Passive Solar Test Research Articles

Three-dimensional and high-resolution building energy simulation applied to phase change materials in a passive solar room

Phase change materials (PCMs) reduce energy consumption and improve indoor thermal comfort in buildings. Various numerical models have been developed to evaluate the thermal performance of the PCMs integrated into building enclosures. To remain computationally efficient, these models typically adopt a trade-off between the ability to investigate complex and realistic configurations and the prediction accuracy of the heat transfer associated with the phase change. This study developed a model to simulate a room with three-dimensional heat conduction in PCM-integrated walls and to analyze the surface heat balances with high resolution. The model was validated using experimental data of a passive solar test cell with a non-uniform and dynamic thermal environment. The model was then applied to investigate the PCMs integrated into the test cell during the summer. The PCM with a narrow phase change temperature range and a thickness of approximately 10mm was highly effective in reducing the indoor temperature fluctuations; the peak surface temperature was reduced by up to 6°C in the sun patch, and the operative temperature fluctuations decreased by up to 2.6°C. The PCM integration could be limited to the sun patch trajectory on the wall surfaces to optimize its utilization and limit the installation cost.

Experimental Full-Scale Test Cell Optimizing for Research of Novel Concepts towards Climatically Active Solar Façade Design

The passive solar test facilities have recently been created in many research centers all over the world to analyse dynamic outdoor phenomena on buildings and their components. The main objective of these research activities is primarily to evolve a methodology, improve test methods, validate numerical models and measure real thermodynamic properties of building components under outdoor climate conditions. An integration of advanced material solutions into buildings need to be investigated within specific conditions related specifically to outdoor test methods. A research project on Contemporary concepts of climatically active solar facades at the Brno University of Technology does have an ambition to create an experimental full-scale test cell for research of thermal aspects in progressive advances of future solar façade concepts exposed to the real climate conditions. This paper describes the design optimization phase preceding the test cell assembly. This phase includes the analysis of energy and thermal properties based on parametric study features. Computer simulations based on finite element and volume methods are involved in the optimization process. The proposed optimized test cell design is confronted with parametrization of typical thermal aspects to present final test cell demonstration.

Heating season performance improvements for a solar heat pipe system

An improved model of a heat pipe augmented passive solar space heating system was tested. Computer simulations showed that the new model, featuring key design modifications including a copper absorber, thicker insulation, a rubber adiabatic section, and one condenser exposed directly to room air, has significantly improved heat delivery to the room and reduced losses. The new prototype was tested alongside the previous prototype in a two-room passive solar test facility during January–February of 2013. Results showed that modifications implemented for the new model contributed to increased rate of useful thermal gains to thermal storage and to the room, and decreased rate of thermal losses to ambient. Average daily peak efficiencies for the previous system and the new system were 80.7% and 85.0%, respectively. Furthermore, the average storage temperature for the new model, over the entire testing period, was 13.4% higher than that of the previous model; while the average room temperature over the same period was 24.6% greater for the new system. Simulations matched well with experimental data from the new prototype after parametric adjustments were made to the thermal capacitance of the room and conductances between evaporators and condensers, storage tank and room, solar wall insulation, and the load to collector ratio.

Development of a neural network heating controller for solar buildings

Artificial neural networks (ANN's) are more and more widely used in energy management processes. ANN's can be very useful in optimizing the energy demand of buildings, especially of those of high thermal inertia. These include the so-called solar buildings. For those buildings, a controller able to forecast not only the energy demand but also the weather conditions can lead to energy savings while maintaining thermal comfort. In this paper, such an ANN controller is proposed. It consists of a meteorological module, forecasting the ambient temperature and solar irradiance, the heating energy switch predictor module and the indoor temperature-defining module. The performance of the controller has been tested both experimentally and in a building thermal simulation environment. The results showed that the use of the proposed controller can lead to 7.5% annual energy savings in the case of a highly insulated passive solar test cell.

Solar building—European Union Research and Development Programmes

The European Commission's (EC) energy R&D programmes have completed two decades of progress. In the building sector special attention has been given to technology transfer and research dissemination, because of the particular problems which arise given the characteristics of the European construction industry, its diversity and fractured structure, and rather conservative nature. Projects such as the earlier Project MONITOR and BUILDING 2000, and the more recent INNOBUILD and SOLINFO projects and the Solar House programme together represent an unusual, if not unparalleled, effort aimed at bringing about technical change in building design and providing the necessary design and evaluation support and tools to professional architects and students and, to a lesser extent, to engineers. These projects are complemented by (and draw heavily from) an ambitious but clearly-targeted series of research projects investigating major energy-related issues concerning the heating, cooling and daylighting of buildings and deficiencies in knowledge of climate and human comfort, and building performance; activities such as the construction of passive solar test centres in ten EU Member States, each typically with four identical test cells equipped with interchangeable south walls, identical heating and cooling systems, sensors, and data acquisition systems. There is now in Europe considerable emphasis on the challenges of building in warmer climates, and on advancing daylighting design and performance and developing new materials.

Time series analysis of test cell field data

Response factors of physical processes offer an accurate way to characterize the performance of building components. In this work a new methodology for estimating response factors; this methodology is based on time series analysis techniques. In this work a new time series method of estimating the response factor values is applied to data collected from a passive solar test cell. The response factors of the test cell to the radiation component of the energy budget during the day time and the night time were estimated. From these response factors the night time long wave loss, the day time short-wave gain at the external and internal surface of the north wall of the test cell are evaluated and discussed. Specific short periods of data were selected so that values at the meteorological extremes could be estimated. These values help the designer to identify the appropriate range of performance characteristics of the building under study. The effects of infiltration rate on the estimated long wave loss and short-wave gain are also presented and discussed. This work is part of a broader study that is examining aspects of response factor estimation and its application to the performance assessment in the building environment.

Measurement of Air Velocity Components of Natural Convective Interzonal Airflow

Recent flow visualization tests performed at the National Bureau of Standards Passive Solar Test Facility indicated that the natural convective interzonal flow through a doorway is three-dimensional with the velocity components perpendicular to the plane of the opening and the plane of the floor appearing dominant. In order to further investigate the velocity components of the interzonal airflow through a doorway, an experimental study was undertaken. A simple one-dimensional model is modified to apply to two-dimensional airflow. Empirical expressions for the X velocity component and interzonal mass flow rate are developed. The measured velocity and mass flow rate data and the resulting empirical expression are compared with the values predicted by the simple one-dimensional model. It is found that the natural convective interzonal airflow may be adequately represented by two one-dimensional equations, one for the outflow and a different one for the inflow, provided that proper values of the outflow and inflow discharge coefficients are known.

半地下試験家屋における透過日射を阻止した状態での熱環境性能に関する長期実測

In order to obtain the fundamental data on the thermal performance of semi-underground house, a twin-type test house was constructed in the campus of Tohoku University in September 1984. The test house has two rooms with the southfacing windows above the grade and the corridor situated between two rooms. The floor plan is the same as that of the passive solar test house already constructed in 1981. The floor level is 1.3 meter below the ground surface. The insulation of 0.1 meter depth and 1.35 meter width horizontally installed at the level of 0.3 meter below the ground surface surrounding the room on the east designated Room D. This insulation is called the Horizontal Insulation. The room on the west designated Room C has not such insulation. Total heat transmission factor of the construction above the grade is about 1 kcal/h℃ per floor area. The equivalent leakage areas per floor area for ΔP=1.0mmAq of Rooms C and D are 1.86 and 1.45cm^2/m^2, respectively. Both of the two rooms were remarkably airtight, compared to other recently constructed detached houses in Japan. Before the long-term field measurement, the profiles of two room temperatures and isotherms of soil surrounding the construction below the ground surface were estimated by computer simulation using two-dimensional finite element method, in order to investigate the effect of falling in of ground surface from the point of 4 meters apart from the east side of Room D. Calculations were made hourly for a year under the standard Sendai climate conditions. As calculated results, it was estimated that falling in of ground surface has little effect on room temperatures. All windows were insulated with weather shutters to avoid disturbing the heat gain due to solar radiation since October 1984. The outdoor air temperature, room temperatures, soil temperatures surrounding the construction, etc. were measured from 2 December 1984 to 8 October 1985. The results of the long-term field measurement are shown as follows : (1) The amplitude of yearly fluctuation of room temperature is half that of outdoor air temperature. Room D installed with the Horizontal Insulation is warmer in winter and cooler in summer than Room C. The difference of temperatures between Rooms C and D is less than 1.6℃ at the maximum, appearing in February. (2) The amplitude of daily fluctuation of outdoor air temperature is about 15℃. But that of room temperatures is less than 2℃. (3) The isotherms in the soil covered with the Horizontal Insulation at the level of 0.3 meter below the ground surface is very different from that without such insulation. Generally, the temperature of soil covered with the insulation is higher in winter and lower in summer.

パッシブソーラーシステム試験家屋を用いた各種直接熱取得方式の熱的性能に関する実験的研究

This paper reports the experimental results of the performance evaluation of direct gain systems using a twintype passive solar test house. Bricks were used as thermal storage material. For purpose of our investigation, one test room having a brick floor with the depth of 30 cm was used for a reference, while the other for various types of direct gain systems. After the measurement of the temperatures at various points and the amount of solar radiation over a period of two to three weeks, the effects of the depth of bricks, the surface area of bricks in contact with room air, the carpet covering the brick floor, etc., on the room temperature profiles was evaluated by examining the two factors, "difference in daily mean temperature between inside and outside" and "difference between the maximum and minimum temperatures". The results were obtained as follows : (1) The room temperature fluctuation decreases with an increase in brick surface in contact with the room air. When the room has both a brick floor and brick walls 20 cm in depth, the temperature fluctuation decreases by 20 %. In such cases, the heat capacity equals that of the reference room with a 30 cm deep brick floor, and the brick surface area is 1. 5 times larger than that of the reference room. (2) An increase in the amount of thermal storage material is effective in decreasing the room temperature fluctuation. But when the depth of the brick floor is over 20 cm, the heat storage capacity of the portion over 20 cm under the floor surface has no significant effect on the room air temperature fluctuation. Therefore, it is more effective to increase the brick surface area and to decrease the depth of the bricks rather than to increase the depth of bricks. (3) The ratio of the air temperature fluctuation of a room having a brick floor covered with a carpet to that of a room without carpet turned out to be 1.3 to 1.4, because the absorption of solar heat and its release are restrained by the carpet. (4) When a room is equipped with brick floor and brick walls, the volume of which is 1.5 times greater than that of reference room and has an insulated weather shutters used at night as well as windows with triple glazings, the maximum air temperature is 23℃ during the daytime, and the minimum air temperature is 13℃ at day-break. It can be said that auxiliary heating is unnecessary in actual dwellings equipped with the same level of insulation and thermal storage as found in this type under the climatic conditions of Sendai.

パッシブソーラーシステムの性能を評価するための試験家屋の熱的性能と基礎実験

This paper shows the experimental results on the thermal performance of the passive solar test house. The house contains two rooms which are south-facing and one corridor settled between the two test rooms. At first, it is confirmed that the two test rooms have the same air-tightness and the same daily air temperature profile. For one part of our investigation, one test room is equipped with a passive system and the other one is not equipped. For another part of our investigation, each room was equipped with a different type of passive system. After measuring the room temperature, the solar radiation etc., over a period of two or three weeks, the performance of the passive system is evaluated by comparing the indoor temperature profiles of the two rooms. The results of the experiments are shown as follows. (1) It was confirmed that the two test rooms had the same degree of airtightness and the same daily air temperature profile under the same conditions. (2) The air temperature of the room which gains solar radiation through the south-facing window reaches 45℃ in the daytime. The daily mean temperature of this room is about 10℃ higher than that of the room with no solar radiation. (3) The air temperature of the room with the night insulating weather shutter is about 5℃ higher during the night than that of the room with no shutter. (4) When the room is furnished with a partition made of insulating material, the air temperature of the northern portion of the room which gains solar radiation through the clearstory is 10℃ higher than that of the northern portion of the other room which receives no solar radiation.

Comparison between Measured and Model ( LBLand BRE) Predicted Infiltration Rates for a Passive Solar Test Cell

The pressurization technique is applied to the test cell at the JRC, Ispra, and important parameters for the LBL and BRE air infiltration models are calculated. The predictions of these models are compared with the tracer gas (SF6) measurements. The differences between measured and predicted values of the air infiltration rates axe quite large. When the model parameters calculated from the tracer gas measurements are used, both models predict infiltration rates in good agreement with the field measurements. This means the physical models are acceptable but there is a need to refine the procedure for determination of model parameters.

Sensitivity of direct gain space heating performance to fundamental parameter variations

A computer program has been developed for analyzing the performance of direct gain passive solar heated enclosures. The computer program is validated by comparison with data from passive solar test cells at LASL. The results of a sensitivity study involving variation of fundamental design parameters is presented.