> From the sixteenth to the twentieth century, urban farmers grew Mediterranean fruits and vegetables as far north as England and theNetherlands, using only renewable energy.
These crops were grown surrounded by massive “fruit walls”, which stored the heat from the sun and released it at night, creating a microclimate that could increase the temperature by more than 10°C (18°F). Later, greenhouses built against the fruit walls further improved yields from solar energy alone. <
Everybody knows the effect of a sun heated stone wall, even after sunset. The micro climate it creates is much warmer than the surrounding area. Adding a glass cover that keeps the warm air, and possibly mats, that increase insulation at night, improves that effect even more.
Great article on http://lowtechmagazine.com