Indoor Illumination Level Research Articles

A 6-m OOK VLC Link Using CMOS-Compatible p-n Photodiode and Red LED

This letter presents an on – off -keying visible-light-communication (VLC) link realized over 6-m distance. The transmitter is implemented with a commercially available red LED source at 650 nm. While most of the reported high-performance VLC links are using p-insulator-n photodetectors, this receiver employs a simple CMOS-compatible p-n photo-detector. A 150-Mb/s optical wireless transmission is measured with a bit-error rate of $1.3\times 10^{{\mathbf {-6}}}$ , which falls below the forward error correction limit of $3.8\times 10^{{\mathbf {-3}}}$ . The second-order L-C-R equalization is used in both the transmitter and the receiver circuits to achieve maximum bandwidth extension. The VLC link is realized with a low illuminance of 250 lux. This power is below the common indoor illumination levels which enables advanced lighting-compatible VLC applications. The receiver and the source circuits consume around 240 and 105 mW, respectively, which represents to our knowledge a record energy-per-bit level of 2.3 nJ/b.

Joint Dimming Control and Transceiver Design for MIMO-Aided Visible Light Communication

The multiple-input multiple-output (MIMO) concept has been readily invoked in visible light communication (VLC) for increasing data rate. In this letter, we conceive a general solution of dimming control and MIMO transceiver design for VLC, which is capable of minimizing the mean-squared error between the transmitted and received signals, while at the same time, maintaining a specific indoor illumination level. We take into consideration practical optical constraints in the design, including the LED non-linearity and the specific dimming requirements. An efficient solution of our design problem is derived by conceiving a projected gradient algorithm. Our numerical results show that the proposed scheme achieves better bit error rate performance as well as significantly higher convergence speed than its benchmarker conceived in 2015.

Adaptation of Kriging in daylight modeling for energy simulation

Kriging is a group of geo-statistical techniques used to interpolate the value of a random field at an unobserved location from discrete observed values at nearby locations. Kriging has been very popular in oceanic research used for predicting the variance of geographical conditions. However, it has been difficult to find a similar application in the built environment. This paper aims to uncover possibilities of using Kriging for built environment studies, specifically focusing on indoor daylight modeling.Currently, most energy simulation tools use algorithms that are based on Daylight Factor (DF) [1] to capture the complexity of daylight behavior. However, DF has limitations in its ability to fully account for realistic daylight conditions. Thus, efficiently integrating the light domain with thermal calculations remains a major hurdle for building energy simulation tools [2].For this reason, the paper aims to find possibilities of using Kriging for daylight modeling. Kriging will use sample points to predict illuminance values of nearby locations. Kriging will considerably reduce the number of points needed to map indoor light intensity profiles. Furthermore, Kriging will be able to provide a more seamless daylight model for energy simulation tools. This proposed method can produce light distribution, such as illuminance (lux), while obtaining more realistic results than DF and at the same time reduce computational expense through statistical methods.The paper first investigates accuracy to determine whether Kriging modeling can interpolate the profile of illuminance from a select sample of data points. To validate the daylight model used in this paper, real indoor illuminance levels were measured for different days and compared with the daylight simulation model. Further, this paper tests Kriging predictions and compares them with both advanced physics-based light simulation and energy simulation to determine possibilities and limitations of the proposed method.In comparison with RADIANCE, this paper found that the proposed Kriging model was able to predict better than the energy simulation daylight model. The difference between Kriging and RADIANCE was 25.52lux. The Kriging model showed great promise since it was able to cut the full RADIANCE simulation time in half and proved to be much closer to RADIANCE predictions than other methods.

Energy and visual performance of the silica aerogel glazing system in commercial buildings of Hong Kong

To achieve a more comfortable indoor environment while still retaining low energy consumption level is an exciting challenge for designers and owners of buildings. In this paper, a silica-aerogel filled super-insulating glazing system was proposed. A numerical study was conducted to analyze the energy performance and visual performance of the proposed glazing system. Two popular building simulation programs namely EnergyPlus and Radiance were applied in the numerical study. In the study of the energy performance, three control strategies (space temperature control, operative temperature control and PMV control) were applied to simulate the occupant’s control behavior toward the air-conditioning system in reality. The result indicated that compared with conventional single clear glazing, the silica aerogel glazing could retain a 4% longer thermally comfort period, while the energy consumption of HVAC system was reduced by 4–7%. The performance of the silica aerogel glazing was almost equal to that of the state-of-art low-e glazing. It is also concluded that as the occupant’s request on thermal comfort got stricter, the performance of the silica aerogel glazing would became better. In the visual comfort point of view, it can be concluded that the glare effect and near-window bright zone could be reduced significantly while indoor illumination level still met the requirement.

Towards a 100 Gb/s visible light wireless access network.

Potential visible light communication (VLC) data rates at over 10 Gb/s have been recently demonstrated using light emitting diodes (LEDs). The disadvantage is, LEDs have an inherent trade-off between optical efficiency and bandwidth. Consequently, laser diodes (LDs) can be considered as a very promising alternative for better utilization of the visible light spectrum for communication purposes. This work investigates the communication capabilities of off-the-shelf LDs in a number of scenarios with illumination constraints. The results indicate that optical wireless access data rates in the excess of 100 Gb/s are possible at standard indoor illumination levels.

The effect of indoor office environment on the work performance, health and well-being of office workers.

BackgroundThe effect of indoor environment may have an influence on the performance, productivity health and well-being of office workers.MethodsEnvironmental factors such as indoor temperature and illumination have been investigated at three levels. A neurobehavioral test (NBT) has been proposed for the evaluation of office workersc performance. A field lab to emulate an office has been created. In controlled condition of environmental factors, the neurobehavioral test was conducted. The response time and the number of errors in each test have been recorded. A randomized block factorial design was used to analyze the responses of office worker’s performance.ResultsThe results revealed that the independent and interaction effect of temperature and illumination have significant effect on the office workers’ performance. The effect of indoor room temperature has more influences than the effect of illumination. The effect of indoor temperature has 38.56% of contribution on the performance. The optimum levels of indoor temperature at 21°C and illumination at 1000 lux have improved the work performance and health of office workers.ConclusionThe indoor room temperature and illumination are more influence on the performance of the office workers. It may be concluded that the impact of indoor room temperature (38.56%) is more on the office worker’s performance than the effect of illumination (19.91%). Further, it may be concluded that the optimum level of indoor room temperature (21°C) and illumination (1000lux) have improved the work performance, health and productivity of office workers.

High-Speed Bi-directional Optical Wireless System in Non-Directed Line-of-Sight Configuration

We propose and experimentally demonstrate the first bi-directional optical wireless link operating in non-direct line-of-sight (Nd-LOS). The system is based on visible light emitting diode (LED) for downlink and infrared LED for uplink. We achieve around 250 Mbit/s for both downstream and upstream transmission, with the ambient light noise of usual indoor illumination level (500 lx), produced by warm-white LED. 100 Mbit/s are guaranteed inside 12 m $^{2}$ of a common room scenario, without LOS tracking. An optimized discrete multi-tone modulation gives bit-error-ratios always below of the common forward-error-correction threshold of 1.5 ×10 $^{-3}$ . These results indicate that this scheme has great potential for practical VLC system implementation.

Sunlight Penetration through Sloped Window Apertures

Indoor illuminance levels vary frequently during the day due to the presence or absence of direct sunlight, cloudiness and content of atmosphere. In spaces equipped with roof windows these illumination effects of direct sunlight are more remarkable than in more common designed rooms with vertical windows. To study these effects the variable in form of orientation in relation to cardinal points, can be used and obtained different sizes of an area on a working plane directly illuminated by sunlight. This contribution presents a study of the impact and effects of direct sunlight, penetrated trough sloped window apertures on the working plane.

Analysis of Historic Buildings in Terms of their Microclimatic and Thermal Comfort Performances “Example of Konya Slender Minaret Madrasah”

Building envelope plays an important role for a building by protecting and providing the comfort required by the users of the inner building. Fundamental factors to be considered in achieving comfort ability are the indoor air temperature, average surface temperatures, air variation ratio, indoor relative humidity, illumination level and brightness. For historic buildings and those of traditional construction an appropriate balance needs to be achieved between building conservation and measures to improve energy efficiency if lasting damage is to be avoided both to the building’s character and significance and its fabric. In this study, one of the best historic historical building and its envelope, the Konya Slender Minaret Madrasah, was taken into consideration and its microclimatic evaluation was made. The results show that the 13th Century Slender Minaret structure complies with the thermal comfort ability criteria when the energy performance criteria are compared with the comfort ability. Under this context, the structure has been found to be a useful work-piece particularly after conducting the wind flow analysis across the building and the evaluation of the wind and heat flow together with the total surface heat flow and solar heat flow where it became clear that the building provided some insights on how other subsequent structures during the Seljuk era should be constructed in terms of comfort and energy conservation.

Using a fuzzy black-box model to estimate the indoor illuminance in buildings

Indoor lighting conditions and the efficient use of solar energy are becoming increasingly important, both in terms of overall living comfort and energy-efficient buildings. Thus, the methods of achieving adequate indoor lighting conditions, by making use of daylight to save energy, while still maintaining other indoor conditions at an acceptable level, and the corresponding control algorithms, have lately become the subject of considerable attention. For this reason, a fuzzy black-box model of indoor illuminance levels is proposed. The model is able to estimate the indoor illuminance levels as its outputs, by using real external conditions as its inputs. In general, the indoor illuminance is a combination of daylighting and electric lighting. Our study has shown that by using a fuzzy illuminance model, with the solar radiation, the external illuminance, the position of the blinds and the status of the lights as its inputs, an indoor illuminance estimation comparable to the measured data can be obtained. Furthermore, the sufficiently small error measures indicate that the presented modelling approach can be incorporated into larger test environments and used for studies on indoor living comfort, energy conservation, control design or even model-based control. Whenever needed, several fuzzy-illuminance models can be used in parallel in order to obtain the illuminance levels for more than one indoor position.

Field Investigation of the Thermal Performance of a Thai Modern Façade Wall

This paper reports on an investigation of the natural ventilation and heat gain reduction of a new façade design referred to as the Thai modern façade (TMF). Two configurations were considered namely: Thai modern façade wall (TMF) and Thai modern façade wall with fin (TMF-WF). The first (TMF) was composed of two layers which consisted of an inner layer of clear glass and an outer layer consisting of a combination of fibre cement and clear glass slats. The second configuration TMF-WF included an external layer made from aluminium fins and installed at the front of the outer layer. The space between the external fins and the outer layer can be adjusted for protection from direct sun radiation penetration into the room space. There are openings located at the bottom (room side) and the top (ambient side). The size of each opening is 0.084 m2/unit. The surface area of the TMF and TMF-WF is 1.284 m2. Two units of each façade were integrated into the south facing wall of rooms each of volume 17.28 m3.Experimental results showed that the TMF-WF could reduce heat gain by up to 227 W/m2. With the TMF-WF, velocity field measurements indicated that the induced airflow rate was between 0.015–0.04 m3/s and the corresponding air change varied between 3–8 ac/h. The indoor illumination level varied between 340–2000 lx. The room temperature of the TMF-WF was lower than that of the TMF by about 2–3 °C in the afternoon. Such performances are quite significant for natural ventilation since the lowering of indoor temperature reduces air conditioner energy consumption if used for cooling. Therefore the proposed configurations, especially the TMF-WF, should be recommended for residential and commercial buildings as a new design alternative for modern sustainable architecture.

Comparative Performance of Internal Venetian Blind and Roller Blind with Respects to Indoor Illumination Levels

Sun shading device provides an opportunity to control natural lighting, ventilation and solar gain, which provide a benefit to the overall building performance. However, if a sun shading device is not chosen properly, it might not enhance the daylight quality that benefit the building occupants. The study is to assess and compare the impact of different internal shading devices on the light intensity in individual office room. Two types of internal blinds are chosen, i.e. the venetian and the roller types. The result shows that the venetian blind provides better average indoor illumination level compared to the roller blind.

Total energy use in air conditioned buildings: Analysis of main influencing factors

This study is related to a research program intended to develop a very friendly and transparent energy evaluation tool, easy to use by designers, other project partners, and administration (in Belgium). The simulation tool is developed on EES solver. The building envelope model involves a dynamic model composed of resistances and capacities associated to a ventilation model able to assess infiltration/exfiltration air flows through the envelope leakages, as well as natural ventilation air flows combined with fan air flows. An analytical study is presented in this article: it is based on a set of comparative simulations performed on a fictitious office building already used as a test case in other projects of the International Energy Agency. All components of final and primary energy consumption are identified in these simulations in order to obtain a complete breakdown of energy consumptions. Special attention is paid to ventilation (effectiveness, impact on heating/cooling demands, and fan consumption) and to lighting (combination between natural and artificial lighting and corresponding consumption), in relationship with occupants’ comfort requirement, which appears as having a rather strong impact on energy consumption. Various control strategies are considered in order to improve the energy efficiency without affecting the comfort in terms of indoor air quality and illumination level.

An analysis of energy-efficient light fittings and lighting controls

Electric lighting is one of the major energy consuming items in many non-domestic buildings. Using appropriate energy-efficient light fittings with dimming controls and proper daylighting schemes can help reduce the electrical demand and contribute to visual comfort and green building development. This paper presents a study on the energy and lighting performances for energy-efficient fluorescent lamps associated with electronic ballasts and high frequency photoelectric dimming controls installed in a school building. Electricity expenditures and indoor illuminance levels for a workshop and a classroom employing high frequency dimming controls were analyzed. Simple prediction methods were used to illustrate the lighting savings. The findings provide the operational and performance information, which would be applicable to other spaces with similar building layouts and lighting schemes.

Application of high-density daylight for indoor illumination

A fiber optic solar concentrator system with a simple parabolic profile is designed and fabricated to deliver a stream of high-density solar flux into the interior of a building for indoor illumination. The system consists of a small dish concentrator (30 cm in diameter), an optical fiber cable and a diffuser at the end. A series of tests are performed using a goniophotometer and spectrometer to investigate the photometric characteristics of the system in terms of luminous intensity distribution and spectral radiance, which are used in link with the actual photometric measurements for a lightless mock-up space of 4.9 m × 4.9 m × 2.6 m. The illuminance on the working plane was continuously monitored at 25 points by using photometric sensors. Measurements clearly indicate the photometric characteristics of the present system where a constant level of indoor illumination is observed depending on the sky clearness.

An evaluation model for indoor environmental quality (IEQ) acceptance in residential buildings

The indoor environmental quality (IEQ) in residential buildings is examined from the prospect of an occupant's acceptance in four aspects: thermal comfort, indoor air quality, noise level and illumination level. Based on the evaluations by 125 occupants living in 32 typical residential apartments in Hong Kong, this study proposes empirical expressions to approximate the overall IEQ acceptance with respect to four contributors, namely operative temperature, carbon dioxide concentration, equivalent noise level and illumination level, via a multivariate logistic regression model. A range of IEQ acceptances for regular residential conditions is determined and the dependence of the predicted overall IEQ acceptance on the variations of the contributors is discussed. The proposed overall IEQ acceptance can be used as a quantitative assessment criterion for similar residential environments where an occupant's evaluation is expected.

A multivariate-logistic model for acceptance of indoor environmental quality (IEQ) in offices

The indoor environmental quality (IEQ) in offices is examined from the prospect of an occupant's acceptance in four aspects: thermal comfort, indoor air quality, noise level and illumination level. Based on the evaluations made by 293 occupants of the IEQ of offices in Hong Kong, empirical expressions have been proposed to approximate an overall IEQ acceptance of an office environment at certain operative temperature ( T o), carbon dioxide concentration (CO 2), equivalent noise level ( L eq) and illumination level (lux). The overall IEQ acceptance is calculated from a multivariate logistic regression model. A range of acceptance in typical office environmental conditions and its dependence on the four parameters stated above are determined for design conditions. The proposed overall IEQ acceptance can be used as a quantitative assessment criterion for an office environment and similar environment where an occupant's evaluation is expected.

Influence of the light source on the low-irradiance performance of Cu(In,Ga)Se2 solar cells

Illumination intensities in indoor environments are usually given in terms of lux, a unit of measurement which only takes into account the spectral distribution of the light source in the sensitivity range of the human eye (380–780 nm). At a given level of illuminance, however, the performance of a solar cell will strongly depend on the spectral distribution of the incoming light and on its spectral response. This work considers the spectral distribution of some typical light sources encountered in indoor environments (natural daylight/AM 1.5, fluorescent tube, halogen lamp with and without cold reflector, and the common incandescent lamp) and calculates the actual amount of light available to a generic solar cell. We then calculate the performance for different indoor illumination levels and spectra of a Cu(In,Ga)Se2 solar cell especially optimised for low-irradiance conditions. Considering as a reference the performance of the cell under a AM 1.5 spectrum at a given level of illuminance, we can expect the performance of the cell to be reduced by a factor 3 and 2, respectively, when using a fluorescent tube and a halogen lamp with cold reflector as the light source, and to be increased by a factor 2 to 3 if the cell is operated under a halogen/incandescent lamp.

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.

Lighting and energy performance of solar film coating in air-conditioned cellular offices

In subtropical Hong Kong, the principal objectives of fenestration design include eliminating direct sunlight and decreasing cooling loads. To avoid the problems of glare, excessive brightness and thermal discomfort, occupants may block the windows with internal shading devices, resulting in poor daylighting performance and very small amount of electric lighting energy savings. Recently, the advances in thin film coatings for window glass products provide a means of substantially reducing heat gain without proportionally reducing daylight transmittance. It has been suggested that film coatings together with photoelectric lighting control systems could minimise the electric lighting and cooling requirements without causing undue visual and thermal discomfort to the occupants. This paper presents field measurements on solar control film coatings in fully air-conditioned offices in Hong Kong. Solar heat gains, indoor illuminance levels and the electricity consumption by the fluorescent luminaires were systematically recorded and analysed. Measurements were made for two cellular offices, one with solar control film coating on the window glass and the other without. The findings showed that the solar film coating could cut down energy expenditures for air-conditioned buildings, especially for spaces with large glazing areas subject to substantial amount of direct sunlight. Results are presented and the design implications discussed.