Eino Tetri

Light quality regulates flowering in FvFT1/FvTFL1 dependent manner in the woodland strawberry Fragaria vesca

Control of flowering in the perennial model, the woodland strawberry (Fragaria vesca L.), involves distinct molecular mechanisms that result in contrasting photoperiodic flowering responses and growth cycles in different accessions. The F. vesca homolog of TERMINAL FLOWER1 (FvTFL1) functions as a key floral repressor that causes short-day (SD) requirement of flowering and seasonal flowering habit in the SD strawberry. In contrast, perpetual flowering F. vesca accessions lacking functional FvTFL1 show FLOWERING LOCUS T (FvFT1)-dependent early flowering specifically under long-days (LD). We show here that the end-of-day far-red (FR) and blue (B) light activate the expression of FvFT1 and the F. vesca homolog of SUPPRESSOR OF THE OVEREXPRESSION OF CONSTANS (FvSOC1) in both SD and LD strawberries, whereas low expression levels are detected in red (R) and SD treatments. By using transgenic lines, we demonstrate that FvFT1 advances flowering under FR and B treatments compared to R and SD treatments in the LD strawberry, and that FvSOC1 is specifically needed for the B light response. In the SD strawberry, flowering responses to these light quality treatments are reversed due to up-regulation of the floral repressor FvTFL1 in parallel with FvFT1 and FvSOC1. Our data highlights the central role of FvFT1 in the light quality dependent flower induction in the LD strawberry and demonstrates that FvTFL1 reverses not only photoperiodic requirements but also light quality effects on flower induction in the SD strawberry.

A smart LED luminaire for energy savings in pedestrian road lighting

In this paper, an energy efficient streetlight for pedestrian roads is introduced. Energy efficiency is achieved via up-to-date light-emitting diode (LED) technology and added intelligence utilising integrated sensors and wireless control. Thermal and electrical design of the luminaire contributed to good technical functionality. The performance of the luminaire was validated with testing. The luminaire was compared with commercial lamp and LED-based street lighting technology by technical values and user acceptance. Energy savings of 19–44% through improved luminous efficacy was demonstrated without added intelligence. With smart control further power saving potential of 40–60% was shown depending on the lighting environment and pedestrian presence. User feedback of a pilot installation comparing commercial luminaires with the newly developed streetlight revealed that on average the users preferred the developed streetlight over the commercial luminaires.

Synergies of Controller-Based LED Drivers and Quality Solid-State Lighting

The present paper emphasizes the importance of electronics and microelectronics towards the future entrance of high-power light emitting diodes (HP-LEDs) in the general lighting market. Electronic controller-based drivers have a key role on the successful and rapid acceptance of solid-state lighting (SSL) products. This paper describes as an example of the SSL potentialities, a LED-base prototype luminaire with adjustable correlated color temperature (CCT) control

Luminance-Corrected 3D Point Clouds for Road and Street Environments

A novel approach to evaluating night-time road and street environment lighting conditions through 3D point clouds is presented. The combination of luminance imaging and 3D point cloud acquired with a terrestrial laser scanner was used for analyzing 3D luminance on the road surface. A calculation of the luminance (cd/m2) was based on the RGB output values of a Nikon D800E digital still camera. The camera was calibrated with a reference luminance source. The relative orientation between the luminance images and intensity image of the 3D point cloud was solved in order to integrate the data sets into the same coordinate system. As a result, the 3D model of road environment luminance is illustrated and the ability to exploit the method for evaluating the luminance distribution on the road surface is presented. Furthermore, the limitations and future prospects of the methodology are addressed. The method provides promising results for studying road lighting conditions in future lighting optimizations. The paper presents the methodology and its experimental application on a road section which consists of five luminaires installed on one side of a two-lane road in Otaniemi, Espoo, Finland.

Luminous and power quality analysis of office building light sources

Important efforts are being made to increase electric energy savings in the field of lighting. Of all the different approaches possible, two are used more frequently than others: The use of lighting control systems and the replacement of old light sources with better ones. One direct effect of the employment of new light sources and light dimming controls is a decrease of the power quality of the electrical network. This paper addresses luminous and power quality measurements of different light sources that are suitable for office buildings. The measurements were performed with and without dimming. In this way, the luminous and the power quality characteristics of the light sources, at different light levels, were established.

User Preferences in Office Lighting: A Case Study Comparing LED and T5 Lighting

Abstract Lighting quality parameters were studied in an office lighting setting for three different luminaire types: 1) square LED panel luminaire (Sq_LED); 2) round LED downlight luminaire (Ro_LED); and 3) rectangular recessed T5 fluorescent lamp luminaire (Re_T5). The lighting conditions were evaluated with subjective assessments and horizontal desktop illuminance measurement in the middle of the task area. Re_T5 lighting was compared to Sq_LED lighting at 300, 600 and 1000 lx. Ro_LED lighting was studied at three different color temperatures: 3000, 4500 and 6000 K. Subjects responded to all nine conditions using identical questionnaires, which contained questions regarding glare, reading task ease, detail distinction from the wall, color naturalness and pleasantness, illuminance level sufficiency and pleasantness, general pleasantness of the lighting, naturalness of the shadows, and the appearance of the luminaires. Subjects also set three lighting conditions: 1) minimum illuminance for brief duration office work using Re_T5 lighting; 2) optimal illuminance for long-time office work using Re_T5 lighting; and 3) optimal illuminance and color temperature using Ro_LED lighting. The illuminance in the test room was preset at 300 lx before a subject entered the room and started these adjustment. The illuminance adjustment ranges were 0-1142 lx for the Re_T5 lighting and 0-738 lx for the Ro_LED lighting. In the CCT adjustment task CCT was preset to 3000, 4500, or 6000 K. Subjects evaluated 600 lx to be equally pleasant to 1000 lx and the reading task was evaluated to be equally easy at these two illuminance levels. However, 1000 lx caused slightly more glare. 300 lx was considered to be less pleasant and the reading and detail distinction from the wall was considered to be more difficult at 300 lx than at higher illuminance levels. At 600 lx the amount of light was considered to be more optimal than at 300 or 1000 lx. There were no significant differences in the user answers between the Re_T5 and Sq_LED lightings at equal illuminance levels. The Ro_LED lighting was considered less pleasant at 6000 K than at 3000 or 4500 K. However, CCT did not have a statistically significant effect on user answers to other questions. When the users adjusted illuminance the overall average preferred illuminance was 648 lx for Re_T5 lighting and 517 lx for the LED lighting; there were large variations in the preferred illuminances between subjects. The Re_T5 lighting had larger illuminance adjustment range than the Ro_LED lighting, which may have affected the preferred settings. The overall mean preferred CCT of the Ro_LED lighting was 4150 K. There were signs that preset CCT affected the user set CCT.

Tutorial: Road Lighting for Efficient and Safe Traffic Environments

ABSTRACT This article discusses various aspects of outdoor lighting energy efficiency by means of new light sources and smart lighting systems. We will also discuss visibility, traffic flow, safety, and environmental and economic aspects. The use of an optimum level of road lighting maximizes the contrast between the background and the object to be seen. This suggests that the combined effect of road lighting and car headlights should be taken into account. Solutions for future measurement need to include 3D modeling of the lighting environment and mesopic photometry. The life cycle environmental impacts of high-pressure sodium (HPS) and light emitting diode (LED) luminaires were found to be on a similar level, but it is expected that LED luminaires will surpass HPS luminaires in environmental friendliness across the whole life cycle in the future. The energy-saving potential is based on new energy-efficient technology, reduced burning hours with smart control, and new lighting dimensioning. The energy saving potential when replacing HPS lamps with LED luminaires is 31% with current technology and 66% with improved technology in the future. Further energy savings are achievable with reduced burning hours enabled with smart lighting. Altogether, the energy-saving potential of the future LED luminaire is 83% compared to current HPS luminaires.

The effect of correlated colour temperature of lighting on thermal sensation and thermal comfort in a simulated indoor workplace

The ‘hue-heat’ hypothesis states that an environment which has wavelengths predominantly toward the red end of the visual spectrum feels ‘warm’ and one with wavelengths mainly toward the blue end feels ‘cool’. In order to test the hypothesis and to study the impacts of the correlated colour temperature of a light source on thermal sensation and thermal comfort, a study was conducted in a test room illuminated with an Light Emitting Diode (LED) lighting system with an adjustable correlated colour temperature where air temperature, air velocity, and relative humidity were kept constant. The correlated colour temperature of lighting inside the test room was changed gradually while keeping the colour rendering index values greater than 90, an illuminance level of 500 lx, and chromaticity difference (Duv) values within the limits of ±0.005. Sixteen study subjects were exposed to a ‘high room temperature’ (25℃) and a ‘low room temperature’ (20℃) on different days. The subjects were adapted to low correlated colour temperature (2700 K), medium correlated colour temperature (4000 K), and high correlated colour temperature (6200 K) lighting for 10 min and subsequently completed the questionnaire about their thermal comfort and thermal sensation. The results of this survey did not provide support for the hue-heat hypothesis and indicated that people felt thermally more comfortable in an indoor workplace at the correlated colour temperature of 4000 K than at the correlated colour temperature of 2700 K or 6200 K.

Veiling luminance and visual adaptation field in mesopic photometry

In mesopic photometry, adaptation luminance is needed to derive the mesopic luminances for the measurement field. The average luminance of the visual adaptation field is considered as the adaptation luminance. The visual adaptation field has yet to be defined in terms of the size, shape, or location within the visual field. A study in three road lighting situations was conducted, in order to determine the feasibility of using the road surface as the adaptation field compared to circular or elliptical adaptation fields. Currently, the road surface is used as the measurement field for calculating road lighting. Using the road surface as the adaptation field resulted in 76–113%, higher average luminance than obtained using circular or elliptical adaptation fields when the road was bordered by a park. High-luminance sources outside of the visual adaptation field cause veiling luminance. Veiling luminance increases the adaptation state, but not the luminance within the measurement field. The bias veiling luminance can cause on mesopic luminance calculations was estimated to be less than 2%. The estimated bias can be considered trivial in practical road lighting measurements.

Rapid prototyping of freeform optics for an LED downlighter with a dynamically adjustable beam

In this paper, an LED downlight producing dynamic beam variation without any mechanically moving parts is presented. The functionality is based on an optics design using compound parabolic concentrators equipped with individual LEDs. With suitable driving of the LEDs, a dynamic far-field beam with an adjustment range of between 16° and 55° is achieved. The luminaire is used as a demonstration of the polyurethane vacuum casting rapid manufacturing method to produce low-cost freeform optics for prototypes. The simulations and measurements on the realized prototype show that the method is suitable for small series and prototype manufacturing, but also reveal potential errors in the rapid manufacturing process to be avoided in the future.