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30th May 2005 << back

Report on Preliminary Test of Bubble Generation System

See more pictures of the bubble generation here

...and there came forth a copious foaming mass
To my surprise a thick continuous flow of bubbles spewed out from the bubble generator the first time I flicked the switch. Somehow, until this moment the system seemed complex and potentially temperamental. Now having operated the generator successfully the process of bubble generation really does seem 'low tech' and surprisingly robust providing a few simple design considerations are adhered to. I'm hoping in time to enhance the performance of the generating system I have installed.

I had to stop the generation before the cavity was completely full being as I have not yet replaced panelling at the top of the cavity. Bubbles were beginning to overflow back into the interior.

Already I can see that drawing air from the bottom of the cavity will not work as part of a bubble regeneration cycle, apart from maybe in the last 25% of the cycle. With this configuration I can either draw free air into both sides of the fan or (free air and air from the bottom trough into the fan). I can also close air intake from north and south troughs independently and also close the free air intake. (I have a bucket with a flap on the end + filter that mounts on the free air intake).

Obviously, restricting air into the fan will lower the production of bubbles, but now I have the capacity to experiment using suction and find out empirically whether it is a dead duct or worth exploring further. One other idea I have been thinking of is using high pressure (low flow rate) water jets to destroy or move old cold bubbles during regeneration cycles. In the systems Rick has developed using linear duct shaped cavities, this additional kind of bubble destruction/moving systems are not necessary. Duct shaped cavity roof structures are a very elegant solution, but I feel it is worth pursuing investigations into good bubble regeneration systems in irregular shaped cavities, as many of the building structures we are now talking about creating will not easily lend themselves to linear segmentation. Geodesic structures are a perfect example of this.

Next Stage
The next stage for me is to get the north side completed and install a computer in the control shed. I want to fill the project with an array of thermo couples and conduct some semi controlled experiments. Over time I'll use the data I collect to optimise the volume of my thermal masses and cycle durations. Eventually the system will be operated directly from the pc, but realistically it will probably be winter before this happens.

Also this week I want to get online some designs I have made for a modular portable structure that could be used for exhibition purposes. I'm also intending that the structure can be used for a workshop/studio space as opposed to a building purely used for growing plant, although, of course plants are an integral part of the buildings working mechanism. I will be using Richard's top level canopy system in this one. I'm calling the structure a Deltico.

Soap Solution

Interestingly, a small amount of bubbles are still present in the cavity over 24hours after I last generated. The solution I used in the end was:-

2 parts Sodium Laureth Sulfate (Sodium Lauryl Ether Sulfate) concentration? (will find out)
1 part Glycerine
30 parts Distilled Water

My first impressions of this solution is that it is still very concentrated and could be diluted much more. It is clear.

At the bottom of this page I've added pictures and comments on the method I used to prime my pump.

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