Urban Building Energy Modeling (UBEM) Tools: A State-of-the-Art Review of bottom-up physics-based approaches

Abstract: Regulations corroborate the importance of retrofitting existing building stocks or constructing new energy efficient district. There is, thus, a need for modeling tools to evaluate energy scenarios to better manage and design cities, and numerous methodologies and tools have been developed. Among them, Urban Building Energy Modeling (UBEM) tools allow the energy simulation of buildings at large scales. Choosing an appropriate UBEM tool, balancing the level of complexity, accuracy, usability, and computing needs, remains a challenge for users. The review focuses on the main bottom-up physics-based UBEM tools, comparing them from a user-oriented perspective. Five categories are used: (i) the required inputs, (ii) the reported outputs, (iii) the exploited workflow, (iv) the applicability of each tool, and (v) the potential users. Moreover, a critical discussion is proposed focusing on interests and trends in research and development. The results highlighted major differences between UBEM tools that must be considered to choose the proper one for an application. Barriers of adoption of UBEM tools include the needs of a standardized ontology, a common three dimensional city model, a standard procedure to collect data, and a standard set of test cases. This feeds into future development of UBEM tools to support cities' sustainability goals.

• The paper reviews bottom-up physics-based Urban Building Energy Modeling (UBEM) tools, classifying them by input, output, workflow, applicability, and target users to guide selection.
• Key challenges highlighted include the lack of data standardization, common city models, and difficulty integrating complex factors like occupant behavior and mobility patterns.
• Future research directions involve enhancing datasets, refining models for district energy systems and microclimate, and improving tool interoperability and usability through standardization.

Review of Bottom-up Physics-based UBEM Tools: Current State and Prospects

This paper provides a comprehensive review of the current state of Urban Building Energy Modeling (UBEM) tools with a focus on bottom-up physics-based approaches. Its primary objective is to aid potential users in selecting appropriate tools by evaluating various aspects such as inputs, outputs, workflow, applicability, and potential users from a user-oriented perspective. Additionally, the paper highlights the ongoing research challenges and outlines paths for future developments in the UBEM domain.

Insights and Comparative Analysis

The paper categorizes the tools primarily based on five features: input requirements, output reports, workflow exploited, tool applicability, and target users. This classification is imperative as it allows researchers to identify suitable tools depending on specific needs such as geographic data availability or computational resources. Major tools like CitySim, SimStadt, umi, CityBES, OpenIDEAS, CEA, URBANopt, and TEASER were analyzed, with insights on their diverse purposes and capabilities. Moreover, the study reveals how some tools use reduced order models to manage large datasets efficiently, while others integrate with high-performance computing for detailed analyses.

Key Findings and Challenges

The findings underscore the significant differences in tools based on their purposes, ranging from large-scale policy comparison to district-level energy optimization. The review highlights major technological challenges hindering wider adoption, such as the lack of a standardized ontology, common city models, and inconsistent nomenclature across tools.

A prominent limitation in UBEM tools is the integration and handling of occupant behavior and mobility patterns within urban settings. These factors play a critical role in determining urban energy demand profiles but remain underdeveloped due to the inherent complexity and computational demands. Only a few tools have made notable progress in this regard, such as integrating stochastic occupancy models or linking with mobility simulators.

Implications and Future Directions

The paper identifies several promising research avenues including the enhancement of datasets, refinement of models to include district energy systems, and improved consideration for urban microclimatic conditions. The integration of GBIs and the analysis of outdoor comfort conditions are pivotal for better urban planning and sustainability analyses. Additionally, improvements in calibration techniques, such as employing Bayesian methods, are necessary to refine model predictions to better reflect real-world scenarios.

The review suggests a dual trajectory for future tool development: one towards heightened detail and integration at the district level, potentially involving Building Information Modeling (BIM), and another towards city-scale applications for policy evaluation. Moreover, the tools' interoperability and usability could greatly benefit from a concerted effort towards standardization, both in terms of data representation and methodological assessments (e.g., using testing standards akin to those in BEM software).

Conclusion

Overall, this review provides a vital resource for both users and developers of UBEM tools, offering critical insights into the current state of bottom-up physics-based modeling. By balancing detail and efficiency, these tools are crucial for advancing urban sustainability goals. The paper's comprehensive analysis and future outlook serve as a strategic roadmap for enhancing UBEM's utility and adoption in addressing pressing urban energy challenges. Through continued innovation and integration, UBEM tools promise to play an indispensable role in the sustainable development of urban areas.