I know people growing banana without electricity, only the help of walipinis, at 58° north
so what the hell are you even talking?
you do not seem to know about the energy, warmth of mother earth (except at the most upper ground in permafrost areas - but there is also warmth and energy, just a little deeper)
maybe have a look at the great sharing of work of @samstonehill :) ?
I gave design and directions on how to build one in my earliest posts.
But, in not near the equator, you really have to make your own design, not exactly a walipini.
I like Mike Oehler's designs.
I know people growing banana without electricity, only the help of walipinis, at 58° north
so what the hell are you even talking?
you do not seem to know about the energy, warmth of mother earth (except at the most upper ground in permafrost areas - but there is also warmth and energy, just a little deeper)
maybe have a look at the great sharing of work of @samstonehill :) ?