Evaluation of Energy and Water Use Efficiencies and Economic Feasibility for a Solar-Powered FCTB Cooling System in Greenhouse Farming

In arid countries like Oman, fan–pad cooling systems are commonly used in greenhouse cultivation. However, in such harsh environmental conditions, a fan–pad cooling system can be inefficient, result in high water and energy consumption, and may cause plant and soil pathogens issues. To address these challenges, this study evaluated the technical performance of a greenhouse designed with the new concept of an on-grid, solar-powered, and fan-chiller tube bank (FCTB) cooling system, focusing on water use efficiency (WUE) and energy use efficiency (EUE) following pot-grown okra. In addition, greenhouse gas (GHG) emissions and financial aspects were evaluated through cost–benefit and cash flow analyses. This research was conducted with a Quonset side-walled single-span greenhouse equipped with a solar-powered FCTB cooling system and automatic scheduled irrigation system. Water and electricity consumption was recorded, and surplus energy supplied to the electricity grid was estimated. The greenhouse efficiencies were evaluated by computing the EUE, total WUE, cooling water use efficiency (CWUE), and irrigation water use efficiency (IWUE). The solar-powered FCTB greenhouse enhanced EUE, achieving a value of 1.16 and a positive net energy of 163.87 MJ·m−2. The WUE, CWUE, and IWUE were 0.91 kg·m−3, 1.63 kg·m−3, and 2.07 kg·m−3, respectively. The economic assessment showed that okra cultivation with a solar-powered FCTB cooling system was economically unfeasible, as indicated by a benefit–cost ratio of 0.88. However, cucumber (IRR 46%, NPV 2.13 × 104 USD) and cherry tomatoes (IRR 38%, NPV 1.98 × 104 USD) demonstrated economic feasibility as supported by positive net present value (NPV) and the internal rate of return (IRR) values. Furthermore, incorporating solar energy with the FCTB cooling system enhanced the greenhouse’s sustainability, efficiencies, and profitability. 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 system to see how the energy and other efficiency components will vary.