Energy Recovery Process Research Articles

Cross-scale analysis of the energy recovery process in pressure exchanger and pipeline system

Cross-scale analysis of the energy recovery process in pressure exchanger and pipeline system

Fuzzy control strategy of pure electric vehicle based on driving intention recognition

The main reason that currently hinders the commercialization of electric vehicles is a bottleneck in battery, motor and electronic control technology, however, an In-depth study of electronic control technology is one of the most effective means to break through this bottleneck at present. The purpose of this paper is to solve the problem that the pure electric vehicle is difficult to meet the driver’s acceleration intention in the urban road cycle acceleration work condition and the brake energy recovery process does not consider the battery state of charge during the deceleration work condition. Proposed a control strategy that can meet the requirements of road cycle conditions and driver’s driving intentions and take account of the vehicle operating status. Use a fuzzy control algorithm to develop a fuzzy controller that taking the motor demand speed change rate and battery state of charge as input, the motor demand torque compensation coefficient as output. The experimental results show that the modified control strategy can improve the actual output power, the actual output torque of the motor and actual driving force of the wheel under the premise of maintaining economy; it also improved the acceleration performance and climbing performance of pure electric vehicles, and can recycle braking energy efficiently. The experimental results show that the secondary development control strategy can meet the requirements of the cycle work condition CYC_ECE_EUDC for the speed and driving force and the driver’s driving intention under the premise of not sacrificing economics.

Integracja procesów odzysku/przekształcenia energetycznego i materiałowego odpadów tworzyw sztucznych pochodzenia komunalnego w krajowym systemie gospodarki odpadami

Integracja procesów odzysku/przekształcenia energetycznego i materiałowego odpadów tworzyw sztucznych pochodzenia komunalnego w krajowym systemie gospodarki odpadami

Experimental characterization of thermal-hydraulic performance of a microchannel heat exchanger for waste heat recovery

Given size and performance advantages, microchannel heat exchangers are becoming increasingly important for various energy recovery and conversion processes. In this study, detailed experimental measurements were conducted to characterize flow and heat transfer performance of a microchannel heat recovery unit (HRU) manufactured using standard photochemical etching and diffusion bonding processes. According to the global flow and temperature measurement, the HRU has delivered the predicted thermal performance under various oil and air flow rates. As expected, the heat transfer effectiveness varies between 88% and 98% for a given air and oil flow rates while it increases with air inlet temperature due to the improved thermal conductivity. However, significant flow mal distribution is identified among the air channels according to the in-depth flow distribution measurement using hot wire. The flow measurement also indicates visible misalignment of the air channels caused by the manufacturing processes. In addition, the excessive pressure drops occurred for both air and oil channels indicating reduced flow areas due to the photochemical etching process. The results of this experimental study can hopefully provide insights in improving designs of microchannel heat exchangers using the same manufacturing processes.

Thermodynamic investigation of a concentrating solar collector based combined plant for poly-generation

The detailed thermodynamic evaluation for combined system assisted on solar energy for poly-generation are studied in this paper. This poly-generation cycle is operated by the concentrating solar radiation by using the parabolic dish solar collector series. The beneficial exits of this integrated plant are the electricity, fresh-water, hot-water, heating-cooling, and hydrogen while there are different heat energy recovery processes within the plant for development performance. A Rankine cycle with three turbines is employed for electricity production. In addition to that, the desalination aim is performed by utilizing the waste heat of electricity production cycle in a membrane distillation unit for fresh-water generation. Also, a PEM electrolyzer sub-component is utilized for hydrogen generation aim in the case of excess power generation. Finally, the hot-water production cycle is performed via the exiting working fluid from the very high-temperature generator of the cooling cycle. Moreover, based on the thermodynamic assessment outputs, the whole energy and exergy efficiencies of 58.43% and 54.18% are computed for the investigated solar plant, respectively.

A tool for assessing the scalability of pressure-retarded osmosis (PRO) membranes

Osmotic energy recovery from hypersaline waters, such as produced water from oil and gas reservoirs and concentrated brine, is strategically significant to water utilization and sustainable energy production. Much attention has been given to pressure-retarded osmosis (PRO) as a potentially viable process for osmotic energy recovery. To predict the performance of various operable PRO configurations in conjunction with prior art membranes, a robust simulation tool has been developed in this work that is based on an equation of state for electrolyte solutions and a detailed mass transfer model. The salinities of draw and feed inlet streams are specified such that they are representative of produced water and seawater, respectively. By integrating fluxes over discrete elements, the simulator is able to capture the effects of continuous dilution on thermodynamic property profiles across the membrane area. This has implications for the scalability of coupon-scale power density measurements. The quantitative impact of electrolyte solution non-ideality on calculated energy recovery is evaluated based on a representative PRO process configuration.

On the importance of phase saturation heterogeneity in the analysis of laboratory studies of hydrate dissociation

Methane hydrates (MHs) have been considered as the future source of energy because of its vast resource volume and high energy density. Energy recovery from MH-bearing sediments has attracted intensifying research activities. Fundamentally, heat transfer, fluid flow through porous media, and the kinetics of hydrate reaction are the three key processes controlling the behavior of MH dissociation and the associated fluid production. Earlier studies have suggested that heterogeneous spatial distribution of SH is inevitable in MH-bearing samples synthesized in laboratory. In this paper, we extend our study to analyze numerically the simulation results from the two realizations of the samples (homogeneous and heterogeneous) to identify differences in the fluid production and to determine if they are sufficiently different. Additionally, we conduct a sensitivity analysis and a statistical analysis on the key transport and kinetic rate parameters that could affect hydrate dissociation and fluid production in the context of a heterogeneous hydrate-bearing sample, in an effort to provide insights that could lead to improved designs for laboratory experiments and (possibly) field applications. Our results suggest that the approximation of an artificial hydrate-bearing core with heterogeneous phase saturations by an assumption of uniform phase saturation distributions results in practically similar fluid production profile except for the very early stage with maximum 20.0% deviation in the water production. From the sensitivity and statistical analysis, we determine that gas production depends strongly on the kinetic rate constant, Kd0 and the composite thermal conductivity of the hydrate-bearing sediments, λθ; while, water production is very sensitive to Kd0 and the absolute permeability of the sandy medium, k. Understanding the effect of phase heterogeneity and the relative importance of key parameters on the production behavior of hydrate-bearing sediments could provide basis for novel production technologies that lead to enhanced gas production and energy efficiency in the energy recovery process.

Wastewater sludge to energy production. A review

Global economic and social development involves increasing demands for water use for various purposes: domestic, public, industrial. Wastewater treatment in these processes results in increasing volumes of sewage sludge. The elimination of this sludge is a permanent concern at global level because of the dangers to the environment, consisting of the high content of organic pollutants, toxic and heavy metals. However, a significant amount of renewable energy can be recovered from sludge from sewage treatment, with several paths being possible: anaerobic digestion, combustion and co-combustion, pyrolysis, gasification. Each of these pathways is characterized by advantages and disadvantages, benefits and technological limitations. This paper proposes a review of current conversion methods and technologies for energy recovery from sewage sludge, anaerobic digestion, incineration and co-combustion especially. Processes present in current literature and practice are described, resulting in the influence of the properties of sludge fuels and their impact on the energy recovery process when these fuels are used in combustion plants. There are also scientific researchers conducted to improve operational and environmental performance and cost competitiveness.

Coupling carbon dioxide and magnetite for the enhanced thermolysis of polyvinyl chloride

To valorize plastic wastes, pyrolysis of polyvinyl chloride (PVC) was conducted as a case study. In an effort to build the more sustainable pyrolysis platform for PVC, CO2 was particularly employed as a reactive gas medium, and magnetite (Fe3O4) was used to explore the feasibility of enhancing CO2-assisted PVC pyrolysis. The favorable effect of Fe3O4 on syngas generation from pyrolysis of PVC was apparent to yield highest concentration of H2 (0.28 mol% at 590 °C) and CO (4.34 mol% at 800 °C) in the presence of 0.1 g Fe3O4/1 g PVC. The GC-TOF analysis of tar generated from thermal decomposition of PVC evidenced more breakdown of PVC hydrocarbons in the presence of Fe3O4, which led to the enhanced production of syngas. In the presence of 0.01 g Fe3O4, the evolution of CO was observed at lower temperature (7.1 mol% at 680 °C) than the case without Fe3O4, and further addition of Fe3O4 up to 0.5 g gradually increased the CO level in the latter stage of pyrolysis (up to 4.5 mol% at 900 °C), which is attributed to the enhanced Boudouard reaction. Good adsorption ability of biochar products was also demonstrated in the removal of methylene blue. Collectively, the use of Fe3O4 in CO2-assisted pyrolysis of plastics could open the possibility of utilizing waste plastics in thermo-chemical process for energy recovery and environmental application.

Geothermal energy from flooded mines: Modeling of transient energy recovery with thermohaline stratification

Geothermal energy from flooded mines is a high-potential clean energy resource that can provide heating to large communities with power comparable to small-scale power plants. The transient energy recovery process for utilizing this energy resource, however, has not been well understood, especially those involving the heat transfer in mine water with the widely-observed layering phenomenon where the temperature and salinity are stratified. To better understand the transient energy recovery process considering such a layering phenomenon, this study presents a numerical analysis of transient heat extraction from a flooded mine shaft with mine water dominated by thermohaline stratification. The numerical analysis is conducted based on a realistic case using an open-loop heat pump system. The simulation results show that, when normal pumping rates are used, the water temperature available to heat pumps almost keeps unchanged because the transient energy recovery using an open-loop system only leads to a temperature reduction of 0.2–0.3 K. By comparison, the simulation results in this study are consistent with those measured from real demonstration projects, showing the accuracy of the simulations and confirming the high efficiency and reliability of this energy innovation. The modeling results in this study also reveal that heat extraction does not affect the stability of thermohaline stratification when normal pumping rates, e.g.,0.0014–0.03 m3/s, are adopted, but will break thermohaline stratification with pumping rates over a hundred times of the commonly-used ones. These findings provide guidelines for future applications at different scales, and the methodology reported in this study can be used to assist the design of the energy recovery systems.

Seasonal variation of the organic and inorganic composition of sugarcane vinasse: main implications for its environmental uses.

Sugarcane vinasse is the main waste stream of the Brazilian agroindustry. The typical composition of sugarcane vinasse gives it a high polluting potential that implies the necessity to define sustainable strategies for managing this waste. Knowledge of the inorganic and organic composition of vinasse and its seasonal variation is extremely important to conduct scientific research to define alternative managements for vinasse disposal other than fertigation. This study evaluated the variability of vinasse composition throughout the same harvesting season and among three harvesting seasons of one Brazilian annexed biorefinery (2015-2017). The contents of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total solids (TS), suspended solids (SS), salinity (K+, Na+, Ca2+, Mg2+, Cl-, F-), nutrients (N, P, S), trace metals (Al3+, As2+, Ba2+, Cd2+, Cr3+, Co2+, Cu2+, Fe2+, Pb2+, Mn2+, Hg2+, Mo2+, Ni2+, Se2+, Zn2+), and specific soluble organic compounds (sugars, alcohols, and organic acids), as well as pH and conductivity, were monitored in 13 samples. The results indicated that sugarcane vinasse is a suitable feedstock for biological treatments, such as anaerobic digestion processes for energy recovery, as well as substrate for biomass (e.g., microalgae, energy crops, lignocellulosic biomass) growth. The application of a previous treatment makes vinasse a more environmentally friendly natural fertilizer for land fertigation.

Biogas Potential from the Anaerobic Digestion of Potato Peels: Process Performance and Kinetics Evaluation

This article intends to promote the usage of potato peels as efficient substrate for the anaerobic digestion process for energy recovery and waste abatement. This study examined the performance of anaerobic digestion of potato peels in different inoculum-to-substrate ratios. In addition, the impact of combined treatment with cow manure and pretreatment of potato peels was examined. It was found that co-digestion of potato peel waste and cow manure yielded up to 237.4 mL CH4/g VSadded, whereas the maximum methane yield from the mono-digestion of potato peels was 217.8 mL CH4/g VSadded. Comparing the co-digestion to mono-digestion of potato peels, co-digestion in PPW/CM ratio of 60:40 increased the methane yield by 10%. In addition, grinding and acid hydrolysis applied to potato peels were positively effective in increasing the methane amount reaching 260.3 and 283.4 mL CH4/g VSadded respectively. Likewise, compared to untreated potato peels, pretreatment led to an elevation of the methane amount by 9% and 17% respectively and alleviated the kinetics of biogas production.

Comparative analyses of three olive mill solid residues from different countries and processes for energy recovery by gasification

Biomass is a renewable energy source which may provide a significant contribution to the reduction of fossil fuels consumption and the associated environmental impacts. The use of agricultural or agro-industrial waste such as solid residues from olive oil production is particularly relevant since it may combine several benefits. Gasification is a promising waste-to-energy technique for this type of lignocellulosic residues. The technology however is adapted to a relatively limited panel of solid waste fuels of defined specifications, which must therefore be characterized properly to assess their adaptation. The purpose of this research was to analyze and compare three different olive mill solid residues by complementary techniques such as Fourier transform infrared spectroscopy (FTIR) and thermochemical methods, in order to characterize these residues as potential fuels for gasification. The results obtained underlined the complex nature of the residues and indicated that they were mainly organic, with very little mineral matter. In addition to the major organic components (cellulose, hemicelluloses and lignin), the presence of several minor organic constituents was shown by thermogravimetry coupled to differential scanning calorimetry and FTIR. The gas produced from pyrolysis was analyzed by gas chromatography and mass spectrometry. It was found to contain several degradation products from lignocellulosic material and olive oil, such as hydroxyacetone, furfural and methoxyphenols. The influence of the olive oil extraction process (two-phase or three-phase) was also demonstrated. It was shown that the thermochemical degradation of olive mill residues followed a complex pathway but the composition of the residues met the requirements for gasification for most parameters.

Energy analysis and multi-objective optimization of waste heat and cold energy recovery process in LNG-fueled vessels based on a triple organic Rankine cycle

Due to the high level of pollutant emissions from traditional marine diesel engines, Liquefied Natural Gas (LNG) as clean energy is becoming a better choice for main engines to replace the traditional fuels. Meanwhile, in order to improve the energy efficiency of the marine power system, the Organic Rankine Cycle (ORC) has been regarded as the most suitable solution to recover the waste heat for the power generation of vessels. In this paper, both the waste heat of the main engine and the cold energy of LNG have been fully considered, and a novel triple ORC process has been proposed for the waste heat and cold energy recovery of LNG-fueled vessels. It adopts the exhaust gas of the main engine and the cooling water from the engine jacket as heat sources, and uses the cold energy of LNG and the sea water as cold sources. Based on the 15 optional working fluid conditions, the heat source utilization rate, system exergy efficiency, net output power, and system cost are, respectively, combined as two objectives, and the multi-objective adaptive firefly algorithm is used to optimize the thermodynamic performance of the system. The optimization results of different heat and cold sources as well as the design parameters have been discussed. Finally, the system's exergy loss has been analyzed to make suggestions for further improvement. The results show that this novel ORC system can better meet the energy recovery requirements of LNG-fueled vessels, with higher net output power, lower cost, and greater energy recovery efficiency. The largest exergy loss of the system exists in the condensers of the stages 2 and 3, and the expanders in the various stages. Therefore, subsequent cooling energy recovery and the use of Stirling engines can be considered to further improve the system efficiency.

Modeling of integrated processes for the recovery of the energetic content of sugar cane bagasse

AbstractSugar cane bagasse is an agro‐based residue that is a very good feedstock for energy recovery processes. The aim of this study was to use ASPEN Plus v8.8 to develop thermodynamic simulation models for energy‐recovery from sugar cane bagasse and to predict product yield and composition based on the inherent characteristics of the feedstock and other process factors. Two simulation flowsheets were developed for energy recovery from sugar cane bagasse: one for a pyrolysis process and the other for a combined pyrolysis‐steam reforming process. The simulation predictions revealed a very good yield of bio‐oil (63.4%) from sugar cane bagasse. The oil was composed of hydrocarbons of different lengths, aromatic compounds, and pyrolytic water (8.1%). For the pyrolysis steam‐reforming simulation, the optimal conditions were a temperature range of 600–700°C, pressure of 1 atm, and steam‐to‐feed ratio (STFR) of 10 kg kg−1. Factor interactions were examined from response surface plots. A theoretical model for the prediction of hydrogen yield was also developed by regression, with a good R2 value. Analysis of variance (ANOVA) results revealed that the model was significant but pressure was not a significant factor in the steam reforming process. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

Numerical study on combustion characteristics of six-stroke-cycle gasoline compression ignition engine with continuously variable valve duration valve technology

Engine performance and emissions of a six-stroke gasoline compression ignition engine with a wide range of continuously variable valve duration control were numerically investigated at low engine load conditions. For the simulations, an in-house three-dimensional computational fluid dynamics code with high-fidelity physical sub-models was used, and the combustion and emission kinetics were computed using a reduced kinetics mechanism for a 14-component gasoline surrogate fuel. Variation of valve timing and duration was considered under both positive valve overlap and negative valve overlap including the rebreathing of intake valves via continuously variable valve duration control. Close attention was paid to understand the effects of two additional strokes of the engine cycle on the thermal and chemical conditions of charge mixtures that alter ignition, combustion and energy recovery processes. Double injections were found to be necessary to effectively utilize the additional two strokes for the combustion of overly mixed lean charge mixtures during the second power stroke. It was found that combustion phasing in both power strokes is effectively controlled by the intake valve closure timing. Engine operation under negative valve overlap condition tends to advance the ignition timing of the first power stroke but has minimal effect on the ignition timing of second power stroke. Re-breathing was found to be an effective way to control the ignition timing in second power stroke at a slight expense of the combustion efficiency. The operation of a six-stroke gasoline compression ignition engine could be successfully simulated. In addition, the operability range of the six-stroke gasoline compression ignition engine could be substantially extended by employing the continuously variable valve duration technique.

Modeling of giant magnetostrictive vibration energy harvesting

Vibration energy recovery technology, as an important way to alleviate energy pressure, has a broad application prospect in the electromechanical field. With the excellent performance of giant magnetostrictive materials (GMM), the giant magnetostrictive vibration energy recovery technology has attracted attention. In view of the shortcomings of current giant magnetostrictive vibration energy recovery research, this paper designs a column-rod vibration energy recovery device based on the material properties of giant magnetostrictive materials, and introduces its working principles. Combined with the structural characteristics of the device, this paper establishes the output model of the energy recovery process, calculates and analyzes the voltage output of the energy recovery, and obtains the output curves under different excitation energies were obtained, providing reference for the optimal design of the device and its further engineering application.

Cooperation of a Horizontal Ground Heat Exchanger with a Ventilation Unit During Winter: A Case Study on Improving Building Energy Efficiency

Renewable energy sources have a significant impact on improving a building’s energy balance. These sources are increasingly used in modern construction. One such source is a ground air heat exchanger (earth-air heat exchanger – EAHX), which is used in a building’s mechanical ventilation system. This solution allows for the initial preparation of inlet air in a ventilation unit prior to the exhaust air energy recovery process (recuperation). As a result, the solution reduces the energy demand for the heating or cooling of rooms. This article expands upon a previous study on the possibilities of improving energy efficiency of a horizontal earth-air heat exchanger (EAHX) working in cooperation with a ventilation unit. This study adds to the knowledge gained in the previous study (Romańska-Zapała et al., 2017) performed during the summer of 2016. This previous study found that, in the summer, the continuous operation of these exchangers is not optimal; therefore, there is a need for dynamic control of the ventilation unit’s fresh air source. This is due to changes in the exchanger’s operating status between heating and cooling, as a result of external temperature fluctuations. The thesis statement of this previous paper emphasized that this relationship is not only appropriate on an annual basis for the transitional seasons (spring and autumn), but also on individual days during the potentially most favorable seasons of exchanger work (summer and winter). This article presents the results of in situ measurements of the horizontal, tubular ground air heat exchanger which supports building heating by preheating the inlet air of the cooperating ventilation unit in the winter season, in southern Polish climatic conditions. In particular, this article provides details on the experimental verification of the previous paper’s thesis regarding the possibility of sub-optimal performance of an EAHX exchanger subject to continuous operation during the winter season. The experiment in this paper was performed using a ventilation unit (intake – exhaust) connected to three independent fresh air sources: a direct external air intake located on the wall, and two air intakes located outside of the building that directs air into the pipes of two earth-air heat exchangers. This article illustrates how the exchanger’s work changes the ventilation unit’s inlet air temperature. For a majority of the experiment, the exchanger – ventilation unit system was working optimally. Therefore, the system did not require intervention of the control system. However, due to several temporary increases in outdoor temperature, the occasional cooling state operation of the EAHX exchanger was also recorded. Even before the occurrence of these undesirable states, an exchanger should be switched off and a bypass should be used to directly collect external air and reduce the unnecessary load of electric fan drives. Considering the results of this study, it can be concluded that in the winter, it is favorable to automatically control the selection of a ventilation unit’s fresh air source depending on external conditions. However, in the winter, the energy effect of the control is comparatively lower than in the summer.

Sludge footprints of municipal treatment plant for the management of net useful energy generation beyond energy neutrality

The paper devised a unified basis for energy recovery processes in municipal treatment plants based on sludge footprints. Emphasis was placed upon innovative energy recovery technologies to test whether energy neutrality could be sustained or even, net useful energy could be produced. In this context, it evaluated first the energy potential of municipal wastewater treatment plant based on sludge footprints: it adopted a unified perspective where energy recovery was considered as an integral part of energy conservation in sludge. Sludge footprints of different activated sludge configurations were first analyzed based on latest concepts of process stoichiometry and modeling. The performance indicators of process modifications were analyzed and interpreted for energy conservation for a wide range of sludge age between of 0.5–50 d. An influent COD level of 500 mg/L was adopted, also defining all significant COD fractions compatible with related characterization studies. The role of primary sedimentation was accounted for where applicable. Calculations showed that 1259 kcal/m3 (75%) to 379 kcal/m3 (23%) of COD energy could be preserved in sludge as the sludge age was increased between the range of 0.5–50 d. Conventional activated sludge (CAS) conserved around 35–40% energy, corresponding to 600–650 kcal/m3. Primary sedimentation boosted the overall energy conservation to 901–990 kcal/m3, corresponding to 54–59% of the available energy in sewage COD. As expected, energy recovery by means of anaerobic digestion (biogas), remained far below the energy consumption in the treatment plant. This study envisaged syngas production by means of high temperature pyrolysis as a novel alternative instead of sludge digestion. Pyrolysis revealed a potential to yield a net useful energy (positive net energy) of 0.08–0.49 kWh/m3 for systems operated at sludge ages of 2–10 d without primary sedimentation; much higher net useful energies of 0.33–0.59 kWh/m3 could be obtained in systems with primary sedimentation operated at sludge ages 2–14 d. The study provided conclusive evidence that the real problem in establishing energy neutrality in treatment systems was the low energy recovery of the conventional sludge digestion and not the level of energy conservation in the activated sludge process; therefore, the step forward should look for more effective energy recovery processes such as high temperature pyrolysis (syngas generation) or similar novel technologies.

냉열회수 공정을 적용한 LNG 연료 추진선용 연료공급시스템의 개념 설계

냉열회수 공정을 적용한 LNG 연료 추진선용 연료공급시스템의 개념 설계