نشریه مهندسی مکانیک تبدیل انرژی
سال نهم شماره 3 (پیاپی 32، پاییز 1401)

Lithium-ion batteries have become the mainstay of energy storage for off-grid solar products due to their high efficiency, low cost, high capacity, lack of memory effect and long cycle life. Lithium ion is an evolving technology that was first introduced to the market in the early 1990s, and research and development work continues to improve safety, performance, and longevity. Lithium-ion batteries have many features that are well-suited for use in off-grid applications. They have a long cycle life and do not suffer from their discharge speed and high memory effect of nickel cadmium and nickel metal hydride batteries. The charging efficiency of lithium ion batteries is up to 99%. Lithium-ion systems must be properly designed to perform well and avoid the serious safety hazards that can result from battery cell misuse and malfunction. Overcharging, overheating, short circuit, or damage to a charged lithium-ion battery can result in fire or explosion. Proper design and testing can prevent these hazards and ensure the safety, high performance and long-term performance of off-grid products.

In this study, thermodynamic evaluation and regional analysis of a new cogeneration system based on a combination of multi-effect desalination and compressed air energy storage were performed. The study system consists of heliostat subsystems, gas turbine, multi-effect desalination plant and compressed air energy storage system. Thermodynamic software for solving EES engineering equations has been used to model the studied system and also to obtain the results of system analysis. In this study, 8 different scenarios were studied, taking into account the charging time, discharge time, number of sunny hours and the number of different desalination effects, and finally the best scenario was selected for the study. Also, at the end of the parametric study, it should be said that the best scenario, scenario number 5, in which there were 7, was selected. Because in this scenario, the best performance of the system, ie the amount of reciprocal exergy efficiency (ERTE), reciprocal efficiency (RTE), the amount of system power and the rate of fresh water produced by the system were at their highest rate. According to the studies performed on the parameters affecting the system outputs, the number of heliostat, turbine efficiency and compressor efficiency can be mentioned. Also, the exergy analysis of the system showed that the most exergy degradation was related to the CAES unit and the solar unit, respectively.

The increasing need for electricity has led to the construction of countless thermal power plants around the world. Increasing the amount of carbon dioxide entering the atmosphere and intensifying the greenhouse phenomenon is one of the most important problems of creating new power plants. In the meantime, carbon capturing and storage which removes and stores carbon dioxide output from power plants plays a very important role in reducing the greenhouse effect. The main and fundamental problem of carbon absorption units is the lack of production of a product with high economic value, and practically, a very significant reduction in the return on investment ratio makes it uneconomical. By determining optimal process conditions and reducing exergy loss, the establishment of these units can be justified to an acceptable extent. In this article, the carbon captur unit of one of the country's power plants is simulated first and then analyzed from exergy loss point of view, and finally, by determining the optimal operating conditions, the unit's utility consumption reduced as much as possible. According to the conducted studies, the utility consumption and exergy loss of the unit are directly related to the temperature of the fluid entering the amine recovery tower. After performing the calculations and determining the optimal conditions compared to the reference state, it was found that in the medium range of carbon recovery, exergy loss is reduced to about 15% and utility consumption is reduced to 3%.

In this paper, the thermodynamic performance of a solar assisted high temperature heat pump with water heating application is investigated. The comprehensive simulation and analysis of energy and exergy was done by Haysis and MATLAB software. This analyzes produce some convincing results due to the use of environmentally friendly and environmentally friendly energy sources. Thermodynamic analysis in thermal energy systems is very important due to the identification of high-consumption equipment and determining the location and level of inefficiency of the system equipment. According to the results of the system energy, among the equipment of the P100 pump system and the HX1 heat exchanger, it has the lowest and the highest energy consumption, respectively. 2.09 and 22669.11 kW. Also, the exergy analysis shows that the highest amount of exergy of currents with 367092 kW is related to the input flow of the tank and the highest exergy destruction of the equipment is 15563 kW related to the solar collector. This exergy destruction of the solar collector with temperature changes throughout the year with the lowest destruction in July at the rate of 14342 kW and the highest exergy destruction of 15678 kW relates to the month of June. Among the rotating equipment, the most exergy destruction is related to the k101 compressor of the water heat transfer cycle.

The present study conducts an energy evaluation of a new solar tri-generation design for cooling, heating, and power generation of a hospital complex. The proposed system contains linear Fresnel concentrating collectors and photovoltaic thermal absorbers, which use solar energy to produce electrical and thermal energy for sale and partially provide the energy for cooling and heating cycles. The proposed cooling system in this structure is a single effect LiBr-H2O absorption chiller. For the cases of cooling and heating systems, energy demand is more than solar energy production; gas fire backup heaters are intended. The annual system performance under the air conditioning load of the hospital complex is presented. The results show that the solar cycle provides 30% of the system's annual energy supply. In addition, the proposed structure also generates 77.7 MWh of electrical energy. The understudy system provides all its required energy from solar energy on the hottest day of the study from 9 to 15. The proposed collector has a better performance than photovoltaic thermal and concentrating Thermal collectors.

The purpose of this research is to experimentally investigate the role of copper oxide nanoparticles in improving the tribological properties of the lubricant. This research consists of three stages. In the first stage, copper oxide nanoparticles with weight percentages of 0.1, 0.2 and 0.5 were added as an additive to Behran Super Turbo Diesel SAE 15W-40 oil. An ultrasonic bath was used to disperse the nanoparticles in the fluid, and span80 surfactant was used to stabilize the fluid and prevent solid nanoparticles from settling. In the second stage of the experimental tests, including the wear test using the pin-on-disk wear test device and the thermal conductivity test, were performed. In the third stage, the results of the analysis and the performance of the nano-fluid blends were compared with the base fluid. The results of this research showed a decrease in friction coefficient values, a decrease in wear rate and an increase in thermal conductivity of nano-lubricant blends compared to the base fluid. Based on the results, the lowest coefficient of friction, the lowest amount of wear and the highest coefficient of thermal conductivity are related to the nano-lubricant mixture containing 0.5% by weight of copper oxide nanoparticles. The friction coefficient reduction rate of this nano-lubricant mixture was 37.1% compared to the base oil, the wear reduction rate was 58.3% and the thermal conductivity increase rate was 3.84% compared to the base oil. The results show the positive role of copper oxide nanoparticles as an additive in improving the tribological properties of the working fluid.