In the following video, we compare the performance results between the traditional Chinese style passive solar greenhouse and the SolaRoof greenhouse. Critical issues have surfaced this way. After digging out the problems, we show a way to retrofit using the existing framework. A wonderful DIY project for you to start fresh or convert your existing greenhouse, to fully utilizing the wonderful properties of soap liquid bubbles.
Want to watch the version without comparison studies? See below…
The folloiwng infrared imaging profiles of the Chinese style passive solar greenhouse (click for source) indicate why it is not much of use in making the North wall opague and pack-filling it with dirt, a practice that most people have been taught to do so without understanding the issue clearly:
For those who would like to study Mr Jianyi Dong’s greenhouse that I mentioned above in the video, please click here.
Now you know everything about the difference!
2 replies on “Must View: The Critical Issues with Conventional Chinese Style Passive Solar Greenhouses Revealed – How to Solve with an Easy Retrofit Plan”
Aubrey –
Thanks for sharing Richard\’s bubble insulation SolaRoof design. I found your site when searching for more information on Dong Jianyi\’s greenhouse after seeing the webinar video you reference.
For more persistent bubbles (longer interval between bubble generating cycles) you might consider adding J-Lube, a veterinary obstetric lubricant. On his YouTube channel, the \”Honey Do Carpenter\” discusses adding this to shampoo based foam to make a more persistent foam for mixing foamed concrete.
Also, the thermal modelling results you show for the Chinese greenhouse seems to use a relatively low mass north wall compared to some I have seen in pictures (meters thick earthen wall). Especially at high latitudes, I suspect that a (nearly) vertical absorber (whether active or passive) is beneficial in mid-winter, and if it is an active absorber, it could better control temperature spikes at mid-day. I don\’t think the north wall needs to be an either/or proposition, though. It can be both a good absorber and be well insulated. I am at 47 degrees north latitude, but that is still well south of Jianyi, but much farther north than most of China and a good bit of Mongolia, if I am not mistaken. We also average in excess of 200\” of snow per winter, and have had as much as 360\” in a season, so snow load design is an important consideration for me.
An active absorber system can also be fabricated quite inexpensively, for example, here:
https://www.builditsolar.com/Experimental/MTD/MTD%20RH&JC.pdf
It might be possible to use the same pump system as for the foam nozzles to circulate through the absorber panels, though the requisite pressures and flow rates might not be a good match between the two systems. However, both systems should be able to share the same water mix, I think. Circulating warm water through the soil on cool night could also be beneficial for the plants.
Thanks again. You\’ve given me much food for thought.
Kevin
Kevin, thank you for your comment and concern!
In our case, persistence of bubbles is not the major issue, as long as you have bubble foam insulating the double layer cavity in winter and liquid film inside the cavity for cooling, you are roughly on the right track. The north wall issue, take a look at this IR imaging first, then you will know it is not that critical either – finding the critical and determinating factors is critical:
That is why in our design of my backyard build of PyraPOD, we came up a simpler approach to the geo thermal gain: we create a underground poopl filled with gravels and water. As simple as that!