All Terrain Thinking

A Compendium of things I think are Important

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Improved soda water bottle pasteurizer

The soda water bottle pasteurizer shown at the solar cooking archive can be improved as shown here to simplify construction and improve performance.

The cut off base, inverted, provides a stand for the blackened pop can (or other suitable black container).  The taper of the inverted base eliminates the need for tabs--the cut off top just jams down over the inverted base.

Performance should be better for three reasons. First, the stand raises the pop can so that its bottom can be illuminated. (Be sure to blacken the bottom of the pop can.) Second, raising the pop can improves its bottom insulation. Third, the air leaks are below the bottom of the pop can. Since all of the air in the bottle above the stand is hotter and lighter than outside air,  this stable arrangement of cool outside and hot inside air resists air leaks. In the original design, the air leaks are above the pop can, promoting outward leakage of hot air and inward leakage of cool air.

A further improvement

As the water in the pop can gets hot, most of the heat loss will occur from condensation of water vapor on the upper inner sloping sides of the soda bottle.  We can greatly reduce the rate of heat loss from this condensation by  double glazing the upper part of the soda bottle using the top portion of a second soda bottle as a hat on the first soda bottle.

The hat will accelerate the final portion of the temperature rise, or allow reaching a higher temperature (to make tea?), or allow successful pasteuration on less sunny days.

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