Evaluation of the Water–Energy–Land Nexus (WELN) Using Exergy-Based Indicators: The Chilean Electricity System Case

Abstract

The competition and interlinkages between energy, water, and land resources are increasing globally and are exacerbated by climate change and a rapid increase in the world population. The nexus concept has emerged for a comprehensive understanding related to the management and efficiency of resource use. This paper assesses water-energy-land nexus (WELN) efficiency through integration of the principles of Life Cycle Assessment (LCA) and exergy analysis, using the Chilean energy sector (CES) as a study case. The cumulative exergy consumption (CExC) and cumulative degree of perfection (CDP) are used as indicators for WELN efficiency. The results show the production of 1 MWh of electricity required 17.3 GJ ex , with the energy component of WELN (fossil and renewable energy sources) being the main contributor (99%). Furthermore, the renewable energy technologies depicted higher CDP of the water-energy-land nexus due to lower CExC and higher technology efficiency concerning non-renewables. The water and land resources contributed slightly to total exergy flow due to low quality in comparison with the energy component. Nevertheless, water availability and competition for land occupation constitute important issues for reducing environmental pressures and local conflicts. This study demonstrated the feasibility of exergy analysis for the evaluation of WELN efficiency through a single indicator, which could facilitate the comparison and integration with different processes and multi-scales.Energies 2020, 13, 42 2 of 20The nexus concept is an systematic approach for improvement of resource management, which can reach high degrees of complexity depending on scales and processes [9]. Consequently, different qualitative and quantitative methods for conceptualizing the relationship between natural resources have been proposed. Ringler et al.[10] developed a comprehensive qualitative framework for assessing the water, energy, land and food nexus (WELF), highlighting the relevance of land in the nexus. Nevertheless, the authors did not provide methods for the WELN-nexus evaluation. Siciliano et al. [11] have recently reported on the effect of large scale farm investment in the European Union on the water-energy-land-food (WELF) nexus, using indicators related to resource availability, scarcity and access. Although the authors describe several interlinkages between the resources, the quantitative evaluation of the nexus is not clearly highlighted. Karabulut et al. [12] studied the ecosystem-water-food-land-energy (WFLE) nexus by considering the ecosystem as the main issue within this nexus. The authors highlightsthe relationship between interventions and environmental impacts. In this case, the nexus evaluation is qualitative, and the matrix proposed can be adapted to different scales to investigate the trade-offs, synergies and antagonisms.Different approaches have been used to quantitatively evaluate the WELN. Silalertruska and Gheewala [13] carried out the evaluation of the WELN of sugarcane production in Thailand, using wat...