Saturday, May 4, 2013

Waterbag Solar Water Heating Collector Using Inflatable Film Cover and Soap Bubble Insulation

This is an innovative new wrinkle on the Integral Collector Storage (ICS) design from Nick Pine.
With ICS solar water heaters, the collector and the storage are combined into a single unit. Basically they consist of a water container that typically sits inside of of a glazed enclosure. Solar radiation heats the water container during the day. This is an example of a commercial ICS design.

One of the downsides of the nice simple ICS design is that it tends to lose quite a bit of heat at night through the glazing. Nick has addressed this problem by filling the area between the water container and the glazing with soap bubbles at night. The soap bubbles are good insulators and greatly reduce the night heat loss.

The design has several other innovations:
  • A film bag is used to hold the water, which reduces the cost of the water container.
  • A greenhouse polyethylene film cylinder is used for the glazing and is inflated to hold its shape -- a significant cost saving over conventional glazing. Similar to a hoop style greenhouse.
  • The north half of the glazing cylinder is reflectorized to reflect more solar onto the water bag.
One upshot of the inexpensive materials used in Nick's design is that it is not expensive to build a solar water heater with a large collection area and a large storage capacity -- this increases the solar fraction.

Thanks to Jay Burch for this diagram.

To transfer the heat stored in the bag to the domestic water, a large coil of PEX pipe is immersed in the bag, and the cold water from the house takes ones pass through this large coil of PEX and is heated by the water in the bag. This heat exchanger scheme has been used quite successfully on the $1K solar water heater.

Be the first on your block to build one!

If you have any thoughts or ideas on this design, please leave them at the link above.


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