Revision of Threshold Luminance Levels in Tunnels Aiming to Minimize Energy Consumption at No Cost: Methodology and Case Studies

The influence of dimming-induced luminance change on driving safety in tunnels

Although dimming the light in tunnels brings salient benefits to energy saving, the effects of dimming-induced luminance changes on driving safety have been rarely explored. Adopting the visual performance experiment, the present study investigated the impacts of the dimming-induced luminance change rate (V) on the safety of driver's perception, judgment, and operation in the threshold zone of the tunnel under different seasons and weather conditions. The results show that the reaction times (RTs), pupil area change rate (v _p), and blink frequency (f _b), increased with the increase of V. When the luminance before the beginning of dimming (L) was higher, drivers reacted faster and stood a lower level of the mental load and fatigue. Compared with decreasing the luminance through dimming, when increasing the luminance through dimming, the present study found that each of the visual performance indices was about 10% lower, and the changes with V became smaller. Based on the safety thresholds of RT, v _p, and f _b, the present study obtained the thresholds of V which can meet the safety requirements of driver's perception, judgment, and operation. Finally, a theoretical model between the thresholds of V and L was developed, and this model will shed light on the control of V in the threshold zone of the tunnel under different seasons and weather conditions.

Use of Polar Heliostats to Improve Levels of Natural Lighting inside Buildings with Little Access to Sunlight

The growing need to increase environmental and energy sustainability in buildings (housing, offices, warehouses, etc.) requires the use of solar radiation as a renewable source of energy that can help to lower carbon footprint, making buildings more efficient and thereby contributing to a more sustainable planet, while enhancing the health and wellbeing of its occupants. One of the technologies deployed in the use of solar energy in buildings is heliostats. In this context, this paper presents an analysis of the performance of a heliostat illuminator to improve illumination in a classroom at the Campus of Rabanales of the University of Cordoba (Spain). A design of a system in charge of monitoring and measuring daylighting variables using Arduino hardware technology and free software is shown. This equipment develops the communications, programming and collection of lighting data. In parallel, installation of an artificial lighting system complementary to the natural lighting system is implemented. Finally, an analysis of the impact of the proposed solution on the improvement of energy efficiency is presented. Specifically, it is estimated that up to 64% of savings in artificial lighting can be achieved in spaces with heliostatic illuminators compared to those without them.

Energy Poverty and Low Carbon Just Energy Transition: Comparative Study in Lithuania and Greece

EU has set ambitious commitment to achieve low carbon energy and economy transition up to 2050. This low carbon transition means sustainable energy development path based on renewable energy sources and first of all should address the energy poverty vulnerability and justice issues. The main goal of the paper is to develop indicators framework for assessing low carbon just energy transition and to apply this framework for analysis how climate change mitigation policies in households targeting enhancement of energy renovation of residential buildings and promotion of the use of micro-generation technologies and other policies are affecting household's energy poverty and vulnerability in selected countries: Lithuania and Greece. This framework allows to assess three main dimensions of sustainable energy development: environmental, social and economic. The paper provides policy recommendations how to deal with just low carbon energy transition which means addressing energy poverty issues during moving to 100% renewables in power generation based on performed case studies.

An Approach for Designing Mixed Light-Emitting Diodes to Match Greenhouse Plant Absorption Spectra

We report a methodological approach for simulating luminary output radiation, which is achieved by mixing light-emitting diodes (LEDs) in order to match any plant absorption spectrum. Various recorded narrow-band LED spectra of different colors were first characterized and then fitted with a multi-Gaussian model. An optimizing procedure computed the optimal weighting of the relevant parameters so as to minimize the discrepancy between the combined spectrum and the reference target curve. The particle swarm optimization (PSO) method was applied because it is the most suitable technique for mono-objective situations. Within the useful spectral interval, the worst relative standard deviation between the optimized curve and recorded LED spectral power distribution (SPD) was 3.4%. When combining different LED types, the simulated light output showed that we could limit ourselves to selecting only five colored sources. This work will help us to design an optimized 200 W laboratory luminaire with a pulse-width switched-mode power supply.

Systematic Literature Review on Behavioral Barriers of Climate Change Mitigation in Households

Achieving climate change mitigation goals requires the mobilization of all levels of society. The potential for reducing greenhouse gas (GHG) emissions from households has not yet been fully realized. Given the complex climate change situation around the world, the importance of behavioral economic insights is already understood. Changing household behavior in mitigating climate change is seen as an inexpensive and rapid intervention measure. In this paper, we review barriers of changing household behavior and systematize policies and measures that could help to overcome these barriers. A systematic literature review provided in this paper allows to define future research pathways and could be important for policy-makers to develop measures to help households contribute to climate change mitigation.

Examining the Impact of Daylighting and the Corresponding Lighting Controls to the Users of Office Buildings

Daylight utilization significantly contributes to energy savings in office buildings. However, daylight integration requires careful design so as to include variations in daylight availability and maintain a balance between factors such as lighting quality and heat gain or loss. Designers with proper planning can not only improve the visual environment and create higher-quality spaces, but simultaneously minimize energy costs for buildings. The utilization of photosensors can exploit the benefits of daylighting by dimming the lighting system, so that no excessive luminous flux is produced, thus leading to energy savings as well as visual contentment. However, the human factor is crucial for the proper function of a lighting control system. Without its acceptance from the users, energy savings can be minimized or even negligible. The objective of this paper is to present a post-occupancy evaluation regarding occupant satisfaction and acceptance in relation to daylighting in offices equipped with automated daylight controls. In addition, the response of the users was compared with lighting measurements that were performed during the post-occupancy evaluation. Three case studies of office buildings with installed daylight-harvesting systems were examined. The age of the occupants was a crucial factor concerning their satisfaction in relation to the lighting levels. Aged users were more comfortable with lighting levels over 500lx, while young users were satisfied with 300lx. The impact of different control algorithms was outlined, with the integral reset algorithm performing poorly. The acceptance of the users for the closed loop systems maintained the expected energy savings of the daylight harvesting technique. Most of the occupants preferred to use daylight as a light source combined with artificial light but having the control to either override or switch it on and off at will. The results shown that a post-occupancy survey along with lighting measurements are significant for making an office environment a humancentric one.

Experimental Investigation of Natural Lighting Systems Using Cylindrical Glass for Energy Saving in Buildings

This research focuses on the use of natural lighting integrated into buildings. Cylindrical glass was fitted into the top of our test model, which was 1 m × 1 m × 1 m, which enhanced the light inside it. The glass fitted comprised a single layer (G), two layers (2G), or two layers of glass filled with distilled water (2GW). Each combination of glass increased the number of glass cylinders from two to six. The nine formats were tested indoors using a light intensity of 1000 W/m2 and the temperature was controlled at 25 °C. The lowest temperature averaged 34.4 °C, which was recorded using only two glass cylinders that had two layers of glass filled with distilled water. The average internal illumination was 549 lux, which agreed with the CIE standard. Then, the two layers of glass filled with water were examined under natural conditions. It was found that the highest average inside temperature was 40.4 °C at 1:30 p.m. The average illuminant values for three days were in the range of 300–500–750 lux, which concurred with the CIE standard. Additionally, the use of the 2S-2GW resulted in the conservation of electrical energy consumed by the cooling load and the illumination of the building between 9:00 a.m. and 3:00 p.m.