This paper provides an overview of a new method for modelling the total solar energy transmittanc... more This paper provides an overview of a new method for modelling the total solar energy transmittance. It is implemented in the ESP-r building simulation program to model complex façades such as double glazed façades with external, internal or integrated shading devices. This new model has been validated and tested for several cases. The new model required changes to the solar control simulation algorithm and the user interface, so a new "Advanced optics menu" was also introduced into ESP-r. The paper presents the interface development and application of the new technique to different simulation configurations (especially different complex façades with shading devices) in a standard office building.
This report presents a current overview of available technologies for facade-integrated solar the... more This report presents a current overview of available technologies for facade-integrated solar thermal systems. First, glazings are anaylised, followed by available absorber technologies. Then, available collectors and systems are presented, fluid-based ones as well as with air as heat transfer medium, vacuum tubes as well as semitransparent collectors.
Within the European research project RETROKIT (http://www.retrokitproject.eu) and supported by a ... more Within the European research project RETROKIT (http://www.retrokitproject.eu) and supported by a partner network all over Europe, a low-cost building-integrated photovoltaic thermal (BIPVT) component was developed. This component is part of a prefabricated façade that can be easily retrofitted on old residential buildings with little or no energy efficiency infrastructure. The innovation of this project lies in two basic aspects. First of all, it is customizable and can be installed and maintained easily, making the refurbishing process more simple and systematic. Additionally, due to the component's low cost it is accessible for residential owners who represent a high potential market. This RETROKIT facade consists of different layers. The first layer, at the front surface of the module is the PV element of the collector and is constructed with the CIGS thin film PV technology. Behind the PV component, there are capillary tubes to remove the solar thermal energy. And at the bac...
Transparent solar thermal collectors (TSTC) as presented by Figure 1 indicate primary energy savi... more Transparent solar thermal collectors (TSTC) as presented by Figure 1 indicate primary energy savings – even in comparison with an opaque wall [1, 2]. Figure 1 Schematic drawing of a TSTC. An absorber with openings and slats is mounted inside of three glass panes. [2] While conventional collector measurements focus on predicting the collector gain, TSTC need to quantify the heat flux into the building and the solar transmission, too. This paper presents the measurement equipment as well as the modelling based on the measurement results. A detailed physical model of TSTC [3] offers predictions of the benefits, easy collector optimizations and more, but also the possibility of quantifying the uncertainties of the simulation. The method to determine these uncertainties is presented in the last subsection.
Innovative building-integrated components provide solar heating, solar control and visual contact... more Innovative building-integrated components provide solar heating, solar control and visual contact to the exterior. However, their contributions to the building are challenging to predict. This paper presents the results of a detailed physical model which show that the g value depends not only on the position of the sun, but also on the collector operation mode. For successful marketing of such innovative components, a new standard would be helpful which clarifies when a detailed model can be considered to be validated by measurements. Customers could then check different applications with easy-to-use models. Keywords: variable g value, transparent solar thermal collector (TSTC), building-integrated solar thermal systems (BIST), TRNSYS
This paper presents a simplified model for Transparent Solar Thermal Collectors (TSTC). An existi... more This paper presents a simplified model for Transparent Solar Thermal Collectors (TSTC). An existing, validated detailed model was used to identify the formula’s coefficients by comparing the simulation results of both models. The accuracy of the simplified model as well as the influence of the set of simulations used to establish the model has been investigated. The simplified model has been compared to other formulas. The model has proven to be able to predict accurately the collector efficiency.
ABSTRACT To prevent the overheating of a well-insulated building in summer, facade elements with ... more ABSTRACT To prevent the overheating of a well-insulated building in summer, facade elements with switchable U-value are a possible solution. A new translucent element with switchable U-value is presented. The convection around a translucent insulation panel is controlled by moving this panel vertically within the double glazing unit. Measurements of such elements show a possible switching of more than +100% of the U-value between the insulating and conducting state. Various geometries have been measured, and the influence of CO2 in the cavity has also been investigated. Based on the experimental results, TRNSYS simulations have been performed to investigate the overall performance of such a new element integrated in a real building. An optimized element could lead to a reduction of the cooling demand of up to 29.6% of the useful energy and to large improvements in the summer comfort.
ABSTRACT A new Radiance-based modelling approach called Fener is presented. The motivation is to ... more ABSTRACT A new Radiance-based modelling approach called Fener is presented. The motivation is to be able to perform detailed analyses of complex fenestration systems (CFS) from the energetic and daylighting points of view in a computationally efficient manner, so the benefits of innovative products can be easily quantified. The model couples daylighting and thermal simulations in a time-step basis, so that shading control strategies that depend on thermal variables, such as indoor air temperature and energy load, can be simulated without iterating between full-year simulations of a thermal model and a daylighting model. Fener is a single-zone energy model that uses the three-phase method and bi-directional scattering distribution functions (BSDF) to predict the transmitted solar irradiance and indoor illuminance of office spaces with CFS. An evaluation of the model is presented. Fener is tested against EnergyPlus and classic Radiance for different fenestration systems and sky conditions. Cooling and heating energy demand, transmitted solar irradiance and indoor illuminance are compared. As an exemplary application, Fener is used to assess the performance of an innovative perforated lamella system together with a control strategy that depends on indoor air temperature.
1. Einführung Bei der Integration von Fassadenkollektoren in den Sichtbereich des Innenraums spie... more 1. Einführung Bei der Integration von Fassadenkollektoren in den Sichtbereich des Innenraums spielen nicht nur energetische Aspekte, sondern auch der visuelle Komfort eine Rolle. Dabei ist darauf zu achten, dass sowohl eine Durchsicht nach draußen als auch ein Blendschutz gewährleistet ist. Eine Röhre eines fassadenintegrierten Vakuumröhrenkollektors bildet vom Innenraum aus betrachtet bei Bestrahlung zwei vom Auge wahrnehmbare helle Örtlichkeiten an den Mantelrändern der Glasröhre. Abbildung 1 veranschaulicht diese hellen Orte. Die Strahlung fällt dabei orthogonal zur Röhrenachse ein. Abbildung 1: Helle Örtlichkeiten an den Mantelrändern einer Glasröhre unter Bestrahlung
... Professor Erell's research has also included studies of the urban microclima... more ... Professor Erell's research has also included studies of the urban microclimate, such as an investigation ... AND THE HEAT ISLAND EFFECT The heat balance in densely built urban environments is ... for Tokyo, New York and Paris, and found a very important increasing trend (see ...
We present the first study of coherent intersubband polarizations in a pure electron plasma by fe... more We present the first study of coherent intersubband polarizations in a pure electron plasma by femtosecond four-wave mixing in the midinfrared. Resonantly excited polarizations between consecutive conduction subbands of narrow GaInAsAlInAs quantum wells decay ...
ABSTRACT The authors investigate the effect of the coating of various internal blinds on the oper... more ABSTRACT The authors investigate the effect of the coating of various internal blinds on the operative room temperature in an office space. It is very important to correctly evaluate the impact of solar protection and daylight/glare systems on building comfort, and the resulting influence on human behaviour. Many building energy simulation programmes consider the Mean Radiant Temperature (MRT) independently of the actual emissivity of the internal surfaces. This approximation is acceptable for normal constructions with emissivity close to 1, but leads to considerable errors if low-emissivity paint or coatings are used. Starting from the theory of the net-radiation in a grey enclosure, the authors evaluate the MRT, assuming that the incoming flux and the radiated flux are the same. This method is based both on an ESP-r integrated whole-building-simulation programme and on an analytical method which allows for the correct evaluation of the thermal radiant field induced by considering the presence of surfaces with low-e coatings. The method can be used either ‘stand-alone’ for comparisons of different façade variants or within a building simulation. The simulations carried out indicate that when an ‘absorptive blind’ surface faces outwards, the summer temperature can be reduced by about 1 K at a position close to the façade.
This paper provides an overview of a new method for modelling the total solar energy transmittanc... more This paper provides an overview of a new method for modelling the total solar energy transmittance. It is implemented in the ESP-r building simulation program to model complex façades such as double glazed façades with external, internal or integrated shading devices. This new model has been validated and tested for several cases. The new model required changes to the solar control simulation algorithm and the user interface, so a new "Advanced optics menu" was also introduced into ESP-r. The paper presents the interface development and application of the new technique to different simulation configurations (especially different complex façades with shading devices) in a standard office building.
This report presents a current overview of available technologies for facade-integrated solar the... more This report presents a current overview of available technologies for facade-integrated solar thermal systems. First, glazings are anaylised, followed by available absorber technologies. Then, available collectors and systems are presented, fluid-based ones as well as with air as heat transfer medium, vacuum tubes as well as semitransparent collectors.
Within the European research project RETROKIT (http://www.retrokitproject.eu) and supported by a ... more Within the European research project RETROKIT (http://www.retrokitproject.eu) and supported by a partner network all over Europe, a low-cost building-integrated photovoltaic thermal (BIPVT) component was developed. This component is part of a prefabricated façade that can be easily retrofitted on old residential buildings with little or no energy efficiency infrastructure. The innovation of this project lies in two basic aspects. First of all, it is customizable and can be installed and maintained easily, making the refurbishing process more simple and systematic. Additionally, due to the component's low cost it is accessible for residential owners who represent a high potential market. This RETROKIT facade consists of different layers. The first layer, at the front surface of the module is the PV element of the collector and is constructed with the CIGS thin film PV technology. Behind the PV component, there are capillary tubes to remove the solar thermal energy. And at the bac...
Transparent solar thermal collectors (TSTC) as presented by Figure 1 indicate primary energy savi... more Transparent solar thermal collectors (TSTC) as presented by Figure 1 indicate primary energy savings – even in comparison with an opaque wall [1, 2]. Figure 1 Schematic drawing of a TSTC. An absorber with openings and slats is mounted inside of three glass panes. [2] While conventional collector measurements focus on predicting the collector gain, TSTC need to quantify the heat flux into the building and the solar transmission, too. This paper presents the measurement equipment as well as the modelling based on the measurement results. A detailed physical model of TSTC [3] offers predictions of the benefits, easy collector optimizations and more, but also the possibility of quantifying the uncertainties of the simulation. The method to determine these uncertainties is presented in the last subsection.
Innovative building-integrated components provide solar heating, solar control and visual contact... more Innovative building-integrated components provide solar heating, solar control and visual contact to the exterior. However, their contributions to the building are challenging to predict. This paper presents the results of a detailed physical model which show that the g value depends not only on the position of the sun, but also on the collector operation mode. For successful marketing of such innovative components, a new standard would be helpful which clarifies when a detailed model can be considered to be validated by measurements. Customers could then check different applications with easy-to-use models. Keywords: variable g value, transparent solar thermal collector (TSTC), building-integrated solar thermal systems (BIST), TRNSYS
This paper presents a simplified model for Transparent Solar Thermal Collectors (TSTC). An existi... more This paper presents a simplified model for Transparent Solar Thermal Collectors (TSTC). An existing, validated detailed model was used to identify the formula’s coefficients by comparing the simulation results of both models. The accuracy of the simplified model as well as the influence of the set of simulations used to establish the model has been investigated. The simplified model has been compared to other formulas. The model has proven to be able to predict accurately the collector efficiency.
ABSTRACT To prevent the overheating of a well-insulated building in summer, facade elements with ... more ABSTRACT To prevent the overheating of a well-insulated building in summer, facade elements with switchable U-value are a possible solution. A new translucent element with switchable U-value is presented. The convection around a translucent insulation panel is controlled by moving this panel vertically within the double glazing unit. Measurements of such elements show a possible switching of more than +100% of the U-value between the insulating and conducting state. Various geometries have been measured, and the influence of CO2 in the cavity has also been investigated. Based on the experimental results, TRNSYS simulations have been performed to investigate the overall performance of such a new element integrated in a real building. An optimized element could lead to a reduction of the cooling demand of up to 29.6% of the useful energy and to large improvements in the summer comfort.
ABSTRACT A new Radiance-based modelling approach called Fener is presented. The motivation is to ... more ABSTRACT A new Radiance-based modelling approach called Fener is presented. The motivation is to be able to perform detailed analyses of complex fenestration systems (CFS) from the energetic and daylighting points of view in a computationally efficient manner, so the benefits of innovative products can be easily quantified. The model couples daylighting and thermal simulations in a time-step basis, so that shading control strategies that depend on thermal variables, such as indoor air temperature and energy load, can be simulated without iterating between full-year simulations of a thermal model and a daylighting model. Fener is a single-zone energy model that uses the three-phase method and bi-directional scattering distribution functions (BSDF) to predict the transmitted solar irradiance and indoor illuminance of office spaces with CFS. An evaluation of the model is presented. Fener is tested against EnergyPlus and classic Radiance for different fenestration systems and sky conditions. Cooling and heating energy demand, transmitted solar irradiance and indoor illuminance are compared. As an exemplary application, Fener is used to assess the performance of an innovative perforated lamella system together with a control strategy that depends on indoor air temperature.
1. Einführung Bei der Integration von Fassadenkollektoren in den Sichtbereich des Innenraums spie... more 1. Einführung Bei der Integration von Fassadenkollektoren in den Sichtbereich des Innenraums spielen nicht nur energetische Aspekte, sondern auch der visuelle Komfort eine Rolle. Dabei ist darauf zu achten, dass sowohl eine Durchsicht nach draußen als auch ein Blendschutz gewährleistet ist. Eine Röhre eines fassadenintegrierten Vakuumröhrenkollektors bildet vom Innenraum aus betrachtet bei Bestrahlung zwei vom Auge wahrnehmbare helle Örtlichkeiten an den Mantelrändern der Glasröhre. Abbildung 1 veranschaulicht diese hellen Orte. Die Strahlung fällt dabei orthogonal zur Röhrenachse ein. Abbildung 1: Helle Örtlichkeiten an den Mantelrändern einer Glasröhre unter Bestrahlung
... Professor Erell's research has also included studies of the urban microclima... more ... Professor Erell's research has also included studies of the urban microclimate, such as an investigation ... AND THE HEAT ISLAND EFFECT The heat balance in densely built urban environments is ... for Tokyo, New York and Paris, and found a very important increasing trend (see ...
We present the first study of coherent intersubband polarizations in a pure electron plasma by fe... more We present the first study of coherent intersubband polarizations in a pure electron plasma by femtosecond four-wave mixing in the midinfrared. Resonantly excited polarizations between consecutive conduction subbands of narrow GaInAsAlInAs quantum wells decay ...
ABSTRACT The authors investigate the effect of the coating of various internal blinds on the oper... more ABSTRACT The authors investigate the effect of the coating of various internal blinds on the operative room temperature in an office space. It is very important to correctly evaluate the impact of solar protection and daylight/glare systems on building comfort, and the resulting influence on human behaviour. Many building energy simulation programmes consider the Mean Radiant Temperature (MRT) independently of the actual emissivity of the internal surfaces. This approximation is acceptable for normal constructions with emissivity close to 1, but leads to considerable errors if low-emissivity paint or coatings are used. Starting from the theory of the net-radiation in a grey enclosure, the authors evaluate the MRT, assuming that the incoming flux and the radiated flux are the same. This method is based both on an ESP-r integrated whole-building-simulation programme and on an analytical method which allows for the correct evaluation of the thermal radiant field induced by considering the presence of surfaces with low-e coatings. The method can be used either ‘stand-alone’ for comparisons of different façade variants or within a building simulation. The simulations carried out indicate that when an ‘absorptive blind’ surface faces outwards, the summer temperature can be reduced by about 1 K at a position close to the façade.
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Papers by Tilmann Kuhn