S06 - Session P1 - Increasing night temperature in a tunnel without heating system

Authors: Ariane Grisey *, Justine Garnodier, Vincent Stauffer

During the day, greenhouses are solar heat collectors that maintain a higher internal temperature compared with external temperature. During the night, particularly in cold areas, it is necessary to heat greenhouses to optimise crop development. For many years, several studies have aimed at recovering the energy captured by greenhouses, storing it and reusing it at night to increase the temperature. A tunnel equipped to store energy (called bioclimatic tunnel) has been studied in the climate condition of southern France. The experiment was carried out in a double plastic cover tunnel with black water tanks covering soilless strawberry crop. A passive heating power of 70 W/m² was provided by the storage system during night-time. Temperature, humidity, radiation and production were measured in the bioclimatic tunnel in comparison to two control non-heated tunnels (simple plastic cover and double inflated plastic film cover). In the bioclimatic tunnel, temperatures were up to 10°C higher, the risk of condensation was lower, production was earlier (2 to 9 days according to strawberry varieties) and economic balance was more efficient than in the control tunnels. This system is a real opportunity for organic greenhouses which are obliged to use renewable energy to heat the greenhouses by 2025 in France.