Understanding building and urban environment interactions: An integrated framework for building occupancy modelling

Improving building energy efficiency requires accurate modelling and a comprehensive understanding of how occupants use building space. This thesis focuses on modelling building occupancy to enhance the predictive accuracy of occupancy patterns and gain a better understanding of the causal reasons for occupancy behaviour. A conceptual framework is proposed to relax the restriction of isolated building analysis, which accounts for interactions between buildings, its occupants, and other urban systems, such as the effects of transport incidents on occupancy and circulation in buildings. This thesis also presents a counterpart mapping of the framework that elaborates the links between modelling of transport and building systems. To operationalise the proposed framework, a novel modelling approach which has not been used in the current context, called the hazard-based model, is applied to model occupancy from a single building up to a district area. The proposed framework is further adapted to integrate more readily with transport models, to ensure that arrivals and departures to and from the building are consistent with the situation of the surrounding transport systems. The proposed framework and occupancy models are calibrated and validated using Wi-Fi data and other variables, such as transport and weather parameters, harvested from the South Kensington campus of Imperial College London. In addition to calibrating the occupancy model, integrating a travel simulator produces synthetic arrivals into or around the campus, which are further distributed over campus buildings via an adapted technique and feed the occupancy simulations. The model estimation results reveal the causal reasons for or exogenous effects on individual occupancy states. The validation results confirm the ability of the proposed models to predict building occupancy accurately both on average and day by day across the future dataset. Finally, evaluating occupancy simulations for various hypothetical scenarios provides valuable suggestions for efficient building design and facility operation.Open Acces

An approach for building occupancy modelling considering the urban context

Building occupancy, which reflects occupant presence, movements and activities within the building space, is a key factor to consider in building energy modelling and simulation. Characterising complex occupant behaviours and their determinants poses challenges from the sensing, modelling, interpretation and prediction perspectives. Past studies typically applied time-dependent models to predict regular occupancy patterns for commercial buildings. However, this prevalent reliance on purely time-of-day effects is typically not sufficient to accurately characterise the complex occupancy patterns as they may vary with building’s surrounding conditions, i.e. the urban environment. Therefore, this research proposes a conceptual framework to incorporate the interactions between urban systems and building occupancy. Under the framework, we propose a novel modelling methodology relying on competing risk hazard formulation to analyse the occupancy of a case study building in London, UK. The occupancy profiles were inferred from the Wi-Fi connection logs extracted from the existing Wi-Fi infrastructure. When compared with the conventional discrete-time Markov Chain Model (MCM), the hazard-based modelling approach was able to better capture the duration dependent nature of the transition probabilities as well as incorporate and quantify the influence of the local environment on occupancy transitions. The work has demonstrated that this approach enables a convenient and flexible incorporation of urban dependencies leading to accurate occupancy predictions whilst providing the ability to interpret the impacts of urban systems on building occupancy

Multishell Precursors Facilitated Synthesis of Concentration-Gradient Nickel-Rich Cathodes for Long-Life and High-Rate Lithium-Ion Batteries

The rational design of concentration-gradient (CG) structure is demonstrated as an available approach to improve the electrochemical performances of high-energy nickel-rich cathodes for lithium-ion batteries (LIBs). However, the complicated preparing processes, especially the CG-precursors, generally result in the less-than-ideal repeatability and consistency that is regarded as an extreme challenge for the widespread commercialization. Thus, the innovative strategy with facile steps and the feasibility of large-scale preparation for commercialized applications should be urgently developed. Herein, through the temperature-tunable cation diffusion, the feasibility of controllable preparation of nickel-rich CG-LiNi_0.7Co_0.15Mn_0.15O₂ (NCM) from multishell precursors is first demonstrated. As expected, the Li/CG-NCM half cells show much enhanced cycle-life, rate property, and safety because of the mitigated side-reactions and fast Li⁺ kinetics. Besides, the Li₄Ti₅O₁₂/CG-NCM full cells also exhibit long-term lifespan, 95% capacity retention even after 2000 cycles, and high-rate behaviors. Importantly, by contrast with the conventional techniques that prepare CG cathodes from CG precursors, the proposed new synthesis strategy from multishell precursors is suitable for large-scale preparation. Overall, this multishell precursor-facilitated synthesis probably promotes the practical applications of CG cathodes for state-of-the-art LIBs and also can be easily expanded to controllably preparing spinel- and olive-type CG cathodes