Modular Building Envelope Panel with Heating and Cooling Capability

In order to reduce the energy consumption and CO2 emissions, we are supposed to find some ways to diminish our reliance on fossil fuel .Generally, energy use in residential, commercial and public buildings account for %36 of total global final energy consumption in Iran.(Secretariat of Energy and Electricity، 44 :2013) In this regard, renewable energy resources have become vital for heating and cooling. Using solar systems is an appropriate measure towards reduction of fossil fuel consumption and mitigation of adverse environmental impacts. According to the huge potential of solar radiation in Iran, integration of heating and cooling systems in the building envelope is a necessity if the systems are to be economically feasible. The integration is possible only if the design of the passive technology is included in the early stages of the design process. Space heating is the most important building energy use in regions with cold climate and one of the passive solar technologies which is used in mentioned regions is Trombe-wall. Classic Trombe-wall is a passive solar system made up of a south-facing massive wall painted in black on the external surface, an air layer and glazing on the exterior. The wall is equipped with vents at the top and at the bottom for the air thermo-circulation in the air gap. The Trombe-wall systems function by absorbing solar rays and converting their energy. A Trombe-wall stores energy during the sunshine and supplies energy when a building’s occupants require it. It has been widely studied regarding winter behavior, but in summer the system can cause undesired heat gains and overheating phenomena, especially in well insulated buildings. Only few studies focus on their summer behavior. Overshadowing on Trombe-wall’s glazing in summer is an action recommended by several authors. “Modular building envelope panel with heating and cooling capability” is inspired from Trombe-wall in heating scenario and looking forward to improving its summer behavior by the use of evaporative cooling system. In the current study, water was used instead of conventional masonry material, according to its thermal capacity, transparency and fluidity. In summer, the water is discharged and cooling loads are reduced using evaporative cooling. This strategy results in overall building efficiency improvement. (Abolhasani, 2014:21) We attempted to design a modular system for the façade. Modularity offers many advantages and solves some parts of the problems in using conventional built in-situ solar walls. It facilities industrial mass production with high quality and ease of installation, repairing and maintenance. Fully modular products could allow components to be replaced without affecting other elements and reduces the total cost of the entire product. Modular design facilitates design standardization by identifying the component’s performance clearly and minimizing the incidental interactions between a component and the rest of the product. We assessed energy performance of proposed panel using EnergyPlus 8.1 simulation software and investigated influence of it on heating and cooling loads. In order to do that, a series of hour-by-hour simulations carried out on two different models that are made of some thermal zones. The first one is a single room with the dimensions 3m*4m*3m which its south facing side is a double glazed curtain wall. The other model is a room with proposed panel which consists of two zones – a room with the same dimension as that of the first model, named “Room zone” and a zone dimensioned 0.1m*4m*3m, named Trombe zone. These two zones must have an inlet and an outlet “node” to link them in an air loop within the simulation. Air Loop is formed by defining nodes and components. We defined different components in different seasons. We used a supply plenum exposed to sun, for winter and evaporative cooler component, for summer.
For winter simulation we made use of water as collector and storage material and supposed air loop between trombe zone and room zone. For summer behavior, water is supposed to be discharged to activate evaporative cooler component in the air loop. Comparing the output of simulations showed that designed panel decreases heating and cooling loads in our assumed model. We iterated the simulation in room with proposed panel to optimize different parameters and characteristics of constitutive elements. We optimized thickness of water layer as a thermal mass. The results showed that in thicknesses under 125mm, increasing the thickness decreases heating load significantly, however over 125mm, the decreasing rate slows down. The thickness of 125mm reduces 65 percent of heating load in working hours. In order to select the best exterior glazing material, a series of simulations carried out on 6 types of glazing. The effect of glazing type was investigated using net heat gain. Low emission coating showed the best performance. Using low emission glazing instead of single glazing for a Tromb-wall system not only reduced heat losses in winter but also enhanced passive cooling in summer. Results also proved that natural ventilation cannot reduce cooling demand in cold climate condition. It can be alleviated by evaporating cooling and reduction of sensible heat and have a positive impact on summer performance. To improve energy efficiency in designed panel, a forced air circulator was used. In evaporative cooling scenario water consumption and airflow rate was optimized by simulations. The results showed the best performance in an air flow rate ranging from 0.10 up to 0.15 m3/s (equivalent to 300-200 cfm). Finally, the optimized values were used to redesign details of the panel. Proposed panel consists of polycarbonate plenum, low emission glazing on exterior side, dampers, ultrasonic evaporative cooler, movable shading, centrifugal fan and horizontal stud- in order to increase resistance of plenum against static pressure of water. Evaluation of suggested system in the sample model proved its effectiveness in reduction of annual energy demand -heating and cooling loads. The results of this research is based on the weather data of Tabriz, Iran, and the specific sample, so these values cannot be applied to the other climate regions and building conditions. Independent studies should take place for various climate conditions. Also, it would be better to do some experimental surveys to validate the results of the research.