Lighting Control Systems for Energy Saving and User Acceptance: State-of-the-art and future directions

Lighting accounts for one-fifth of global electricity use. In Sweden, energy demand for lighting corresponds to 20% of the total electricity use in office buildings. Lighting retrofit measures are considered to be among the most cost-efficient way to reduce energy use in buildings. In particular, the use of advanced lighting control systems promises energy savings of between 2 and 60%, but system failures and poor user acceptance have been significant limitations so far. This thesis uses literature reviews and field studies to investigate the effect of lighting control systems on energy use and user acceptance. In the first part of the thesis, an extensive literature review on lighting control systems indicates that manually controlled systems are generally more accepted by the users. Systems with high automation and no manual override tend to be deactivated or even sabotaged. Consequently, user behavior plays a fundamental role in ensuring proper function and actual energy savings of the lighting control system. The review also showed that presence and absence detection are often combined under the overarching category ‘occupancy strategies’, although they yield very different energy savings. The review of daylight harvesting systems highlighted critical issues relating to design and commissioning. Two field studies in individual offices were conducted. Absence and presence detection, daylight harvesting and a simple task light were tested in a real-life work environment, where energy use and user acceptance were monitored. The studies showed that the definition ‘occupancy strategies’ is not completely appropriate, since ‘absence’ and ‘presence’ detection yield different energy savings and user acceptance. The second field study showed that daylight harvesting systems could perform well, on condition that careful design and commissioning are performed along with provision of a manual override. However, the field study showed that the use of sensors and microcontrollers raised the energy demand for parasitic power (standby), which might be significant in relation to final energy use, especially with low occupancy rates and high-efficiency light sources. Lighting control systems based on wireless networks and integrated in the building management system are expected to increase during the coming years. This will overcome many of the current issues with advanced lighting control systems, but it will also require additional skills on the part of the designer and installer. In the meantime, occupancy strategies represent a good alternative in energy-efficient lighting retrofit

Evaluating the Potential of Annual Solar Heat Gains from Manually Operated Shading System

Occupant behavior towards manual solar shading systems affects the energy performance of buildings. Behavior depends on several aspects which interact in a nontrivial way. This paper presents a simple prediction model of behavior based on self-reported use of manual shading and a user survey. The specific model is applicable to the case study building, which is an office building in Gothenburg, Sweden, but the approach can be extended to other buildings. The model was tested against a hypothetical automated solar shading system for the same building. The results show that cooling loads increased by at least 25 % with the manual model in respect to the automatic system due to fewer blind movements. The results show that not accounting for occupant behaviour leads to a significative performance gap between predicted and actual building energy use

Identifying Potential Indicators of Neighbourhood Solar Access in Urban Planning

Solar access describes the capacity of urban spaces to receive sunlight and daylight. Rapid urbanization and unbridled densification pose a threat to sustainable solar access, reducing the penetration of sunlight and daylight into cities. To effectively assess solar access at such an early design stage, at the urban planning level, it is critical that evaluation metrics are simple and reliable. This paper examines a cross section of solar metrics, from simple to more complex ones, to find potential solar performance indicators for urban planning evaluations. The metric datasets were created based on iterations of homogeneous neighbourhood designs, based on the three commonest typologies in the Swedish context: courtyard, slab, and tower. The results were validated using case studies sampled from districts of Malmö. The findings indicate that simple geometrical and latitudinal metrics may be suitable for assessing the solar access of urban designs due to high correlation with built density. Potential performance indicators aimed at indoor and outdoor evaluation of daylighting (VSC, SVF) and sunlighting (ASH_F, RD_G) in urban planning stages were suggested. Possible methods of applying the provided metric database into assessments were proposed. Future work should find evidence-based thresholds for the metric values to establish performance benchmarks

Low-cost smart solutions for daylight and electric lighting integration in historical buildings

Research have shown that the correct integration of daylight and electric lighting reduces the energy use in buildings, while improving visual comfort. Smart shading systems, especially those electrically controlled, play an important role to control solar radiation. Similarly, smart and dimmable/tunable lighting can help to adjust the artificial light to the real users' needs. This paper presents preliminary results of an ongoing living lab study investigating how artificial lighting systems can be integrated with shading systems, placing human comfort at the heart of the study and yet saving energy. A manually controlled, commercial and low-cost smart system integrating two motorized shading devices and six dimmable LED luminaires with a different selection of CCT were installed in a private office in a historical building. Indoor and outdoor lighting conditions and energy consumption associated to the lighting system are constantly monitored to assess how the people use shading and lighting upon varying the boundary conditions.. Preliminary results highlight that users prefer to maximise daylight on the work plane as well as they generally use both shading and electric lighting systems in response to boundary conditions that cause serious discomfort

Selection of Weather Files and Their Importance for Building Performance Simulations in the Light of Climate Change and Urban Heat Islands

Building performance predictions and their reliability rely heavily on weather data inputs. Climate is affected by spatial and temporal differences related to climate change and urban heat island effects, but the weather files used in building performance simulations (BPS) often remain unchanged and may represent weather observations generated from inadequate space and time for their application. This study investigated Swedish weather data using statistical methods and analysed i) the local differences related to rural and urban microclimates and ii) the country-wide differences linked to climate change; by comparing recent observation data to the respective EnergyPlus Weather (EPW) files. The findings reveal that there are significant differences between rural and urban temperature means, and that outdated model years of weather data files make them unsuitable for BPS. The impact of using an inadequate weather file based on changes in recent climate in Sweden can lead to an overestimation of heating demand by 6.5 % on average, while the impact is higher for warmer climates-up to 12 %. The combined impact including climate change and urban heat island effects can lead to a heating energy overestimation by 12 % to 19 %, based on the Stockholm example. On the other hand, it was found that although the global radiation means saw a slightly increasing trend, its impact on the BPS remains inconclusive. The study highlights the importance of selection of adequate weather data for BPS keeping in mind the spatial and temporal influencing factors

Methodology and parameters to analyse daylighting and energy use in dense cities: A literature review

Low energy buildings are key to reduce global energy use. However, achieving low energy use and good daylight levels simultaneously in dense cities is challenging. This article reviews relevant studies dealing with energy use and daylighting in dense residential urban blocks located in Nordic climates. The literature review combines a systematic and a ‘snowball’ search approach. Findings indicate that previous research relies heavily on parametric design as a tool. Few density metrics were found particularly relevant to describe the interplay between density, daylight, and energy use.However, the limited body of research achieved so far in the Nordic climate makes it difficult to draw a clear conclusion, suggesting that additional research is required

Integrated Solutions for Daylighting and Electric Lighting: IEA SHC Task 61/EBC Annex 77, Subtask D – Proposal and First Results

The integration of daylight and electric lighting, considering user satisfaction and energy savings potentially can contribute significantly to reduce energy demand for lighting, that represents 18% of global energy demands. This paper presents the work and first results of IEA SHC Task 61/EBC Annex 77 “Integrated Solutions for Daylighting and Electric Lighting: From component to user centered system efficiency”, a joint project activity between the Solar Heating and Cooling (SHC) and Energy in Buildings and Communities (EBC). The project deals with the idea that an integrated design approach for the whole system, combining daylighting, electric lighting, the associated lighting controls and the users’ interaction, can achieve higher energy saving than the simple energy-efficient design of single components. First results show the main experience from three completed case studies

Social interaction in local public squares after dark

This paper explores social interaction in local public squares under different lighting conditions. At its best public squares are social spaces that engender a sense of belonging, increase the quality of life and wellbeing of individuals. It is proposed that outdoor lighting would be essential to the use of the public realm after dark, but empirical results regarding lighting conditions and social aspects of life in public squares are limited. Based on a socio-physical conceptual model of the transactional relationship of the user, the lit environment andthe behavioural outcome, this study investigated active social interaction in daylight compared to after dark. A field study was conducted in two local public squares in Malmö, Sweden. The occurrences of which visitors were being alone, in pairs, or in groups of three or more (N=2522), and verbal or non-verbal interaction amongst those in company of another person were recorded.The lit appearance of the two squares after dark, was assessed with HDR-photography and photometric measurements; portraying dissimilar spatial, spectral and intensity characteristics.The results of social interaction show dissimilar patterns of the two squares; an increase in social interaction in EL after dark was observed in one of the squares, while a decrease in the afternoon and no significant difference was displayed in the evening after dark in the other square. It is suggested that lighting may sustain patterns of social interaction after dark, however it might be, that the company of another is especially important after dark

Energy use of buildings in relation to occupancy rates

This paper presents basic data of the energy demand for district heating and plug loads logged by a building management system of an energy-efficient academic building located in Lund, Sweden. The data refers to the years 2019 and 2020 when occupancy varied significantly due to the Corona pandemic. The data shows that the building energy demand adapts poorly to fluctuating occupancy rates. With a possible increase of smart working in the future, building codes should account for more fluctuating occupancy rates in the modelling of the energy demand of buildings

Future possibilities of green walls in a medium sized Hungarian town: A case study of Kecskemét

Reflector edges, sharp acceptance angles and by-pass diodes introduce large variations in the electrical performance of asymmetrical concentrating photovoltaic/thermal modules over a short incidence angle interval. It is therefore important to quantify these impacts precisely. The impact on the electrical performance of the optical properties of an asymmet-rical photovoltaic/thermal CPC-collector was measured in Maputo, Mozambique. The measurements were carried out with the focus on attaining a high resolution incidence angle modifier in both the longitudinal and transversal directions, since large variations were expected over small angle intervals. A detailed analysis of the contribution of the diffuse radiation to the total output was also carried out. The solar cells have an electrical efficiency of 18% while the maxi-mum measured electrical efficiency of the collector was 13.9 % per active glazed area and 20.9 % per active cell area, at 25 °C. Such data make it possible to quantify not only the electrical performance for different climatic and operating conditions but also to determine potential improvements to the collector design. The electrical output can be increased by a number of different measures, e.g. removing the outermost cells, turning the edge cells 90°, dividing each receiver side into three or four parts and directing the tracking, when used, along a north-south axis