum gap above coil, or would the walls and cost make it not worth it?

Temperature Probes

• Attach right above the hose adapters
• Wires go where?

Paint

• Most likely standard black paint, but the darker, the better
• Not 100% needed, but is a cheap way to increase absorbtion

Heat Exchanger?

• Open Source Liquid-Liquid Heat Exchanger

BOM

• ~1m Sheet Metal (what metal?)
• Fiberglass insulation
• Foam Insulation
• Either copper piping, or an OTS refrigeration coil
• Fittings
• Optional temperature sensors
• Perhaps Wood or Plastic Exterior

Plastic Tube Panel

Rigid High Temp PVC Pipe

• Used for the top and bottom pipes (ie feed and return)

Flexible (Black) High Temp Hosing

• Used to get up and down from the panel, and for the panel's "runs"

Attachment Points

• Either OTS fittings, or some custom solution
• Screw in/otherwise attach to the top and bottom pvc pipes, holding the runs in place, and connecting them to the system
• Modular, as as many as wanted can be added to a cut section of HT PVC Pipe

Control Box

• Arduino and/or Rpi
• Takes Sensor Data, and IO Settings in
• Controls the Pump

Temperature Probe

• 1 at each end of the collector panel (two total)
• 1 in the working fluid tank
• 1 at each end of the tank (ie to and from panel)

Pump

• Small electric pump (calculate head needed)

Working Fluid

• Most likely some sort of oil (higher viscosity, but will not freeze?
• Also stores heat better

External Links

• The Wikipedia Page on Solar Water Heaters
• An Energy.gov page on Working Fluids for Indirect Systems
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