This publication discusses the growing importance of large-scale energy storage systems in harnessing the full potential of renewable energy sources like wind and solar power. It highlights the potential of secondary sodium-based batteries as a key technology due to their high energy density, cost-effectiveness, and ease of maintenance. However, it points out that the current state of materials is not yet ready for mass commercialization. The focus of the work is on the development of polyurethane-based membranes using recycled polyvinyl butyral (PVB) from laminated glass waste, with a view to repurpose this material for energy storage. The study includes detailed characterization of these membranes and their performance as separators in lithium- and sodium-based cells, indicating promising results for sustainable and low-cost energy storage solutions.