Urban albedo computation in high latitude locations: An experimental approach
Lead Research Organisation:
Brunel University London
Department Name: Mechanical and Aerospace Engineering
Abstract
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People |
ORCID iD |
| Maria Kolokotroni (Principal Investigator) |
Publications
Kolokotroni M
(2021)
Urban Microclimate Modelling for Comfort and Energy Studies
Nikolopoulou M
(2022)
Urban albedo: developing a canyon albedo calculator
Salvati A
(2020)
Built form, urban climate and building energy modelling: case-studies in Rome and Antofagasta
in Journal of Building Performance Simulation
Salvati A
(2022)
Impact of reflective materials on urban canyon albedo, outdoor and indoor microclimates
in Building and Environment
Salvati A.
(2019)
Microclimate data for building energy modelling: Study on ENVI-met forcing data
in Building Simulation Conference Proceedings
| Description | The University of Kent has developed a 1:10 scale physical model of a residential area in Islington, London, identified as representative of the urban settings of London, incorporating variations in block geometry, canyon geometry and surface materials. It was built at the University of Kent campus for logistical reasons. The model includes asphalt for the ground surface, and has been built with brick building blocks, as brick is the most commonly used material in London, and roof tiles for the pitched roofs. A bespoke monitoring plan was developed to capture detailed incoming solar irradiance and reflected radiation at different points within the experimental model, by means of back-to-back pyranometers, where the upward- and downward-looking pyranometers measured incident and reflected radiation respectively. The experimental phases of the physical model included application of different colours, as well as integration of building materials, such as glazing, cladding, and concrete paving to reflect gradual changes, aimed at evaluating the impact of materials and colour on canyon albedo alongside the canyon's reflective power in the infrared, and the impact of rain. The results highlighted that the addition of concrete paving at street level tarmac increased the street canyon albedo with a similar effect found from application of façade colour, while the substitution of tarmac with grass increased canyon albedo by 70%. Brickwork and aluminium cladding façades were seen to contribute to significantly higher canyon albedo than curtain wall across the measured solar irradiance spectrum. The results also revealed the highly dynamic nature of canyon albedo, which presented diurnal and seasonal variations, and a consistent rainfall-induced reduction of albedo in the range 22-36% throughout the experimental phases. The study also used radiation measurements from the physical model to calibrate the digital model and examine computationally some of the parameters affecting urban albedo by means of the highly-sophisticated lighting simulation tool, RADIANCE. The variations in canyon geometry (H/W ratio), building geometry and orientation was also investigated through different scenarios, at ground and roof levels. The effect of orientation was found to be significant for the canyon albedo but not for the urban albedo, for the typical H/W ratios studied. The results demonstrated that increasing the H/W ratio has the most significant impact on urban albedo. They highlighted the substantial impact of urban materials and their position on urban albedo and demonstrated the dominant effect of horizontal ground surfaces. The impact of vertical surfaces on the radiation exchange within the street canyon becomes more significant with increasing building height. Brunel has carried out a modelling study of urban albedo, with the model calibrated using field monitoring in the case-study urban area in Islington, London, and measurements from the 1:10 scale model built at Kent. It used ENVImet to carry out the simulations and evaluated the IVC algorithm for radiation transfer. The algorithm showed a good agreement with measurements for reflections computation within urban canyons. It also used EnergyPlus to evaluate the impact on indoor conditions. The simulation results showed that increasing the road reflectance has high absolute and relative impact on Urban Canyon Albedo (UCA) in wide canyons. In deeper canyons, the absolute impact of the road reflectance is reduced while the relative impact of the walls' reflectance is increased. It also showed that increasing surface reflectance in urban canyons has a detrimental impact on outdoor thermal comfort, due to increased inter-reflections between surfaces leading to higher mean radiant temperatures. This can be avoided by using reflective materials only on the top half part of the canyon façades. Increasing the road reflectance also increases the incident diffuse radiation on adjacent buildings, producing a small increase in indoor operative temperatures. The findings can be used to formulate design strategies to improve the urban thermal environment by using reflective materials in urban canyons without compromising outdoor thermal comfort or indoor thermal environments. The most effective strategies to increase urban albedo are (a) Increasing the reflectivity of roads in low-rise urban canyons and (b) Increasing the reflectivity of the top half of the canyon's façades in high-rise urban canyons. Loughborough University has developed protocols for materials degradation testing using weathering chambers and test standardization along with characterisation. The three Universities collaborated in the development of a model for urban albedo computation. The urban albedo calculator, currently designed for latitude 51° N/S, enables the calculation of hourly or mean daily albedo of a 2D street canyon, at eaves level, any time of the year, under different sky conditions. Other user inputs include façade orientation, time of the day and month, sky conditions (sunny or cloudy) and materials. The calculator was designed with flexibility and extensibility in mind to allow future inputs and alterations. Outputs for building practitioners: • Series of design guidance on the influence of design decisions for materials and geometry, their impact on urban albedo and implications for urban design and planning. • Artificial weathering and characterisation protocols for various materials commonly used in facades were developed • An Urban Albedo calculator tool with simple inputs to predict changes in urban albedo in relation to changes in urban fabric and solar altitude. This is based on fundamental equations cross-checked with the computational, field and experimental results. Possible economy and health impacts: - Economic aspects: reflective materials are a cost effective solution as they are relatively low cost and easy to apply to surfaces - Health aspects: reflective materials can reduce overheating risk outside and reduce heat transfer to buildings thus reducing overheating inside. |
| Exploitation Route | The outcomes of this funding will be taken forward by disseminating findings to: • Materials manufacturers: through the European Cool Roofs Council (ECRC) - https://coolroofcouncil.eu/ • Building Professionals: through CIBSE's Resilient Cities Group - https://www.cibse.org/resilientcities |
| Sectors | Construction,Energy,Environment |
| URL | https://research.kent.ac.uk/urbanalbedo/ |
| Description | The results of the project were summarised in a publication by the Chartered Institute of Building Services Engineers, CIBSE Research Insight 03 - Urban albedo: developing a canyon albedo calculator published in September 2022. The publication can be downloaded freely from CIBSE's website. A webinar was organised in November 2022 to further disseminate the publication which was attended by more than 200 professionals from the UK and internationally. |
| First Year Of Impact | 2022 |
| Sector | Construction,Environment |
| Impact Types | Policy & public services |
| Description | UKRI COVID-19 Allocation |
| Amount | £21,408 (GBP) |
| Organisation | United Kingdom Research and Innovation |
| Sector | Public |
| Country | United Kingdom |
| Start | 10/2020 |
| End | 01/2021 |
| Title | Urban canyon wind speed calculator |
| Description | This dataset accompanies the paper Salvati A, Palme M, Chiesa G, and Kolokotroni M (2020). Built form, urban climate and building energy modelling: case-studies in Rome and Antofagasta. Journal of Building Performance Simulation. https://www.tandfonline.com/doi/full/10.1080/19401493.2019.1707876 and describes how the wind speed was calculated. It is available in: https://brunel.figshare.com/articles/dataset/Urban_canyon_wind_speed_calculator/11371272 |
| Type Of Material | Database/Collection of data |
| Year Produced | 2020 |
| Provided To Others? | Yes |
| Impact | The academic community can use the methods presented in the paper. |
| URL | https://brunel.figshare.com/articles/dataset/Urban_canyon_wind_speed_calculator/11371272 |
| Description | IEA Annex 80 on Resilient Cooling for Buildings |
| Organisation | International Energy Agency (IEA) |
| Country | France |
| Sector | Charity/Non Profit |
| PI Contribution | The objective of the Annex80 is to support resilient low energy and low carbon cooling systems and overheating protection technologies to respond to the rapid increase of air conditioning of buildings, driven by multiple factors, such as urbanisation and densification, climate change and elevated comfort expectations together with economic growth in hot and densely populated climate regions of the world. More info can be find here: https://annex80.iea-ebc.org/ Within the project, Agnese Salvati co-leads the "Weather data task force group", to generate future weather files and heat wave data to be used in building dynamic simulations, to assess the resilience of buildings and cooling technologies under climate change scenarios. |
| Collaborator Contribution | We are contributing to the project along with other 34 teams from 13 countries all over the world. This has brought benefits to the project on the work of other teams on resilient cooling and overheating in cities and how to improve thermal comfort in the cities. |
| Impact | We are contributing to the reports of this international project |
| Start Year | 2018 |
| Description | CIBSE CPD Webinar |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | The successful events of the CIBSE Build2Perform Live 2019 at Olympia in London provided the basis for a series of online CPD events organised by CIBSE. The Urban Albedo project was the focus of the seminar on 'Urban Design', where Professor Nikolopoulou and Professor Kolokotroni presented the work of the Project. This CPD took place in 24 June 2020. |
| Year(s) Of Engagement Activity | 2020 |
| Description | On-line lecture to IEA Annex 80 participants |
| Form Of Engagement Activity | A formal working group, expert panel or dialogue |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | The Annex 80 organises monthly lecture series to talk about annex-related research projects and to exchange knowledge between participants. We participated to the Annex80 lecture series with the lecture "Urban Albedo and microclimate. Impact on outdoor thermal comfort and building overheating" on the 1st of December 2020, presenting the modelling results from the Urban Albedo project. |
| Year(s) Of Engagement Activity | 2020 |
| Description | Presentation to Build4Perform Exhibition - Urban Albedo and microclimate |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | The session was held at the CIBSE Build2Perform Live 2019 at Olympia in London on Wednesday 27th November 2019. The session ran through how the Urban Albedo collaborative research project is looking at the impacts of the urban fabric to the urban temperatures and how new material can improve urban climate. |
| Year(s) Of Engagement Activity | 2019 |
| Description | Research Workshop at the Univeristy of Rosario, Argentina |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Research Visit (28 March - 12 April 2019) to Univeristy of Rosario, Argentina by Dr Agnese Salvati - Presented workshops on UHI effect and Urban weather Generator. Discussions on the possibility to apply the Urban Albedo tool to the city of Rosario, Argentina. |
| Year(s) Of Engagement Activity | 2019 |
| Description | URBAN ALBEDO: DIGITAL TOOLS FOR URBAN RESILIENCE AND GROWTH |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | The project team along with the Greater London Authority and the London Climate Change Partnership (LCCP) organised a very successful workshop at London's Living Room, City Hall on Monday 15th October 2018, marking the beginning of Green GB week. The workshop 'Urban Albedo: Digital tools for urban resilience and growth', which was chaired by the former President of the Urban Design Group, Colin Pullan, brought together leading urban and building scientists, as well as practitioners from different backgrounds, to inform the impact of urban morphology and materials on urban albedo and its importance for health and well-being. |
| Year(s) Of Engagement Activity | 2018 |
| URL | https://research.kent.ac.uk/urbanalbedo/news-and-meetings/workshop-1-importance-of-urban-albedo-the-... |
| Description | Urban Albedo at the Urban Climate Walk |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Professional Practitioners |
| Results and Impact | As part of on-going research into the relationship between Built Form, Microclimates & Critical Infrastructure, Dr Julie Futcher organised a City of London urban climate walking tour, to report the latest findings, alongside discussing the role of built form as a critical infrastructure in the climate emergency. During this, Dr Agnese Salvati, Research Fellow at Brunel University and a member of the Urban Albedo Consortium, discussed how urban surface geometry and materials impact on heat island intensity, thermal comfort and building energy performance. |
| Year(s) Of Engagement Activity | 2019 |
| Description | Urban Climate Modelling for Building Performance Simulation: shadows, ventilation and other effects Workshop |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | At the IBPSA international conference BS2019, 2-4 September 2019 in Rome, Dr Agnese Salvati co-organised and participated to the discussion panel "Urban Climate Modelling for Building Performance Simulation: shadows, ventilation and other effects" with Massimo Palme (Universidad Católica del Norte, Chile), Michael Bruse (Institute of Geography, Johannes Gutenberg-Universität Mainz and is CDO at ENVI_MET Essen), Anna Laura Pisello (University of Perugia), Drury B. Crawley (Bentley Systems) and Benoit Beckers (Université de Pau, France). The panel discussion focused on the need of including urban context in building performance simulation, considering all the urban climate modifications such as shadow, urban air circulation and thermal environment modifications determined by built form and materials. |
| Year(s) Of Engagement Activity | 2019 |
| Description | Urban climate led design: a planning tool for liveable places-Understanding the issues at the street scale |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | The presenation took place in a dedicated workshop at FutureBuild, held on 5th March, London Excel, 12:00 - 13:10 Urban Infrastructure Hub. The title of the workshop was: Urban climate led design: a planning tool for liveable places. Abstract of the workshop: Whilst higher urban densities offer the possibility of improved efficiency, their success requires a good understanding of the influence of building and urban form on the urban climate. However, currently within the UK there is no reference within existing policy to the specific urban climate measurements needed, or to the criteria to indicate when mitigation efforts are required. In part, this oversight not only results from understanding the complexities of the interdependent nature of the vast range of built-form driven urban climate effects, but from our underestimation of the mitigating potential that building and urban form offers towards improved efficiency. In this session we discuss the growing and urgent need to demonstrate the impacts of a proposed development on the urban climate; here an inter-disciplinary group of experts explore how outcomes could be improved if the impact of built form on the urban climate were a planning requirement. This session was developed with Urban Generation. Chair Richard Lorch, Editor, Buildings and Cities Speakers Impacts of urban climate on public health Carl Petrokofsky, Public Health Specialist Advisor, Public Health England. Understanding the issues at an urban scale Professor Sue Grimmond, Professor of Meteorology, University of Reading. Understanding the issues at a neighbourhood scale Dr Julie Futcher, Independent consultant on applied urban climatology and co-founder of Urban Generation Understanding the issues at the street scale Dr Agnese Salvati, Research Fellow, Brunel University London Understanding the Scope and Limits of Planning Professor Michael Hebbert, Emeritus Professor of Town Planning, Bartlett School of Planning, UCL The conference and seminar programmes are now live on the Futurebuild website. (https://www.futurebuild.co.uk/). |
| Year(s) Of Engagement Activity | 2019 |
| Description | Webinar (CIBSE) |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | This webinar was organised by CIBSE and was based on the publication 'Research Insight Urban albedo: developing a canyon albedo calculator' published in October 2022 by CIBSE. The publication was a summary for designer on how the results of the project can be implemented in practice. |
| Year(s) Of Engagement Activity | 2022 |
| URL | https://www.cibse.org/knowledge-research/knowledge-resources/growyourknowledge-webinars/past-growyou... |
| Description | Webinar - Presentation to CIBSE Resilient Cities Special Interest Group - Urban Albedo and microclimate |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | The presentation was part of a webinar with two more speakers organised by the CIBSE Resilient Cities Special Interest Group. The webinar title was 'The Heat is On! Looking Beyond the Building, Cooling City Microclimates' and addressed current challenges for cities and overheating. There was a good discussion at the end of the webinar where the results of the project were explained further and how they can be used to improve thermal comfort in cities. |
| Year(s) Of Engagement Activity | 2020 |
| URL | https://www.cibse.org/networks/groups/resilient-cities/past-events-and-presentations |