Mathematical modeling of a binary ORC operated with solar collectors. Case study-Ecuador

Abstract

[EN] The present study is significant because it can contribute to developing sustainable energy strategies and expanding knowledge about renewable energies in Ecuador, specifically by modeling two modules: the thermal module (parabolic solar collectors and energy storage tank) and the Organic Rankine Cycle (ORC) module. The objective was to determine a region in Ecuador where the thermal module exhibits the highest efficiency for solar collectors. Subsequently, a detailed analysis of the ORC module was conducted, considering the working fluid, boiling temperature, condensation temperature, pinch point temperature, solar collector area, and the collector area-to-energy storage volume ratio (Ac/V). Finally, an economic analysis was performed based on the Net Present Value (NPV), Internal Rate of Return (IRR), and payback period of implementing this type of system. After conducting all the respective analyses in the thermal module, while considering the yearly average meteorological data of ten years (2012-2022), it was determined that due to its meteorological conditions, ambient temperature (14.7 celcius) and solar beam radiation (184.5 W/m2), the efficiency of the collectors in the Sierra region of Ecuador is higher. This efficiency is further enhanced by using Therminol VP-1 as the thermal fluid, as it possesses better thermodynamic properties than the other fluids analyzed. Similarly, the ORC module analysis results determined that cyclohexane is the working fluid for the ORC, thereby leading to a higher ORC efficiency (25%) and overall system efficiency (20%). Finally, the system was optimized to maximize the IRR and minimize the Ac/V of the collector for a nominal power of 92 kW. As a result, the optimal operating conditions of the system include a solar collector area of 1600 m2, an energy storage tank volume of 54 m3, an electricity production of 23757 MW/year, a total system efficiency of 22%, an IRR of 15.65% and a payback period of 9.81 years.