Search Results (14)

Energy is crucial for the development of the newest technologies that support human life and its needs, as well as industry and its uses. Due to the growing demand for energy, it is very important to find appropriate and excellent solutions, methods, and technologies in terms of environmental and economic impact. The organic Rankine cycle (ORC) is optimal for power generation in today’s environmental and economic considerations. In this paper, the thermodynamic performance analysis and design of an ORC driven by solar energy for power generation were investigated. This study included the installation of the system for solar energy, where the thermal energy is used as an input for the organic Rankine cycle. Five different systems were developed as follows: basic (ORC), recuperative (ORC), regenerative (ORC), recuperative–regenerative (RR) (ORC), and basic (ORC) with reheat. Also, five different types of working fluids, toluene, R123, R11, n-pentane, and R141b used to compare the effect of changing parameters such as the temperature of the evaporator, temperature of condenser, difference in superheated temperature, and pressure of regenerative and reheat. The RR ORC system using toluene as a working fluid showed the best results for power, efficiency, and cost savings, which were 128.7 kW, 25.83%, and $1872/month, respectively. Full article

Increasing energy efficiency and promoting the use of sustainable energy sources are crucial for addressing global energy challenges. Organic Rankine cycle (ORC) technology offers a promising route for efficient decentralised power generation. This study examines the energy performance of a biomass-fired recuperative ORC for micro-scale applications. The investigation proposes an extensive experimental analysis to characterise the ORC behaviour under design and off-design conditions due to the limited data in the literature. The work examines the impact of different operating parameters (e.g., pump speed, hot source temperature, superheating degree, expander inlet pressure) to provide suitable insights for the efficient design and operation of recuperative micro-generation units fuelled by biomass. The experimental analysis highlights that the micro-scale ORC properly operates under a wide range of operating conditions. Electric power ranges between 0.37 kW and 2.30 kW, and the maximum net electric efficiency reaches 8.55%. The selection of the proper operating conditions guarantees efficiency higher than 7% for power larger than 800 W, demonstrating that biomass-fired recuperative ORC systems represent a valuable option for low-carbon micro-scale generation, with good performance in design and off-design conditions. For this purpose, the pump speed and the superheating degree at the expander inlet are essential parameters to maximise the performance of the investigated recuperative ORC. Full article

Energy shortage and greenhouse gas emission have become bottlenecks in current society development. Improving the efficiency of energy conversion and utilization systems through waste heat recovery and reduction of greenhouse gas through CO₂ capture/conversion are important solutions. Both can be achieved simultaneously by utilizing high-temperature flue gas or CO₂ in flue gas for organic matter gasification, which is called the flue gas chemical recuperative cycle. This paper provides a meaningful review of the latest advancements in the flue gas chemical recuperative cycle system, focusing on its application in diverse gasification systems for organic matters such as methane, sludge, etc. Additionally, this paper reviews methods for the integration of flue gas gasification into energy conversion and utilization systems under the application scenarios of gas turbine flue gas, air combustion flue gas, and oxy-fuel combustion flue gas. Subsequently, in order to improve the conversion efficiency of the chemical recuperative cycle, the applications of emerging gasification technologies in the field of the flue gas recuperative cycle, such as microwave gasification, plasma gasification, etc., are briefly summarized, offering an in-depth analysis of the mechanisms by which new methods enhance the process. Finally, the prospects and challenges of the field are discussed, and a comprehensive outlook is provided to guide future research. Full article

The organic Rankine cycle (ORC) system is an important technology for recovering energy from the waste heat of internal combustion engines, which is of significant importance for the improvement of fuel utilization. This study analyses the performance of vehicle ORC systems and proposes a rapid optimization method for enhancing vehicle ORC performance. This study constructed a numerical simulation model of an internal combustion engine-ORC waste heat recovery system based on GT-Suite software v2016. The impact of key operating parameters on the performance of two organic Rankine cycles: the simple organic Rankine cycle (SORC) and the recuperative organic Rankine cycle (RORC) was investigated. In order to facilitate real-time prediction and optimization of system performance, a data-driven rapid prediction model of the performance of the waste heat recovery system was constructed based on an artificial neural network. Meanwhile, the NSGA-II multi-objective algorithm was used to investigate the competitive relationship between different performance objective functions. Furthermore, the optimal operating parameters of the system were determined by utilizing the TOPSIS method. The results demonstrate that the highest thermal efficiencies of the SORC and RORC are 6.21% and 8.61%, respectively, the highest power outputs per unit heat transfer area (POPAs) are 6.98 kW/m² and 8.99 kW/m², respectively, the lowest unit electricity production costs (EPC) are 7.22 × 10⁻² USD/kWh and 3.15 × 10⁻² USD/kWh, respectively, and the lowest CO₂ emissions are 2.85 ton CO_2,eq and 3.11 ton CO_2,eq, respectively. The optimization results show that the RORC exhibits superior thermodynamic and economic performance in comparison to the SORC, yet inferior environmental performance. Full article

Thermoelectric cooling is a prospective technology that has a lot of advantages; however, its main drawback is its low efficiency compared to other technologies. A lot of scientific research is aimed at the improvement of the efficiency of thermoelectric cooling, including the development of new thermoelectric materials, innovative structures, and better power management strategies. The present work further explores a self-developed recuperative power management approach, which takes advantage of the thermoelectric element’s ability to work as an electrical generator. This study relied on the thermal–electrical analogy method to develop a model that is capable of describing the impact of recuperation on the cooling performance while preserving the simplest configuration possible. The influence of different variables was estimated by three suggested quantities for evaluating the gains, losses, and rationality of the recuperative approach. A recovery of up to 10% of the electrical energy supplied to the thermoelectric element was observed experimentally. The ratio between the recovered energy and induced heat losses did not exceed a factor of 0.9. It is concluded that the recuperation process is reasonable only in the case of unavoidable interruption of the cooling process when average-performance thermoelectric elements are used. Full article

The ankle joint (AJ) is a crucial joint in daily life, responsible for providing stability, mobility, and support to the lower limbs during routine activities such as walking, jumping, and running. Ankle joint injuries can occur due to sudden twists or turns, leading to ligament sprains, strains, fractures, and dislocations that can cause pain, swelling, and limited mobility. When AJ trauma occurs, joint instability happens, causing mobility limitations or even a loss of joint mobility, and rehabilitation therapy is necessary. AJ rehabilitation is critical for those recovering from ankle injuries to regain strength, stability, and function. Common rehabilitation methods include rest, ice, compression, and elevation (RICE), physical therapy, ankle braces, and exercises to strengthen the surrounding muscles. Traditional rehabilitation therapies are limited and require constant presence from a therapist, but technological advancements offer new ways to fully recover from an injury. In recent decades there has been an upswing in research on robotics, specifically regarding rehabilitation. Robotic platforms (RbPs) offer several advantages for AJ rehabilitation assistance, including customized training programs, real-time feedback, improved performance monitoring, and increased patient engagement. These platforms use advanced technologies such as sensors, actuators, and virtual reality to help patients recover quicker and more efficiently. Furthermore, RbPs can provide a safe and controlled environment for patients who need to rebuild their strength and mobility. They can enable patients to focus on specific areas of weakness or instability and provide targeted training for faster recovery and reduced risk of re-injury. Unfortunately, high costs make it difficult to implement these systems in recuperative institutions, and the need for low-cost platforms is apparent. While different systems are currently being used, none of them fully satisfy patient needs or they lack technical problems. This paper addresses the conception, development, and implementation of rehabilitation platforms (RPs) that are adaptable to patients’ needs by presenting different design solutions (DSs) of ankle RPs, mathematical modeling, and simulations of a selected rehabilitation platform (RP) currently under development. In addition, some results from practical tests of the first prototype of this RP are presented. One patient voluntarily agreed to use this platform for more rehabilitation sessions on her AJ (right leg). To counteract some drawbacks of the first prototype, some improvements in the RP design have been proposed. The results on testing the improved prototype will be the subject of future work. Full article

The existence and development of modern society require significant amounts of available energy. Combustion engines are the main sources of heat. Their operation is accompanied by the formation of large volumes of emissions, which have different temperatures and contain harmful substances ejected into the environment. Therefore, the urgent problem today is the reduction in heat emissions. This might be achieved through a reduction in the amount of these pollutants by improving primary heat engines, converting to new, alternative types of fuel, and at the same time, to carbon-free fuel. However, such measures only reduce the temperature level of waste heat but not its volume. Conventional technologies for the utilization of heat emissions are ineffective for using heat with temperatures below 500 K. Thermoacoustic technologies can be used to convert such low-temperature heat emissions into mechanical work or electricity. This article is focused on analyzing the possibilities of improving the thermoacoustic engines of energy-saving systems through the rational organization of thermoacoustic energy conversion processes. An original mathematical model of energy exchange between the internal elements of thermoacoustic engines is developed. It is shown that the use of recuperative heat exchangers in thermoacoustic engines leads to a decrease in their efficiency by 10–30%. From the research results, new methods of increasing the efficiency of low-temperature engines of energy-saving systems are proposed. Full article

Achieving net-zero emissions by 2050 will require tackling both energy-related and non-energy-related GHG emissions, which can be achieved through the transition to a circular economy (CE). The focus of climate change crisis reversal has been on the energy-related continuum over the years through promoting renewable energy uptake and efficiency in energy use. Clean energy transition and efficiency gains in energy use alone will not be sufficient to achieve net-zero emissions in 2050 without paying attention to non-energy-related CO₂ emissions. This study systematically reviews the CE literature across different themes, sectors, approaches, and tools to identify accelerators in transitioning to a CE. The study aims to understand and explore how technology, finance, ecosystem, and behavioral studies in the CE paradigm can be integrated as a decision-making tool for CE transition. The material analysis was carried out by identifying the main characteristics of the literature on CE implementation in the agriculture, industry, energy, water, and tourism sectors. Results of the literature survey are synthesized to engender clarity in the literature and identify research gaps to inform future research. Findings show that many studies focused on technology as an accelerator for CE transition, and more studies are needed regarding the CE ecosystem, financing, and behavioral aspects. Also, results show that CE principles are applied at the micro-, meso-, and macro- (national, regional, and global) levels across sectors with the dominance of the industrial sector. The agriculture, water, and energy sectors are at the initial stages of implementation. Additionally, the use of carbon capture and utilization or storage, conceptualized as a circular carbon economy, needs attention in tackling CE implementation in the energy sector, especially in hydrocarbon-endowed economies. The major implication of these findings is that for CE to contribute to accelerated net-zero emission by 2050, coordinated policies should be promoted to influence the amount of financing available to innovative circular businesses and technologies within an ecosystem that engenders behavioral change towards circularity. Full article

Exploitation of lignite in continuous surface mines requires removing masses of overburden, which are hauled to a dumpsite. There are some technological arrangements where the overburden is transported several dozen meters down to a spreader operating on a lower located dumping level. Depending on an angle of a declined transportation route, there is a possibility to convert the potential gravitational energy of conveyed down overburden masses into electric energy. To recover the maximum percentage of stored energy, an energy-effective and fully loaded belt conveyor should work in a generator mode. Due to the implementation of such a solution, a lignite continuous surface mine, which is a great electric energy consumer, can obtain the status of an electricity prosumer and reduce its environmental impact, in particular demonstrating significant savings in primary energy consumption. Though lignite surface mining is phasing out in Europe, the recuperative, overburden conveyors for downhill transport match up the targets of sustainable mining, understood as getting the maximum benefits from the exploited natural resources. According to the analyzed case study, an investment into the installation of regenerative inverters for the electric power supply of the declined overburden conveyor would pay off within 3–4 years. Full article

The main objective of this paper is to present and analyze an innovative configuration of integrated solar combined cycle (ISCC). As novelties, the plant includes a recuperative gas turbine and the conventional bottoming Rankine cycle is replaced by a recently developed double recuperative double expansion (DRDE) cycle. The configuration results in a fuel saving in the combustion chamber at the expense of a decreased exhaust gas temperature, which is just adequate to feed the DRDE cycle that uses propane as the working fluid. The solar contribution comes from a solar field of parabolic trough collectors, with oil as the heat transfer fluid. The optimum integration point for the solar contribution is addressed. The performance of the proposed ISCC-R-DRDE design conditions and off-design operation was assessed (daily and yearly) at two different locations. All results were compared to those obtained under the same conditions by a conventional ISCC, as well as similar configurations without solar integration. The proposed configuration obtains a lower heat rate on a yearly basis in the studied locations and lower levelized cost of energy (LCOE) than that of the ISCC, which indicates that such a configuration could become a promising technology. Full article

In this study, a directly irradiated, milli-scale chemical reactor with a simple nickel catalyst was designed for dry reforming of methane for syngas. A milli-scale reactor was used to facilitate rapid heating, which is conducive to combating thermal transience caused by intermittent solar energy, as well as reducing startup times. Milli-scale reactors also allow for a distributed and modular process to produce chemicals on a more local scale. In this setup, the catalyst involved in the reaction is located directly in the focal area of the solar simulator, resulting in rapid heating. The effects of mean residence time and temperature on conversion and energy efficiency were tested. The process, which is intended to store thermal energy as chemical enthalpy, achieved 10% thermal-to-chemical energy conversion efficiency at a mean residence time of 0.028 s, temperature of 1000 °C, and molar feed ratio of 1:1 CO₂:CH₄. A significant portion of the thermal energy input into the reactor was directed toward sensible heating of the feed gas. Thus, this technology has potential to achieve solar-to-chemical efficiency with the integration of recuperative heat exchange. Full article

In the framework of the European research project LEMCOTEC, a section was devoted to the further optimization of the recuperation system of the Intercooled Recuperated Aero engine (IRA engine) concept, of MTU Aero Engines AG. This concept is based on an advanced thermodynamic cycle combining both intercooling and recuperation. The present work is focused only on the recuperation process. This is carried out through a system of heat exchangers mounted inside the hot-gas exhaust nozzle, providing fuel economy and reduced pollutant emissions. The optimization of the recuperation system was performed using computational fluid dynamics (CFD) computations, experimental measurements and thermodynamic cycle analysis for a wide range of engine operating conditions. A customized numerical tool was developed based on an advanced porosity model approach. The heat exchangers were modeled as porous media of predefined heat transfer and pressure loss behaviour and could also incorporate major and critical heat exchanger design decisions in the CFD computations. The optimization resulted in two completely new innovative heat exchanger concepts, named as CORN (COnical Recuperative Nozzle) and STARTREC (STraight AnnulaR Thermal RECuperator), which provided significant benefits in terms of fuel consumption, pollutants emission and weight reduction compared to more conventional heat exchanger designs, thus proving that further optimization potential for this technology exists. Full article

Italy is a leading country in the biogas sector. Energy crops and manure are converted into biogas using anaerobic digestion and, then, into electricity using internal combustion engines (ICEs). Therefore, there is an urgent need for improving the efficiency of these engines taking the real operation into account. To this purpose, in the present work, the organic Rankine cycle (ORC) technology is used to recover the waste heat contained in the exhaust gases of a 1 MW_el biogas engine. The ICE behavior being affected by the biogas characteristics, the ORC unit is designed, firstly, using the ICE nameplate data and, then, with data measured during a one-year monitoring activity. The optimum fluid and the plant configuration are selected in both cases using an “in-house” optimization tool. The optimization goal is the maximization of the net electric power while the working fluid is selected among 115 pure fluids and their mixtures. Results show that a recuperative ORC designed using real data guarantees a 30% higher net electric power than the one designed with ICE nameplate conditions. Full article

This work is focused on the thermodynamic optimization of Organic Rankine Cycles (ORCs), coupled with absorption or adsorption cooling units, for combined cooling heating and power (CCHP) generation from biomass combustion. Results were obtained by modelling with the main aim of providing optimization guidelines for the operating conditions of these types of systems, specifically the subcritical or transcritical ORC, when integrated in a CCHP system to supply typical heating and cooling demands in the tertiary sector. The thermodynamic approach was complemented, to avoid its possible limitations, by the technological constraints of the expander, the heat exchangers and the pump of the ORC. The working fluids considered are: n-pentane, n-heptane, octamethyltrisiloxane, toluene and dodecamethylcyclohexasiloxane. In addition, the energy and environmental performance of the different optimal CCHP plants was investigated. The optimal plant from the energy and environmental point of view is the one integrated by a toluene recuperative ORC, although it is limited to a development with a turbine type expander. Also, the trigeneration plant could be developed in an energy and environmental efficient way with an n-pentane recuperative ORC and a volumetric type expander. Full article