• Energy Research
• Energies close

Electricity is fundamental to modern societies and will become even more so as its use expands through different technologies and population growth. Power generation is currently the largest source of carbon-dioxide (CO2) emissions globally, but it is also the sector that is leading the transition to net zero emissions through the rapid rise of renewables. The impacts of COVID-19 on the electricity sector led to a reduction in the demand for electricity, while at the same time, the current global energy crisis has placed the security and affordability of electricity at the top of the political agenda in many countries. In this way, the decrease in the demand for electricity, as well as its gradual recovery, makes it necessary to carry out energy planning that considers the adverse effects caused by global events with a high socioeconomic impact. In this article, the Low Emission Analysis Platform (LEAP) 2020 software has been used to determine the distribution of energy sources to 2050 for Mexico. The variables that lead to the possible profiles for 2050 are social, economic, and technological. The results correspond to a possible future based on official data from the National Electric System (SEN) of Mexico. The forecast for 2050 indicates that the electricity sector will have almost double the current installed capacity; however, emissions do not correspond to twice as much: they are practically 50% higher.

The heat transfer in double pipe heat exchangers is very poor. This complicates its application in absorption cooling systems, however, the implementation of simple passive techniques should help to increase the heat and mass transfer mainly in the absorber. This paper carried out a simulation and its experimental comparison of a NH3-H2O bubble absorption process using a double tube heat exchanger with a helical screw static mixer in both central and annular sides. The experimental results showed that the absorption heat load per area is 31.61% higher with the helical screw mixer than the smooth tube. The theoretical and experimental comparison showed that the absorption heat load difference values were 28.0 and 21.9% for smooth tube and the helical mixer, respectively. These difference values were caused by the calculation of the log mean temperature difference in equilibrium conditions to avoid the overlap of solution temperatures. Therefore, the theoretical and experimental results should be improved when the absorption heat is included in the heat transfer equation or avoiding the operation condition when output is lower than input solution temperature.

Absorption systems are a sustainable solution as solar driven air conditioning devices in places with warm climatic conditions, however, the reliability of these systems must be improved. The absorbing component has a significant effect on the cycle performance, as this process is complex and needs efficient heat exchangers. This paper presents an experimental study of a bubble mode absorption in a plate heat exchanger (PHE)-type absorber with NH3-LiNO3 using a vapor distributor in order to increase the mass transfer at solar cooling operating conditions. The vapor distributor had a diameter of 0.005 m with five perforations distributed uniformly along the tube. Experiments were carried out using a corrugated plate heat exchanger model NB51, with three channels, where the ammonia vapor was injected in a bubble mode into the solution in the central channel. The range of solution concentrations and mass flow rates of the dilute solution were from 35 to 50% weight and 11.69 to 35.46 × 10−3 kg·s−1, respectively. The mass flow rate of ammonia vapor was from 0.79 to 4.92 × 10−3 kg·s−1 and the mass flow rate of cooling water was fixed at 0.31 kg·s−1. The results achieved for the absorbed flux was 0.015 to 0.024 kg m−2·s−1 and the values obtained for the mass transfer coefficient were in the order of 0.036 to 0.059 m·s−1. The solution heat transfer coefficient values were obtained from 0.9 to 1.8 kW·m−2·K−1 under transition conditions and from 0.96 to 3.16 kW·m−2·K−1 at turbulent conditions. Nusselt number correlations were obtained based on experimental data during the absorption process with the NH3-LiNO3 working pair.

High consumption of electricity represents an economic and social problem in warm places, caused by the massive use of cooling machines. Absorption systems are a sustainable method for air conditioning applications. However, environmental conditions should be analyzed to avoid crystallization problems of the working mixture. This article presents a thermal analysis of a solar absorption cooling system in dynamic conditions using NH3-H2O, H2O-LiBr, NH3-NaSCN, NH3-LiNO3, and H2O-LiCl working mixtures using Equation Engineering Solver (EES) and TRaNsient SYstem Simulation (TRNSYS) software. A solar collector area of 42.5 m2 was selected to carry out the thermal analysis. The results showed that H2O-LiCl obtained the maximum solar (0.67) and minimum heating (0.33) fraction. However, it obtained the maximum lost heat fraction (0.12), in spite of obtaining the best coefficient of performance (COP) among the other working mixtures, due mainly to a crystallization problem. The gain fraction (GF) parameter was used to select the adequate solar collector number for each working mixture. NH3-LiNO3 and NH3-H2O obtained the highest GF (up 6), and both obtained the maximum solar (0.91) and minimum heating (0.09) fraction, respectively, using 88.8 and 100.4 m2 of solar collector area, respectively.

The energy consumption for space cooling is growing faster than for any other end-use in buildings, more than tripling between 1990 and 2016. Energy efficiency is an important topic in the drive to reduce the consumption of electricity, particularly in air conditioning. This paper presents a simulation of an absorption cooling system with a parabolic trough collector under dynamic conditions using TRaNsient SYstem Simulation (TRNSYS) software. The thermal analysis seeks to evaluate a storage tank at three different configurations: (1) sensible heat, (2) latent heat, and (3) latent heat incorporating a tempering valve. The latent heat storage tank is a rectangular heat exchanger using MgCl2·6H2O as the phase change material, programmed in EES software; in addition, water and synthetic organic fluid were analyzed as heating fluids. The process was analyzed while varying the solar collector area from 20 to 40 m2 and the storage tank volume from 0.25 to 0.75 m3. The results showed that the solar collector of configuration 1 is unable to satisfy the energy demand. Configuration 2 can satisfy the demand with water and a storage tank volume above 0.50 m3 and 30 m2, while configuration 3 can satisfy the demand above 0.50 m3 and 20 m2 with water.