Farid Jalili Jamshidian

Energy is a crucial component of the agri-food sector since almost 30% of the world’s energy is consumed by this sector. Under such circumstances, the employment of renewable energies can be a sustainable solution to mitigate the adverse environmental impacts as consequences of the greenhouse gas (GHG) emissions from the agri-food supply chain. Generation of electricity using photovoltaic (PV) technology to supply the power demand of the agriculture and food production sectors requires large areas of land. To solve this problem, the co-generation of solar PV electricity and crop production (agrivoltaic concept) is expected to relieve this restriction. An emerging agrivoltaic technology is the installation of concentrating PV (CPV) systems in crop cultivation environments to both provide the power demand and produce food on the same land. This study presents an overview of agrivoltaic systems and CPV technology with a special focus on the advent of CPV modules in agricultural environments. In this case, the main benefits and challenges of this technology are presented and discussed.

Agrivoltaic is a strategic and innovative approach that combines photovoltaic (PV) energy conversion with agricultural production, enabling synergies in the production of food, energy, and water, as well as the preservation of the ecological landscape. Shading management, intensity adjustment, and spectral distribution allow innovative PV systems to generate significant amounts of electricity without affecting agricultural production. Demonstration projects have already been developed around the world and there is a wealth of experience with various design solutions for commercial use. One of these new technologies is concentrator photovoltaics (CPV). The CPV has excellent spectral processing capabilities and highly concentrated power generation efficiency, which makes it a perfect solution for integrating with photosynthesis. This study aims to present the working principle of CPV modules considering agricultural applications and discuss the recent advancements in concentrating agrivoltaics. In this method, the problem of shading is mitigated by two main strategies: (i) parabolic glasses covered with a multilayer dichroic polymer film that reflects near-infrared (NIR) radiation onto the solar cells installed at the focal area and transmits photons in the range of photosynthetically active radiation (PAR), and (ii) highly transparent sun-tracking louvers or Fresnel lenses that concentrate direct sunlight onto the solar cells to generate electricity. In the latter solution, the remaining diffuse sunlight is directed to the ground for use by growing plants. Although the CPV development trend has been slow due to the lower cost of crystalline silicon, the development of CPV for agriculture with accurate spectral separation could revitalize this industry. In this regard, more research and development are needed to evaluate the suitability of materials that split solar radiation and their impacts on the electrical performance of CPV modules, taking into account the physiology of plants.

Water is a crucial ingredient for human health and one of the very few vital needs of human beings. More than 1.2 billion people around the work suffer from a deficiency of safe drinking water so that it is estimated that 14% of the global population lives in water-scarce regions by 2050. Although desalination has been used as conventional water providing technology for a long time in the Middle East and the Mediterranean, it has extensive capacities in the USA, Europe, and Australia as well. Interest in investment in desalination sector has been extending beyond these regions of the world which are driven by water stress concerns. Even though desalination has the potential to increase the water supply in water-scarce regions, its associated adverse consequences and constraints cannot be ignored. Brine disposal is the primary environmental consequence that should be considered and studied when installing a desalination plant. Therefore, essential steps must be taken to ensure safe and sustainable brine disposal. Implementation of a proper brine disposal method incorporated with a qualified design and construction procedure can mitigate the destructive effects of the desalination plants on the water environments and groundwater aquifers. Using solar power as a renewable source can both imitate the environmental impacts of the conventional brine disposal methods and an increase in the evaporation rate of the solar traditional evaporation ponds. Directing the brine effluent into the solar saltworks can possibly produce salt, and therefore, the desalination plant would be zero liquid discharge (ZLD). This method requires large land areas and thus is only applicable in arid and semi-arid regions where the evaporation rates are high and the value of the land is low. Also, expensive liners are needed to avert salt seepage from the soil and the groundwater contamination. If the evaporation rate is improved, the need for the same amount of land would consequently be reduced. Enhancing the rate of evaporation would have two benefits of the flexibility to increase the amount of the brine wastewater flows out of an evaporation pond and a reduced amount of land that would be needed to achieve the same rate of evaporation.

The performance of a developed brackish water reverse osmosis (BWRO) desalination unit integrated with a stand-alone hybrid photovoltaic-thermal (PVT) module was evaluated under the climatic conditions of Tehran (35.68° N latitude 51.42° E longitude). From the experimental results, the maximum surface temperature of the PV module and thermal efficiency of the PVT module were recorded as 60.38 ​°C and 83.7%, respectively at the set-point temperature of 50.00 ​°C for the thermostat, and under the average solar radiation of 971.34 ​W/m2. During the evaluation, the maximum average productivity of the BWRO unit was obtained as 13.98 ​L/h when temperature values of the PV module, soft water, and brackish feed water (BFW) were recorded as 52.94 ​°C, 28.97 ​°C, and 36.60 ​°C, respectively. From the results, it was also found that the temperature of BFW positively affects the PVT module’s thermal performance and improves the whole unit’s productivity. Also, water quality parameters of pH, TDS, EC, and DO for treated water were evaluated. The economic analysis of the system revealed that the cost of the produced freshwater for the BFW’s salinity of 15,000 ​ppm is 18.96% higher in comparison with 5000 ​ppm for all cases, indicating a closer value to freshwater cost of conventional large-scale RO plants.

In this study, an existing thermal multi-effect distillation (MED) plant was assumed to be integrated with reverse osmosis (RO) desalination system in a way that both heat and electricity demands of the hybrid RO-MED plant could be provided by a solar combined heat and power (CHP) system composed of parabolic trough concentrators (PTCs). For this purpose, the climatic conditions of Bushehr province (latitude 28.7621° N; longitude 51.5150° E), located in the south of Iran, was considered as the case study, and the water demand of 1,000 m³/day was assumed. In the first step, new algorithms were developed to integrate RO and MED desalination plants, and an incorporated thermal energy storage (TES) system was designed using the MATLAB program. Additionally, the whole system including the RO-MED plant and the solar CHP system was mathematically modeled and their performance was technically and economically evaluated. To perform this, four scenarios including recovery values for RO and MED as 50% and 30% (scenario 1), 50% and 35% (scenario 2), 55% and 30% (scenario 3), and 55% and 35% (scenario 4) were deemed. The results revealed that, first of all, the fourth scenario yields the highest total recovery amounts in all considered shares of freshwater production between two desalination plants. Secondly, under this scenario, the optimum total recovery can be obtained when each desalination plant produces 50% of the required freshwater, leading to a 15% rise in total recovery in hybrid mode, compared to the use of a single MED unit. Moreover, it was found that the integration of the TES unit can extend the working hours of the system by 30% under daylight irradiation. From calculations, the number of required PTCs in the solar field was calculated as 188 with a total aperture area of 17,869 m². The economic evaluation of the designed system illustrated that the integration of a RO plant with an existing MED system could reduce the total cost of the produced freshwater for 6700 people from 2.08 US$/m³ for a single solar-powered MED plant to 1.918 US$/m³ for the solar-powered RO-MED plant.

In the world today, fossil fuels as conventional energy sources have a crucial role in energy supply since they are substantial drivers of the “Industrial Revolution”, as well as the technical, social, and economic developments. Global population growth along with high levels of prosperity have resulted in a significant increase in fossil fuels consumption. However, fossil fuels have destructive impacts on the environment, being the major source of the local air pollution and emitter of greenhouse gases (GHGs). To address this issue, using renewable energy sources especially solar energy as an abundant and clean source of energy, has been attracted considerable global attention, which can provide a large portion of electricity demand. To make the most of solar energy, concentrated solar power (CSP) systems integrated with cost effective thermal energy storage (TES) systems are among the best options. A TES system has the ability to store the thermal energy during sunshine hours and release it during the periods with weak or no solar radiation. Thus, it can increase the working hours as well as the reliability of a solar system. In this paper, the main components of the solar thermal power systems including solar collectors, concentrators, TES systems and different types of heat transfer fluids (HTFs) used in solar farms have been discussed.