Utilization of renewable energy for warming greenhouse cucumber during winter season [electronic resource].

Includes reference.

To insure optimum fruit yields of greenhouse cucumber crop in mid delta, in late fall and winter, when the prices are high, planting is dictated to be in late September to early May. Two identical experimental greenhouses (8.0 x 4.0 x 3.25 m) were utilized to grow, develop and produce cucumber crop during winter season of 2005-2006 under Northern Province conditions of Egypt. Each one equipped with completely solar heating system (solar panel, storage tank, and heat distributing system). Each greenhouse was provided with 60 plastic pots (30 cm high and 28 cm diameter) as a cultivation system, and drip irrigation system for watering pots. The air temperature inside the greenhouses was controlled by an on-off controller to initiate heating at 16°C and interrupt it at 18°e. Air temperature, air relative humidity, and total solar radiation, were measured to analyses their correlation with cucumber crop yield response. Electrical and biogas energies were used as an auxiliary source of heating when the solar energy was insufficient. The obtained results showed that, the overall thermal efficiency of the two solar collectors was on average 72.68%. The daily average solar energy available was 18.429 kWh/day of which, 12.458 and 10.956 kWh/day were stored in the storage tanks sited inside and outside the two greenhouses, respectively. Consequently, the storage tank situated inside the greenhouse was on average 13.71% more efficient than the outside tank. The obtained data also revealed that, the daily averages total energy consumed by solar, electrical, and biogas for the two greenhouses, respectively, were 20.598 and 18.735 kWh/day, which provided 73.81% and 62.75% of the total energy consumed. The heat energy supplied resulting in increase the air temperature within the two greenhouses above the outside (10.6°C) by on average 5.8°C and 5.5°C, respectively. The nightly average air relative humidity inside the two greenhouses was on average 67.3% and 71.5%, respectively. It could be concluded that, due to control of microclimatic conditions inside the two greenhouses at a desired level particularly at nighttimes during cold winter season, the total fresh yield of cucumber crop for the two greenhouses was on average 6.250 kg/m² and 5.563 kg/m², respectively.

Summary in Arabic.

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