Solar Air Heater #3 - The Sponge
Solar Air Heater #3 - The Sponge
Our third look at solar air heaters, takes us all the way to Sydney. This model was designed by David and Nicole Jones.
The Solar Sponge - Solar Air Heater
This design for a solar collector, comprises a black metal plate which absorbs the solar radiation and converts it into heat and a sealed cavity on top to trap the heat within. The heat is extracted from the back of the plate (via another sealed cavity) and circulated by fans. This is often known as the “dead air space” design.
Air flow through solar heater
Box view of solar collector
That’s all there is to it. Such designs have been around for many decades. We built our entire collector box out of aluminium, which made it easy to work with various pre-made sheets and tubing sizes from the local hardware store.
Another key aspect to the Solar sponge design is the use of very thin (<1mm) polycarbonate sheeting for the front cover. This drastically reduced our cost compared to glass or thicker 3mm polycarb sheeting. Polycarbonate sheeting has similar transmissive properties (around 90%) of the purpose designed low-iron SunPlus glass, but at a fraction of the cost. It is also extremely tough and can withstand hail.
- Air flow with spacer bars
Internal channels were added to “snake” the air around the box, picking up heat as it goes. With a 1.5m long box, this equates to a total air path of 4.5m, a length long enough to pick up sufficient heat.
Based on the length of ducting required to get to and from your solar heater, you’ll need to add a number of fans. David added a total of 4 fans for his solar collector which was mounted on the roof.
For full instructions on how to build this unit, please drop by David and Nicole’s website The Solar Sponge.
Which Solar Air Collector is Best?
My own personal opinion would be a mix of the Solar Sponge and the Heater Gabber from Mother Earth. I’d use the window mount and insulate the box. I’d mix with that, the dead air design and the snake air flow from The Sponge. With the snake design, I’ll likely need to add a fan.
What are your thoughts?
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