The modern glass greenhouse requires massive inputs of energy to grow crops out of season. That’s because each square metre of glass, even if it’s triple glazed, loses ten times as much heat as a wall.
However, growing fruits and vegetables out of season can also happen in a sustainable way, using the energy from the sun. Contrary to its fully glazed counterpart, a passive solar greenhouse is designed to retain as much warmth as possible.
Research shows that it’s possible to grow warmth-loving crops all year round with solar energy alone, even if it’s freezing outside. The solar greenhouse is especially successful in China, where many thousands of these structures have been built during the last decades.
Fruit Walls: Urban Farming in the 1600s
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