Dynamic modeling, control and energy simulation of a solar-assisted hydronic space heating system in a multi-function building

A dynamic model of a solar-assisted hydronic space heating system for a multi-function building has been developed. The system performance under different control strategies and the model-based energy simulations studies have been conducted. The system consists of several components including a boiler, heat exchangers, flat-plate solar collectors, a water storage tank, baseboard heaters and a radiant floor heating system. The model consists of nonlinear differential equations which were programmed and solved using the MATLAB software. Two control strategies have been explored to compare the system performance: (i) a conventional PI control and (ii) a gain-scheduling adaptive (GSA) PI control. The simulation results indicate that the system performance under GSA PI control is better than the conventional PI control with respect to disturbance rejection and stability. An optimization problem was formulated and solved to study the energy performance of the system. Preliminary simulation results with assumed outdoor temperature profiles showed that the optimized set-point operating strategy contributes 7% and 14.87% to boiler energy saving in mild and warm day conditions compared with constant set-point strategy. One week energy simulations under actual weather conditions based on typical meteorological year (TMY) data have been conducted to investigate the percent contribution of solar energy to space heating. The simulation results show that the solar system contributes less energy during cold winter conditions such as in the month of December. However, it can reduce 16.94% of boiler energy supplied to the radiant floor heating system in the month of March. Besides, the implementation of the optimal GSA PI control strategy can result in higher solar fractions of 5.71% and 30.36% as compared to the base case PI control under cold (December) and mild (March) weather conditions, respectively.