Renewable energy development is one of the most promising approaches for tackling global warming, fulfilling the ever-increasing energy demand, and protecting the environment. Among the various renewable energy sources available nowadays, salinity gradient energy, also known as blue energy, is regarded as a particularly attractive solution for the generation of sustainable clean energy and has thus attracted great attention in recent years. In a typical blue energy conversion process, power generation is attained through the transport of ions through nanopassages, such as nanopores in membranes. This review commences by exploring the many opportunities and challenges involved in performing ion transport through the nanopassages provided by one-, two-, and three-dimensional membranes. Novel strategies for enhancing the ion transport and upscaling the size of the membrane for increasing the performance of harvesting the blue energy in such systems are then introduced and discussed. Especially, we discuss the mechanism of how to enhance ion transport through nanopores. The review concludes with a brief perspective on the future development of the salinity gradient power generation field.