(428g) Optimal Design and Operation of an Organic Rankine Cycle (ORC) System Driven By Solar Energy with Sensible Thermal Energy Storage

Since the energy demand is rapidly increasing and climate change deteriorates, the conventional fossil fuel power generation technologies are facing challenges related to greenhouse gas emissions. Environmentally friendly and energy-efficient power generation from renewable energy is a promising way to generate electricity due to the advancements in the renewable energy field beyond hydroelectric power. Among the more recent renewable energy sources, solar energy is the most promising one because of its abundance. However, solar energy has its own weakness such as intermittency and low energy density. To overcome the intermittency of solar energy, the implementation of energy storage allows for more predictable and stable power output systems. Solar energy technologies for electricity production has proven to be a viable option for green energy production. There are a number of different potential power cycles that can convert heat into power. The most versatile and common cycle for this purpose, is the organic Rankine cycle (ORC) for solar energy utilization. Although the conventional steam Rankine cycle dominates in terms of efficiency when utilizing heat sources at temperatures of 400 centigrade or higher, these temperatures are out of reach for conventional solar collector technologies. In addition, the organic Rankine cycle is more compact and less costly compared with conventional steam Rankine cycle power plants.

In this study, we investigate the optimal operation of an ORC system driven by solar energy. The main objective is to develop a model describing an organic Rankine cycle driven by solar energy with constant power output. A sensible energy storage system is configured to overcome the intermittency of solar energy. A circulating fluid that connects the solar collector and the ORC system plays a critical role in this system. The mass flow rate of the circulating fluid determines both the temperature of the circulating fluid and the amount of heat absorbed from the solar collector. Among the concentrating solar collectors, the parabolic trough collector (PTC) has reached the highest level of commercial maturity and accounts for the largest share of the current concentrated solar power market. A simulation-based optimization model is developed in this work. Process simulation of the ORC is performed in Aspen HYSYS, and the mathematical model of the energy storage system and the parabolic trough collector is developed in Matlab. The optimal operation of the system including the mass flow rate of the circulating fluid, operating conditions of the ORC, the inlet and outlet temperature of the circulating fluid are determined jointly based on this model. The control strategy of the system can be determined based on the results of this work. The efficiency of the ORC system can be maximized with the proposed system configuration.