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Atmospheric Boundary Layer Flows Their Structure And Measurement

Discomfort glare in open plan green buildings

The current climate change is calling for a drastic reduction of energy demand as well as of greenhouse gases. Besides this, cities also need to adapt to face the challenges related to climate change. Cities, with their complex urban texture and fabric, can be represented as a diverse ecosystem that does not have a clear and defined boundary. Multiple software tools that have been developed, in recent years, for assessment of urban climate, building energy demand, the outdoor thermal comfort and the energy systems. In this review, we, however, noted that these tools often address only one or two of these urban planning aspects. There is nonetheless an intricate link between them. For instance, the outdoor comfort assessment has shown that there is a strong link between biometeorology and architecture and urban climate. Additionally, to address the challenges of the energy transition, there will be a convergence of the energy needs in the future with an energy nexus regrouping the energy demand of urban areas. It is also highlighted that the uncertainty related to future climatic data makes urban adaptation and mitigation strategies complex to implement and to design given the lack of a comprehensive framework. We thus conclude by suggesting the need for a holistic interface to take into account this multi-dimensional problem. With the help of such a platform, a positive loop in urban design can be initiated leading to the development of low carbon cities and/or with the use of blue and green infrastructure to have a positive impact on the mitigation and adaptation strategies.

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A review of assessment methods for the urban environment and its energy sustainability to guarantee climate adaptation of future cities

This study presents the largest-known, investigation on discomfort glare with 493 surveys collected from five green buildings in Brisbane, Australia. The study was conducted on full-time employees, working under their everyday lighting conditions, all of whom had no affiliation with the research institution.

The survey consisted of a specially tailored questionnaire to assess potential factors relating to discomfort glare. Luminance maps extracted from high dynamic range (HDR) images were used to capture the luminous environment of the occupants. Occupants who experienced glare on their monitor and/or electric glare were excluded from analysis leaving 419 available surveys. Occupants were more sensitive to glare than any of the tested indices accounted for.

A new index, the UGP was developed to take into account the scope of results in the investigation. The index is based on a linear transformation of the UGR to calculate a probability of disturbed persons. However all glare indices had some correlation to discomfort, and statistically there was no difference between the DGI, UGR and CGI. The UGP broadly reflects the demographics of the working population in Australia and the new index is applicable to open plan green buildings.

A review of open loop control strategies for shades, blinds and integrated lighting by use of real-time daylight prediction methods

On-site monitoring and subjective comfort assessment of a sun shadings and electric lighting controller based on novel High Dynamic Range vision sensors

Self-commissioning glare-based control system for integrated venetian blind and electric lighting

High dynamic range imaging has been shown to be a reliable tool to assess luminance maps and glare risk probability in buildings. However, there are some limitations of image capturing time, especially when dealing with highly dynamic and contrasted daylight situations. We used a newly developed prototype of a digital camera which contains a high dynamic range pixel array chip, with a logarithmic scale for encoding. This type of camera allows to effectively assessing luminance, contrast and contrast directions, by taking only a single image or by performing real time recordings. The device was equipped with a fisheye lens and V-lambda filters to adapt the camera’s spectral sensitivity to the human eye. After spectral as well as photometric calibration and vignetting correction, the device was tested to perform luminance mapping of real scenes. The results showed that luminance maps of a room can be efficiently assessed under dynamic daylight and mixed day- and electric lighting conditions in a very short time (i.e. 100 ms), when compared to classical HDR imaging techniques. This allows us to calculate glare indexes of a scene simultaneously. The camera opens a variety of new applications as a useful tool for architects, building designers and lighting experts. The device can be used to easily monitor daylight availability and glare indexes in existing buildings and further developments for advanced (day-) lighting control can be envisaged.

A new device for dynamic luminance mapping and glare risk assessment in buildings

In spite of an abundant research on visual comfort models and integrated day- and electric lighting systems, the lighting engineering and research community is restricted to the use of ceiling-mounted luminance sensors, which do not faithfully reproduce the visual comfort sensations of building users in day-to-day practice. Moreover, the discomfort glare indices suggested in the past are evaluated through the luminance mapping of visual scenes generated by the wa y of a laborious High Dynamic Range (HDR) imaging process: this approach cannot be integrated into building automation. On the other hand, mitigation of the electricity demand for lighting by applying ‘easy’ photometric metrics, such as the luminance monitored from the ceiling, leads mostly to non-optimal situations regarding visual comfort and performanc e. In order to overcome these issues, a novel embedded HDR vision sensor fitted with a fisheye lens and capable of performing real-time, accurate and reliable luminance mapping together with an assessment of discomfort glare indices, is suggested. This novel device was successfully validated against the Evalglare software and its robustness on an embedded platform for long-term visual comfort assessments was demonstrated. Preliminary experiments were carried-out with two calibrated HDR vision sensors in order to deepen our knowledge regarding visual comfort in an office room of the LESO solar experimental building located on the EPFL campus in Lausanne (Switzerland). These experimental results are beneficial for the design phase of a sun shading and electric lighting control system that will be shortly evaluated on-site within the same occupied office room.

Validation and preliminary experiments of embedded discomfort glare assessment through a novel hdr vision sensor

A meteorological tower was installed on the EPFL campus in a semi-urban environment for the high frequency monitoring of the micro-climate This project was done in the larger framework of the measurement of the meteorological profiles and also a quantification of the energy consumption and the outdoor human comfort A long-term monitoring of various meteorological variables like wind speed, air temperature, turbulence, humidity is realized by the use of 3D sonic anemometers, surface temperature sensor and a meteorological station so as to analyse the micro-climate in an urban context The preliminary results from the experimental setup confirms that the wind speed is considerably modified in the urban canopy We show that the decrease in the wind speed will have a significant effect on the heat convection coefficient Furthermore, we demonstrate that it is possible to reconstruct the air temperature along the vertical axis with a correction using the data from the meteorological station In the near future, a net radiometer will be installed to analyse the influence of the incoming and outgoing radiation in the urban setup on the energy balance of the district

Laurent Deschamps

Papers

On-site monitoring and subjective comfort assessment of a sun shadings and electric lighting controller based on novel High Dynamic Range vision sensors

Self-commissioning glare-based control system for integrated venetian blind and electric lighting

A new device for dynamic luminance mapping and glare risk assessment in buildings

Validation and preliminary experiments of embedded discomfort glare assessment through a novel hdr vision sensor

Measurement of the impact of buildings on meteorological variables