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This research paper presents a review of the state of the art of desalination in Mexico, with the aim of clarifying the main challenges and opportunity areas for desalination as the main solution to overcome water stress. First, the current situation and forecasts on the availability of water resources in Mexico are described, followed by the main economic, social, and legislative issues of desalination. Mexico's installed capacity for the different desalination technologies and their evolution in recent years was investigated, followed by a comparison with global trends. The current state of research and development in desalination technologies carried out by Mexican institutions was also studied. The results show that membrane technology plants account for 88.85%, while thermal technology plants account for the remaining 11.15%. Although Mexico presented a 240% increase in its desalination capacity in the last 10 years, it has not been enough to overcome water stress, so it is concluded that in the future, it is necessary to increase its capacity in greater proportion, specifically in the areas with greater scarcity, which can be achieved with the joint participation of academy–industry–government through the creation of autonomous organizations, social programs, and/or public policies that promote it. [ABSTRACT FROM AUTHOR]

Solar collector technologies operate with better performance when the Sun beam direction is normal to the capturing surface, and for that to happen despite the relative movement of the Sun, solar tracking systems are used, therefore, there are rules and standards that need minimum accuracy for these tracking systems to be used in solar collectors' evaluation. Obtaining accuracy is not an easy job, hence in this document the design, construction and characterization of a sensor based on a visual system that finds the relative azimuth error and height of the solar surface of interest, is presented. With these characteristics, the sensor can be used as a reference in control systems and their evaluation. The proposed sensor is based on a microcontroller with a real-time clock, inertial measurement sensors, geolocation and a vision sensor, that obtains the angle of incidence from the sunrays' direction as well as the tilt and sensor position. The sensor's characterization proved how a measurement of a focus error or a Sun position can be made, with an accuracy of 0.0426° and an uncertainty of 0.986%, which can be modified to reach an accuracy under 0.01°. The validation of this sensor was determined showing the focus error on one of the best commercial solar tracking systems, a Kipp & Zonen SOLYS 2. To conclude, the solar tracking sensor based on a vision system meets the Sun detection requirements and components that meet the accuracy conditions to be used in solar tracking systems and their evaluation or, as a tracking and orientation tool, on photovoltaic installations and solar collectors. [ABSTRACT FROM AUTHOR]

In this paper, the opto–geometric performance of fixed-focus solar concentrators (FFSCs), namely, the high temperature concentrator (HTC), the Scheffler concentrator and the Scheffler-type solar concentrator (STSC), is analysed. The goal of this study is to determine the behaviours of FFSCs as a function of their dimensions and to compare the results to the results of parabolic dish (PD) solar concentrators. An algorithm based on opto–geometric models of these concentrators was developed, and numerical calculations were performed for each type in a range of thermal power of 1–50 kW. The numerical results indicate that FFSCs require a reflector with a diameter 45% larger than the diameter of a PD concentrator and increase the diameter of the solar image at the receiver by 350% compared with a PD concentrator. The increase in the diameter of the solar image by the fixed receiver in the FFSC produces a lower concentration. For thermal demands of less than 10 kW, FFSCs do not have significantly large dimensions. The proposed algorithm can be employed to evaluate the potential use of FFSCs and an FFSC instead of a PD concentrator because of the operational advantages of the fixed receivers of the different types. [ABSTRACT FROM AUTHOR]

Abstract: This study develops and applies a new mathematical model for estimating the intercept factor of a Scheffler-type solar concentrator (STSC) based on the geometric and optical behaviour of the concentrator in Cartesian coordinates, and the incorporation of a thermal model of the receptor is performed using numerical examinations to determine the technical feasibility of attaching the STSC to a 3kWe Stirling engine. A numerical validation of the mathematical model is determined based on the experimental results reported for the WGA500 concentrator and the CNRS-PROMES system receiver. The numerical results allow for the design of the STSC and a comparison with a parabolic dish that provides the same thermal demand. Our findings show that the highest concentration was obtained with an edge angle of 45°, which was observed in the parabolic dish as well, but the STSC receiver shows a 7% increase in the thermal efficiency compared with the efficiency of the parabolic dish receiver. Finally, the STSC is appropriate for regions where the solar height allows for a reduction of convective thermal loss. [Copyright &y& Elsevier]

This paper presents a methodology for the sizing of linear Fresnel reflectors with curved mirrors and inverted compound parabolic concentrator cavity. The objective of the paper is to determine the geometrical parameters of the concentrator to obtain the maximum solar energy collection. The proposed methodology uses an analytical procedure in conjunction with a ray trace technique. A parametrical study evaluating the operation hours for a representative day in the critical month for the city of Mexicali, Baja California, Mexico, was carried out. For a concentrator with seven curved mirrors of 34.3 cm width and tubular absorber of 4.2 cm diameter, the resulting dimensions were: 10 cm spacing between mirrors, 1.8 m focal distance and 19.7 cm width cavity. With these dimensions, a geometrical concentration of 11.9 and collection efficiency of 82.4% are obtained. [ABSTRACT FROM AUTHOR]

The design and evaluation of several configurations of evaporative cooling systems for air conditioning of a dwelling for low-income sectors in Mexicali, Mexico using simulation with TRNSYS 16.A is presented in this paper. The configurations studied include direct as well as indirect evaporative cooling with heat exchange and also systems with solid desiccant. The main rating parameters to classify the different configurations are the internal comfort conditions, the efficiency and the number of required equipments. The results show that the best configuration is one that includes a heat exchanger that pre-cools the air inlet stream with a cooling stream delivered by air coming from the dwell, but there is a small fraction of the time during the day that comfort is not met. If thermal comfort is to be met during the whole day, solid desiccant systems are the best choice. [ABSTRACT FROM AUTHOR]

The objective of the present work is to dimension and evaluate an absorption LiBr-H2O cooling system assisted by solar energy and natural gas for air conditioning of a group of housings in Mexicali, Baja California, Mexico. The analysis of the hourly, daily and monthly operating performance in the period with more cooling demand is carried out by mean of TRNSYS 16, and it is seeking the least collection area and the highest solar fraction; that which is translated in the minimum operation cost and initial investment. It was found that the system generates conditions of the space between comfortably warm and comfortably cold, according to ISO 7730 (2005), with 287 m² of evacuated tubes which contribute 90% of the required energy. The system is technically feasible, since it covers the cooling demand during the summer period and it requires a similar collecting area to the available one in the housing compounds. [ABSTRACT FROM AUTHOR]

This paper presents the design criteria, methodology. and results of the basic and detailed engineering for a descending film ammonia absorber using air cooled finned tubes, which is part of an advanced absorption cooling system (solar generator absorber heat exchange cycle). The design consists in determining all the construction parameters for the air cooled ammonia absorption unit, starting with the operating conditions defined by a thermodynamical simulation of the process considering both physical and operational design restrictions. The chosen option was based on a comparison between the advantages and disadvantages of each possible array, type, and geometry. After performing the operational simulation, thermal and mechanical designs, and the consistency analysis, it was found that an absorption unit using 29 5/8 NPT 14 (BWG) steel carbon ASTM A-179 tubes, with pure SB-234 aluminum fins was the best option. The tubes are arranged in an equilateral triangle fashion, with crossed air flow cooling. [ABSTRACT FROM AUTHOR]

This paper proposes the configuration of an Organic Rankine Cycle (ORC) coupled to a solar domestic hot water system (SDHWS) with the purpose of analyzing the cogeneration capacity of the system. A simulation of the SDHWS was conducted at different temperatures, observing its performance to determine the amounts of useable heat generated by the solar collector; thus, from an energy balance point of view, the amount of heat that may be used by the ORC could be determined. The working fluid that would be suitable for the temperatures and pressures in the system was selected. The best fluid for the given conditions of superheated vapor at 120 °C and 604 kPa and a condensation temperature of 60 °C and 115 kPa was acetone. The main parameters for the expander thermodynamic design that may be used by the ORC were obtained, with the possibility of generating 443 kWh of annual electric energy with 6.65% global efficiency of solar to electric power, or an overall efficiency of the cogeneration system of 56.35% with a solar collector of 2.84 m2. [ABSTRACT FROM AUTHOR]