Storage and transport of energy without potential losses

• Use of natural ventilation for air temperature and humidity control in Mediterranean greenhouses.
•Greenhouse covered by a plastic film.
• Passive use of renewable energies for greenhouse climate control.
• Reduction of the energy consumption together with the increase of renewable energy used in the greenhouse.

Two types of passive greenhouses are predominantly used in the Mediterranean area: pitched roof greenhouses (Almería-type or Canary-type) with a structure of vertical pillars and a double wire grids in the cover and curved roof multi-span greenhouses with metallic structure and arches in the cover. These greenhouses use plastic cover and are provided of side and roof vents, equipped with insect-proof screens.

Both type of greenhouses uses natural ventilation to regulate air temperature and humidity opening the windows: the excess of heat produced by solar radiation and the excess of humidity produced by the transpiration of the plants are removed. However, in winter period, ventilation simultaneously induced important thermal energy losses, reducing excessively inside temperature.

In pitched roof greenhouses, vent openings are operated manually. In multi-span greenhouses, windows are automatically opened and closed by a climate control system, based in inside air humidity and temperature. The solution with the multi-span greenhouse includes the use of an inside double roof, considered as passive energy saving system, which allows to reduce energy losses by infrared radiation and convection in the cover.