Wilfried Pohl - Academia.edu (original) (raw)

Papers by Wilfried Pohl

Scientific Reports

Attention is essential to the work. This study investigated the effects of two different light pu... more Attention is essential to the work. This study investigated the effects of two different light pulses on a simple attention task. In addition, the effects of subsequent exposure to constant but different illuminance levels on the continuation of the simple attention task and a subsequent complex attention task were examined. A total of 56 subjects were assigned in random order to two white light interventions that were repeated five times during the morning. Each light intervention consisted of a brief light pulse followed by constant light exposure and differed in temporal dimming dynamics and corneal illuminance. Subjective and psychometric parameters were recorded several times during light exposure. Heart rate variability (HRV) was derived from continuous electrocardiograms. Subjects showed improved reaction speed in the simple attention task, accompanied by higher HRV under a brighter light pulse without habituation by repetition. This difference in simple attention performance...

The main objective of ADASY ® (Active Daylighting System) work is to design a façade static dayli... more The main objective of ADASY ® (Active Daylighting System) work is to design a façade static daylighting system oriented to office applications, mainly. The goal of the project is to save energy by guiding daylight into a building for lighting purpose. With this approach we can reduce the electrical load for artificial lighting, completing it with sustainable energy. The collector of the system is integrated on a vertical façade and its distribution guide is always horizontal inside of the false ceiling. ADASY ® is designed with a specific patent pending caption system, a modular light-guide and light extractor luminaire system. Special care has been put on the final cost of the system and its building integration purpose. The current ADASY ® configuration is able to illuminate 40 m2 area with a 300lx-400lx level in the mid time work hours; furthermore it has a good enough spatial uniformity distribution and a controlled glare. The data presented in this study are the result of simul...

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 license r... more This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 license references iSo ISO/FDIS 7730:2005, International Standard, Ergonomics of the thermal environment-Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria. En iSo 15927-4 Hygrothermal performance of buildings-Calculation and presentation of climatic data-Part 4: Hourly data for assessing the annual energy use for heating and cooling.

Bright light therapy is an effective treatment option for seasonal and non-seasonal affective dis... more Bright light therapy is an effective treatment option for seasonal and non-seasonal affective disorders. However up to now, no study has investigated effects of dynamic bedroom lighting in hospitalized patients with major depression. A bedroom lighting system, which automatically delivered artificial dawn and dusk and blue-depleted nighttime lighting (DD-N lighting) was installed in a psychiatric ward. Patients with moderate to severe depression were randomly assigned to stay in bedrooms with the new lighting or standard lighting system. Patients wore wrist actimeters during the first two treatment weeks. Additionally, hospitalization duration and daily psychotropic medication were retrieved from patients’ medical charts. Data from thirty patients were analyzed. Patients under DD-N lighting generally woke up earlier (+20 minutes), slept longer (week 1: +11 min; week 2: +27 min) and showed higher sleep efficiency (+2.4%) and shorter periods of nighttime awakenings (-15 minutes). In t...

Energy Procedia, 2017

The presentation of merchandise often happens undifferentiated with a high level of brightness ca... more The presentation of merchandise often happens undifferentiated with a high level of brightness causing high energy demand. For human perception this results in intense light pressure and risk of increased glare. We developed and investigated lighting concepts with various lighting distributions and colour contrasts which were investigated in a perception study. 30 participants rated homogeneous, zonal single-coloured and zonal colour-contrasted lighting scenes regarding their brightness impression at two 1:10 scale shop models. Compared to homogeneous reference lighting scenarios, the zonal lighting scenarios can be operated with about 30% reduced overall room illuminance values while being perceived as similar bright.

Energies

Work processes and sociological structures can differ significantly between organizations. These ... more Work processes and sociological structures can differ significantly between organizations. These organizational aspects determine user behavior, which in turn exerts considerable influence on the key performance indicators of artificial lighting systems. Accordingly, the use of generalized assumptions about user behavior in the building design phase can lead to large discrepancies between design and operation. In the following work, the possible influences of different occupancy schemes, an essential aspect of user behavior and shaped by the organization, on energy demand and workplace-related daylight dose are evaluated. For this purpose, calculations are made based on real measurement data of an open-plan office with zoned lighting. Multi-level calculation models are used to determine improved user distributions in the room to ensure optimization according to the desired target criteria. The results show that occupancy schemes have a significant impact on energy demand, contributi...

This report has been developed in the frame of the IEA SHC Task 61 Subtask A “User requirements”.... more This report has been developed in the frame of the IEA SHC Task 61 Subtask A “User requirements”. The main objective was to rethink and reformulate user requirements to lighting (daylighting and electric lighting) in public buildings on the basis of a thorough literature study. The work is a joint effort of a number of scientists and represents collective knowledge in this topic. The concept of Lighting quality is the one, among many lighting concepts, which expresses the user perspective best. Lighting quality is the important goal of lighting designers and planners; however, it is difficult to define and to measure.

As the interface between interior and exterior spaces, the façade plays a key role for the therma... more As the interface between interior and exterior spaces, the façade plays a key role for the thermal and visual conditions in buildings. Advanced daylighting systems should fulfill various and in parts contradictory requirements: they must provide sufficient and adequately distributed natural lighting, avoid visual discomfort (glare) while allowing visual contact to the exterior, provide solar gains for heating in winter and protect from high radiation against overheating in summer. Integrating these functionalities often results in products which are more complex than conventional sunshading systems and thus are often not properly characterized and cannot be applied in standard design workflows. We present approaches for the characterization of advanced daylighting systems and introduce DALEC, a simplified tool for combined lighting and thermal simulations that can account for such systems. A comparison between DALEC and TRNSYS proves that the simplified approach is adequate for inte...

Energy efficient lighting is said to be one of the most cost-effective approaches to save energy ... more Energy efficient lighting is said to be one of the most cost-effective approaches to save energy and reduce C02 emissions. In order to stimulate the application of lighting retrofits of good quality, IEA Task 50, Subtask B "Daylighting and Electric Lighting solutions" has looked into the assessment of existing and new technical retrofit solutions in the field of façade and daylighting technology, electric lighting and lighting controls. The document provides information for those involved in the development of retrofit products or involved in the decision making process of a retrofit project, such as buildings owners, authorities, designers and consultants, as well as the lighting and façade industry. This source book addresses both electric lighting solu¬tions and daylighting solutions, and offers a method to compare these retrofit solutions on a common basis, including a wide range of quality criteria of cost-related and lighting quality aspects. Simple retrofits, such as replacing a lamp or adding interior blinds, are widely accepted, often applied because of their low initial costs or short payback periods. The work presented in this report aims at promoting state-of-the-art and new lighting retrofit approaches that might cost more but offer a further reduction of energy consumption while improving lighting quality to a greater extend.

Journal of Integrative Cardiology Open Access, 2020

Purpose: Light is an important environmental stimulus influencing everyday life. However, informa... more Purpose: Light is an important environmental stimulus influencing everyday life. However, information about the impact of coloured light on the autonomic nervous system (ANS) is sparse. In general, red light (RL) is thought to act as an adrenergic trigger, while there is evidence that blue light (BL) induces parasympathetic activation. This is a pilot study to find out, if RL and/or BL affects heart rate variability (HRV). Methods: Participants were randomly exposed first to neutral light (NL) and then to RL and BL for 120 minutes in a special light cabin. During each test run, HRV measurements were performed using both wrist training computers and Holter-ECGs. Furthermore, heart rate, arrhythmias and blood pressure were analysed. All parameters were measured during neutral and repeated during RL or BL in 10 supraventricular tachycardia patients, in 10 patients with heart failure and 10 athletes. Results: During exposure to both RL and BL an increase of blood pressure, improvements ...

Journal of Physics: Conference Series, 2019

In this paper we present some of the challenges faced when upscaling optical microstructures from... more In this paper we present some of the challenges faced when upscaling optical microstructures from a lab scale 1x1 cm sized proof of concept sample to a square meter sized object that can be installed in a building. The optical microstructure in question is obtained by a chain of fabrication steps, all linked with each other and with a certain level of complexity. Each of the total of 8 distinct steps presented difficulties that will be briefly introduced in this paper. On a less technical level, long term commitment of public funding and industrial partners was the base for the first upscaling of this complex technologies for pilot production. Taking the best from two worlds: industry and academia has proven effective in the development of such a novel technology.

Frontiers in Aging Neuroscience, 2019

Introduction: Many physiological signals yield fractal characteristics, i.e., finer details at hi... more Introduction: Many physiological signals yield fractal characteristics, i.e., finer details at higher magnifications resemble details of the whole. Evidence has been accumulating that such fractal scaling is basically a consequence of interaction-dominant feedback mechanisms that cooperatively generate those signals. Neurodegenerative diseases provide a natural framework to evaluate this paradigm when this cooperative function declines. However, methodological issues need to be cautiously taken into account in order to be able to provide reliable as well as valid interpretations of such signal analyses. Methods: Two conceptually different fractal analyses, i.e., detrended fluctuation analysis (DFA) and analysis of cumulative distributions of durations (CDDs), are applied to actigraphy data of 36 geriatric in-patients diagnosed with dementia. The impact of the used time resolution for data acquisition on the assessed fractal outcome parameters is particularly investigated. Moreover, associations between these parameters and scores from the Mini-Mental-State-Examination and circadian activity parameters are explored. Results: Both analyses yield significant deviations from (mono-)fractal scaling over the entire considered time range. DFA provides robust measures for the observed breakdown of fractal scaling. In contrast, analysis of CDDs results in measures which highly fluctuate with respect to the time resolution of the assessed data which affects also further derived quantities such as scaling exponents or associations with other (clinically relevant) assessed parameters. Discussion: To scrutinize actigraphic signal characteristics and especially their (deviations from) fractal scaling may be a useful tool for aiding diagnosis, characterization, and monitoring of dementia. However, results may, besides contextual aspects, also substantially depend on specific methodological choices. In order to arrive at both reliable and valid interpretations, these complications need to be carefully elaborated in future research.

Journal of Environmental Psychology, 2019

There exists initial evidence for beneficial daylight effects in hospital bedrooms. However, stud... more There exists initial evidence for beneficial daylight effects in hospital bedrooms. However, study results with automatically controlled dynamic bedroom lights were so far inconclusive. It can be hypothesized that inclusion of critically ill patients and unpleasant fixed bright light stimuli so far could have masked non-visual light effects on patient´s sleep, mood and circadian physiology. Therefore, a temporarily adjustable dynamic light was installed in double bedrooms in a maternity clinic. Although mothers were exposed to fixed morning bright light under dynamic light they were allowed to adjust light intensities the rest of the day. In contrast, light colours were automatically changed over 24 hours and could not be altered. Double bedrooms with standard switchable light were utilized as active control condition. A sample of 72 women, giving birth to healthy term babies, were randomly assigned to bedrooms with dynamic or standard light. Light conditions adjusted by mothers, sleep quality, mood and diurnal melatonin level, as well as physical activity levels of mothers and neonates, were recorded. Mothers exposed themselves and their babies to higher daytime and lower evening light levels under dynamic light compared to standard light after the period of fixed morning bright light exposure had ended. Although no overall effects on maternal parameters could be observed under dynamic light, we could reveal an earlier daily onset of neonatal physical activity levels in these bedrooms. To conclude, this study indicates that an adjustable dynamic light may substantially affect indoor light exposure in a maternity ward. Further studies are necessary to explore light effects on mothers and substantiate study results on neonates.

Building and Environment, 2017

Gerontology, Jan 20, 2017

Light interventions typically exert their mood-related effects during morning bright light exposu... more Light interventions typically exert their mood-related effects during morning bright light exposures over several weeks. Evidence about immediate ambient room light effects on depressed individuals is still sparse. The present study aimed at examining the acute effects of a single moderately bright room light exposure on mood, and behavioural and cardiac stress reactions of mildly depressed geriatric inpatients during a short cognitive stimulation and while resting. Twenty-one inpatients were tested in a balanced cross-over design on 2 consecutive days under either conventional room light (standard light) or artificial sunlight conditions for 30 min. Room illumination was implemented with an artificial skylight, which perfectly imitated solar indoor illumination (e.g., cloudless sky and bright artificial sun). Light-induced changes of mood, heart rate, and heart rate variability were recorded while performing a perseveration test (acted as cognitive stimulation) twice. Additionally,...

International Journal of Ventilation, 2011

Abstract European CEN Standard EN 15251 (2007) requires indoor thermal comfort conditions to be a... more Abstract European CEN Standard EN 15251 (2007) requires indoor thermal comfort conditions to be assessed and to fall within a category system for different levels of expectation and building purpose. The COMMONCENSE project has prepared and provided information about the energy implications of the Standard and in particular whether the Standard is encouraging high–energy buildings in the case of new buildings and major rehabilitations. Qualitative and quantitative information about the energy implications of the Standard are given, using a range of different cooling and heating techniques and building forms. More specifically, the required energy consumption of twenty eight buildings of different types (offices, hospitals, schools, residences) in Europe was calculated, assuming that the buildings belong to each of the three thermal comfort categories I, II, III as described in the Standard. From these calculations, it was determined if the thermal comfort categories of the Standard express real satisfaction with the environment and, at the same time, if low energy buildings could easily comply with the Standard. The calculated energy consumption for each type of building was compared against the existing national benchmarks. In general, by changing the thermal comfort category from I to II or to III as defined in EN 15251, a passage of the building from a higher to a lower energy category is noticed, according to each the existing national benchmarks and legislation. Finally, new forms for future standards which are more in keeping with the aspirations of the European Energy Performance of Buildings Directive (EPBD) are suggested. The new standard should be framed in order to encourage low energy buildings since buildings must be comfortable and energy efficient at the same time.

Chronobiology international, Jan 31, 2016

Short-wavelength and short-wavelength-enhanced light have a strong impact on night-time working p... more Short-wavelength and short-wavelength-enhanced light have a strong impact on night-time working performance, subjective feelings of alertness and circadian physiology. In the present study, we investigated acute effects of white light sources with varied reduced portions of short wavelengths on cognitive and visual performance, mood and cardiac output.Thirty-one healthy subjects were investigated in a balanced cross-over design under three light spectra in a simulated night-shift paradigm without circadian adaptation.Exposure to the light spectrum with the largest attenuation of short wavelengths reduced heart rate and increased vagal cardiac parameters during the night compared to the other two light spectra without deleterious effects on sustained attention, working memory and subjective alertness. In addition, colour discrimination capability was significantly decreased under this light source.To our knowledge, the present study for the first time demonstrates that polychromatic ...