Night Insulation Research Articles

SPCM@PNIPAm-PAM hydrogel thermochromic smart windows with multi-stage optical modulation for building energy saving

As a bridge connecting indoor and outdoor environment, windows cause extremely high energy consumption, and near infrared light entering rooms is the primary reason for the increase of cooling load in summer. Thermochromic smart windows, which dynamically regulate light transmittance through stimulus–response mechanism, aroused enormous interest in building energy-saving. However, the development of traditional thermochromic smart windows is often limited by single function and inappropriate response temperature. Herein, a novel fully autonomous multi-stage thermal-response@storage (MTRS) smart window that responds to the ambient temperature was designed by using the thermoresponsive SPCM@PNIPAm-PAM hydrogel for energy-saving and privacy protection. The SPCM@PNIPAm-PAM hydrogel exhibited satisfactory luminous transmittance of 62.70 % and solar modulation ability (ΔTsol,25-40°C=27.39 %, ΔTsol,40-55°C= 19.28 %). With the temperature changing from low (<28 °C) to medium (28–45 °C) to high (>45 °C), the MTRS smart window realized the multi-stage reversible transition from opaque to transparent to opaque, which achieved privacy protection at night and thermal insulation during the day. The obtained MTRS smart window achieved a peak temperature drop of 12.14 °C compared with the regular window on a certain day in the midsummer in Tianjin region. Based on this day’s temperature data, the cooling load of was calculated, and the energy saving was further calculated, which was as high as 21.37 %. The proposed work has a great significance for further development of effective smart windows and deserves attention for the future design of windows for energy saving.

Thermal performance of a solar heat collection and storage wall with night insulation in winter: A numerical study

The application of phase change material (PCM) in Trombe walls (TW) can improve all-day indoor thermal comfort. However, the heat loss via the glass is relatively large, resulting in low thermal efficiency at night. This paper designs a double glass and a thermal insulation curtain used to increase the thermal efficiency of a TW with PCM at night. In addition, a mathematical model based on the implicit difference method was established to study the thermal efficiency and heat loss of the proposed wall in Beijing. The findings indicate that the thermal efficiency at night is improved by 16.23 % compared to a traditional TW, while heat loss at night drops by 7.75 %. The heat gain at night first increased and then decreased with the augment of phase change temperature. As the latent heat or thermal conductivity of PCM increases, the heat gain declines during the day and increases during the night. The most suitable thickness of PCM is 0.02 m. The farther the insulation curtain is from the inner glass, the greater the heat loss and the smaller the indoor heat gain at night. And the later the opening time of the air vents during the day, the smaller the heat gain during the day and the greater the heat loss. But the resulting increase in nighttime heat gain is not significant. This study can offer design suggestions for enhancing indoor thermal comfort and nighttime insulation performance.

Impact of bioclimatism and passive solutions on thermal performance: Feedback from an experimental wood-concrete house in a Mediterranean climate

This article is based on the analysis of the thermal behavior of an experimental house in a Mediterranean climate. This well insulated house presents 3 specificities: inertial elements mainly in the heart of the house with a wood frame envelope, large bay windows, and an interior patio facilitating the safe opening at night. The work focuses on the contribution of passive solutions: the valorization and management of solar gain, natural ventilation at night, thermal inertia and thermal insulation. Dynamic thermal simulations complete the analysis of the measurements. The concept has demonstrated its interest in the summer period with a comfort that can be maintained provided that the available passive solutions are used adequately. The thermal inertia coupled with the natural night ventilation allows to maintain a stable maximum daily indoor temperature lower than the outdoor temperature with a daily thermal amplitude up to 13 °C. The concrete slab of the ground floor exchanges with the indoor air up to 10 W/m2 during the day and up to 25 W/m2 with the natural night ventilation. The flow rate of the latter is estimated at 3.5 to 5.5 vol/h. In winter, the thermal inertia of the slab allows to make better use of solar gains, with for example a thermal flux penetrating the slab that can reach up to 60 W/m2, and represents, cumulated over the day, an energy transferred to the slab up to 300 Wh/m2. This energy is diffused throughout the night with an intensity of about 10 W/m2.

Analysis of an integrated collector storage system with vacuum glazing and compound parabolic concentrator

The basic problems encountered in Integrated Collector Storage (ICS) devices are the heavy evening-to-morning heat losses, the weak ability to capture solar radiation and the thermal losses due to the heat transfer in front of the single glazing. In this study, a new ICS with Compound Parabolic Concentrator (CPC) for domestic uses was designed, constructed, tested and numerically studied. The novelty in the designed ICS system is the use of transparent vacuum insulation in the annulus between double half-cylindrical plexiglass, the use of automated insulation system which suppresses heat loss during night. Experimental results showed that the loss coefficient of the ICS decreased from 5.41 W/K.m2 to 3.34 W/K.m2 when we created the vacuum and used the night insulation system. Numerical study was also accomplished by using FORTRAN simulation program solving energy balance equations of the ICS. The program was used to study the effect of pertinent parameters namely night insulation, CPC reflectivity and vacuum on the thermal performance of the system. The analysis results of the water storage tank, the absorber and the plexiglass temperatures showed the validity of the developed model. The parametric study clearly showed that an increase of the concentrator reflectivity yields to an increase of the system efficiency. Numerical study also showed that if we succeed in making perfect night insulation and vacuum, the daily efficiency reaches 58.62% and the loss coefficient decreases significantly to1.68 W/K.m2.

The Efficiency of Night Insulation Using Aerogel Filled Polycarbonate Panels During the Heating Season

Heat retention is important in achieving building energy efficiency during the heating season. Minimizing heat loss through a building’s glass envelope during the night is one means of heat retention. Movable insulation is one way to increase the insulation value of the building envelope and reduce heat loss towards the outdoors. This research examines the performance of aerogel filled polycarbonate movable panels in a building located on a Midwestern college campus in the USA. Onsite measurements were taken using air and surface temperature sensors to determine the effectiveness of the system. Computer simulations were run using Therm 7.2 to explore alternative design options. A cost analysis was also performed to evaluate the feasibility of utilizing movable insulation to reduce the heating bills during winter. Results showed that sealed movable insulation reduces heat loss through the glazing by 67.5%. Replacing aerogel with XPS panels reduces this percentage to 64.3%. However, it reduces the cost of the insulation material by 98%.

Do elementary school children eat less in noisy cafeterias?

Twenty years ago, the increased occupant productivity linked with high performance, LEED, green, sustainable, Passivhaus, and day-lit buildings was generally backed by anecdote. A flurry of recent research, however, has consistently confirmed the once-anecdotal narrative: when buildings perform better, workers do more, students learn more, and sales spike. After a substantial financial investment in a high performance building, owners can expect meaningful energy savings with modest payback times, but for buildings where occupant performance has a value, both the construction costs and energy savings are a rounding error relative to occupant productivity benefits. Geothermal and passive thermal systems are explored as opportunities to align low-energy thermal systems to acoustics; passive ventilation and thermal mass are explored as low-energy thermal comfort strategies that challenge acoustic concerns. The author’s recent research in daylighting, thermal mass, night insulation, and the effects of cafeteria noise on the eating habits of elementary school children will be highlighted.

Development of a simplified and dynamic method for double glazing façade with night insulation and validated by full-scale façade element

The study aims to develop a simplified calculation method to simulate the performance of double glazing façade with night insulation. This paper describes the method to calculate the thermal properties (U-value) and comfort performance (internal surface temperature of glazing) of the double glazing facade with the night insulation. The calculation result of the internal glazing surface temperature has been validated with experimental data collected in a full-scale façade element test facility at Aalborg University (DK). With the help of the simplified method, dynamic U-value of the facade with night insulation is calculated and compared with that of the facade without the night insulation.Based on standards EN 410 and EN 673, the method takes the thermal mass of glazing and the infiltration between the insulation layer and glazing into account. Furthermore it is capable of implementing whole year calculation at different time steps. Acceptable accuracy and simplicity inputs are also the advantages of the method, which make it a suitable tool to evaluate the performance of night insulation during the design stage of buildings. The result calculated by the method proves that the facade with the night insulation performs much better than that without the night insulation.

Comparative performance investigation of integrated collector-storage solar water heaters with various heat loss reduction strategies

SUMMARY A detailed comparative assessment is reported on the thermal performance of integrated collector-storage (ICS) solar water heaters with various strategies for reducing top heat losses. The objective of this investigation is to assess and compare heat loss reduction strategies. The shape of ICS solar water heater considered in present investigation is rectangular. The thermal performance of the solar water heater is evaluated and analyzed for the following cases: (1) single glass cover without night insulation; (2) single glass cover with night insulation; (3) double glass cover without night insulation; (4) transparent insulation with single glass cover; and (5) insulating baffle plate with single glass cover. Energy balances are developed for each case and solved using a finite difference technique. The numerical assessment of the system performance is performed for a typical July day in Toronto. Each strategy is observed to be beneficial, reducing top heat losses, and improving system performance. The greatest performance enhancements are observed for the water heater with a single glass cover and night insulation and for the system with a double glass cover and without night insulation. Copyright © 2010 John Wiley & Sons, Ltd.

Available remodeling simulation for a BIPV as a shading device

A building integrated photovoltaic system as a shading device is used as an application and remodeling model. This study applies the simulation program SOLCEL and the computational fluid dynamics method to cases with solar irradiance components analysis and a ventilated double façade remodeling of the BIPV. For the validation of the theoretical work, experimental results of the Samsung Institute of Engineering and Construction Company building are used with a wind velocity of the weather data of Suwon area, Korea, where the real building is located. A photovoltaic system can be used only to generate electricity, but if a photovoltaic module can be used as an element of a double envelope, it could be more useful at the point of view of renewable energy usage and night insulation. Increase of PV module surface temperature is negative for power generation by installing PV module as an element of double envelope. A reasonable combination between renewable energy usage and power generation should be well analyzed for better usage of natural energy to design a BIPV.

Heating performance investigation of a bidirectional partition fluid thermal diode

A novel thermal diode, bidirectional partition fluid thermal diode (BPFTD) that is fabricated by integrating a thermal insulation partition and a movable control blade into a water tank, is proposed. The bidirectional configuration allows the BPFTD to serve both passive solar heating in winter and passive cooling in summer. BPFTD heating performances are tested with two side-by-side hot boxes and compared experimentally with a water-wall having optimum thickness. Two stages of experiments are conducted. The first stage is to investigate an appropriate position of BPFTD partition, and the second compares the BPFTD with the water-wall. The test results show that the BPFTD has much better heating performances than the water-wall. Analysis indicates that the BPFTD may increase heat supply by around 140% when a single glazing cover without night insulation is used and by around 70% in case of using a double glazing cover without night insulation.

Influence of movable reflector on thermal response of an atrium building

This paper presents the influence of a movable reflector on the thermal response of an atrium building. Various positions of thermal insulation in the building envelope were used to control thermal dynamics, while the atrium roof with reflector was used for solar heating. The influence of the roof reflector was calculated on a large number of cases differing with regard to wall structures, use of night insulation on the atrium roof and operational heating mode. The heating energy used in the building was assessed by the computer program KAMRA-RW using the actual weather data during typical time periods. This program had been previously tested on a scale model in real-time conditions and compared with the results obtained by the TRNSYS program. The tests showed acceptable consistency. The research proved that a reflector mounted on the atrium roof accelerates the dynamics of the thermal response of a building and substantially diminishes the quantity of the required heating energy.

Analysis of the thermal performance of a building design located at [formula omitted]: Antalya-Saklikent National Observatory guesthouse

This study is based on thermal performance analysis and evaluation of the National Observatory guesthouse with the software SUNCODE-PC. The study is unique owing to its high-altitude site ( 2465 m ) in a remote area, harsh climate (with almost no data available), and functional restrictions of astronomical facilities. The design is thermally evaluated through different modes of application of insulation, materials, types of glazing, window/wall ratios, Trombe walls, winter night insulation, summer ventilation and shading.

Effect of baffle plate on the performance of a triangular built-in-storage solar water heater

The triangular design of a solar water heater not only enhances the overall gain to the system but also improves the natural convection between the absorbing plate and the water, leading to better performance of the system. A night insulation cover is used at the top surface of the heater to reduce the losses from the system during the off-sunshine hours. Another way to reduce the losses from the system is by using an insulating baffle plate in the tank. This plate divides the tank water into two portions, the water above this plate is known as the upper column and below is known as the lower column. The water of the two columns is in contact with each other with the help of the incoming and outgoing vents provided in the baffle plate. This plate also suppresses losses from the lower column during the off-sunshine hours. In this paper, we have studied the effect of a baffle plate on the performance of a triangular built-in-storage solar water heater. To obtain the thermal behavior of the system, the energy balance equations are written at the different nodes, and the well-known finite difference forward time step marching technique is used for their solution. The proposed system is studied by varying the vent area, the water mass in the two columns and under a constant flow rate for different durations. The effects of the thermal conductivity and thickness of the baffle plate on the water temperature are also investigated. It is found that the presence of the baffle plate greatly improves the system performance during off-sunshine hours.

Transient analysis of a triangular built-in-storage solar water heater under winter conditions

In this paper, the performance of a triangular built-in-storage solar water heater under winter conditions has been studied. The triangular cross-section of the system results in higher solar gain and enhances the natural convection leading to a higher water temperature. The forward finite difference technique is employed and initial conditions are derived from the assumption that the water temperature and the temperature at each node are in equilibrium with the ambient temperature. The performance of the system is analyzed under no flow, constant flow rate and intermittent flow rate conditions. The effect of the night insulation cover is also analyzed. A comparative study of the triangular water heater with a rectangular one is also made. The effect of the tilt angle on the water heater is also discussed. The efficiency of the system under various conditions is also discussed.

Heating performance of an experimental passive solar house in Tunisia

In Tunisia, heating requirements in winter are not very high; solar radiation is abundant and offers a high potential of energy for heating. Passive conversion seems suitable due to the low associated extra costs. Moreover, the high thermal capacity required for solar buildings is usually present in single family houses. The National School for Engineers of Tunis has built a solar passive pavilion which has been carefully instrumented. We present, in this paper, an analysis of the recorded measurements. One important question to investigate is whether, in our climate, passive solar energy can totally fulfil the heating requirements. Another interesting aspect is the simultaneous presence of Trombe wall and object gain elements, which are complementary in many respects. It is found that direct gain element shows a higher efficiency, but Trombe wall supplies energy gains, which are very appreciable at evening. Thermal circulation in its air gap has shown to be useless in our climate. The combined effect of the two elements results in autonomy in heating requirements. Experimental testing has been completed by computer simulations, which have indicated that thermal insulation is decisive for the average room temperature, but thermal capacity results in high temperature stability. Simulations have also shown that the constructed Trombe wall is too thick, and that double glazing is more efficient than night insulation to protect this element; whereas for the direct gain element, double glazing is hardly justified in our climate. Experimental and simulation results demonstrate that in Tunisian conditions, proper design of passive components can guarantee heating autonomy at low cost.

Analysis of the performance of direct gain systems in Alexandria, Egypt

The present paper presents an analysis of the performance of the direct gain systems using the weather data of Alexandria, Egypt (latitude 31.2°). The weather data file of Alexandria contains monthly average values of daily radiation on a horizontal surface, clearness index, ambient temperature, wind speed and relative humidity. Since TRNSYS needs hourly values of the previous parameters, the weather data generator developed at the Solar Energy Laboratory at Madison-Wisconsin is used to generate hourly data from the monthly average data available for Alexandria. TRNSYS is a transient simulation program developed at the University of Wisconsin-Madison. A numerical model is used to calculate the energy flows across the window to the building. The window model is then incorporated into TRNSYS to determine the thermal performance of the direct gain systems. The effect of the number of glazing, the building capacitance, and the night insulation resistance on the direct gain systems performance is studied. Finally, a comparison between the performance of the direct gain system and the collector-storage wall composed of concrete is carried out.

THE PERFORMANCE OF A COLLECTOR-STORAGE WALL IN ALEXANDRIA, EGYPT

This investigation presents an analysis of the performance of a collector-storage wall composed of concrete using the weather data of Alexandria, Egypt. An energy balance on the collector-storage wall is used to predict the energy flows into and out of the wall. The numerical model is then incorporated into TRNSYS to determine the thermal performance of the wall. The effect of the wall thickness, the number of glazing, the building capacitance, and the night insulation resistance on the performance of the collector-storage wall in Alexandria, Egypt are studied.

Performance studies of an integrated solar collector-cum-storage water heating system with transparent insulation cover

In this paper the effect of transparent insulation on the performance of a 100 dm 3 capacity built-in-storage type solar water heater is theoretically investigated. The materials of transparent insulation in covering 1 m 2 area of the top surface are Honeycomb hexagonal PS, Honeycomb hexagonal PA and Honeycomb square PC as suggested by Pfluger et al. (paper presented at the ISES Solar World Congress, Hamburg, 1987). Performance of the third material is compared with a glass cover with and without night insulation cover. Also, the performance of a similar system with an area of 0.5 m 2 on its top surface but with the same capacity and with transparent insulation on top and on all the side walls is studied. Finite difference forward time step marching technique is used in solving the energy balance equations. A comparison between the three materials shows that the system with Honeycomb square PC presents the best performance, but it is inferior to the system with night insulation cover.

Discrete fourier series models for building auxiliary energy loads based on network formulation techniques

This paper presents a discrete Fourier series methodology for determining auxiliary energy loads in buildings. By applying network theory, flexible and efficient computer formulation techniques for the nodal frequency domain equations are developed. Two types of auxiliary sources are modelled; in the first one the room air temperature profile is specified, while in the second one an auxiliary heating/cooling source is modelled as a proportional control heat source. Unlike analytical frequency domain approaches such as those based on the Fourier transform, the discrete frequency domain methodology employed allows complex heat transfer mechanisms such as longwave radiant exchanges between room surfaces to be directly included in the formulation, and time-varying conductances such as that for a window with night insulation are also modelled. Thus, the methodology is particularly suitable for passive solar analysis.

Enhancement in daily production of biogas system

In this communication, a straightforward analysis of a conventional biogas system (KVIC) integrated with a greenhouse at the top of the dome has been presented. The effect of the use of movable insulation during off-sunshine hours has been included in the analysis. The use of night insulation reduces the heat losses from the top of the system, which causes an appreciable increase in the production of the biogas system. Numerical calculations have been made for a typical winter day in Delhi.