Low concentrating photovoltaic/thermal collectors: technology development and performance evaluation for buildings and industrial applications

Abstract

The following research work is a compilation of different endeavors that intended to evaluate the technical, economic, and environmental performance of a low concentrating PVT (LCPVT) technology in industrial and buildings applications. The LCPVT technology is a hybridization of a small-size solar thermal parabolic trough manufactured by a Mexican company. The performance evaluation was based on the development and validation of numerical models at the collector and system levels using sofware packages such as the Engineering Equation Solver (EES) and TRNSYS.\\ The model uses the thermal and electrical characteristics of the LCPVT technology calculated by the collector level model to calculate the instantaneous thermal and electrical performance at given operational conditions determined by the system. Two different applications of the proposed LCPVT technology were numerically evaluated: large buildings and industrial processes. The first one consists of a PVT plant as the main energy generation system of a university wellness and sports center building in Monterrey-Mexico. The second one is the hybridization of a currently installed parabolic trough-based solar thermal system and the assessment of its performance considering other locations in Mexico. Additionally, a coupled dynamic-prospective model was developed to assess the technical and $\mathrm{CO_2}$ abatement potential of the massive deployment of the LCPVT technology in the Food \& beverages industrial sector in Mexico. Furthermore, a PVT collectors testing facility was designed based on international standards performance assessment guidelines (ISO 9806 and IEC 61215). The testing facility will allow to development of performance tests of PVT collectors under steady-state or quasi-dynamic procedures with the PV modules working at the maximum power point. This laboratory is the first of its kind in Mexico. \\ The results of the system level simulations suggest that the technical and economic performance of PVT collectors follow a non-intuitive behavior that depends on several variables such as weather conditions, available solar resources, technology cost, energy tariffs, and end-user energy demand and application. The proposed technology may supply up to 72\% of the hot water demand of the university building; in addition to the electric production, and can achieve a specific $\mathrm{CO_2e}$ emission reduction of 77.87 kg$\mathrm{CO_2e}$ per square meter of the required installation area. Nevertheless, the reduced natural gas cost; which is the main heat source in the building, hinders the adoption of the technology. The hybridization of industrial solar-thermal plants in Mexico may present a promising performance when the electricity to fuel cost ratio is the closest to one, which is currently achieved with diesel, LPG, and fuel oil. A PVT plant with an installed capacity of 70.4 kW_t and $\mathrm{16.2 kW_e}$, can achieve a payback period of nearly 5 years. The dynamic-prospective model showed that the Food\&Beverages industry in Mexico has a potential to install up to 7.25 million $\mathrm{m^2}$ of the PVT technology that was here studied. By 2030, the deployment of this technology can represent a $\mathrm{CO_2e}$ emissions reduction of up to 51.7\% from 2018 levels. Finallly, Based on the enhancement opportunities identified in the first prototype, the design of a second LCPVT prototype was developed and proposed in this document. Both; the second prototype and the PVT laboratory design will allow future work on the development, testing and characterization of industrial PVT collectors in Mexico (joint project with the Imperial College London).