State Space Model for Thermal Analysis of Integrated Structure of Flat Plate Solar Collector and Building Envelope

Active types of integration of flat plate solar collectors and building envelopes are studied in this paper. The integrated structure of flat plate solar collector and building envelope includes glass cover, absorber plate, tubes, back insulation, and building envelope (we will call it integrated structure later in this paper). With the solar collector integrated with building, the boundary conditions of heat transfer both for the solar collector and the building envelope are changed significantly, and the thermal performance of solar collection and building heat transfer characteristics influences each other. The state space model for thermal analysis of the integrated structure is proposed in this paper, and method for solving this state space model is provided. Moreover, thermal analysis for a particular integrated structure was conducted both by state space model and fluent simulation, then the results were compared and agree well. The state space model has great advantages in time-spending over fluent simulation and it can be used for long-term (several months or a whole year) simulation of the integrated structure. Comparison were made between the integrated structure, detached solar collector and detached single wall based on results calculated by state space method. It shows that (1) integration has little impact on the thermal efficiency of solar collection and the useful heat gain of the integrated structure are nearly the same as that for the single detached solar collector under the same ambient conditions; (2) integration has significant impact on the heat flux across the wall, and the heat flux of the integrated structure is much less than the detached single wall.