Here is another example of what I consider to be a good use of technology that doesn’t fit neatly into the Permaculture toolbox. The reason it doesn’t fit is because one of our primary design principles is to work with nature rather than against her. Well if you are trying to heat a greenhouse over winter you are fighting nature.
To further that thought, every time we heat a greenhouse (even with electric) we are using what the Duke over at Permies affectionately refers to as icky stuff to do it. Being that energy resources are one of the bigger problems we are dealing with, this could be counter productive.
The reason I think it is a good idea to set up these kind of unnatural growing situations is very similar to my defense of aquaponics. That reason is I believe we can do them in such a way that we are reducing the energy requirements to bring products to market, and some of these products people really want at market….eg oranges and bananas.
The key to doing this successfully will be to design our tropical greenhouses to use massive amounts of passive heat storage, in conjunction with using rocket mass heaters or the like (because I am sure someone will science up something similar but better as energy shortages become more real…Ernie and Erica’s designs are awesome, but man do humans get smart when the sheesh hits the fan).
When we have managed to create energy efficient heating systems for our greenhouses we will be able to enjoy all of our tropical fruits in addition to our cold hardy ones in temperate zones with a fraction of the energy usage.
So get on it.