Improvements to a Beer Can

Solar Air Heater

...........................................to increase the output temperature


When I recently considered making a Beer Can Solar Air Heater, I naturally did a preliminary scan of the internet for articles on the subject, that would give me advice from previous constructors.

Whilst most of the information I found was very useful and practical, I was a bit reluctant to follow the usual route described for the initial modification of the beer can to provide the required air path.

Beer Can Airflow diagrams

Most constructors suggested cutting a relatively small hole (approx 25mm dia) in the centre of can base, for entry of the air, allowing it to exit at the top through the existing ring-pull hole.

My reasoning was that, as the heat generated in the aluminium wall of the can was only effectively conducted to the outermost layer of air, having small inlet and outlet holes would mean that this layer would be relatively stagnant, compared to the smaller, central column of un-heated air, resulting in a lower than optimum output temperature.

To avoid this problem, I therefore considered how to remove the complete end cap of the beer can, in order to free up this outer air layer.

Tools

Tools for beer can modification

To remove the complete ring-pull end cap, I found that a 50mm dia hole saw located snuggly inside the raised rim, and that a few turns by hand were enough to cut through the thin material.

A different method was needed to remove the partially-domed bottom cap, and I found that the simplest way was to just file across the bottom (although using a belt sander would probably achieve the same result).

Here's the resulting parts:

The removed beer can parts

I was about to discard all the removed parts, when a thought struck me that the domed bottom cap could possibly be re-used to an advantage, by inverting it for use as a deflector to direct the circulating air close to the can wall.

Modifying the bottom end cap

In order to hold the inverted end cap in a position that would allow a small annular gap for air to enter the can, I needed to form a set of three legs that could be used to glue the cap to the base of the can.

I first made up a cardboard template with a hole cut out that matched the diameter of the domed end cap, then I marked around the edge of the hole where the three equispaced legs would be.

With a small pair if side cutters, I then made pairs of cuts around the lid, approx 6mm apart and 8mm deep, at each of the marked points.

Then, using a pair of long-nosed pliers, I shaped each of the legs with a double bend such that the whole set would form a good location to the base of the beer can.

Domed end cap modification

Assembling the deflector

All that then remained was to glue the inverted end cap back onto the base of the beer can (I used Araldite adhesive) and allow to cure.

The assembled end cap deflector

NOTE: For the 'wall air layer' idea to work successfully, it is vital that all the cans that make up a column of the complete solar air heater have deflectors fitted at their lower ends, otherwise the guidance effect will soon be dissipated.

This might seem like a lot of work, but my experience has shown that output temperatures of over 50C are quite easy to obtain even when the ambient temperature is only just above freezing.

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For pictures of my complete Solar Air Heater, please visit my Photo Gallery page.

If you would like any further information on my method of construction, then please feel free to contact me.

webmaster_burywsd@live.com

Website created: October 2010 - Last updated:18 October 2010
Author and webmaster: Peter Attwood




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