FIRST RESULTS OF HEATING GREENHOUSES BY A PASSIVE SOLAR SYSTEM IN GAFSA (SOUTH-WEST OF TUNISIA)
The results were a gain of minimum temperature about 5 to 9°C compared to the control and also for leaf temperature and soil temperature at 0.1m depth. We have noted a gain of precocity of 2 or 3 weeks and more income (0.400 D.T./m2/year). This gain will justify widely the investment needed for this equipment which is estimated to 0.150 D.T./m2/year. Moreover, the system is easily to use by small farmers and should be spread all over south of Tunisia, mainly wherever we don't find geothermal water and were we can use only solar energy which exist in great quantity, even in winter because we have an average of 7 to 9 hours of sunshine/day with an average minimum of 240 cal/cm2 in this period.