Involving energy security and a Water–Energy-Environment nexus framework in the optimal integration of rural water–energy supply systems

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This paper addresses the problem of evaluating the Water–Energy-Environment nexus and energy security in the design of water and energy supply systems in isolated off-grid rural communities. Since the evaluation of the nexus requires addressing multiple design objectives, a strategy, based on normalization and sub-setting of objective functions, is proposed to visualize conflicts in problems with many objective functions. To test this idea, the optimal design of a water and energy supply system in a rural indigenous community with traditional household buildings in central Mexico is presented. The Water–Energy-Environment nexus is dealt with using the objective functions of water consumption from local sources, energy efficiency of the system, land use and local CO2 balance. The focus of the analysis is the performance of the nexus components contrasted with the economic performance and energy security of the system. The energy security is evaluated using the Shannon–Wiener index. The results indicate that diversification of primary supply sources increases the impacts and accentuates conflicts in both the nexus and economic performance. For the case study presented, maximizing the Shannon–Wiener Index increases the participation of photovoltaic and wind power, but the total annual cost of the system increases up to 63%. On the other hand, there are considerable impacts on land use and CO2 emissions associated with wood combustion. The proposed strategy for visualizing conflicts in problems with multiple objective functions has the potential to be used as a complement to traditional tools such as the Pareto front.