Large Window Areas Research Articles

A reflective textile metasurface for indoor signal coverage enhancement

The design of a reflective metasurface solely based on flexible textile material is presented for indoor signal coverage enhancement in a specific scenario – reflecting and reallocating radio frequency energy that would have leaked through a large window area. The proposed reflective metasurface design, reflective metasurface is composed of layers of square conductive textile patches and dielectric textile substrates. For the unit cell design, a reflective phase difference of up to 90° can be achieved via varying the size of the conductive patches. Meanwhile, a phase difference of up to 180° can be achieved by the alignment of conductive patches on different textile substrate layers, which is an ideal design philosophy for textile material. The proposed metasurface, consisting of 12 × 12 unit cells, can achieve a main reflected beam pointing in the direction of ±35° and a secondary reflected beam at ±63°. Simulated results show that the reflected beams remain relatively stable under the crumpling conditions often seen for curtains. A prototype of the design was fabricated and tested in a real-world scenario. A maximum signal strength enhancement of 15 dB and an average enhancement of 5.97 dB in a wide range of directions can be achieved with the reflective metasurface applied.

Electrical and thermal performance of multidimensional semi-transparent CdTe PV window on offshore passenger ships in moored and sailing condition

Utilizing solar energy is an effective method to decrease fossil energy consumption in marine field. Horizontally installed deck photovoltaic (PV) systems have been widely investigated to reduce navigation energy consumption on ocean-going ships. However, energy saving rate is unsatisfactory because of the low energy density of solar energy and the shadow caused by ship body. As for large amount of offshore small ships, it's even harder to utilize the existing technology since deck space is limited. In this paper, semi-transparent CdTe PV window system is proposed for offshore passenger ships without enough deck spaces but with large window area around ship cabin. Multidimensional PV windows can increase PV area and reduce heat gain inside the cabin, shadow effect caused by ship body is also avoided. Energy saving can be both achieved by electrical generation actively and cooling load reduction passively. Dynamic mathematical models of multidimensional PV window under moored and sailing conditions are established. Simulation results indicate that the daily electrical generation and average electrical efficiency are 0.74 kWh & 14.65% in moored condition and 0.83 kWh & 16.24% in sailing condition. Navigation leads to higher received solar radiation (18.2%), higher electrical generation (12.1%) and higher electrical efficiency (10.85%). Electricity created by PV window can support 6 h' continuous operation for auxiliary system on board. With PV windows, the average air temperature in cabin is decreased by 6.5 °C compared with ordinary windows. The average heat fluxes through four directions of PV windows are decreased by 75.44%, 73.64%, 47.52% and 75.33% compared with ordinary windows.

Precise Filtration of Chronic Myeloid Leukemia Cells by an Ultrathin Microporous Membrane with Backflushing to Minimize Fouling.

A cell filtration platform that affords accurate size separation and minimizes fouling was developed. The platform features an ultra-thin porous membrane (UTM) filter, a pumping head filtration with backflush (PHF), and cell size measurement (CSM) software. The UTM chip is an ultrathin free-standing membrane with a large window area of 0.68 mm2, a pore diameter of 5 to 9 μm, and a thickness of less than 0.9 μm. The PHF prevents filter fouling. The CSM software analyzes the size distributions of the supernatants and subnatants of isolated cells and presents the data visually. The D99 particle size of cells of the chronic myeloid leukemia (CML) line K562 decreased from 22.2 to 17.5 μm after passage through a 5-μm filter. K562 cells could be separated by careful selection of the pore size; the recovery rate attained 91.3%. The method was compared to conventional blocking models by evaluating the mean square errors (MSEs) between the measured and calculated filtering volumes. The filtering rate was fitted by a linear regression model with a significance that exceeded 0.99 based on the R2 value. The platform can be used to separate various soft biomaterials and afford excellent stability during filtration.

Preliminary Evaluation of the Heating and Cooling Capability of an Insulating Glass Unit

AbstractIn order to achieve maximum transparency of the buildings, architects plan large facades and large window areas. These glass surfaces have the disadvantage that they form a cold surface in winter and the sun heats the room in summer. It is desirable to use the potential of the huge surfaces of the glass for controlled heating and cooling. To be able to use an insulating glass unit as a heater, the temperature must be distributed uniformly over the glass. Existing solutions rely on heating wires between the panes of a laminated glass, but these are visible for the user. To create an invisible system, the cavity of the insulating glass can be used. The idea is to fill the cavity with helium instead of argon or krypton. Due to the good thermal conductivity of helium, temperatures in the cavity can be distributed over the whole glass. Content of this paper is the basics research, experimental research of the gas tightness with helium in the cavity and the first functional tests for heating and cooling with helium. The results give a first look at the heating and cooling capability of and insulating glass unit and include the basics for further researches on this topic. These are the first results of a current research project of the Institute of Building Construction at the TU Dresden.

Ventilation performance of solar chimney integrated into a multi-storey building

Previous studies have mainly focused on solar chimneys in single-chamber/zone or single-story buildings. Its theoretical development in multi-chamber or multi-story buildings is lagging, which hampers its practical applications in multi-storey buildings. This study investigated ventilation capacity characterized by volume flow rates numerically and theoretically for a multi-storey building with a solar chimney. Three mathematical methods based on simplified models were introduced to predict the ventilation rates for each floor. By comparing the three methods, Method 1, based on the bifurcation hypothesis, was found suitable for two-storey or single-storey cases; and Method 3, based on empirical flow equations, is practical for those cases greater than two-storey. To optimize the ventilation rate, a wider cavity gap and a higher stack height for a multi-storey solar chimney were the most effective ways compared to the single-zone/floor cases. A larger window area and air inlet size promoted the ventilation capacity, where the growth rate of volume flow was small and critical values exist. It was observed that the solar chimney dimensions show a more significant effect on the volume flow rates than the solar radiation intensity. The main contribution of this study is that it establishes the links between the single-zone and the multi-storey theoretical models and proposed practical mathematical methods to obtain acceptable prediction accuracy of ventilation rates for a solar chimney in a multi-storey building.

Electrochromic Glass system in Norwegian Climate: Control strategies and Impact on the indoor thermal conditions

This work investigates by simulations the impact of the use of Electrochromic (EC) windows in a modern wooden cabin with large window area in a colder climate. The climatic areas considered are 4 different locations in Norway. Three different automatic control systems were used and compared. The windows were alternatively equipped with a textile integrated external blind and an EC glass. The results show that the use of EC glass has a quantifiable impact in term of reduction of peak temperature by 2°C and reduction of number of hours with high indoor temperature. The control system that seems to perform better is based on external solar radiation. In the particular situation of a cabin, where the visual comfort and the surrounding view has the greatest importance, a more complex control algorithm needs to be developed.

Active energy-controlling windows incorporating transparent photovoltaics and an integrated transparent heater

Despite being essential interfaces between interior spaces and their surrounding environments, windows are often considered as being among the least important energy components in buildings, houses, and vehicles. The proportionally large window areas of man-made structures mean that smarter window design would lead to more efficient energy control. Here we report large-scale transparent photovoltaics and their integration with a transparent heater for an energy-efficient active window unit. The latter possesses high average visible transmittance (>60%), low transmission haze (<7%), neutral color perspective, and excellent thermal protection, and its heating function is powered by solar energy and the electric energy from the transparent photovoltaics. This active window unit may overcome some of the limitations of conventional passive windows for power consumption, with electrical power being generated from transparent solar cells and the energy flow being governed by the window’s temperature-control scheme. Active energy system incorporating transparent energy platforms for window applications High-transparency (>60%) energy windows have transparent photovoltaics and heaters Transparent heater is driven by power from TPVs for active energy platforms Despite being essential interfaces between interior spaces and their surrounding environments, windows are often considered as being among the least important energy components in buildings, houses, and vehicles. Patel et al. report large-scale transparent photovoltaics and their integration with a transparent heater for an energy-efficient active window unit.

Characterizing the performance of a passive solar house with hydronic floor energy capture system – Heating season experiments

Large south-facing window areas can significantly reduce space heating demands – the dominant energy demand in houses in cool and cold climates – by increasing passive solar gains. However, due to the risks of overheating in highly glazed spaces, reduced window areas or passive cooling strategies which sacrifice some of the available solar resource are often implemented. Active cooling strategies that can put excess passive solar gains towards useful means have not been widely considered. An energy capture system consisting of hydronic floors coupled to a water-water heat pump and energy stores has been conceived to enable larger south-facing window areas to permit greater passive solar gains. By capturing excess passive solar gains that occur at certain times, the system can protect against overheating and make use of the captured and stored energy to provide hot water heating and future space heating demands. A prototype of the concept has been designed and implemented at a full-scale experimental facility in Ottawa, Canada. Measurements were taken during two sunny and cool days in February to assess the design and operation of the system. These results show that the system can prevent overheating even when passive solar gains exceeded 10 kW (greater than the house’s peak heating load) and has the ability to capture and store these solar gains to heat domestic hot water and provide space heating at night. The results also revealed opportunities for improving the design and operation of the system.

Thermal and visual comfort, energy use and environmental performance of glazing systems with solar control films

Buildings with large window areas tend to have more heat gains/losses through the glazing systems, which increase the cooling and heating loads. Applying solar control films (SCFs) on glazing systems can reduce the heat gain, annual energy consumption and peak demand load. The main objective of the present study is to assess the (thermal and visual) comfort, energy and environmental performance of different types of SCFs applied on glazing systems. Three adjacent office rooms located in a university building in Lisbon were used as case study. A building energy simulation model, calibrated from experimental results, was used to simulate the performance of the glazing systems. The most reflective SCF (τvis = 16%; g = 0.15) has the highest thermal and optical performance due to its low visible transmittance and solar heat gain coefficient, making it possible to achieve temperature and glare comfort during 41% and 43% of working hours. The spectrally selective film with τvis = 63% and g = 0.40 has the highest energy performance, enabling to achieve an annual reduction of 38% of energy consumption and CO2 emissions. From a multi-criteria evaluation approach, the best alternative is the most reflective film when assigning preferred importance to thermal and visual comfort, and the most spectrally selective film when energy cost saving and CO2 emission reduction are taken as the decision criteria.

Fabrication and characterization of sample-supporting film made of silicon nitride for large-area observation in transmission electron microscopy

In transmission electron microscopy (TEM), silicon nitride (SiN) films are widely used as sample-supporting films owing to their robustness. We fabricated large-scale SiN films deposited by low-pressure chemical vapor deposition (LPCVD). This preparation method is advantageous for large window areas, since it yields films with control over properties such as tension and thickness. We fabricated large SiN windows for mounting large ultrathin sections and for acquiring large-area TEM images. Thus, sample sections sliced by conventional sample preparation techniques were successfully mounted on these sample-supporting films. We successfully obtained a 680 × 250 μm2 TEM montage image of a whole Drosophila embryo.

Analyses of phase change materials’ efficiency in warm-summer humid continental climate conditions

The usage of phase change materials (PCMs) is a way to store excess energy produced during the hot time of the day and release it during the night thereby reducing the overheating problem. While, in Latvian climate conditions overheating is not a big issue in traditional buildings since it happens only a couple of weeks per year air conditioners must still be installed to maintain thermal comfort. The need for cooling in recently built office buildings with large window area can increase significantly. It is therefore of great interest if the thermal comfort conditions can be maintained by PCMs alone or with reduced maximum power of installed cooling systems. Our initial studies show that if the test building is well-insulated (necessary to reduce heat loss in winter), phase change material is not able to solidify fast enough during the relatively short night time. To further investigate the problem various experimental setups with two different phase change materials were installed in test buildings. Experimental results are compared with numerical modelling made in software COMSOL Multiphysics. The effectiveness of PCM using different situations is widely analysed.

Correlation of energy efficiency and thermal comfort depending on the ventilation strategy

Designing energy efficient building it is important to achieve low level of energy consumption and to provide high parameters of the thermal comfort. This research is devoted to ventilation which has effect on both the comfort of the building and its energy efficiency. The IDA-ICE 4.7 software was used as a tool providing a detailed study of the building’s indoor climate, energy balance and energy efficiency. The thermal properties, the hourly loads for equipment, occupancy and lighting were set for the two-storey residential building situated in Baltic sea costal. Natural and mechanic ventilation was simulated and analyzed. The comparison of internal air overheating and energy consumption depending on the ventilation strategy was made. The results show that use of natural ventilation with window’s opening is effective in case of large window area but in case of north oriented room with 50% window to wall ratio mechanic system is more efficient.

Field study of thermal comfort and occupant satisfaction in Canadian condominiums

ABSTRACTIn Canada and much of the world, high-rise residential buildings with large glazing areas are increasing in popularity. These buildings are associated with lower thermal resistance envelopes and higher solar gains than more traditional construction with smaller windows. This study explores the comfort implications and usability in condominiums by performing a field study of 20 units: 10 with large window areas (LW) and 10 with medium-sized window areas. Occupant comfort was assessed in summer and winter, through two open-ended surveys, infrared thermography, and recorded interior temperature and humidity. LW occupants more often report uneven interior temperature distributions and windows as a source of discomfort in winter. One quarter of condo units experience condensation on windows, indicating window and frame improvements may benefit both groups. This exploratory study identifies key issues and occupant preferences within condominiums to guide future research on this building type.

The effect of external walls on energy performance of a Korean traditional building

As one possible approach to improving the energy performance of the eco-friendly Korean traditional building, this study develops an energy simulation model to investigate the influence of five types of alternative walls – a mud brick wall, a cement brick wall, an ALC block wall, a CRC board wall, and a chaff charcoal wall – on the energy performance of Korean traditional buildings in three different climate zones in South Korea – a central region, a southern region, and a Jeju Island region. The results of the simulation study indicate that the cement brick wall provides the highest energy saving and the mud brick wall provide the lowest energy saving for all three climate regions. For five types of alternative walls, the Korean traditional building with small window area shows a better energy performance than the traditional building with large window area in all three climate regions. The results of this study can be used as basis data for estimating the potential energy saving with the replacement of alternative walls under the regional climate consideration.

Impact of façade window design on energy, daylighting and thermal comfort in nearly zero-energy houses

Appropriate window solutions are decisive for the design of ‘nearly zero-energy’ buildings with healthy and comfortable indoor environment. This paper focuses on the relationship between size, orientation and glazing properties of façade windows for different side-lit room geometries in Danish ‘nearly zero-energy’ houses. The effect of these parameters on space heating demand, daylighting and thermal environment is evaluated by means of EnergyPlus and DAYSIM and presented in charts illustrating how combinations of design parameters with minimum space heating demand can be selected within a solution space defined by targets for daylighting and thermal comfort. In contrast with existing guidelines, the results show an upper limit for energy savings and utilisation of solar gains in south-oriented rooms. Instead, low U-values are needed in both north- and south oriented rooms before large window areas lead to reductions in space heating demand. Furthermore, windows in south-oriented rooms have to be carefully designed to prevent overheating. Design options for prevention of overheating, however, correspond well with options for low space heating demand. Glazings with solar control coating are therefore obvious alternatives to dynamic solar shadings. Regarding room geometry, deep or narrow south-oriented rooms show difficulties in reaching sufficient daylight levels without overheating.

A methodology for identifying the influence of design variations on building energy performance

In building performance simulation, understanding the potential for parameter variations to cause a disproportionately large change in a performance metric is an important aspect of the modelling and design process. This is especially true if the proposed building is expected to meet a performance target such as net-zero energy consumption. In the context of this paper, variations refer to design modifications which lead to large changes in a performance metric. This paper proposes a methodology to identify influential variations around a performance criterion. This methodology aids in the understanding of possible discrepancies between predicted and realized building performance. A net-zero energy house case-study demonstrates the methodology. A variability analysis of the case-study indicated that combinations of variations caused energy consumption to be larger than on-site generation in 20% of variational scenarios. A back-tracking search identified that 8 of 26 variables were responsible for significant changes in net-energy consumption. In particular, energy-related occupant behaviour, solar orientation, and variables related to the sizing of a roof-based photovoltaic system can significantly influence net-energy consumption. The case-study helped quantify two optimal approaches for passive solar design – one relying on high insulation levels and lower window areas, and the other relying on good insulation levels and large window areas.

Thermal Performance Analysis for Ventilated and Unventilated Glazed Rooms in Malaysia (Comparing Simulated and Field Data)

Glazed windows can cause intensive overheating due to solar radiation within buildings in hot climates. These glazed windows, according to their apertures, can also provide cross-ventilation which is necessary for cooling and improving thermal comfort of occupants. Many computerized environmental simulation tools are available to help designers to predict the environmental performance of their design at the early stage. The thermal comfort study presented in this paper involved the use of field measurement and computer simulation tool, i.e. Ecotect. Validation of Ecotect was carried out by comparing the computer simulation results with the field measurements of the east-facing room at Fajar Harapan Hostel, University Science Malaysia, which has a 50% glazed area-to-wall ratio. Output data from Ecotect were compared to the fieldwork data in terms of indoor/outdoor air temperatures and indoor air velocity. The impact of reducing the glazed area from window wall ratio = 50% in the base case to 25% and 00% (i.e. window less) was investigated. The results showed that the simulation compared well with the field data with a difference of less than 0.9°C, indicating that rooms with a large glazed window area would be relatively cool during night-time only, and a smaller glazed window area would perform well during daytime as well as night-time.

Increasing Building Energy Efficiency with Wireless Monitoring and Control

ABSTRACT This article describes the results of a study that was conducted to establish a plan for maximizing the energy efficiency of a child care center located in Hammond, Indiana, and thereby increase the green attributes of its design, including passive solar. Technology is described that can provide options for enhancing energy efficiency strategic planning efforts. The design of the building considered in this effort includes several large window areas that serve multiple purposes. The building was initially constructed with several passive features, but over time, operating practices greatly reduced their effectiveness. Rather than gaining the benefit of the available solar radiation, the building operation often increased energy losses in the winter and increased cooling load in the summer. A building energy survey was conducted and recommendations were made to improve the energy efficiency of the facility, including the use of wireless control and monitoring equipment in a design that eliminates ...

A new fabrication method of low stress PECVD SiN x layers for biomedical applications

A new fabrication method to produce low residual stress PECVD SiN x layers at high deposition rates was developed and their biomedical applications were reported in this paper. This new method employed up to 600 W high power to fabricate low stress SiN x layers in high frequency (13.56 MHz). By adjusting the composition of reactant gases, the residual stress can be lowered to 4 MPa and high deposition rate up to 320 nm/min can be achieved. In addition, this paper also investigated the influence of other important parameter, such as pressure, power and gases flow rates. Moreover, by using this optimized process, an 11 μm thick low stress SiN x layer was produced, which will be used to fabricate large window area for cell culture. Finally, a successful cell culture test involving cultivating mouse stem cells onto the porous membrane made of these low stress PECVD SiN x layers indicated that these layers are biocompatible and are suitable for biomedical applications.

ステレオマッチング法による二相ステンレス鋼破面の３次元再構築

The algorism of the reconstruction of three-dimensional topography from stereoscopic SEM fractographs has been developed. This is an area-based multi-step stereo matching algorithm in order to achieve high accuracy, that is, the corresponding points in stereo photography were searched using a large window area and search area without occurrence of mismatching for the first step. For the next step, the sizes of widow area and search area were set smaller than those of the first step around the first corresponding point and then the second corresponding point is determined. This procedure is repeated up to fourth step.DEMs (Digital Elevation Model) of the fracture surfaces of ferritic-austenitic duplex stainless steels were reconstructed using the developed algorithm. The DEMs showed slanted surfaces, and direct comparison of the cross sectional topography between the reconstructed DEMs and the real surface was performed. The reconstructed DEM revealed exactly the shape of the dimple patterns and detailed features on the fracture surface.