Daylight-linked Lighting Controls Research Articles

Linear regression based indoor daylight illuminance estimation with simple measurements for daylight-linked lighting control

Accurate prediction of indoor daylight illuminance is crucial for daylight-based lighting controls. However, determining the illuminance using physics-based simulation tools requires significant amounts of information, e.g. grid of sensors, sky model, 3D geometry of a target building and surroundings, etc. In this study, the authors suggest a daylight illuminance estimation method with minimal data of two reference sensors and two prior measurements. It is shown that the daylight coefficient and sky luminance distribution can be substituted by the illuminance of the reference points and illuminance of two or more target points at past times. The method was validated on a large open space with north-facing skylight windows and showed an 11.9% mean absolute percentage error. Additionally, a reference point selection method is presented. The proposed method is practical for daylight-based lighting control applications.

An Analysis of Real-Time Measured Solar Radiation and Daylight and Its Energy Implications for Semi-Transparent Building-Integrated Photovoltaic Façades

For analyzing cooling loads, day-lighting, and building-integrated photovoltaic (BIPV) systems, solar radiation and daylight illuminance data are required. However, these data are sparse. Furthermore, studies have shown that the energy potential of building-integrated photovoltaic (BIPV) systems for the entire building skin (BS) and unconventional orientations, such as east, west, and north need further exploration. Thus, this study presents findings from measured solar data and an energy analysis of semi-transparent BIPV. Firstly, solar radiation and daylight data measured from June 2019 to May 2020 in Hong Kong are presented. The analyzed solar-radiation data were used to determine the solar-energy potential of BIPV for BS and the four principal building orientations (i.e., N, E, S and W). With a simple analytical approach, the solar data’s building-energy implications for semi-transparent BIPV were assessed. The findings showed that the annual average horizontal global-, diffuse-, and direct-irradiance values were 291.8, 164.3, and 127.5 W/m2/day, respectively. Similarly, 120, 72, and 107 klux were obtained as the peak global, diffuse, and direct illuminance, respectively. Furthermore, the results show the potential of using BIPV on the entire BS in Hong Kong. It was also observed that a semi-transparent BIPV façade integrated with daylight-linked lighting controls could offer significant energy savings in electric lighting and cooling while also producing energy. In particular, BIPV façades with a large window-to-wall ratio (WWR) of 80% can provide an overall energy benefit of up to 7126 kWh.

Performance risks of lighting retrofit in Energy Performance Contracting projects

In Energy Performance Contracting (EPC) projects, Energy Service Companies (ESCOs) often provide guarantees on the energy savings of proposed retrofit measures based on a simplified engineering method. In order to assess the risk of saving shortfalls, there is a need to develop an evaluation method based on the probabilistic approach. This study focuses on a proposed probabilistic approach to evaluate the performance risks of common lighting retrofit measures such as replacement of existing lighting, installation of daylight-linked lighting controls and occupancy-based controls. The proposed approach considers the variations in the influential factors affecting energy performance, including daylight availability, occupancy rates, lamp conditions and lighting use patterns. Empirical data is used to develop the probability distribution functions of those influential factors. A hypothetical 40-storey office building with typical design features (such as regularly shaped open plan) in Hong Kong was modeled using EnergyPlus to demonstrate the application of this probabilistic approach. The results indicate that the variations in actual energy savings can be substantial in lighting retrofit projects, ranging from 1,267,000 kWh (43% of pre-retrofit consumption) to 1,927,000 kWh (65% ditto) with 90% statistical significance, posing risk on the achievement of guarantee savings in an EPC project setting.

Study of daylight data and lighting energy savings for atrium corridors with lighting dimming controls

Daylighting has been recognized as an essential element in architecture for enhancing visual comfort, energy-efficiency and green building developments. An appropriate lighting control linked with daylight can save electric lighting energy consumption and reduce peak electrical demands. In well day-lit spaces such as atria, daylight-linked lighting controls can provide substantial energy reductions. This study presents the visual performance and electric lighting energy use for an atrium building using high frequency dimming controls. The general features and characteristics of the results including electric energy expenditures and daylight illuminance were reported. Simple prediction approaches were used to demonstrate the lighting savings. The findings revealed that the dimming controls could be applicable to places with similar architectural layouts and lighting schemes.

Analysis and prediction of daylighting and energy performance in atrium spaces using daylight-linked lighting controls

In subtropical Hong Kong, a certain amount of electricity is used to create visually comfortable interior spaces through electric lighting, which is the second major electricity-consuming item in commercial buildings, accounting for 20–30% of total electricity use. The burning of fossil fuels for electricity generation has many adverse effects on the environment. Daylighting is an important and useful strategy for enhancing visual comfort and reducing the need for the electricity consumed by light fittings. The rational use of daylight through tools such as photoelectric lighting controls can effectively reduce buildings’ electricity consumption and the related pollutants and greenhouse gas emissions. Daylighting design techniques are often best demonstrated via field measurements that provide reliable operational and energy performance data for establishing design guidelines. An atrium provides an environmentally controlled indoor public space that introduces daylight into the hearts of large buildings. In circulation areas such as corridors, people expect the way ahead to be sufficiently lit and daylight-linked lighting controls can deliver excellent energy savings. This paper presents the daylighting and energy performance of an atrium space using daylight-linked lighting controls. The cost, energy and environmental issues related to various daylight illuminances are estimated and design implications are discussed.

Economic analysis of the daylight-linked lighting control system in office buildings

The objective of this study is to perform an economic analysis of the daylight-linked automatic on/off lighting control system installed for the purpose of energy savings in office buildings. For this, a building was chosen as a typical example, and the energy cost was calculated by using the daylight and building energy analysis simulation. When the lighting control was utilized, an economic analysis was performed using a payback period that was calculated by comparing the initial cost of installing the lighting control system with the annual energy cost which was reduced thanks to the application of the lighting control. The results showed that the lighting energy consumption, when the lighting control was applied, was reduced by an average of 30.5% compared with the case that there was not lighting control applied. Also, the result for total energy consumption showed that, when lighting control was applied, this was reduced by 8.5% when the glazing ratio was 100%, 8.2% for 80%, and 7.6% for 60% when compared to non-application. The payback period was analyzed in terms of the number of floors in a building; 10 floors, 20 floors, 30 floors, and 40 floors. Hence, the building with 40 floors and glazing ratio 100% resulted in the shortest payback period of 8.8 years, the building with 10 floors and glazing ratio 60% resulted in the longest period of 12.7 years. In other words, the larger the glazing ratio and the number of building floors are, the shorter the payback period is.

A review of daylight illuminance determinations and energy implications

Daylighting is recognized as an important element in architecture and a useful strategy in energy-efficient building designs. Daylight gives a sense of cheeriness and brightness that can have a significant positive impact on the people. There is a scope for integrating daylight with electric light to reduce building energy use. The amount of daylight entering a building is mainly through window openings, which create in the indoor environment a more attractive and pleasing atmosphere, in addition to maximise visual access to the pleasant views of the outside world. Determinations of the exterior and interior daylight and lighting energy savings are key issues to demonstrate the benefits based on daylighting designs. This paper provides a review of daylight illuminance determinations and the lighting energy reductions due to daylighting schemes. The study includes daylight measurements, prediction of daylight illuminance under various sky conditions and potential electric lighting energy savings from daylight-linked lighting controls. The article aims at providing building professionals, practitioners and researchers more information and a better understanding of daylight for promoting effective daylighting designs and evaluations.

Energy and cost studies of semi-transparent photovoltaic skylight

Sustainability is the trend of the modern building designs, in which solar energy conversion systems and daylighting schemes are widely considered as the important building energy strategies to reduce the peak cooling and electrical demands, generate clean energy and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a renewable energy product producing electricity via solar cells and allowing natural light entering into the interior spaces for daylighting designs. The PV modules are effective in reducing the cooling demand, especially for the skylight atrium that often receives large solar heat gains. This paper studies the thermal and visual properties, energy performance, environmental and financial issues of such semi-transparent PV skylights. Field measurements including solar irradiance, daylight illuminance and electricity generated were carried out. Case studies based on a circulating atrium were conducted to evaluate the energy use, cooling requirements and monetary implications when the PV skylights together with the daylight-linked lighting controls were applied. The results indicated that such an integrated system could save the overall electricity expenditures and benefit to the environmental and financial aspects.

Energy and cost analysis of semi-transparent photovoltaic in office buildings

Solar energy conversion systems and daylighting schemes are important building energy strategies to produce clean energy, reduce the peak electrical and cooling demands and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a building component generating electricity via PV modules and allowing daylight entering into the interior spaces to facilitate daylighting designs. This paper studies the thermal and visual properties, energy performance and financial issue of such solar facades. Data measurements including solar irradiance, daylight illuminance and output power for a semi-transparent PV panel were undertaken. Using the recorded results, essential parameters pertaining to the power generation, thermal and optical characteristics of the PV system were determined. Case studies based on a generic reference office building were conducted to elaborate the energy and cooling requirements, and the cost implications when the PV facades together with the daylight-linked lighting controls were being used. The findings showed that such an integrated system could produce electricity and cut down electric lighting and cooling energy requirements to benefit the environmental, energy and economic aspects.

Lighting and cooling energy consumption in an open-plan office using solar film coating

Abstract In subtropical Hong Kong, solar heat gain via glazing contributes to a significant proportion of the building envelope cooling load. The principal fenestration design includes eliminating direct sunlight and reducing cooling requirements. Daylighting is an effective approach to allow a flexible building facade design strategy, and to enhance an energy-efficient and green building development. This paper studies the lighting and cooling energy performances for a fully air-conditioned open-plan office when solar control films together with daylight-linked lighting controls are being used. Measurements were undertaken at two stages including the electricity expenditures for the office using photoelectric dimming controls only (first stage) and together with the solar control film coatings on the windows (second stage). Electric lighting and cooling energy consumption, transmitted daylight illuminance and solar radiation were systematically recorded and analysed. The measured data were also used for conducting and validating the building energy simulations. The findings showed that the solar film coatings coupled with lighting dimming controls cut down 21.2% electric lighting and 6.9% cooling energy consumption for the open-plan office.

An analysis of daylighting performance for office buildings in Hong Kong

Daylighting has often been recognized as a useful source of energy savings and visual comforts in buildings. Occupants expect good daylight in their working spaces. The quality and quantity of natural light entering a building depend on both internal and external factors. In Hong Kong, commercial building accounts for the major building energy use and electric lighting is one of the major electricity-consuming items. This paper studies the daylighting performance and energy implications for office buildings. A total of 35 commercial buildings have been selected in the survey. Key building parameters affecting daylighting designs are presented. Two typical office blocks were further analysed based on a lighting simulation program. The daylighting performance was evaluated in terms of daylight factor, room depth and glare index. It has been found that the daylighting performance for office buildings is quite effective. About one-third of the office areas that are near the perimeter regions have an average daylight factor of 5%. For inner region of deep plan offices, some innovative daylighting systems such as light redirecting panels and light pipe could be used to improve the daylighting performance. In general, the office building envelop designs are conducive to effective daylighting and proper daylight linked lighting controls could save over 25% of the total electric lighting use.

Occupant preferences and satisfaction with the luminous environment and control systems in daylit offices: a literature review

This paper presents an overview of peer-reviewed investigations of subjective issues linked to the use of daylighting in office buildings, particularly studies of preferred physical and luminous conditions in daylit office environments, and studies of occupant satisfaction and acceptance of electric lighting and window shading controls. The literature shows a consistent strong preference for daylight and a wide distribution between individuals in relation to the preferred illuminance levels in daylit offices. Existing knowledge about how people respond to daylight-linked lighting and shading controls in the workplace is very limited; therefore, this paper presents a summary of knowledge gaps in the field of daylighting and its interaction with the occupants. The resulting key directions for future research highlight issues for which a better understanding is required for the development of lighting and window shading control systems that are both energy efficient and suitable for the office occupants.

Total Energy Performance of Atria with Daylight

The current design trend for commercial buildings in Hong Kong is to introduce shopping arcade at the lower floors and provide atrium with daylight. If daylight is properly utilised, the electrical lighting energy can be saved. On the other hand, introduction of atrium will allow the entrance of solar heat which will introduce extra cooling load to the air-conditioning systems. What would be the overall energy performance of a daylighted atrium? Could the saving on electrical lighting power compensate the additional energy expenditure on cooling due to the introduction of atrium? This paper presents a study carried out for three different types of atria in Hong Kong. Energy performance of atria with assumed daylightlinked lighting control is analysed using Computer simulation programs Ecotect and HTB2. The field-measurement of average daylight factor was conducted in real atrium site to validate the simulation results. Different design alternatives on lighting strategies, fenestration glazing types, as we...

Lighting and energy performance for an office using high frequency dimming controls

Artificial lighting is one of the major electricity consuming items in many non-domestic buildings. Recently, there has been an increasing interest in incorporating daylight in architectural and building designs to reduce the electricity use and enhance greener building developments. This paper presents field measurements for a fully air conditioned open plan office using a photoelectric dimming system. Electric lighting load, indoor illuminance levels and daylight availability were systematically measured and analyzed. The general features and characteristics of the results such as electric lighting energy savings and transmitted daylight illuminance in the forms of frequency distributions and cumulative frequency distributions are presented. Daylighting theories and regression models have been developed and discussed. It has been found that energy savings in electric lighting were over 30% using the high frequency dimming controls. The results from the study would be useful and applicable to other office spaces with similar architectural layouts and daylight linked lighting control systems.

An analysis of lighting energy savings and switching frequency for a daylit corridor under various indoor design illuminance levels

Visual comfort and electric lighting energy issues are essential criteria to justify daylighting schemes. The evaluation of energy efficiency due to daylight linked lighting control systems is best demonstrated by case studies. This paper presents field measurements on daylighting for a fully air-conditioned daylit corridor. Artificial lighting load, brightness of the fluorescent luminaires, daylight availability for various switching illuminance levels were systematically recorded and analyzed. The general features and characteristics of the findings including the number of switching operations and electric-lighting energy savings are presented and discussed. Daylighting theories, using cumulative frequency distribution of outdoor illuminance and regression models based on brightness of light output, outdoor illuminance and electric light power to estimate daylight-linked lighting control savings, have been developed and assessed. It has been found that data from both approaches show reasonably good agreements with measured results. The findings from this study provide some operational and energy information, which would be useful and applicable to other interior spaces with similar architectural designs.

Energy performance of daylight-linked automatic lighting control systems in large atrium spaces: report on two field-monitored case studies

This paper presents the field-measured energy performance of two common types of daylight-linked lighting control systems, continuous dimming and automatic on/off installed in two existing large atrium spaces located in Canada. The daylighting performance was evaluated based on the daylight contribution to the indoor illuminance and the amount of electrical lighting displaced by daylighting via the daylight-linked lighting control systems. Measured daylighting contribution to the space indicates that significant lighting energy savings can be achieved in atrium spaces if the daylight-linked lighting control system is appropriately selected, installed and commissioned throughout its existence. Results extrapolated from measurements collected during summer and winter indicate that as installed, the continuous dimming lighting control system provides 46% annual savings in electrical lighting consumption, while the automatic on/off saves between 11and 17% in lighting energy. These savings account for 68% of the lighting energy consumed during main occupancy for the continuous dimming system, and 31.5% for the automatic on/off. Operation irregularities such as a reduced dimming linearity and an incorrect adjustment of the phases of the dimming control system, as well as the inadequate location of the photocell controlling the automatic on/off lighting system, the improper maintenance of the skylight during winter and the oversizing of the lighting system reduced the energy efficiency of the lighting control systems by 30–65%.

An investigation of daylighting performance and energy saving in a daylit corridor

Daylighting has often been recognised as a useful source of energy savings in buildings. For daylit spaces, daylight-linked automatic lighting control can give excellent energy savings. The evaluation of energy efficiency due to daylighting is best demonstrated by case studies. This paper presents field measurements on daylighting for a fully air-conditioned daylit corridor. Electric lighting load, brightness of the fluorescent luminaires, daylight illuminance levels and the room parameters affecting daylighting designs were recorded and analysed. Traditional daylighting theories have been applied to illustrate how well daylighting measures can perform in reality. It has been found that energy savings in electric lighting was about 70% using dimming control system. The results from this study provide some operational and energy performance data, which would be useful and applicable to other interior spaces with similar architectural designs.

Predicting lighting energy use under daylight linked lighting controls

For daylight to make a real contribution to energy efficiency, appropriate control of electric lighting is essential. This paper outlines methods to predict electric lighting use for various different types of control, given internal daylight illuminances. Two different kinds of calculation are considered. Annual lighting use can be determined from yearly daylight data, usually in the form of a cumulative distribution. More sophisticated computer programs use hourly daylight data to give a continuous profile of lighting use and the consequent energy flows and environmental conditions within a building. For both types of application, appropriate algorithms are given to quantify the savings from various types of photoelectric and manual controls. Pour que la lumière du jour apporte une réelle contribution au rendement énergétique, il est essentiel de bien contrôler l'éclairage électrique. Cet article décrit brièvement les méthodes qui permettent de prévoir l'éclairage électrique utilisé en fonction de différents types de contrôle, compte tenu de l'éclairement assuré par la lumière du jour intérieure. Deux types différents de calcul sont pris en considération. L'utilisation annuelle de l'éclairage peut être déterminee à partir des données annuelles relatives à la lumière du jour, généralement sous la forme d'une distribution cumulative. Des programmes informatiques plus complexes utilisent des données horaires sur la lumière du jour pour obtenir un profil continu de l'utilisation de l'éclairage ainsi que les flux d'énergie correspondants et les conditions d'environnement d'un bâtiment. Les auteurs donnent pour deux types d'application des algorithmes appropriés qui permettent de quantifier les économies correspondant à divers types de commandes photoélectriques et manuelles.