A Unified PV–BESS Capacity Estimation Framework for Rural Microgrids: From Equatorial Roots to Global Regions

The reliable sizing of photovoltaic (PV) and battery energy storage systems (BESS) remains a central challenge for rural microgrid development, particularly in data-scarce environments where advanced optimization tools are inaccessible. Previous work introduced a simplified, simulation-light framework for PV-BESS capacity estimation based on daily demand and Global Horizontal Irradiance (GHI), validated for near-equatorial regions. This paper extends the framework to twelve representative cities across diverse Köppen-Geiger climatic zones, spanning tropical, arid, temperate, and continental contexts. Using Typical Global Horizontal Irradiance Year (TGY) datasets, both cosine-based normalization $1 / \cos \theta$ and half-cosine adjustment $2 /(1+\cos \theta)$ are applied to mitigate latitude-induced bias, while commercial load archetypes are used to test sensitivity to variability. As a result, normalization according to latitude with half cosign adjustment significantly improved the accuracy of PV capacity estimation and allowed the new formula to be extended to a latitude range of up to $\mathbf{5 0}^{\boldsymbol{\circ}}$. Similarly, the BESS capacity can be more accurately estimated using the new formula, which employs cosine normalization. The study establishes a generalized, zone-inclusive extension of the equatorial framework, offering a practical pre-feasibility tool for microgrid planners and decisionmakers in rural electrification initiatives in a wide range of areas.