I remember reading in an old "Organic Gardening" (actually, it was an old "Organc Gardening and Farming", which is an indication of just
how old it was

) about someone re-purposing a cupboard in their kitchen. It was floor to ceiling, I think, though I don't suppose it matters. Anyway, they installed a porcelain light socket on the floor of the cupboard, with an incandescant light bulb (for heat) and then, I think, they hung a board over that as a baffle, to let the heat rise, but shield the light. And then they put cleats along the sides, to hold shelves, and made shelves out of hardware cloth framed with 1"x1". They must have also put some sort of vent near the top. The bottom shelves were warmer, and were used for dehydrating. Further up was a good spot for incubating yogurt, and proofing bread. And the very top was where the cereal and crackers were stored; the residual heat kept them crisp. I have held this thought for, probably, 30 years, since it sounds like such a good idea. Unfortunately I have never had a suitable cupboard

.