Multi-criteria feasible optimisation of a sustainable aquaponic system for rural areas in Cape Verde

Abstract

Background: Climate change is exacerbating the lack of fertile land and the scarcity of irrigation water. To guarantee food security in this context, aquaponic systems have been developed. An aquaponic system achieves the simultaneous production of plants and fish by recirculating water through both subsystems. Combining these two production technologies provides an efficient and sustainable method of growing fish and producing plants. These types of systems are often installed in rural areas, where the electrical grid is not completely reliable. Methods: This work assesses a Hybrid Renewable Energy System to improve the sustainability and efficiency of isolated aquaponic production systems. The simulated systems are based on renewable energy sources using photovoltaic, wind, diesel and battery technologies. The main contribution of this study is the improvement in the decision-making process for selecting the optimal hybrid system for each project. A multi-criteria decision-making procedure based on technical and economic variables of the project is proposed. The criteria used in this study are NPC (20 and 10 years), payback, initial cost, O&M cost and renewable fraction (%) cover by the system. The procedure requires calculating hourly simulations of the energy flow in the installation with different hybrid configurations. In this work, a case of a hybrid system located on the island of Santo Domingo (Cape Verde) is presented using more than 1680 different sizing configurations. Results: The solution obtained improves the results offered by other hybrid system optimisation software. The investment in the multi-criteria solution is 20 k€ less expensive than that obtained using other software and provides a payback period of four years, half a year less without affecting the rest of the decision criteria. Compared to the diesel base case, the solution saves more than 200 k€ in 20 years and will save more than 28 tonnes of CO2 per year. Moreover, this approach ensures the selection of a technically feasible configuration that aligns with the constraints of each project. Conclusions: This study will have an impact on the circular economy of experimental aquaponic farming production systems, making them more accessible in agricultural areas with energy problems.