• Energy Research

Abstract A sustainable building design should be compliant with the even more pressing energy saving requirements – as in NZEB – and high levels of Indoor Environmental Quality. Despite it is accepted that different facets of IEQ could have antagonistic effects on building energy demand, relatively few studies are aimed at investigating the mutual interaction among its four components. From this point of view, the hue-heat hypothesis is based on the idea that light and colors can affect the thermal perception. Particularly, spectral power distributions of light shifted to short wavelengths seem to promote a cooler thermal perception and vice-versa. To verify this still debated hypothesis, this paper is focused on a subjective investigation carried out in a special mechanically conditioned test room provided with white-tuning LED sources. 163 volunteers have been exposed to two different lighting scenarios characterized by warm (3000 K) and cool lights (6000 K) at a fixed work-plane illuminance value (300 lx) at two different operative temperature values (20 °C and 25 °C). Obtained results seem to confirm that warm light results in a warmer thermal sensation. Probably due to thermohygrometric conditions relatively close to comfort, no effects on thermal evaluation, and thermal preference were found under both microclimatic scenarios. This was also about the effects of CCT on humidity perception and game performances.

AbstractThe use of automated lighting control systems allows to reduce lighting costs and to achieve significant energy savings. The energy performances of controls are affected by many factors, the impact of which is very difficult to account for during the design process. The goal of this paper is to describe the factors that influence the control systems’ energy performances, to analyze how the currently available calculation tools take them into account and finally to propose a simple method to adjust results obtained from the simulation software.

Abstract The application of “shiftable” or “modulable” load (i.e. washing machine, dishwasher, etc.) in a Smart Grid, can provide energy saving or modify the power flows in the grid, allowing a reduction of the electrical power peak. This paper explores the possibility to modulate the indoor artificial lighting to support this reduction. The study examines the impact of two different measures of power shaving. On the one hand, the change of Correlated Colour Temperature of the light source, and, on the other hand, the dimming of its luminous flux. The possibility to merge the above-mentioned technical solutions is also analyzed. Based on these strategies, several daily schedules of lighting management are defined, and the corresponding energy saving during some critical time slots are assessed. Results show that in all cases, it is possible to achieve a significant reduction of the absorbed power and a consequent increment of energy savings (up to 59%) also in specific time ranges. Furthermore, considering the application of a Daylight-linked control system, it was observed that power regulation associated with the exploitation of the daylight represents itself a way to dynamically reduce the electric loads on the grid.

Abstract This paper is the second step of a research project aimed at investigating the impact of the use of different weather data files on daylight simulations’ results. Simulations were carried out for a simple standalone office using three weather files (IWEC, Meteonorm and Satel-Light) for two European locations (Copenhagen and Rome); moreover the office’s exposure was changed according to the four main orientations (North, East, South and West). Results were analyzed both in terms of Annual and Monthly Light Exposures, dynamic daylight performance metrics (DA, DAcon, UDI) and sunlight’s incidence. It was demonstrated that differences between the results obtained with the different weather files are more significant considering Annual and Monthly Light Exposures (highest value 20%), whereas they decrease when analyzing illuminances with a statistical approach (DA, DAcon, UDI). The analysis of sunlight’s incidence also determined similar results using the three weather data files and the maximum difference is 5% independently from the orientation.

Abstract This paper illustrates the results of daylight simulations of a simple standalone office carried out using different weather data files (IWEC, Meteonorm, Satel-Light and TRY), for five European locations (Copenhagen, London, Milan, Nancy, Rome). The aim was to analyze the impact of choosing one weather file or another on the prediction of daylight availability in an indoor environment. Results were analyzed both in terms of Annual and Monthly Light Exposures and dynamic daylight performance metrics. It was demonstrated that IWEC, Meteonorm and Satel-Light weather files determine similar outcomes, instead TRY weather data always produces considerably lower values. Moreover the differences between the results obtained with the different weather files appear more significant considering Annual and Monthly Light Exposures, whereas they decrease when analyzing illuminances with a statistical approach (DA, DAcon, UDI).

Abstract Nowadays, there is an in-depth debate about the suitability of daylight saving time. The shift of one hour during summer time allows a better use of daylighting reducing energy consumptions. However, the impact of daylight saving time on the human health has not been quantified in most of the scenarios. The aim of this study is to determine the impact of daylight saving time on the health of occupants (by calculating Circadian Stimulus Autonomy) and on the energy consumptions for lighting (by calculating Daylight Autonomy) in office buildings. A standard office is analyzed in eleven representative locations of Europe and for three different time schedules: with daylight saving time, with continuous winter time and with continuous summer time. Despite restricted to a specific case study, results provide elements useful to evaluate pros and cons in maintaining daylight saving time, confirming that they are strongly dependent on the geographical position and on the local luminous climate. It was demonstrated that, abolishing daylight saving time, maintaining the local time all the year (winter time), would determine a reduction of Daylight Autonomy generally lower than 6% and that this decrease would be more consistent for cities characterized by higher latitude. At the same time an increase of Circadian Stimulus Autonomy values would be obtained, more consistent for northern cities (maximum observed increment 16%). On the other hand, applying the one-hour shift for the entire year (summer time) would not determine benefits in terms of energy savings nor of impact on circadian system.

AbstractThe current standard for lighting of indoor work places (EN 12464-1) essentially prescribes values of photometric quantities (illuminance, Unified Glare Index, etc.); therefore it does not allow a comprehensive analysis of the luminous environment. In Italy, educational buildings do not always comply with the standard requirements for lighting. Therefore an analysis of their current state is needed and this paper illustrates two methods, developed by the authors, to carry out this investigation: the former is based on the analysis of luminance maps obtained through the HDR imaging technique whereas the latter focuses on the evaluation of non-visual effects of light.

Abstract Evaluating indoor daylight availability is extremely important in order to define the characteristics of an environment in terms of visual comfort and energy performances of lighting systems. The criticism of the static calculation approach based on Daylight Factor led to the development of the Climate Based Daylight Modeling (CBDM) one. Dynamic simulations are performed thanks to the use of specific software and the choice of a calculation tool or another could provide different output results. Therefore the aim of this paper is to compare results of dynamic daylight simulations carried out with two different software, Daysim and 3ds Max Design® and referred to a simple office located in 4 different cities and exposed according to the 4 main orientations. It demonstrates that differences in results are more or less significant depending on several factors: outdoor daylight conditions, window’s orientation and considered internal calculation point.