Assessment of water reuse and pico-scale hydropower systems in high-rise buildings: A water–energy–carbon nexus approach for urban sustainability

With the intensification of the global climate crisis, sustainable development has become a priority worldwide. Given the strong interconnections among water, energy, and carbon, addressing the climate crisis effectively requires research grounded in a water–energy–carbon nexus perspective. In this study, six integrated scenarios were designed for rainwater, greywater, pico-scale hydropower generation, and water reuse in high-rise buildings. These scenarios were applied to two cities, and for each case, the amounts of generated electricity, reused water, CO₂ reduction, and cost savings were estimated. Subsequently, the level of the installation floor of the greywater tank as well as the roof area were varied to evaluate how these two variables influenced the outcomes across the scenarios. Among the scenarios, those prioritizing water reuse yielded the most favorable results in terms of both CO₂ reduction and cost savings. The generated electricity was maximized when the greywater tank was installed on the middle floor of the building, as determined by the governing equation, whereas the reused greywater volume reached its maximum at approximately two-thirds of the building height, where supply and demand were balanced. This study can serve as a valuable reference for achieving carbon neutrality and sustainable development in response to the climate crisis, while also contributing to enhanced water resource security.