Carlos D. Rodriguez-Gallegos

Optimal PV and storage sizing for PV-battery-diesel hybrid systems

This paper studies the sizing problem of PV-battery-diesel hybrid systems using convex optimization approach. The case study takes place in an Indonesian island where the load demand fully depends on a single diesel generator (DG). The goal is to optimize the number of solar panels and batteries to be installed to reduce the total cost of the system over the lifetime of 25 years. Real solar irradiance and temperature profiles, together with forecasted diesel prices, are used. A heuristic method, particle swarm optimization, is also employed as a benchmark for performance evaluation. Our results show that the total cost obtained from our proposed method is the lowest since it reaches the global optimal solution. The advantage of a PV-battery-diesel hybrid system over systems operated by a single DG and systems formed by a single DG and solar panels is exposed as, in comparison to them, it achieves a reduction of the total cost (between 7% to 11% and 0% to 4%, respectively) and of the CO2 emissions (between 19% to 29% and 10% to 21%, respectively).

Placement and Sizing Optimization for PV-Battery-Diesel Hybrid Systems

This paper proposes a new method to determine the sizing and siting of diesel generators (DGs), photovoltaic (PV) solar panels, and batteries for off-grid systems. In this work, the objective is to reduce the total system cost while fulfilling the load demand and maintaining the power quality of the system, among other constraints. This is achieved by employing a two-stage particle swarm optimization algorithm; the first for siting and sizing of the system and the second for its scheduling. Three case studies, namely only DGs, DGs + PV, and DGs + PV + batteries systems, based on the energy requirement of an Indonesian island are presented. In addition, real solar irradiance and temperature data are utilized together with a measured load profile. The results reveal that a system that relies only on DGs is not able to keep the system voltage within the tolerable range (from 0.95 to 1.05 p.u.), while yielding a lifetime cost of 104 million USD. The DGs + PV system requires a lower lifetime cost, 67 million USD. Nevertheless, the voltage of the system reaches values lower than 0.95 p.u. for certain nodes during night-time as the PV are not able to provide power. Finally, the DGs + PV + batteries system yields the lowest cost, 64 million USD, and is able to keep the values of the voltage within the desired range, as batteries can provide power when PV are not operating.

Impact of femtosecond laser processing on dielectric layers for solar cell applications

Laser ablation using ultrashort pulses is becoming more relevant in the fabrication of solar cells due to their ability to produce well-defined grooves. In this work, laser grooving of dielectric layers using laser pulses of 480  femtosecond and 515 nm (green) wavelength at various pulse fluences and pulse overlaps is presented. The dielectric is either a single-layer film (SiNX) or a double-layer stack (AlOX/SiNX or SiO2/SiNX). An analytical model that enables one to determine the laser groove depth and width by calculating the equivalent fluence along the midpoint of the groove and by extracting the single-pulse ablation properties (threshold fluence, spot radius, and energy penetration depth) of the dielectrics is presented. The modeled groove dimensions match with the experimentally measured values, thereby allowing precise patterning of the dielectrics. Micromachining considerations such as the ablation rate and ablation efficiency are calculated from the modeled groove depth which enables one to optimize the ablation process. The optimum fluence zone, where the process yields >90% of its maximum ablation rate and efficiency, is identified to be just above the threshold fluence. Moreover, the results indicate that the optimum fluence zone remains practically unaffected irrespective of the chosen laser average power. Hence, the precise calculation of groove dimensions and processing under the optimum fluence zone provides a well-defined and efficient laser grooving process that is essential for high-efficiency solar cell architectures.Laser ablation using ultrashort pulses is becoming more relevant in the fabrication of solar cells due to their ability to produce well-defined grooves. In this work, laser grooving of dielectric layers using laser pulses of 480  femtosecond and 515 nm (green) wavelength at various pulse fluences and pulse overlaps is presented. The dielectric is either a single-layer film (SiNX) or a double-layer stack (AlOX/SiNX or SiO2/SiNX). An analytical model that enables one to determine the laser groove depth and width by calculating the equivalent fluence along the midpoint of the groove and by extracting the single-pulse ablation properties (threshold fluence, spot radius, and energy penetration depth) of the dielectrics is presented. The modeled groove dimensions match with the experimentally measured values, thereby allowing precise patterning of the dielectrics. Micromachining considerations such as the ablation rate and ablation efficiency are calculated from the modeled groove depth which enables one to opt...