Jorge Ovidio Aguilar Aguilar

Photovoltaic thermal concentration has emerged as a method to enhance the energy efficiency and performance of photovoltaic installations. This approach addresses the growing demand for renewable energy aimed at reducing emissions and mitigating climate change. It represents a significant solution for applications requiring both thermal and electrical energy under constraints of a limited available area for solar energy harvesting. However, currently developed devices rely on expensive photovoltaic cells, incorporate complex geometries that are difficult to manufacture and maintain, and employ tracking systems that complicate interconnection with similar units. The objective of this study is to design and numerically evaluate a hybrid thermal–photovoltaic modular linear Fresnel solar concentrator (H-MLFRC) based on commercial silicon cells. The proposed system allows series and parallel interconnection and is suitable for both islanded and grid-connected configurations. Its development was guided by integrated optical, photovoltaic, and thermal analyses, which defined the system geometry, characteristic parameters, and operating conditions. The results indicate that the maximum operating temperature of the device is 70 °C under a nominal operating mass flow rate of 0.45 kg/s. Additionally, the thermal and photovoltaic efficiencies are 49% and 16%, respectively, resulting in a combined efficiency of 65%.

The parametric design of a low-power (A_r = H/R = 2.6–3.0), number of blades (2–5), and a swept-area constraint of 4 m². The parametric study shows that fewer blades increase Cp, although a three-blade rotor improves start-up torque, vibration mitigation, and load smoothing. The recommended configuration—three blades, A_r = 2.6, σ = 0.30 and S1046 (or NACA 0018) operated near λ ≈ 3.75—balances efficiency and start-up performance. For the representative mean wind velocity of 5 m/s, typical of the Yucatán Peninsula, the VAWT achieves a maximum output of 136 W at 220 rpm. Under higher-wind conditions observed in specific sites within the region, the predicted maximum output increases to 932 W at 380 rpm.

This study presents a theoretical analysis of the solar flux distribution within the receiver of the high-flux solar furnace at IER-UNAM. The furnace comprises an array of 409 first-surface spherical facets, each hexagonal in shape with a side length of 20 cm, and all mounted on a spherical framework. Each facet is carefully adjusted to focus sunlight onto a single focal point. Initially, the distribution of solar radiation is evaluated based on measurements obtained in Temixco, Morelos, Mexico (18°50′21″ N, 99°14′7.5″ W). Using these data, an analytical model is proposed to describe the solar radiation distribution using a Gaussian approximation. An additional analytical model is then developed to estimate the concentration distribution and its geometric shape at the furnace’s focal point, considering the solar width’s root mean square (RMS) value along with the optical errors associated with the heliostat and the reflective facets. Ultimately, by applying the concept of the effective solar source, an analysis of the solar flux distribution within the furnace receiver is conducted. This results in an analytical equation that characterizes the two-dimensional and three-dimensional distribution of the concentrated solar flux. Calculations reveal that the system captures approximately 30 kW of power, with peak concentrations reaching around 10,000 suns.

Parabolic Trough Collectors (PTCs) are a well-established technology for efficiently generating hot water and low-enthalpy steam. For instance, PTCs can be used in steam power systems to drive small Organic Rankine Cycles (ORCs). This study evaluated the thermal efficiency of a PTC equipped with a receiver tube featuring a concentric annular cross-section. This receiver design consists of a tube with a concentric rod inside, forming an annular gap through which the working fluid flows. A thermodynamic model was developed to assess the PTC’s thermal efficiency in hot water and low-enthalpy steam applications. The evaluation considered the First and Second Laws of Thermodynamics, factoring in environmental losses. The model included a bare receiver tube with three-rod diameters—3/8, 1/2, and 3/4 inches—and a range of volumetric flow rates from 1 to 6 L per minute. The results showed improved heat transfer with the annular cross-section receiver compared to a conventional circular one, particularly at lower flow rates of 1 and 2 L per minute. The highest increase in thermal efficiency was observed with the 3/4-inch rod at a flow rate of 1 L per minute, where the maximum efficiency reached 40%.

En el presente trabajo se desarrolló el estudio de un rotor de aerogenerador Darrieus tipo Phi de 2 m de altura (para baja potencia) mediante los métodos Double Multiple Streamtube (DMS) y Qblade lifting line theory (QLLT) con la finalidad obtener los parámetros de configuración adecuados para el posterior diseño de un aerogenerador de eje vertical (VAWT) de dimensiones similares. Se realizó la comparación de ambos métodos con resultados experimentales reportados por otros autores, utilizando como referencia la estimación del coeficiente de potencia (Cp) en función de la relación de velocidad específica (TSR). Se encontró que el método QLLT es una mejor solución en términos de estimación del coeficiente de potencia, con un error absoluto máximo de 35 % y error promedio de 5 %. Sin embargo, dado el alto tiempo de cómputo en comparación con el método DMS es recomendable su uso en etapas avanzadas de diseño. Por otro lado, el método DMS con una capacidad de estimación inferior (error absoluto máximo de alrededor de 60 %, error promedio de 11 %) es adecuado para las primeras etapas de diseño dado su bajo tiempo de Cómputo.

This paper aims to evaluate different design configurations of a combined heat and power (CHP) plant with post-combustion CO₂ capture. Three cases are involved in this study: case 1 consists of three trains and each train has a configuration of one gas turbine with a heat recovery steam generator (HRSG); case 2 consists of three trains and one steam turbine; and case 3 consists of only two trains. The third case presented the highest CHP efficiency of 72.86% with 511.8 MW net power generation. After selecting the optimum configuration, a parabolic-trough collector (PTC) was incorporated to generate additional saturated steam at 3.5 bar for the capture plant, adding greater flexibility to the CHP because more steam was available. In addition, the efficiency of the cycle increased from 72.86% to 80.18%. Although case 2 presented lower efficiency than case 3, it has a steam turbine which brings the possibility of increasing the amount of electricity instead of steam production. When the PTC was incorporated in case 2, the power generated in the steam turbine increased from 23.22 MW to 52.6 MW, and the net efficiency of the cycle from 65.4% to 68.21%.