Sorry for some other idea:
https://www.researchgate.net/figure/Structure-of-the-traditional-Chinese-solar-greenhouse-1-concrete-north-wall-2-the_fig1_232010209
Structure of the traditional Chinese solar greenhouse: 1, concrete north wall; 2, the back roof; 3, the heat insulation mattress; 4, the frame of the front roof; 5, the ditch for preventing greenhouse heat loss through horizontal soil heat conduction.
This would be an other great idea to use only natural energy. The extra job you have when the sun goes down is to roll down the straw insulation over the plastic insulation and in the morning when it is light to put the insulation it back up. This way in winter at China -10 degrees C day time and -40 degrees C ( concinous a lot of degrees below freezing point of water... The sun heats a 1 meter thick wall 3 foot thick, black dirt. And 4 meters high 13 feet, keeping the plants inside always above freezing point. I have seen hundreds in the north east of China.
They copy the best working system so that they have food!
Best Regards
Gert-Jan Jonkman From Holland, service engineer, formerly world wide job...
