Urban microclimate modeling for side-facade farming and agrivoltaic deployment in town estates

Abstract

Singapore, a highly urbanized island city with limited land and agricultural space, faces significant challenges due to climate change and the urban heat island effect (UHIE). This study investigates the feasibility and potential benefits of integrating vertical farming (VF) on building facades and agrivoltaic (AV) systems on the rooftops of public housing (HDB) estates as sustainable solutions. To evaluate local microclimatic conditions, solar irradiance mapping was conducted using ClimateS-tudio across three HDB estates, representing both old and new buildings, to identify suitable facade surfaces for VF systems. The irradiance data were further analyzed using an energy balance equa-tion to assess surface temperatures, while additional parameters such as Daily Light Integral (DLI) and Photosynthetically Active Radiation (PAR) were incorporated to determine facade suitability for crop cultivation. The simulation results indicate that VF systems on HDB facades provide a sub-stantial cooling effect by reducing heat transfer into buildings through the replacement of conven-tional materials with vegetation. This effect contributes to lower internal temperatures and en-hances urban thermal comfort. Suitable crops were identified based on facade conditions: (i) green pepper, suitable for high-light environments; (ii) cabbage, ideal for mid-rise facades; and (iii) let-tuce, which thrives in shaded areas. Additionally, the study examined the design and feasibility of modular AV systems on HDB rooftops using Grasshopper and PVSyst simulation software. Various AV configurations were evaluated to optimize agricultural productivity and solar energy generation. Findings suggest that incorporating crops within AV systems not only supports food production but also enhances photovoltaic efficien-cy by mitigating panel temperatures. The combined implementation of VF and AV systems presents a promising strategy for reducing carbon emissions associated with vegetable transportation, con-tributing to urban sustainability goals. This research demonstrates the feasibility and benefits of deploying VF and AV systems on HDB buildings, supporting Singapore's objectives for food security, renewable energy, and climate resilience.