Search Results (37)

Environmental and social governance targets, as well as the global transition to cleaner renewable energy sources, push for advancements in hydrogen-based solutions for energy generators due to their high energy per unit mass (energy density) and lightweight nature. Hydrogen’s energy density and lightweight nature allow it to provide an extended range of uses without adding significant weight, potentially revolutionizing many applications. Moreover, a variety of sources, including renewable energy, can produce hydrogen, making it a potentially more sustainable option for energy storage despite its main limitations in production and transportation costs. In this framework we are proposing an innovative energy generator that might merge the benefits of batteries and hydrogen. The energy generator is based on a worldwide patented solution introduced by MIEEG s.r.l. regarding the shape of the chambers. This innovative solution can be used to design a 100% H2-fed microturbine with a high power/weight/volume ratio that works as a range extender of battery packs for a comprehensive, high-efficiency hybrid powertrain. In fact, it runs at 100,000 rpm and is designed to deliver about 100 kW in about 15 L of volume and 15 kg of weight (alternator excluded). The system is highly complex due to high firing temperatures, long life requirements, corrosion protection, mechanical and vibrational stresses, sealing, couplings, bearings, and the realization of tiny blades. This paper analyzes the main design challenges to face in the development of such complex generators, focusing on the hot gas path components, which are the most critical part of gas turbines. The contribution of additive manufacturing techniques, the adoption of special materials, and coatings have been evaluated for system improvement. Full article

This study evaluates three scenarios’ technical and economic viability for implementing a microgeneration power plant using biogas derived from the anaerobic digestion of food waste. The case study focuses on the Federal University of Pernambuco (UFPE) campus in Recife, northeastern (NE) Brazil, targeting the organic fraction of solid waste from food units (restaurants, canteens, and kiosks). The analysis was based on field data, the chemical composition of the waste, and the electric energy consumption. Biogas production of 166 m³/day from 1 ton/day of food waste was estimated using an anaerobic reactor of 126 m³. This amount of biogas could generate about 360 kWh/day of electricity if the plant operates at peak hours using a generator set with an alternative internal combustion engine of 120 kW, with a consumption of 66 m³/h and fuel efficiency of 30%. The system could generate 390 kWh/day of electrical energy using a microturbine, with a consumption of 78 m³/h and 30% efficiency. The scenario utilizing a tubular reactor and an internal combustion engine demonstrated the best economic viability. While this study focuses on financial aspects, the findings suggest significant potential contributions to sustainability, including reducing greenhouse gas (GHG) emissions and advancing renewable energy solutions. This model can be adapted for small NE Brazil municipalities, offering economic and environmental benefits. Full article

Solid oxide fuel cells (SOFC) could facilitate the green energy transition as they can produce high-temperature heat and electricity while emitting only water when supplied with hydrogen. Additionally, when operated with natural gas, these systems demonstrate higher thermoelectric efficiency compared to traditional microturbines or alternative engines. Within this context, although digitalisation has facilitated the acquisition of extensive data for precise modelling and optimal management of fuel cells, there remains a significant gap in developing digital twins that effectively achieve these objectives in real-world applications. Existing research predominantly focuses on the use of machine learning algorithms to predict the degradation of fuel cell components and to optimally design and theoretically operate these systems. In light of this, the presented study focuses on developing digital twin-oriented models that predict the efficiency of a commercial gas-fed solid oxide fuel cell under various operational conditions. This study uses data gathered from an experimental setup, which was employed to train various machine learning models, including artificial neural networks, random forests, and gradient boosting regressors. Preliminary findings demonstrate that the random forest model excels, achieving an R² score exceeding 0.98 and a mean squared error of 0.14 in estimating electric efficiency. These outcomes could validate the potential of machine learning algorithms to support fuel cell integration into energy management systems capable of improving efficiency, pushing the transition towards sustainable energy solutions. Full article

This study aims to analyze the influence of adding Aeroshell 500 oil on physicochemical properties. It was found that the oil’s kinematic viscosity is much higher than that of diesel and Jet A, with a higher density and flash point as well. Elemental analysis revealed a higher carbon content and lower hydrogen content in Aeroshell oil compared to Jet A and diesel, with lower calorific power. Adding 5% oil increases the mixture viscosity, flash point, and density; decreases the calorific power; and increases the carbon content for both diesel and Jet A. In the second part, mathematical models determined the combustion temperatures for Jet A, diesel, Jet A plus 5% Aeroshell 500 oil, and diesel plus 5% Aeroshell 500 oil, based on an air excess from one to five. Elemental analysis determined the oxygen and air quantities for these mixtures and stoichiometric combustion reaction for CO₂ and H₂O. Regarding the CO₂ quantity, adding 5% Aeroshell 500 to Jet A increases it from 3.143 kg to 3.159 kg for each kilogram of mixture burned in the stoichiometric reaction. Similarly, adding the oil to diesel in a 5% proportion increases the CO₂ quantity from 3.175 to 3.190 in the stoichiometric reaction. Through experimentation with the Jet Cat P80 microturbine engine across four operating regimes, it was observed that the combustion chamber temperature and fuel flow rate are lower when using diesel with a 5% addition of Aeroshell 500 oil compared to Jet A with the same additive. However, the thrust is slightly higher with diesel + 5% Aeroshell 500 oil. Moreover, the specific fuel consumption is higher in regimes one and two for diesel + 5% Aeroshell 500 oil compared to Jet A + 5% Aeroshell 500 oil, while the differences are negligible in regimes three and four. At maximum operating conditions, the excess air was determined from the measured values, comparing the combustion chamber temperature with the calculated value, with a 7% error, extrapolating the results for the scenario when oil is not used. Also, during the testing campaign, the concentrations of CO and SO₂ in the exhaust gas jet were measured, with higher concentrations of CO and SO₂ observed for diesel compared to Jet A. Full article

Climate-change-related events are increasing the costs of power outages, including losses of product, revenue, and productivity. Given the increase in meteorological disasters in recent years related to climate change effects, the number of costly blackouts, from an economic perspective, has increased in a directly proportional manner. As a result, there is increasing interest in the use of alternators to supply dependable, instantaneous, and uninterruptible electricity. Traditional research has focused on the installation of diesel backup systems to ensure power requirements without deeply considering the resilience capabilities of systems, which is the ability of a system to recover or survive adversity, such as a power outage. This research presents a novel approach focusing on the resiliency impact of backup systems’ storage-free dispatchable solutions on buildings and compares the advantages and disadvantages of biomethane microturbines, natural gas engines, and diesel engines backup systems, discussing the revenue resulting from the resilience provided by emergency generators. The results show that, for several diesel fuel and natural gas safety assumptions, natural gas alternators have a lower probability of failure at the time of a blackout than diesel generators, and therefore, resilience increases. Full article

Renewable energy is a promising substitute for fossil fuels when corelated with P2G technology. To optimise P2G efficiency, there is a need to increase hydrogen fraction in the fuel stream. Simultaneously gas microturbines are widely applied in many industry sectors. These devices are often equipped with diffusion combustors. This situation was investigated in this paper. The P2G and gas microturbines may be integrated together in the future leading to the application of hydrogen-enriched fuel. Hydrogen-enriched fuel causes increase in combustion temperature and velocity. In a nonadapted combustor, these phenomena could result in an increase of NOx emissions and risk of material overheating and failure. In order to adapt the combustors for hydrogen-enriched fuel, the concept of autonomous internal flue gases recirculation (IFGR) system was applied to this issue. In this paper, the IFGR system applied to gas microturbine was studied in terms of hydrogen-enriched fuel application. The obtained exhaust gases recirculation ratios were too low to affect the combustion process as it was expected. The observed combustion modifications in the combustor were hardly linked to the air flow modification in the liner, due to IFGR system implementation. After CFD studies, the proposed IFGR system does not seem to provide the expected effects. Full article

The development of AC distribution systems provides for the seamless integration of low-voltage microgrids with distributed energy resources (DERs). This poses new challenges for the control of normal, emergency, and post-emergency states of microgrids, calling for the creation and development of information and communications technology infrastructure. Power converters/inverters that are used to integrate renewable DERs lack inertia. Along with them, fossil fuel-fired generation units are also being integrated into microgrids. These include gas generator sets, diesel generator sets, and microturbines, having small (up to 1–2 s) values of mechanical inertia constants—Tj. This leads to an increase in the rate of transients by a factor of 5–10. Under these conditions, the technical requirements for the speed of automatic power flow control systems, as well as the methods they rely on, have to be reconsidered. Microgrids include DC microgrids, AC microgrids, and hybrid (AC-DC) microgrids. In the case of hybrid microgrids, DERs are connected to the DC grid and are integrated into the AC grid through a common inverter. The complexity of the task of microgrid control is due to the need to choose properly the type and extent of control actions so as to prevent the emergence and development of accidents. The employed control methods must ensure the reliable power supply to consumers and the quality of power in microgrids, as well as the reliable operation of the external distribution systems into which they are integrated. The article gives an overview of control methods for low-voltage AC and AC-DC microgrids, which allow one to tackle effectively solve the tasks. Full article

This work focuses on the energy and economic evaluation of a power generation system composed of a downdraft gasifier and gas microturbine. The gasification process was studied using wood pellets as fuel, while the influence of two gasification agents (air and oxygen-enriched air) on parameters, such as low heating value (LHV), composition, and yield of syngas, were analyzed. The syngas produced from oxygen-enriched air gasification in a downdraft gasifier had an LHV higher than 8 MJ/Nm³, being suitable to be supplied in the gas microturbine. Subsequently, syngas use in the gas microturbine was evaluated, and the results demonstrated that microturbine efficiency dropped from 33.00% to 21.35%, while its power decreased from 200 kW to 81.35 kW. The power generation system was modeled using Aspen Plus^® v 11.0 software and validated using results obtained from published experimental studies. Accordingly, the integrated generation system presented an overall efficiency of 11.82% for oxygen-enriched air gasification cases. On the other hand, an economic assessment through risk analysis using Monte Carlo simulations was performed using Crystal Ball^® v11.1.2.4.850 software. The economic results indicated that the implementation of a generation system was economically unfeasible, however, if the electricity rate price was increased by 63%, the proposed configuration could be feasible. Full article

Supplied with electricity and natural gas, local energy systems (LESs) with gas-fired generations increase the operational flexibility of urban energy supply. However, the increasing usage of these LESs may lead to adverse impacts on the urban energy system supply via power and/or gas distribution networks. Dynamic interactions between the LESs, electricity, and gas networks subject to different disturbances need to be investigated due to the complexity of the problem. To address this issue, this paper first presents the topology and operating mode of the LESs as well as the relationship with power and gas networks. Second, an extended microturbine model is developed to reflect the nonlinear dynamic propagation of disturbances between the two networks. A general model of the interconnected LESs is developed to analyze the mutual impacts between gas and electricity networks under different modes. Finally, an iterative method is proposed to simulate the mechanism of disturbance propagation between the electricity network, gas network, and LESs, incorporating the impacts of loads and renewables. Case studies reveal that simultaneous regulation of multiple gas-fired generators would reduce the minimum pressure to 50% of the steady-state value. The resulted pressure drop is even lower than the case with higher total gas demand but only one gas-fired generator regulated. Moreover, it is shown that state fluctuations of the gas system last 20 times longer than the electricity system within the LESs. The electrical link between LESs, such as soft opening point with shorter response time, could smooth the fluctuations. Full article

This study quantifies the effluents generated during processing in three industry types, estimates the energy potential from the quantified effluents in the form of biogas generation, and determines the economic viability of the biogas recovered. Data were procured from the relevant scientific publications to quantify the effluents generated from the production processes in the industry types examined, using industrial process calculations. The effluent data generated are used in the 2-module biogas energy recovery model to estimate the bioenergy recovery potential within it. Economic and financial analysis is based on a cash-flow comparison of all costs and benefits resulting from its activities. The effluents generated an average daily biogas of 2559 Nm³/gVS, having a daily potential combined heat and power of 0.52 GWh and 0.11 GWh, respectively. The life cycle analysis and cost-benefit analysis show the quantity of emissions avoided when using the effluents to generate heat and power for processes, along with the profitability of the approach. Conclusively, the study shows that the use of biomass effluents to generate biogas for Combined Heat and Power (CHP) is a viable one, based on the technologies of a reciprocating engine, gas turbine, microturbine, and fuel cell. However, it is recommended that the theoretical estimation be validated using a field-scale project. Full article

Several studies were conducted previously on fuel and biofuel performance of micro-turbines. The present paper combines experimental and statistical approaches to study the vibrational behavior of a gas micro-turbine supplied with different pure fuels and admixed with rapeseed oils. Experimental tests carried out at different operating conditions have allowed us to build a classification model through using discriminant analysis. The classification model can distinguish the vibrational behavior occurring when the turbine is fueled with kerosene, or pure and admixed diesel with rapeseed oil. Moreover, the methodology has even allowed us to highlight differences in vibrational behavior caused by small amounts of rapeseed oil admixed in the fuel. The model reliability, in terms of Cohen’s kappa, results in optimal data classification. Full article

The development of highly efficient and environmentally friendly machines requires the use of new technologies that are created using innovative design solutions and new materials. This also applies to various types of propulsion units, such as gas microturbines or combustion engines. Although these machines have been known for many years, by using new components, it is still possible to improve their performance. This article presents an experimental study conducted on a gas foil bearing using a polymer coating as an anti-friction material. These types of bearings allow for a reduction in friction losses and are not lubricated with conventional lubricants. The dynamic characteristics of the foil bearing structure were determined, which are essential in terms of both rotor dynamics and the entire propulsion system. The research was carried out over a wide range of frequencies, with different loads acting in different directions. Hysteresis loops and vibration orbits were determined. The authors showed that displacements perpendicular to the load in some cases may be relatively large and should not be ignored. The results obtained during the tests can be used to validate numerical models of such bearings, optimize their design and select the structural and anti-friction materials. Full article

The operation of natural gas grids requires electric-powered devices as data acquisition and control systems, surveillance and communication appliances, etc., often located in remote, unpopulated off-the-grid areas, where there is no personnel for surveillance, and maintenance costs are prohibitive. The literature on the power generating systems for these devices is limited to specific applications without a comparison between competing technologies, making their choice a difficult task for natural gas operators. This work presents a comprehensive up-to-date survey of market available technologies for remote power generation in the range of 20–1000 W for gas grid applications: thermoelectric generators, solid acid, direct methanol and solid oxide fuel cells, Stirling engines and microturbines. The work aims at sorting the technologies by techno-energetic, economic and environmental performance while providing specific technological characteristics and limitations. The results indicate well-defined ranges of power in which only some of the technologies are suitable and have very different efficiencies (3–30%). The capital cost of equal power technologies is similar (EUR 5000–30,000) and roughly linear with power (34.8P_el + EUR 6553), whereas operation costs (10–120 cEUR/kWh) and lifetime (0.5–20 yr) significantly depend on the technology. The indications of this review may constitute helpful guidelines to choose properly power generation systems for remote applications. Full article

Data acquisition and processing are areas of research in fault diagnosis in rotating machinery, where the rotor is a fundamental component that benefits from dynamic analysis. Several intelligent algorithms have been used to optimize investigations of this nature. However, the Jaya algorithm has only been applied in a few instances. In this study, measurements of the amplitude of vibration in the radial direction in a gas microturbine were analyzed using different rotational frequency and temperature levels. A response surface model was generated using a polynomial tuned by the Jaya metaheuristic algorithm applied to the averages of the measurements, and another on the whole sample, to determine the optimal operating conditions and the effects that temperature produces on vibrations. Several tests with different orders of the polynomial were carried out. The fifth-order polynomial performed better in terms of MSE. The response surfaces were presented fitting the measured points. The roots of the MSE, as a percentage, for the 8-point and 80-point fittings were 3.12% and 10.69%, respectively. The best operating conditions were found at low and high rotational frequencies and at a temperature of 300 ${}^{\circ }$C. High temperature conditions produced more variability in the measurements and caused the minimum value of the vibration amplitude to change in terms of rotational frequency. Where it is feasible to undertake experiments with minimal variations, the model that uses only the averages can be used. Future work will examine the use of different error functions which cannot be conveniently implemented in a common second-order model. The proposed method does not require in-depth mathematical analysis or high computational capabilities. Full article

This article discusses methods of enhanced power generation using a binary power system with low-boiling fluid as an intermediate energy carrier. The binary power system consists of micro-gas and steam power units and is intended for remote standalone power supply. Trifluotrichloroethane was considered as the working agent of the binary cycle. The developed system was modeled by two parts in MATLAB Simulink and Aspen HYSYS. The model in Aspen HYSYS calculates the energy and material balance of the binary energy system. The model in MATLAB Simulink investigates the operation of power electronics in the energy system for quality power generation. The results of the simulation show that the efficiency of power generation in the range of 100 kW in the developed system with micro-turbine power units reaches 50%. Full article