Thermoeconomic Analysis of Cogeneration Systems Assisted with Solar Thermal Heat and Photovoltaics
Abstract
This work aims to perform a thermoeconomic analysis of a cogeneration system assisted with solar thermal heat and photovoltaic power, and determine the daily optimal operation taking into consideration the effects of thermal energy storage (TES) and hourly variations of solar radiation, energy prices and energy demands. The system is considered to be interconnected to the national electric grid, thus purchase and selling of electricity are possible. A linear programming model was developed to represent the hourly operation of the system. The results presented herein correspond to the optimal operation for a representative day in April. It was shown that the cogeneration module operates at full load throughout the day and the system sells electricity to the grid for a total of 8 hours. The marginal cost analysis showed the different situations in which heat is charged/discharged to/from the TES and how it affects the unit cost of the heat produced. It has been proposed a thermoeconomic model that incorporates a new set of equations to contribute towards a better understanding of the charge and discharge in different time periods in the TES. The obtained unit costs for internal flows and products showed that the electricity and heat produced by the cogeneration system are always cheaper than the separate conventional production (43-53% cheaper for the electricity and 19-67% cheaper for the heat).
Keywords
Cogeneration, Thermal storage, Solar thermal energy, Photovoltaics, Thermoeconomics