Switchable Windows - Spectral Transmission and Switching Times

The switching time and spectral transmission in fully clear and fully opaque states of polymer dispersed liquid crystals (PDLC), suspended particle device (SPD) and electrochromic (EC) switchable windows were evaluated to assess their suitability to control solar heat transmission though glazed façade and comfort to building occupants. The transmission measurement on a SPD film showed a very effective absorption modulation in the visible range but fast decrease in the near infrared region. The switching speed was demonstrated to be related strongly to wavelengths. A SPD film with a larger absorption and faster switching speed in the infrared region was shown to be preferable to control solar heat transfer through glazings and thermal comfort. The PDLC window did not modulate transmission but rather modulated scattering. In the opaque state, the PDLC window was highly scattering resulting in spectral transmission varying at short distances from the window while being constant in the far field. The switching speed measurement demonstrated that liquid-based switchable windows can respond as fast as the eye to have the potential to control spontaneous glare. The EC window demonstrated a lower absorbance efficiency than the SPD in the visible range but appeared to have a much higher efficiency in the infrared region measured. EC windows are characterized by their slow switching speed when compared to SPD and PDLC. This makes them unsuitable for spontaneous glare control and are more suited to predictive solar heat gain control over a defined time horizon. With the increasing integration of adaptive technologies into building facades and to predict the energetical and ambient performance of such buildings and the impact on the occupants’ comfort, this paper emphasises on the importance to provide spectral performance information of switchable windows

A Computational Approach to Evaluating Curricular Alignment to the United Nations Sustainable Development Goals

The United Nations (UN) considers universities to be key actors in the pursuit of the Sustainable Development Goals (SDGs). Yet, efforts to evaluate the embeddedness of the SDGs in university curricula tend to rely on manual analyses of curriculum documents for keywords contained in sustainability lexica, with little consideration for the diverse contexts of such keywords. The efficacy of these efforts, relying on expert co-elicitation in both subject-matter contexts and sustainability, suffers from drawbacks associated with keyword searches, such as limited coverage of key concepts, difficulty in extracting intended meaning and potential for greenwashing through “keyword stuffing.” This paper presents a computational technique, derived from natural language processing (NLP), which develops a sustainability lexicon of root keywords (RKs) of relative importance by adapting the Term Frequency–Inverse Document Frequency (TF-IDF) method to a corpus of sustainability documents. Identifying these RKs in module/course descriptors offers a basis for evaluating the embeddedness of sustainability in 5,773 modules in a university\u27s curricula using classification criteria provided by the Association for the Enhancement of Sustainability in Higher Education\u27s (AASHE). Applying this technique, our analysis of these descriptors found 286 modules (5%) to be “sustainability focused” and a further 769 modules (13%) to be “sustainability inclusive,” which appear to address SDGs 1, 17, 3, 7, and 15. Whilst this technique does not exploit machine learning methods applied to large amounts of trained data, it is, nevertheless, systemic and evolutive. It, therefore, offers an appropriate trade-off, which faculty with limited analytics skills can apply. By supplementing existing approaches to evaluating sustainability in the curriculum, the developed technique offers a contribution to benchmarking curricular alignment to the SDGs, facilitating faculty to pursue meaningful curricular enhancement, whilst complying with sustainability reporting requirements. The technique is useful for first-pass analyses of any university curriculum portfolio. Further testing and validation offer an avenue for future design-science research

Comparison of control parameters for roller blinds

Roller blinds can reduce the heating and cooling building energy consumption required to maintain thermal comfort. The effectiveness of roller blinds is influenced by the strategies and input parameters for their control. This study is the first to identify the most effective of seven alternative control parameters to control roller blinds. It further defines the benefits from using paired control parameters to maximise energy savings and optimise occupants’ comfort. For the particular case studies and conditions examined, it is concluded that operating roller blinds using indoor air temperature as a single control parameter with rule-based controller provided, 16 %, 19 % and 45 % in heating, cooling and lighting energy savings in Dublin, Berlin and Madrid respectively compared to a window without roller blinds, with an average 51 % daylight discomfort reduction. Using both internal temperature and outdoor ambient temperature to control the roller blinds had little effect on energy need, with only a further 0.6 %, 0.5 % and 0.3 % energy savings and an average of 2 % reduction in daylight discomfort achieved compared to using solely indoor temperature as the control parameter

Deployment and control of adaptive building facades for energy generation, thermal insulation, ventilation and daylighting: A review

A major objective in the design and operation of buildings is to maintain occupant comfort without incurring significant energy use. Particularly in narrower-plan buildings, the thermophysical properties and behaviour of their façades are often an important determinant of internal conditions. Building facades have been, and are being, developed to adapt their heat and mass transfer characteristics to changes in weather conditions, number of occupants and occupant’s requirements and preferences. Both the wall and window elements of a facade can be engineered to (i) harness solar energy for photovoltaic electricity generation, heating, inducing ventilation and daylighting (ii) provide varying levels of thermal insulation and (iii) store energy. As an adaptive façade may need to provide each attribute to differing extents at particular times, achieving their optimal performance requires effective control. This paper reviews key aspects of current and emerging adaptive façade technologies. These include (i) mechanisms and technologies used to regulate heat and mass transfer flows, daylight, electricity and heat generation (ii) effectiveness and responsiveness of adaptive façades, (iii) appropriate control algorithms for adaptive facades and (iv) sensor information required for façade adaptations to maintain desired occupants’ comfort levels while minimising the energy use

Optimal temperature-actuated control of a thermally-insulated roller blind

By altering the thermal equilibria between internal and ambient environments, dynamic insulation can minimize heating and cooling building energy requirements. The performance of a thermally-insulated roller blind was evaluated both experimentally and via simulation studies. The variation of blind position was optimized to minimize building energy consumption, maintain thermal comfort, and minimize daylight discomfort for a particular system, location and conditions. The roller blind was adjusted between four positions, from fully-open to fully-closed, optimal indoor temperature switching thresholds found for moving to these blind positions were 15 °C, 18.4 °C, 19.4 °C and 21.4 °C, respectively. Using these resulted in a 15.3% energy savings and a 7% reduction in occupancy daylight discomfort compared with no blind

A Review of Control Methodologies for Dynamic Glazing

With adaptive building façade technologies, a building envelope can provide a comfortable indoor environment under varying external conditions with minimal additional heating or cooling. The control strategy applied to the adaptation of the façade is a key determining factor in the successful integration of these technologies into a building. The building envelope plays a key role in regulating light, heat and mass transfer from the outdoor environment to the indoor. Dynamic glazing can be used to adjust the amount of solar radiation entering a building. The control strategies that ultimately determine the success of these switchable technologies to affect a building’s energy performance and occupant comfort are reviewed in this paper

Comparative Simulations of an Electrochromic Glazing and a Roller Blind as Controlled by Seven Different Algorithms

The use of roller blind as a surrogate for a switchable glazing in a dynamic building environmental simulation is investigated. Seven different control algorithms were applied to simulations of both operations of the blind and of the switchable glazing. The configurations compared were an electrochromic glazing and a roller blind, the controllers used were rule-based, proportional-integral-derivative (PID), anti-windup PID (a PID) and a model predictive controller (MPC). Particular case studies were examined in the weather conditions of Dublin, Ireland to make comparisons of simulated energy savings and occupancy daylight comfort from the use of electrochromic glazing or a roller blind with those for a double-glazed window. The results suggest that previous studies that simulated electrochromic window as an integrated roller blind in a heating-dominated climate would have overestimated building energy loads, and depending on the controller used, overestimated occupancy daylight comfort

An evaluation of a computational technique for measuring the embeddedness of sustainability in the curriculum aligned to AASHE-STARS and the United Nations Sustainable Development Goals

Introduction: SDG 4.7 mandates university contributions to the United Nations (UN) Sustainable Development Goals (SDGs) through their education provisions. Hence, universities increasingly assess their curricular alignment to the SDGs. A common approach to the assessment is to identify keywords associated with specific SDGs and to analyze for their presence in the curriculum. An inherent challenge is associating the identified keywords as used in the diverse set of curricular contexts to relevant sustainability indicators; hence, the urgent need for more systematic assessment as SDG implementation passes its mid-cycle. Method: In this study, a more nuanced technique was evaluated with notable capabilities for: (i) computing the importance of keywords based on the term frequency-inverse document frequency (TF-IDF) method; (ii) extending this computation to the importance of courses to each SDG and; (iii) correlating such importance to a statistical categorization based on the Association for the Advancement of Sustainability in Higher Education (AASHE) criteria. Application of the technique to analyze 5,773 modules in a university’s curriculum portfolio facilitated categorization of the modules/courses to be “sustainability-focused” or “sustainability-inclusive.” With the strategic objective of systematically assessing the sustainability content of taught curricula, it is critical to evaluate the precision and accuracy of the computed results, in order to attribute text with the appropriate SDGs and level of sustainability embeddedness. This paper evaluates this technique, comparing its results against a manual and labor-intensive interpretation of expert informed assessment of sustainability embeddedness on a random sample of 306 modules/courses. Results and discussion: Except for SDGs 1 and 17, the technique exhibited a reasonable degree of accuracy in predicting module/course alignment to SDGs and in categorizing them using AASHE criteria. Whilst limited to curricular contexts from a single university, this study indicates that the technique can support curricular transformation by stimulating enhancement and reframing of module/course contexts through the lens of the SDG