Post-harvest loss is a serious issue to address challenge of food security. A solar-grid hybrid cold storage system was developed and designed for on-farm preservation of perishables. Computational Fluid Dynamic analysis was performed to assess airflow and temperature distribution inside the cold chamber. The system comprises a 21.84 m³ cubical cold storage unit with storage capacity of 2 tonnes. A hybrid solar system comprising 4.5 kWp PV system, 5 kW hybrid inverter, and 600 Ah battery bank was used to power the entire system. A vapor-compression refrigeration system (2 tonnes) was employed coupled with three cooling pads (filled with brine solution) as thermal backup to store cooling (−4 °C to 4 °C). Potatoes were stored at 8 °C for a period of three months (May 2019 to July 2019) and the system was tested on grid utility, solar, and hybrid modes. Solar irradiation was recorded in range of 5.0–6.0 kWh/(m² × d) and average power peak was found to be 4.0 kW. Variable frequency drive was installed with compressor to eliminate the torque load and it resulted about 9.3 A AC current used by the system with 4.6 average Coefficient of Performance of refrigeration unit. The average energy consumed by system was found to be 15 kWh with a share of 4.3 kWh from grid and 10.5 kWh from solar, translating to 30% of power consumption from grid and 70% from solar PV modules. Overall, cold storage unit efficiently controlled total weight loss (7.64%) and preserved quality attributes (3.6 ⁰Brix Total soluble solids, 0.83% Titratable acidity, 6.32 PH) of the product during storage time.

Baking is an energy intensive unit operation. The thermal application of solar energy is getting attention in food processes by eliminating the facts of interrupted supply and fluctuated costs of nonrenewable energy sources. This study has been carried out for the design and development of solar bakery unit which comprises of a 10 m² Scheffler reflector focusing all the beam radiations on a secondary reflector that further concentrate the beam radiations toward the heat receiver of solar bakery unit to heat up the air circulated through baking chamber employing a photovoltaic operated fan. Computational fluid dynamic (CFD)-based three-dimensional (3D) simulation was performed to analyze the design for uniform air distribution in the baking chamber. The system designed configurations gave quite good results for airflow distribution. The receiver temperature reached between 300 and 400 °C while temperature at the inlet of baking chamber was in the range of 200–230 °C, sufficient for most of the products to be baked. The maximum available solar power at receiver was calculated to be 3.46 kW having an average efficiency of 63%. A series of experiments were conducted for the baking of cakes and total energy available in baking chamber was about 3.29 kW and cake utilized 0.201 kW energy to be baked. The average value of energy utilization ratio was found to be 45%. As a base, the study would lead to the development of an appropriate and low cost solar baking units for the maximum retention of quality parameters and energy saving.

Agriculture is the backbone of Pakistan’s economy. Currently, the agricultural sector is facing many challenges, especially post-harvest losses, which result in lower yield and profitability. These losses may be reduced by developing indigenous post-harvest processing technologies, such as drying out of agricultural products to enhancement of their sustainability and reduce transportation costs. The country has the advantage of an abundant amount of solar insulation, which can be effectively utilized to operate post-harvest machinery, particularly solar heaters and dryers. Currently, conventional solar heaters face challenges due to lower efficiencies. Therefore, in this study, a solar air heater (SAH), having a size 1220 × 610 × 65 mm, was designed and developed to be connected to a milk powder spray drying system for converting raw milk to powder. Computational fluid dynamics (CFD) were used to anticipate air flow and temperature distribution across the SAH to evaluate optimal performance parameters. An air mass flow rate of 0.01 kgs⁻¹ was required, with the CFD predicting an outlet temperature of 82 °C compared with the experimental observation of 73 °C. The pressure drop across the SAH was recorded to be 0.0000434 bar at this flow rate, which is negligible, with the SAH operating near ambient pressure. The overall heat loss coefficient for convection was 2.27 W. m ⁻²·K⁻¹. The energy losses from the SAH were 37% and the useful energy was 63% of the total energy provided to the SAH. The breakeven point of SAH at a minimum of 4 h of daily usage was 3700 h or 2.5 years. The solar air heater used as a preheater for a spray dryer can save 30 PKR·kWh⁻¹ of energy.

In this study, for the first time an advanced exergy analysis was applied to a solar hybrid food dehydrator to find out the causes of the inefficacies and to assess the actual improvement potential. The dryer was integrated with an evacuated solar tube collector and gas burner as a heating sources. Drying experiments were performed using bell pepper at 55 °C under three heating options i.e., gas, solar and dual. The rates of exergy destructions were split into unavoidable ($E_d^{UN}$) and avoidable ($E_d^{AV}$) which further split into four parameters termed unavoidable endogenous ($E_d^{UN,EN}$), unavoidable exogenous ($E_d^{UN,EX}$), avoidable endogenous ($E_d^{AV,EX}$) and avoidable exogenous $(E_d^{AV,EN}$). Conventional exergy analysis revealed that drying chamber possess lower improvement potential rate (IP) than heating components while outcomes of advanced exergy analysis showed that both the design and system components interaction of heating unit imparted a major effect on its efficiency. Optimizing the operating conditions of the heating sources could reduce their higher amount of inefficiencies. The values of exergy efficiency for the overall system were calculated to be 86.66%, 84.18%, 83.74% (conventional) and 97.41%, 95.99%, 96.16% (advanced) under gas, dual and solar heating modes respectively.

Renewable-energy-resource-based microgrids can overcome excessive carbon footprints and increase the overall economic profile of a country. However, the intermittent nature of renewables and load variation may cause various control problems which highly affect the power quality (frequency and voltages) of the overall system. This study aims to develop an adaptive technique for the optimization of renewable energy resources (RERs). The proposed grid-tied microgrid has been designed using a wind-turbine (WT) based distributed generation, a photovoltaic (PV) system, a diesel generator as an emergency backup, and battery energy storage system (BESS). The flexible (residential) and non-flexible (industrial) loads are connected with the proposed grid. Matlab/Simulink has been used to evaluate the performance of the proposed optimization technique. Comparison with different in-use techniques shows that the proposed technique is more reliable and efficient than the state of the art optimization techniques currently in use. Moreover, this proposed system provides robust optimization of parameters of concern such as frequency and voltages, makes efficient use of the maximum power point tracking while regulating voltages, reduces the overall system cost, and increases economic profitability.