Dynamic modeling of a compressed air energy storage system in a grid connected photovoltaic plant

Abstract

The main problem of renewable energy power plants is the intermittency of the source of energy. Therefore, instantaneous variations of power demand could not be properly recovered. For overcoming this problem, the best solution, by far, seems to be employing energy storage systems and reclaiming the stored energy by the time of demand. Among all possible energy storage systems, compressed air energy storage (CAES) system is the most efficient candidate due to its high efficiency, lower cost of capital and being environmentally friendly. In spite of huge numerical, theoretical and experimental works conducted on CAES technology, dynamic modelling of a CAES system in a renewable energy source power plant with actual fluctuations has never been studied. On the other hand, as Brazil lies among top countries of the world in terms of solar irradiation reception, and pay attention to the fact that not many solar power plants have been installed in the country yet, this thesis presents a dynamic modeling of a CAES system in a large scale grid connected photovoltaic (PV) plant in Brazil. For this power generation system, it is shown that a CAES system with 50 MW capacity for a PV farm with 100 MWp capacity and a power sales strategy of equal to 70% of its monthly-instantaneously averaged energy production can efficiently damp the power ramps of the power plant and minimize the financial fines that power plant can be exposed to due to its sharp ramps. However, it was also concluded that this power generation system can be enhanced in terms of energy and exergy performance if there is an extra source of energy parallel to the power plant output. As a result, the feasibility of utilizing the power output of a power productive natural gas pressure drop station, also known as city gate station (CGS), along with the first power generation system is studied. The results of simulations prove that not only the energy and exergy efficiencies of the power plant increase considerably, but also the CAES system capacity decreases and the power sales strategy of the power plant is modified considerably.