Experimental study of a building-integrated solar air heating system in cold climate of China

• Unglazed transpired collector (UTC) was tested under transient outdoor conditions.
• Solar radiation and air flow rate are main factors affecting thermal performance.
• Thermal performance of colored UTC is still competitive.
• Both energy savings and payback of UTC are attractive in cold climate of China.

A series of experiments were carried out in Harbin, a typical city of the severe cold climate zone of China under real transient outdoor conditions to investigate thermal performance, color effect and energy savings of a building-integrated solar air heating system based on unglazed transpired collectors (UTCs). The average efficiency of black UTC was 77.64% and 68.92% under high and low air flow rate respectively, which are higher than most glazed flat-plate collectors. Collector's surface color had an effect on its thermal performance. However, the thermal efficiency of colored UTC was still competitive, and therefore it is feasible to use colored UTC on building façade for esthetic reasons. Design heating load of a reference building in Harbin can be reduced by 6.4% due to reduced wall loss with the application of UTC. For a first cost less than 200 $/m2, it is economically viable to use UTC as an energy efficiency measure in Harbin with net present value of 333 $/m2 and payback time of 10.5 years. With better coordination with architectural design at early stage in a project, this building-integrated solar air heating system can be both esthetically and technically viable in cold climate of China.