Planning of survivable nano-grids through jointly optimized water and electricity: The case of Colonias at the Texas-Mexico border

•A water-energy nano-grid is jointly optimized for survivable needs.•Designed a nanofiltration unit, with a photovoltaic component, and battery storage.•Nanofiltration with variable pressure reduced the required battery size and cost.•Operational costs are traded-off with risk via risk-tunable optimization.•The design methodology is generalizable to many other underdeveloped regions. This paper studies a co-design of solar generation-based nano-grid and water treatment in remote areas. The goal is to provide the minimum essential drinking water and electricity needs to communities in remote, underdeveloped regions such as Colonias in South Texas at the United States-Mexico border. It is shown that a portable nanofiltration treatment unit, powered by only a few photovoltaic (PV) panels augmented with batteries and supplemented with water storage tanks, offers crucial flexibility in accommodating solar-powered electricity service which is intermittent in its nature. Given the lack of infrastructure and associated primitive conditions in Colonias, the proposed planning and operation of the nano-grid leverages the flexibility of power consumption for the water filtration process to compensate for the fluctuating solar PV generation. A risk-tunable, scenario-based optimization is formulated to quantify the risks associated with the design, given different weather scenarios. The case study based on bench-scale experiments, optimization, and economic considerations coupled with historical weather data for targeted Colonias in Texas suggest the unique benefits of joint optimization of both electricity and water needs.