TE integrated facade

Abstract

Building industry consumes around 50% of the world’s electricity consumption and space heating and cooling plays an important role in ozone depletion and global warming potential. Solar cooling technologies promise more sustainable approaches with reliance on solar energy as a renewable energy source. Thermoelectric technology is a promising solar cooling technology that is powered by electricity from PV panels and has been researched in recent years for investigation of potentials for building and façade integration. These small devices create a temperature difference between the two sides when applied to electricity and therefore, can be used in generating both cold and heat for conditioning of spaces. As an example of arid to semi-arid climates, Tehran has been selected as the context of this project. This graduation project focuses on designing an integrated façade product that uses thermoelectric technology for providing cooling and heating demands of an office building in Tehran. One of the main challenges of this design was the low performance of the TE system that could be increased in a few ways among which decreasing the temperature difference created at the two sides is the most crucial. An office building was initially selected to represent typical offices in Tehran and a few passive strategies including reductions in WWR, changing glazing type, applying insulation and reducing infiltration rate as well as using natural ventilation were implemented on this office model. The implementation of these passive measures leads to a decrease of 55 percent in the annual heating and cooling loads and 39 and 49 percent in the heating and cooling design capacity, respectively. Having this passive model, a ventilation integrated active cooling and heating system was developed that functions like a heat recovery system and uses extracted ventilation air to cool down the temperature of the hot side in summer. Fresh conditioned air is provided in this system through the cold side of the façade via an underfloor air distribution system. A unitized façade product was then developed to accommodate this integrated concept and it this TE system was proved to be flexible in terms of design and integration. To evaluate the performance of this façade, a comprehensive model was developed, and a code was written in EES to solve the equations simultaneously. A baseline model was set to simulate a summer peak situation and as a result, COP, electricity consumption, and temperature difference values were obtained. Next, all the variables in the model were studied and optimized to obtain the best results for every time step of the year. The annual simulations showed that average COP of 1 to 1.3 and 2.1 to 3.0 could be obtained for summer and winter conditions. Feasibility aspects of this façade unitized system were then studied and compared to other solar cooling technologies to obtain a better understanding of limitations and promises of this façade. It was found out that although in terms of performance and cost the TE façade can compete with other solar cooling technologies, issues such as weight, size requirements, and noise might affect its application in some cases.