This study investigates the interplay between solar irradiance components and weather conditions on photovoltaic (PV) power generation in Amsterdam. We emphasize real-world variations—including various PV tilts and orientations, seasonal shifts, and multi-year climatic trends—to align with the integration of PV in existing built environments.

A multi-year weather dataset was used to drive System Advisor Model (SAM) simulations with key variables including Direct Normal Irradiance (DNI), Diffuse Horizontal Irradiance (DHI), Global Horizontal Irradiance (GHI), ambient temperature, and wind speed. By investigating monthly subsets and including a broad range of tilt and azimuth angles, we reveal that the relationship between GHI and power generation can significantly vary throughout the year. Furthermore, wind speed shows a positive but moderate coefficient, suggesting its underexplored cooling benefits on PV modules, especially under high irradiance conditions.

Ambient temperature once again confirms the negative impact of heating on PV efficiency, but further analysis of monthly data and specific weather events (e.g., heatwaves, storms) indicates substantial short-term variability in power performance. Such temporal and seasonal insights underscore the need to evaluate long-term trends, especially in the context of urban heat islands and the potential rise in ambient temperatures under climate change scenarios. Ongoing work will expand the dataset to multiple years—leveraging publicly available KNMI weather files—to assess interannual fluctuations in both irradiance and temperature. This work provides a framework for performance assessments of rack-mounted PV systems in an open field. 

KEYWORDS: Photovoltaic systems, Global Horizontal Irradiance (GHI), Ambient Temperature, Wind Speed, System Advisor Model (SAM), Urban Heritage, Climate Variability

Fig. 1. Example of illustration of daily cumulative variation of solar irradiance (DNI, DHI, GHI) of Amsterdam in 2019.

Fig. 2. Correlation matrix for PV power generation and related parameters based on the simulations of SAM software, for the example of weather data of Amsterdam in 2019.

How to cite: Hu, G., Loonen, R., and Reinders, A.: Analyzing the Influence of Weather Conditions and Solar Irradiance on Photovoltaic Power Generation: A Case Study in Amsterdam, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-963, https://doi.org/10.5194/icuc12-963, 2025.

Overheating is a pressing issue in the building sector, particularly in urban areas where it is intensified by the urban heat island. Despite significant advancements in Building Energy Modelling (BEM) tools, their accuracy in assessing overheating risks in urban environments is hindered by the lack of precise climate data. While methodologies such as the Urban Weather Generator were proposed for the creation of urban-specific weather files, their adoption remains limited. To help standardise urban climate contextualisation in BEM and foster the widespread use of urban weather data among both researchers and practitioners within the building sector, this work introduces the Urban Weather for Energy Calculations (UWEC). UWEC is intended to stablish predefined sets of urban weather files that capture the intra-urban heat variability within municipalities at the local scale and representative of a common temporal domain. A data-driven methodology, incorporating interpolation techniques, is used to define urban climate severity zones and generate urban weather files that represent typical conditions within each zone. This approach is tested in the city of Madrid, where nine different urban climate severity zones are identified, and their corresponding weather files are generated for the 2008–2017 temporal period. The results show up to 40% variability in cooling energy demand and 20% variability in heating energy demand between zones. This study demonstrates how UWEC can improve the assessment of overheating risks and support more effective urban heat adaptation strategies in the building sector.

How to cite: Núñez-Peiró, M., Sánchez-Guevara Sánchez, C., and Neila González, F. J.: Urban Weather for Energy Calculations: Advancing Building Energy Modelling with Urban Climate Contextualisation, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-446, https://doi.org/10.5194/icuc12-446, 2025.

The integration of intermittent renewable energies requires buildings to adapt their energy needs to energy networks and local climate conditions, while also meeting the needs of occupants. This concept is known as building energy flexibility or demand-side management.

At the building scale, the thermal mass of buildings can be activated as a form of energy storage, for flexibility purposes. While exploiting the flexibility potential of buildings on a city scale increases storage capacity, it also creates sources of flexibility by aggregating the energy needs of buildings, particularly when considering the asynchronous energy demands of residential and commercial sectors.

In order to evaluate building flexibility potential at the city scale, a methodology has been developped for identifying building archetypes representing the different energy flexibility potentials at the city scale. These archetypes will be aggregated in a later stage of the process. The methodology employs clustering techniques to categorize buildings based on their usage, geometry, morphology and urban surrounding, focusing on the characteristics that influence their flexibility potential. This approach represents an original classification system specific to energy flexibility.

The method has been developped for the French city of Nantes, but is also intended to be generalized to other cities, depending on the available data.

How to cite: Ganswindt, A., Rodler, A., Guernouti, S., Ramousse, J., Videau, J.-B., and Gavan, V.: Methodology for classifying buildings at the city scale regarding their energy flexibility potential, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-205, https://doi.org/10.5194/icuc12-205, 2025.

The UK government promotes residential air-source heat pumps (ASHPs) as a cornerstone to achieving Net Zero emissions by 2050. As climate shifts, ASHP could serve both heating and cooling needs, potentially influencing outdoor temperatures in UK residential neighbourhoods in the future. Here, we use a novel multi-scale modelling framework combining an urban land surface model (SUEWS) and a building energy model (EnergyPlus) to assess the implications of ASHP adoption in idealised low-rise UK residential neighbourhoods under mid-century climate scenarios. Results indicate that ASHP cooling could increase median anthropogenic heat emissions by up to 15 W m^-2 and elevate median local air temperatures by up to 0.12 °C during summer in London. Conversely, in winter, ASHP adoption could reduce anthropogenic heat emissions by up to 19 W m^-2 and lower temperatures by up to 0.23 °C in Aberdeen. While the magnitude of temperature changes may vary across UK cities, the relationship between anthropogenic heat changes and air temperature remains consistent. The findings highlight the importance of balancing indoor and outdoor thermal comfort in the transition to sustainable urban energy systems. This work offers useful insights into the thermal impacts of ASHPs in urban contexts, aiding policymakers and planners in developing climate-resilient strategies.

How to cite: Xie, X., Luo, Z., Grimmond, S., and Liu, Y.: Climate Impact by 2050 of Residential Air-Source Heat Pumps in UK Urban Areas , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-288, https://doi.org/10.5194/icuc12-288, 2025.

Cities are transitioning to a decarbonized energy state to contribute to global warming reduction and for energy security.  As cities evolve into this future energy state the compounding effect of a changing local and global climate plays a major background.  Key energy sectors to be transitioned are the transportation (EV) and the buildings.  In Mega-Cities buildings represent the largest energy demand and atmospheric carbon sources mostly due to the energy required for cooling and heating the spaces.  For cold climate cities this transition represents major a major shift to evolve from carbon based space heating into electrification prompting new winter peaks never envisioned with direct implications on the local climate by reduction of the winter Urban Heat Island and potential improvement of the air quality.  This work presents a framework to project new energy demands for New York Metro Region under a transition to full electrification and a changing climate towards 2050.  For this region, buildings account for 70% of the total energy consumed and carbon emissions. We focus on an electrified winter for buildings and EV by evaluating the energy infrastructure and environmental impacts of such major shifts.  For future climate forcing two Socio-Economic Pathways (SSPs) climate scenarios are used of the Sixth Assessment of the Coupled Model Intercomparison Project (CMIP6), 245 and 585. The future climate ensemble used is the downscaled 12 km resolution for the Continental US from the IM3/HyperFACETS Thermodynamic Global Warming Simulation Dataset. The Weather Research and Forecasting model coupled with a multi-layer building environment parameterization and building energy model, is used to perform the analysis. Results indicate a new winter energy peak increase of two fold factor (from 8GW to 16 GW).  The presentation will outline context, methods, results, and challenges to meet these goals.

How to cite: Gonzalez-Cruz, J., Gamarro, H., Montoya-Rincon, J. P., Sookdar, K., and Elgalad, N.: Energy Demand Challenges of Electrification of Cold-Climate Mega-Cities in a Changing Climate: The Case of New York City, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-149, https://doi.org/10.5194/icuc12-149, 2025.

Buildings are major contributors to global energy-related CO₂ emissions, accounting for a significant share of global climate impacts. This has highlighted the critical need to transition toward a carbon-neutral building stock by 2050. Rooftop photovoltaics (PVs) offer substantial potential to reduce energy demand and enhance urban energy self-sufficiency. This work focuses on developing an improved CityBEM framework, an in-house urban building energy model (UBEM), to evaluate the role of rooftop PV systems in decarbonizing urban energy systems. The enhanced methodology enables city-scale, high spatiotemporal resolution simulations of both building energy use and rooftop PV retrofitting while addressing key computational and data limitations commonly faced in UBEM applications.

CityBEM’s robust and scalable approach allows for transient simulations of individual buildings with diverse usage types, making it applicable to large urban areas. The rooftop PV module incorporates physics-based modeling, validation, and optimized designs to account for self-shading effects and maximize energy generation potential.

Currently, the tool is being applied to model the entire city of Montreal. The goal is to generate high spatiotemporal resolution simulations of energy demand and on-site electricity generation from rooftop PVs. This framework aims to provide actionable insights into the role of rooftop photovoltaics in achieving cleaner, energy self-sufficient cities and informing strategies for large-scale urban retrofitting and decarbonization.

How to cite: Rayegan, S., Wang, L. (., and Zmeureanu, R. G.: Urban-scale modeling of building energy self-sufficiency using rooftop photovoltaics , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-186, https://doi.org/10.5194/icuc12-186, 2025.

Large-scale adoption of rooftop photovoltaic (PV) panels has been suggested as a climate mitigation strategy as well as a local heat adaptation strategy since PVs provide shade to the underlying roof surface and simultaneously generate electricity to supply indoor cooling energy. However, PVs can potentially exacerbate daytime warming as a large fraction of incoming solar radiation is converted to heat due to limited electricity production rate, low panel albedo, and minimal panel energy storage. Currently, commercially available PV modules have an electrical energy conversion efficiency of ~ 20%, while PVs with an efficiency up to 50% have been demonstrated in a laboratory. With anticipated advances in PV materials and efficiency, it is important to examine how different PV properties would impact local climate, and assess opportunities for minimization of the potential daytime warming.

In this study, we couple the newly updated and evaluated rooftop PV model, UCRC-Solar, to the single-layer urban canopy model, Town Energy Balance (TEB), and explore various configurations of rooftop PV panels under various climatic conditions for major cities in North America. In particular, long-term offline TEB simulations are conducted for the current climate, driven by the ERA5-Land reanalysis. We investigate how different PV energy production efficiencies, tilt angles, surface emissivities, and panel spacing affect the surface temperature of the roof and the PV modules and sensible heat flux from the roof, PV panels, and the roof-PV systems. Furthermore, an online WRF case study is conducted for Toronto, Canada, under the RCP8.5 scenario with optimized PV configurations to better assess PV impacts on the local climate.

How to cite: Yin, H., Krayenhoff, E. S., and Aliabadi, A. A.: Optimizing rooftop photovoltaic panel configurations: Implications from long-term simulations for North American cities, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-241, https://doi.org/10.5194/icuc12-241, 2025.

Air source heat pumps (ASHPs) are an effective measure to building electrification and decarbonization. In heating mode, ASHPs take in heat from the outdoor air to heat the indoors. Wide adoption of ASHPs may then lower urban air temperature and in turn increase heating demand. This positive feedback loop will not only exacerbate cold temperatures, but also lead to higher-than-expected heating energy use through increased heating load (i.e., larger temperature differences between indoors and outdoors) and reduced ASHP efficiencies (which decreases with decreasing temperature). Dynamic modeling of ASHP energy use and the urban climate is therefore needed for comprehensive assessments of ASHP as a climate mitigation strategy and more accurate energy demand projections. Here, we develop an ASHP modeling scheme in the physics-based urban building energy model of Community Earth System Model (CESM2). We explicitly model urban energy balance accounting for the heat removed from urban canyon for indoor heating, and the temperature dependence of ASHPs’ Coefficient of Performance (COP). We focus our analysis on the United States (US) and United Kingdom (UK), two countries with policy incentives to significantly increase ASHP adoption in the coming decades. Preliminary results show comparing with fossil-fuel-based heating, idealized (100%) ASHP adoption reduces winter air temperature by up to 1.0 K and 0.3 K in the US and UK, respectively. This temperature reduction results in an increase of up to 2% in heating load for both countries. Although lower temperatures penalize ASHP efficiency, the primary energy consumption of ASHP is still much lower than fossil-fuel-based heating, highlighting the climate mitigation benefits of ASHP. Under a high-emission scenario, both the urban temperature and the COP penalties are alleviated in the future. Challenges remain in preparing the electricity grid for increased winter demand and improving ASHPs’ cold temperature performance to meet indoor comfort.

How to cite: Li, X. "., Zhao, L., Luo, Z., Xie, X., and Oleson, K.: Evaluating the energy and micro-climatic effects of large-scale air-source heat pump adoption through urban-resolving Earth system modeling, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-274, https://doi.org/10.5194/icuc12-274, 2025.

A swift transition to renewable energy is essential for meeting global demand and mitigating climate change, yet land scarcity presents a challenge. Installing photovoltaic panels on urban surfaces, such as roofs and walls, offers a promising solution but may alter energy flows and urban microclimates. Before deploying building-integrated photovoltaics, it is crucial to consider:

• How do different layouts affect energy transfer from roofs?
• What are the implications for the magnitude and timing of building energy demand and sensible heat emissions to the urban boundary layer?
• How sensitive are roof responses and heat transfer to variations in meteorological drivers such as shortwave radiation, air temperature, and wind speed?

To address these questions, we developed a multi-element energy budget model to simulate solar roof configurations. Our results show that, in cold climates, solar roofs reduce conduction into the building almost as much as cool roofs, while also generating energy to offset heating demand. In hot climates, inclined panels are preferable in reducing indoor heat gains, outperforming cool roofs while producing clean energy for cooling.

These benefits are not free. Solar roofs increase sensible heating of the UBL relative to a cool roof, exacerbating the urban heat island effect during peak insolation. However, the peaks in sensible heat occur before the peaks in air temperature (moderating the impact on daytime thermal comfort), and notably, solar roofs mitigate nighttime UHI which is critical for reducing heat-related health risks.

An elasticity analysis of heat fluxes reveals that, under intense solar radiation, solar roofs shift more of the excess heat to sensible heat. In warmer climates with higher air temperatures that reduce sensible heat losses, the conduction of heat into the indoor building increases. Although wind generally has a moderate impact on fluxes, its variability modulates heat partitioning, favoring greater sensible heat flux and reduced conduction into the building.

How to cite: Hosseini, E., Bou-Zeid, E., and Burlingame, Q.: Indoor, Outdoor, and Power Implications of Rooftop Photovoltaic Panels Deployment, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-866, https://doi.org/10.5194/icuc12-866, 2025.

Microclimates play a crucial role of how to shape urban environments, influencing both thermal comfort and building energy consumption. Simultaneously, in 2022, 65% of the EU energy consumption in the residential sector was for heating. This paper investigates the relationship between urban morphology, microclimates and building energy demand in cold climates- aiming to lower potential heating loads. The study examines how different urban forms (grid, radial, and mixed layouts) affect local microclimatic conditions and, in turn, influence building energy consumption. Specifically, it explores how urban design impacts wind speed and temperature distribution, two key factors affecting energy demand. To analyse these effects, ENVI-met (a 3D modelling software for urban cooling and climate adaptive planning) was used to simulate microclimatic conditions, while the SIMIEN building energy simulation tool assessed their influence on building energy use. The case study focuses on the area around Nansenparken in Fornebu, Norway, a peninsula in the Oslo Fjord that is undergoing continuous development with the aim of becoming a positive energy district. The findings suggest that urban morphology significantly influences microclimatic conditions, particularly wind patterns. However, only temperature distribution was found to have a significant effect on building energy demand. The impact of urban form on wind patterns presents an interesting avenue for further research. These results can provide valuable insights for future construction and urban planning in Fornebu, offering guidance on optimizing neighbourhood layouts to enhance user comfort and building energy efficiency. Additionally, the study contributes to broader efforts in achieving the goal of transforming Fornebu into a positive energy district.

How to cite: Førde, M., Gaitani, N., and Gustavsen, A.: Shaping the Microclimate: How Urban Form Affects the Energy Demand of Residential Buildings in Fornebu, Norway , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-754, https://doi.org/10.5194/icuc12-754, 2025.

Cooling energy demand can be increased significantly due to the global temperature rise, with substantial economic impacts. However, many existing studies have primarily focused on overall temperature increases while neglecting critical mechanisms such as humid heat, daily temperature variability, and the urban heat island (UHI) effect. In this study, we focus on quantifying UHI intensities across different climate zones and integrating these effects into future cooling energy demand projections.

We first analyzed current Land Surface Temperature variations by Local Climate Zone (LCZ) within each climate zone to identify the seasonal and diurnal UHI intensity patterns based on LCZ composition. These observed UHI patterns were then applied to estimate future gridded Cooling Degree Days (CDD) using CMIP6 climate projections. We defined the UHI-adjusted CDD as a comprehensive metric that encapsulates the impact of urban heat islands on cooling demand.

These UHI-adjusted CDD values were then exogenously provided into the AIM/Hub model, which is CGE based global integrated assessment model to simulate climate policies, to project global future cooling energy demand and evaluate associated regional economic impacts. Our findings represent one of the first systematic evaluations of how LCZ-dependent urban heat islands may modulate future cooling energy requirements under various climate change scenarios. This study provides critical insights for policymakers and urban planners aiming to mitigate the economic burden of rising cooling energy demands in a warming world.

How to cite: Choi, Y. and Park, C.: Does the urban heat island effect matter in the global future cooling energy demand?, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-1000, https://doi.org/10.5194/icuc12-1000, 2025.