Energy Recovery Scheme Research Articles

Research on hydraulic braking energy recovery system of heavy vehicles

The carbon emission of a heavy-duty diesel vehicle is almost equal to the sum of 100 small cars. In the global environment where energy conservation and emission reduction are advocated, the pollution caused by heavy vehicles is non-negligible. A hydraulic brake energy recovery and regeneration system can store the braking energy, convert the energy into kinetic energy and output it to the vehicle transmission system when starting or accelerating, thereby reducing energy consumption and achieving the role of energy conservation and emission reduction. Firstly, this paper mainly summarizes several vehicle energy recovery technology schemes and determines the hydraulic braking energy recovery scheme after a comprehensive comparison. Secondly, the overall structure of the hydraulic brake energy recovery and regeneration system is designed, and the working mode is analyzed. Finally, according to the working characteristics of the main components in the system, the mathematical model is established, the key parameters are simulated and studied, and the appropriate selection and matching scheme is provided.

Research on Speed Control Methods and Energy-Saving for High-Voltage Transmission Line Inspection Robots along Cable Downhill

To ensure the safe operation of high-voltage transmission line inspection robots during downhill descents without power and extend their range after a single charge, this paper proposes an energy-saving speed control method for the inspection robot’s walking wheel motor on downhill slopes by integrating feedback braking and fuzzy PID control. By combining the parameter equation of the overhead catenary line and the structural characteristics of the overhead transmission line, this paper analyzes the relationship between the driving torque of the inspection robot’s wheels and the horizontal displacement along the transmission ground wire before and after descending. Based on this analysis, a speed control and energy recovery scheme is developed for the inspection robot, which combines front-wheel feedback braking with rear-wheel regenerative braking. The fuzzy PID method is utilized to adjust the PWM duty cycle to achieve energy-efficient speed control of the inspection robot’s rear walking wheels. Additionally, to improve the energy density and specific power of the robot’s energy storage unit, a composite power source consisting of lithium batteries and supercapacitors is employed to recover energy from the front walking wheels through feedback braking. The combined simulation results indicate that, compared to fuzzy control and PID control, fuzzy PID control better regulates the robot’s speed under varying slopes, wind resistance, and cable roughness. A downhill speed control system for the inspection of the robot’s walking wheel motor was designed, and its effectiveness was validated through simulated high-voltage line experiments. The fuzzy PID control was demonstrated to effectively maintain the rear walking wheel speed within the targeted range during downhill descents. When descending along a fixed 30° angle cable, the fuzzy PID control resulted in an increase of 5.28% and 14.26% in the state of charge (SOC) of the supercapacitor compared to PID control and fuzzy control, respectively. Moreover, when descending along fixed angle cables of 10°, 20°, and 30°, as well as a variable angle cable ranging from 30° to 0°, the SOC of the supercapacitor increased by 17.55%, 26.25%, 38.45%, and 31.29%, respectively. This demonstrates the effective absorption of regenerative braking energy during the robot’s downhill movement.

Mathematical modelling of the hydromechanical drive of the test bench for plunger hydraulic cylinders with energy recovery

Reliability is a significant parameter of machines, mechanisms, drives, technological equipment and its component parts, including hydraulic motors. Reliability is checked and confirmed by carrying out resource tests, the results of which reveal the characteristics and properties of materials, components and working fluids that are used in the production of hydraulic cylinders and during operation. One of the practical ways to determine reliability is testing. The aim of the work is to improve the theory and methods of calculation and design of the hydromechanical drive system of the service life test bench of plunger hydraulic cylinders through the use of an energy recovery scheme that provides an increase in the energy efficiency of the testing process. Developed on the basis of the application of the theory of volumetric rigidity, a mathematical model of the hydromechanical drive system of the plunger hydraulic cylinder service life test bench made it possible to compare the influence of various design and functional parameters of the elements of the hydromechanical system of the stand on the dynamic performance and energy efficiency of its drive.

On the performance improvement of an inverted Brayton Cycle using a regenerative heat and mass exchanger

Recovery of the low-temperature waste heat for electricity generation has been gaining a significant interest. An Inverted Brayton Cycle (IBC) is often employed to convert the low-temperature waste-heat to electricity while the thermal efficiency and specific work output are poor. In this paper, a new energy recovery scheme is introduced incorporating the IBC with a Regenerative Heat and Mass Exchanger (RHME). The RHME is a heat and mass exchanger that consolidates a recuperator (for thermal efficiency improvement) and an Indirect Evaporative Cooler (for enhanced specific work). Numerical models for RHME and the IBC were judiciously developed where possible condensation in the product air channel was accounted for. The model was validated with the experimental data and the cycle was investigated for various waste-heat sources (50–150 °C). When compared to a conventional air-cooling IBC system, incorporating the current energy recovery scheme increases the thermal efficiency from 8.13% to 14.36% and specific work output from 10.38 to 12.46 kJ/kg equivalent to 76.63% and 20.1% improvements, respectively. The unprecedented performance improvement is realised from the exploitation of the regenerative and air-saturation (cooling) mechanisms for both energy recovery and cooling of the working fluid.

Innovative Energy-Recovery Unit for the LED-Lighting System of Heavy-Duty Vehicles

In this work, the development of an energy recovery control unit to be incorporated in the light-emitting diodes (LEDs) lighting systems of heavy-duty vehicles is presented. This innovative industrial product adopts modern power electronics technology to improve existing trucks’ LED lighting system by eliminating the so far inevitable power consumption by the conventional central control unit of the majority of these vehicles, which is obligatory for the uninterruptable operation of their lighting system. The main idea of this innovative product is its capability to virtually increase the lighting system power consumption without actually consuming this amount of energy, thus facilitating the central control unit requirements regarding these vehicles in an energy-conscious way. Under this light, a mature power converter’s topology is employed to draw the proper amounts of power from the vehicle’s batteries supply, to the level that the central control unit recognizes, and return this energy back to the batteries. The tests results of the developed industrial product highlight the energy saving potential of the proposed energy recovery scheme, while the Life Cycle Cost Analysis (LCCA) results confirm its techno-economical and environmental profit for the truck applications under study.

Multi-criteria decision analysis for optimal planning of desalination plant feasibility in different urban cities in India

Water scarcity is increasing in most Indian cities, exemplified by the recent 2019 Chennai water crisis. Though there were measures initiated at both institutional and local levels, water scarcity has continued. One possible solution is to install energy-efficient renewable energy-powered desalination plants (REpDP) for Indian cities, especially those in favorable climatic zones. The modeling of REpDP combined with multi-criteria decision analysis (MCDA) is proposed to prioritize the optimal site and REpDP selection for providing low-cost freshwater. A standalone seawater reverse osmosis (SWRO) based REpDP that delivers water at a rate of 1.5 m3/h is modeled. Based on the SWRO operation; analytical modeling is carried out to optimize the hybrid energy configuration that combines solar, wind, hydrokinetic with backup energy facilities. The Fuzzy-TOPSIS MCDA with five attributes is performed to rank the modeled alternatives for selected coastal cities. The analysis identified Dwarka in the state of Gujarat, India, as the most suitable urban zone. The results also indicated that the electricity and freshwater production cost for the optimal configuration with an energy recovery scheme provide savings up to 10% and 36.4%, respectively. A comparison is made with EDAS and BWM methods. It provides consistency in results with the Fuzzy-TOPSIS.

Transitioning Wastewater Treatment Plants toward Circular Economy and Energy Sustainability.

Aging infrastructure, increasing environmental regulations, and receiving water environment issues stem the need for advanced wastewater treatment processes across the world. Advanced wastewater treatment systems treat wastewater beyond organic carbon removal and aim to remove nutrients and recover valuable products. While the removal of major nutrients (carbon, nitrogen, and phosphorus) is essential for environmental protection, this can only be achieved through energy-, chemical-, and cost-intensive processes in the industry today, which is an unsustainable trend, considering the global population growth and rapid urbanization. Two major routes for developing more sustainable and circular-economy-based wastewater treatment systems would be to (a) innovate and integrate energy- and resource-efficient anaerobic wastewater treatment systems and (b) enhance carbon capture to be diverted to energy recovery schemes. This Mini-Review provides a critical evaluation and perspective of two potential process routes that enable this transition. These process routes include a bioelectrochemical energy recovery scheme and codigestion of organic sludge for biogas generation in anaerobic digesters. From the analysis, it is imperative that integrating both concepts may even result in more energy- and resource-efficient wastewater treatment systems.

Environmental and energy performances of the Italian municipal solid waste incineration system in a life cycle perspective.

The environmental and energy performances of the Italian municipal solid waste incineration (MSWI) system was investigated by a life cycle assessment approach. On average the 39 MSWIs operating in Italy in 2018 treated about 6,000,000 Mg of residual municipal solid waste (RMSW) recovering on average from 448 kWh Mg-1 RMSW to 762 kWh Mg-1 RMSW of electricity and from 732 kWh Mg-1 RMSW to 1102 kWh Mg-1 RMSW of heat. The average quantity of CO2eq Mg-1 RMSW emitted ranged from about 800 up to about 1000 depending on the size and on the energy recovery scheme of the facility. Avoided impacts (i.e., negative values) were detected for the kg PM2,5eq Mg-1 RMSW and for human health (disability-adjusted life year Mg-1 RMSW). The determination of the hybrid primary energy index (MJ Mg-1 RMSW) indicated that mainly large size facilities and those operating according to a power and heat energy recovery scheme are effectively able to replace other primary energies by the exploitation of the lower heating values of the RMSW.

A Hydrostatic Pressure-Driven Desalination System for Large-Scale Deep Sea Space Station

Compared with the common marine renewable energy sources like solar, wind, and wave energy, etc., the hydraulic pressure stored in the deep seawater can output stable and successive energy flow. Thus, it can be directly coupled with the reverse osmosis (RO) process to supply drinkable mineral water for crews of Deep Sea Space Station (DSSS). We proposed a novel submarine RO desalination system driven by the hydraulic pressure of deep seawater (SHP-RO), composed of a desalination branch to generate fresh water and a back pressure branch to ensure the depth independence of the desalination. The influences of the deep sea environment on the RO were analyzed, based on which the pretreatment of the seawater and the preparation of the drinkable mineral water were studied. The turbine-based energy recovery scheme was investigated in virtue of the CFD simulation on the flow behavior in the different turbine series. It was predicted that, when the DSSS was located at the depth of 1100 m and the operating pressure of the RO process was 6.0 MPa, for a drinkable water production rate of 240 m3/d, the recovered hydraulic pressure energy can achieve 39.22 kW·h, which was enough for driving electricity consumers in the SHP-RO system.

Redundant energy combination and recovery scheme for dual fuel carriers based on thermoelectric harvesting with a large temperature range

Redundant energy combination and recovery scheme for dual fuel carriers based on thermoelectric harvesting with a large temperature range

A New Nonisolated High-Step-Up DC–DC Converter Topology with High Voltage Gain Using Voltage Multiplier Cell Circuit for Solar Photovoltaic System Applications

The solar photovoltaic (PV) source is preferred to be functioned at low voltages. The practical systems such as grid-tied systems require a high output voltage causing a reduction in conversion efficiency. To handle this problem, this paper presents a new nonisolated boost DC–DC converter with a single switch suitable for solar PV applications. This converter comprises dual voltage multiplier (VM) cells, leakage energy recovery scheme, and coupled inductor (CI) techniques to get the desired output voltage from the converter. The double-clamp capacitors are connected to the primary side of the CI. The clamp capacitors can share the current through CI, and it ensures that the leakage inductance energy of CI can be recovered, leading to an expansion in the converter voltage gain and conversion efficiency. In addition, the clamp circuit clamps the voltage stress of the MOSFET switch, and the clamp capacitors will discharge at a specific time to increase the converter gain. A high duty cycle is not necessary for getting a high voltage gain, which avoids the diode reverse recovery issues. The converter can be operated in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). A 500-W experimental prototype is developed for experimental validation, and the supporting simulation results are presented. The maximum efficiency of the converter is 93.94%, and, at full load, the efficiency is 92.55%.

An Innovative Design of Decoupled Regenerative Braking System for Electric City Bus Based on Chinese Typical Urban Driving Cycle

This paper proposes a novel decoupled approach of a regenerative braking system for an electric city bus, aiming at improving the utilization of the kinetic energy for rear axle during a braking process. Three contributions are added to distinguish from the previous research. Firstly, an energy-flow model of the electric bus is established to identify the characteristic parameters which affect the energy-saving efficiency of the vehicle, while the key parameters (e.g., driving cycles and the recovery rate of braking energy) are also analyzed. Secondly, a decoupled braking energy recovery scheme together with the control strategy is developed based on the characteristics of the power assistance for electric city bus which equips an air braking system, as well as the regulatory requirements of ECE R13. At last, the energy consumption of the electric city bus is analyzed by both the simulation and vehicle tests, when the superimposed and the decoupled regenerative braking system are, respectively, employed for the vehicle. The simulation and actual road test results show that compared with the superposition braking system of the basic vehicle, the decoupled braking energy recovery system after the reform can improve the braking energy recovery rate and vehicle energy-saving degree. The decoupled energy recovery system scheme and control strategy proposed in this paper can be adopted by bus factories to reduce the energy consumption of pure-electric buses.

Potential energy recovery scheme with variable displacement asymmetric axial piston pump

Hydraulic systems are widely used in construction machinery and equipment. However, the energy efficiency of hydraulic system is low. In many cases, hydraulic systems output energy to lift the working device. During the lowering process, the potential energy is commonly wasted through the throttling loss of the control valve. Recovering the potential energy is an efficient way to improve the hydraulic system efficiency. In this article, theoretical analysis, simulation calculation, and experimental verification were used to study the energy recovery efficiency of a differential cylinder system controlled by variable displacement asymmetric axial piston pump. Meanwhile, the influence of the load, motor speed, variable displacement asymmetric axial piston pump swashplate angle, accumulator pressure and capacity, and other key parameters on the potential energy recovery efficiency and system performance was analyzed. The results show that the system energy consumption can be reduced effectively by using the potential energy recovery system. When the load, motor speed, pre-charge pressure and capacity of the accumulator, and swashplate angle are 440 kg, 1000 r/min, 2.5 MPa, 1.6 L, and ±5°, respectively, the system’s energy-saving effect can be up to 39.25%. Considering that only the vertical motion of the differential cylinder controlled by variable displacement asymmetric axial piston pump was analyzed, in future work, the corresponding parameter optimization and control strategy will be carried out to obtain good energy recovery effect, and the influence of accumulator pre-charge pressure on the energy-saving effect will be conducted.

BriXs Ultra High Flux Inverse Compton Source Based on Modified Push-Pull Energy Recovery Linacs

We present a conceptual design for a compact X-ray Source BriXS (Bright and compact X-ray Source). BriXS, the first stage of the Marix project, is an Inverse Compton Source (ICS) of X-ray based on superconducting cavities technology for the electron beam with energy recirculation and on a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz, producing 20–180 keV monochromatic X-Rays devoted mainly to medical applications. An energy recovery scheme based on a modified folded push-pull CW-SC twin Energy Recovery Linac (ERL) ensemble allows us to sustain an MW-class beam power with almost one hundred kW active power dissipation/consumption.

Potential energy regeneration method and its engineering applications in large-scale excavators

Hydraulic excavators are essential excavation machines, with more than 3.8 million sets in use in the mining, and engineering and architectural engineering construction fields. However, during the working process, a large amount of gravitational potential energy is wasted, causing low energy efficiency and poor emissions. Taking a large-scale excavator as an example, during a certain 90° excavation process, the gravitational potential energy wastage of the working device is approximately 975.1 kJ, which amounts to at least 20% of the energy consumption of the entire machine, causing significant energy waste and serious pollution. And, during the boom lowering process, the changing rate of potential energy is about 406.4 kW. In order to improve the energy efficiency of hydraulic excavators, the recovery of this huge energy that changes rapidly with low cost and high efficiency is a big problem that must be solved. This paper proposes a gravitational potential energy recovery scheme with an energy conversion cylinder and a hydraulic accumulator. Using this scheme, the gravitational potential energy of the working device can be stored and reused directly, without increasing the cost and install power of the machine largely. In the study, first, the system parameters are designed, following which the multidisciplinary dynamic model of the hydraulic excavator is established. The influence of the accumulator parameters on the energy recovery ratio is studied based on the model. The results demonstrate that with the newly designed system more than 75.9% of the gravitational potential energy can be stored in the accumulator during the lowering process. Moreover, during a certain lifting process, the input energy to the pump can be reduced by 52%. On this basis, a 76 t hydraulic excavator test system is constructed using the above principle. The experimental results match strongly with the co-simulation results. The energy consumption can be reduced to approximately 238 kJ during a certain 90° excavation cycle, and the system can reduce the carbon dioxide emissions by 28088.4 kg per year. The energy-saving and emission-reduction effects are remarkable; furthermore, this principle can directly be applied to other lifting machines.

Parameter matching and braking performance advantage study for all-electric independent driving and braking electric vehicle with four wheels

All-electric integrated brake system is the feature for all-electric independent driving and braking electric vehicle with four wheels (AEIDBEV). Based on its advantages, an integrated simulation platform for parameter matching and performance verification is built. The vehicle control strategy is given. The results of simulation show that all-electric integrated brake system can meet the driver's braking demand and has three advantages. The first is that its braking effectiveness is slightly better than pure mechanical brake system. The second is work time and torque capacity for electromechanical brake (EMB) can be reduced remarkably. This provides a basis for optimising EMB. The third is that it can improve vehicle economy obviously. AEIDBEV has obvious energy saving effect compared with no braking energy recovery scheme and coupled braking energy recovery scheme at three drive cycles of NEDC, Beijing and Changchun.

Parallel Inductor Multilevel Current Source Inverter for Input Ripple Current Reduction in PEM Fuel Cell Applications

ABSTRACT In a power conditioning fuel cell system, the application of a single phase voltage source inverter (VSI) generates a second harmonic (100/120 Hz) ripple current. The harmonic current reduces life, efficiency and performance of the fuel cells due to hysteresis loss effects. This paper proposes current source inverter (CSI) with multilevel features to reduce the second harmonic (100/120 Hz) current ripple drawn from the Proton Exchange Membrane (PEM) fuel cell. The employment of energy recovery scheme in the proposed five-level multilevel current source inverter (MCSI) introduces a single switching state for each output current level. The proposed energy recovery scheme is able to balance the sharing inductor currents effectively. In addition, the proposed MCSI is also integrated with a boost DC current source in order to reduce the size of input DC link inductor and minimize the circuit structure for a reliable power conditioning PEM fuel cell system application.

Low-Power Resonant Clocking Using Soft Error Robust Energy Recovery Flip-Flops

An energy recovery or resonant clocking scheme is very attractive for saving the clock power in nanoscale ASICs and systems-on-chips, which have increased functionality and die sizes. The technology scaling followed Moore’s law, that lowers node capacitance and supply voltage, making nanoscale integrated circuits more vulnerable to radiation-induced single event upsets (SEUs) or soft errors. In this work, we propose soft-error robust flip-flops (FFs) capable of working with a sinusoidal resonant clock to save the overall chip power. The proposed conditional-pass Quatro (CPQ) FF and true single phase clock energy recovery (TSPCER) FF are based on a unique soft error robust latch, which we refer to as a Quatro latch. The proposed C2-DICE FF is based on a dual interlocked cell (DICE) latch. In addition to the storage cell, each FF consists of a unique input-stage and a two-transistor, two-input output buffer. In each FF with a sinusoidal clock, the transfer unit passes the data to the Quatro and DICE latches. The latches store the data values at two storage nodes and two redundant nodes, the latter enabling recovery from a particle-induced transient with or without multiple-node charge sharing. Post-layout simulations in 65nm CMOS technology show that the FF exhibits as much as 82% lower power-delay product compared to recently reported soft error robust FFs. We implemented 1024 proposed FFs distributed in an H-tree clock network driven by a resonant clock-generator that generates a 1–5 GHz sinusoidal clock signal. The simulation results show a power reduction of 93% on the clock tree and total power saving of up to 74% as compared to the same implementation using the conventional square-wave clocking scheme and FFs.

Systematic study on factors influencing the performance of interdetector scatter recovery in small-animal PET.

Interdetector scatter (IDS) is a triple coincidence caused by the Compton scatter of an annihilation photon from one detector block to another which frequently occurs in small-animal positron emission tomography (PET). By finding the true lines-of-response (LORs) of annihilation photon pairs among three possible LORs in IDS events, we can utilize these recovered events to improve the sensitivity of PET systems. IDS recovery should be accurate to yield reliable images with relatively short scan times. We systemically investigated physical factors affecting IDS recovery performance, focusing on the reconstructed image quality of small-animal PET. We evaluated sensitivity increase, recovery accuracy, and image quality by applying different combinations of energy window, recovery scheme, and scanner properties. We used GATE Monte Carlo simulation to acquire coincidence events from a NEMA NU 4-2008 image quality phantom using small-animal PET scanner with axial field of view of 55 mm and diameter of 64 mm. We first defined energy window criteria to obtain valid IDS events. Their role was to assign triple coincidences as IDS events and to restrict the number of LOR candidates to two. We tested three different energy windows around 511 keV. Second, we applied four different recovery schemes (maximum energy, Compton kinematics, neural network, and proportional) to assigned IDS events. To measure the effects of scanner properties, energy resolutions of 0-20% and one to four depth-of-interaction (DOI) layers were simulated. For every combination of the factors, we measured sensitivity increase and recovery accuracy. We also analyzed the reconstructed images for each IDS recovery method in terms of mean pixel intensity, noise, signal-to-noise ratio (SNR), contrast, and recovery coefficients. Sensitivity increase depended on the energy window and energy resolution. The maximum increase in sensitivity was 33% when energy window of [250, 750] keV was applied. Higher energy resolution yielded larger sensitivity increase, especially for narrow windows. Recovery accuracy was affected by all the factors tested in this study. Accuracy increased with narrower energy window, and a neural network scheme was the most accurate. The better energy resolution and DOI capability improved accuracy by providing precise measurement of energies and interaction positions. In image quality analysis, noise and SNR were highly dependent on the sensitivity increase and energy window. When the same energy window was applied, SNR, contrast, and recovery coefficients were higher with higher accuracy of the scheme. Meanwhile, the proportional scheme yielded the best image quality among the schemes and reduced 20% of scan time to achieve the same SNR as that of double coincidence images. As a fundamental research for real implementation of IDS recovery, we conducted a simulation study to evaluate the factors affecting sensitivity increase, recovery accuracy, and image quality. Sensitivity increase was dependent on the energy window and energy resolution, while the recovery accuracy was affected by energy window, recovery scheme, energy resolution, and DOI capability. In image quality analysis, sensitivity increase and recovery accuracy dominantly affected the noise and quantitative accuracy, respectively. Among the recovery schemes, the proportional scheme obtained the best image quality.

Dynamic solar-powered multi-stage direct contact membrane distillation system: Concept design, modeling and simulation

This paper presents a theoretical analysis of the monthly average daily and hourly performances of a solar-powered multi-stage direct contact membrane distillation (SMDCMD) system with an energy recovery scheme and dynamic operating system. Mid-latitude meteorological data from Busan, Korea is employed, featuring large climate variation over the course of one year. The number of module stages used by the dynamic operating scheme changes dynamically based on the inlet feed temperature of the successive modules, which results in an improvement of the water production and thermal efficiency. The simulations of the SMDCMD system are carried out to investigate the spatial and temporal variations in the feed and permeate temperatures and permeate flux. The monthly average daily water production increases from 0.37m3/day to 0.4m3/day and thermal efficiency increases from 31% to 45% when comparing systems both without and with dynamic operation in December. The water production with respect to collector area ranged from 350m2 to 550m2 and the seawater storage tank volume ranged from 16m3 to 28.8m3, and the solar fraction at various desired feed temperatures from 50°C to 80°C have been investigated in October and December.