Building geometry-aware lifecycle optimization of hybrid renewable energy systems with solid gravity storage

Urban buildings face challenges in integrating intermittent-supply renewable electricity sources while conforming to space and economic constraints. Solid gravity energy storage (GS) has not yet been explored in building applications despite its mechanical simplicity and long lifespan. The current literature lacks studies that link GS' optimal capacity to building geometry and energy intensity. This study introduces a novel hybrid energy system for buildings that combines façade-mounted PV panels, small rooftop wind turbines, Li-Ion batteries, and a rope-hoist-based GS. A multi-objective optimization framework is developed to minimize both the levelized cost of electricity (LCOE) and grid dependency (GD), considering realistic dispatch logic and annual operation. The system is optimized for 625 parametric building designs covering different energy use intensities (EUI) and geometric configurations, defined by façade area-to-volume, length-to-width, and height-to-footprint ratios. Tradeoff solutions achieved LCOE values between 0.051 and 0.111 USD/kWh, and GD between 0.195 and 0.888. GS was found to be the most impactful component on system autonomy, with the ratio between its capacity and the building's average daily demand ranging from 0.0 to 1.0 and strongly correlating with GD. Most optimal designs used PV extensively, wind turbines moderately, and batteries minimally. Payback periods ranged from 9 to 17 years, and carbon intensity values remained mostly below the Canadian average. Overall, the study highlights the synergy between the building design and the extent to which GS, as well as solar and wind systems, should be sized, hence offering a practical direction for low-carbon and resilient buildings.