English abstract
Greenhouse farming is one of the best solutions to overcome the harsh environmental conditions in arid countries like Oman. However, the summer season can significantly affect the cooling system's efficiency. The Fan-Pad cooling system is the most commonly used cooling system, and the increased humidity from the evaporative pad can lead to plant and soil pathogen issues. This study aimed to evaluate the performance of a greenhouse developed with a new concept of an on-grid solar-powered, fan-chiller-tube-bank (FCTB) cooling system using pot-grown Okra. In addition to conducting cost-benefit and cash flow analyses. With an on-grid solar system, the income comes from the crop and the sale of excess electricity to the grid. The growth setup was developed with a Quonset side-walled single-span greenhouse, pot-based Okra cultivation with an automatic scheduled irrigation system, and similarly treated control pots in an open-field condition. The greenhouse and cooling system were set up with sensors and a data logging system to measure temperature, humidity, and light intensity variations. The growth parameters of okra and environmental parameters were measured and analyzed. The water consumption and electricity consumption were determined, and the excess energy supplied to the electricity grid was also estimated. In the performance evaluation, crop growth parameters were compared with the control plots, and efficiency parameters such as crop yield, total water use efficiency (WUE), irrigation water use efficiency (IWUE), cooling water use efficiency (CWUE), and energyuse efficiency (EUE) were evaluated.
The results showed that the FCTB cooling system has effectively maintained optimum temperature (23.0°C–34.4°C) and relative humidity (55.2%–69.0%) levels inside the greenhouse, promoting plant growth. Statistically significant differences were observed between the growth parameters of greenhouse and control Okra plants, with greenhouse plants showing superior growth performances. In one cultivation cycle, the greenhouse produced a higher okra yield (3683.79 g) compared to the open field (331.94 g). The greenhouse demonstrated improved EUE, with a value of 1.1579 and a positive net energy of 163.8689 MJ/m2. The WUE, IWUE, and CWUE were 0.91 kg/m3, 2.07 kg/m3, and 1.63 kg/m3, respectively. In addition, the economic performance indicated that growing okra with a solar-powered FCTB cooling system was economically unfeasible with a cost ratio less than one (0.99). The values of Internal Rate of Return (IRR) and Net Present Value (NPV) of cucumber (IRR40%, NPV 7812.99 OMR) and cherry tomatoes (IRR 33%, NPV 7259.46 OMR) indicated profitability of these crops with this greenhouse. Furthermore, the use of solar energy in the FCTB cooling system increases greenhouse efficiencies, economic viability, profitability, and sustainability. This study recommends further research with this system for Oman's seasonal effect with high-value crops and optimizing the size of the solar panel bank, fan, and chiller tube bank system to see how the energy and other efficiency components will be varied.
