Maximum Energy Recovery Research Articles

Study on Regenerative Braking Control Strategy for the Dual-axle Distributed Drive Electric Vehicles

Regenerative braking technology, as a remarkable feature of electric vehicles, can effectively alleviate the driver’s operation burden and extend the driving range. In this paper, a novel regenerative braking strategy is proposed for electric vehicles. First, the brake force distribution relationship of front and rear wheels is studied for enough brake safety. Then an optimal algorithm based on multiple constraints and brake safety is proposed to achieve maximum recover energy. Finally, comparing with the series ECE regulation strategy, the proposed strategy is demonstrated that the enables achieve maximum energy recovery under different driving cycles. Energy recovery rate of the proposed algorithm is improved by 8.40%, 3.84% and 4.09%.

Cost Optimisation of a Flexible Heat Exchanger Network with Fluctuation Probability using Break-Even Analysis

Heat exchanger network (HEN) which is designed to achieve the maximum energy recovery (MER) involves the integration and interactions of multiple process streams. Small disturbances on one stream can affect other connecting streams. In order to manage these disturbances, the process to process and utility heat exchangers with bypass streams installation are typically overdesigned. However, overdesign also means higher capital investment. This study presents the cost optimisation of flexible MER HEN design which considers the fluctuation probability using break-even analysis. Data were extracted for the Pinch study and assessment for flexibility and MER was performed. The MER heat exchanger maximum size (MER-HEM) is able to handle the most critical supply temperature fluctuations while minimising the utility consumption. The overdesign factor can affect the total annualised cost at a certain probability of fluctuation occurrence. Thus, the break-even analysis of the MER-HEM is performed to determine the probability that resulted in high savings of total annualised cost. Two Scenarios (A and B) with different fluctuation probabilities were used to demonstrate the methodology. Application of the proposed methodology on an Illustrative Case Study shows that, for the fluctuation at hot stream H1, the MER-HEM gives the optimum annualised total cost for Scenario A with additional savings of 10 %. For Scenario B, the MER heat exchanger original size (MER-HEO) is the optimum, giving an additional savings of 4 %. For cold stream C1, the MER-HEO is the optimum for Scenario A, giving an extra savings of 4 % whereas the MER-HEM is the optimum for Scenario B, yielding an extra savings of 9 %.

A heat- and mass-integrated design of hydrothermal liquefaction process co-located with a Kraft pulp mill

This paper aims to establish a new standard process for heat and mass integration of hydrothermal liquefaction, co-located with an existing Kraft pulp mill, to produce bio-crude. Hydrothermal liquefaction is an energy-intensive process that operates at high temperature and pressure and produces a biocrude similar to conventional crude oil. The key advantages of installing hydrothermal liquefaction in proximity with a Kraft Mills enables the use of black liquor as a feed to hydrothermal liquefaction, asset repurposing and optimisation, as well as supply chain and logistics integration. This work follows a design process to increase the energy efficiency of the hydrothermal liquefaction process by using an iterative mass and heat integration procedure to optimise mass and energy flows and assets of the hydrothermal liquefaction process. The method uses process simulation tools, Pinch Analysis, heat exchanger network design tool, and the understanding of the process constraints to develop a heat exchanger network for the hydrothermal liquefaction process with maximum energy recovery, minimum number of units and enhanced mass integration. The number of heat exchangers in the network reduced from 14 to 7 when the proposed method was applied. Substituting bio-crude from the new integration hydrothermal liquefaction process for conventional fuels has the potential to decarbonise transport fuels by 11.3 kg CO2-e/GJ of fuel.

Polyzwitterionic Hydrogels in Engines Based on the Antipolyelectrolyte Effect and Driven by the Salinity Gradient.

In this paper, we propose and investigate an original approach to energy conversion based on polyzwitterionic hydrogels, which exhibit an antipolyelectrolyte effect that enables them to swell in salt water and shrink in water of a different (i.e., desalinated water) salinity. The swelling and shrinking processes run cyclically and can move a piston up or down reversibly, thus transforming the antipolyelectrolyte effect into a mechanical force based on the salinity gradient. This phenomenon makes polyzwitterionic hydrogels suitable for use in a smart, polymeric engine. We apply this approach to investigate energy recovery from a polysulfobetaine-based hydrogel. The cross-linking density, external load, particle size, and repeatability of energy recoverability of hydrogels are examined. The maximum energy recovery from 0.4 g of hydrogel in feed (calculated based on dry form) of 102 mJ/kg was obtained by a hydrogel with a 3% cross-linking density, a 200-300 μm particle size, and 100 g external load. Excellent reproducibility of engine cycles was achieved over 10 cycles. This concept is complementary to the osmotic engine concept based on a polyelectrolyte hydrogel. In addition, polyzwitterionic materials have become a benchmark material for preventing biofouling, and the swelling properties of such materials can be further modulated and tuned.

Design of Parallel Braking Control System for Port Hybrid Electric Vehicle

ABSTRACT Zhang, Z., 2018. Design of parallel braking control system for port hybrid electric vehicle. In: Liu, Z.L. and Mi, C. (eds.), Advances In Sustainable Port And Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 513–519. Coconut Creek (Florida), ISS N 0749-0208. Conventional port hybrid vehicles can't effectively recycle tremendous kinetic energy brought by car brake due to the limitation of energy storage element and energy conversion form in energy recovery braking system. A parallel hydraulic hybrid power control system is designed to solve the contradiction between braking safety stability and realizing the maximum energy recovery. The linear proportional electromagnetic valve is adopted to control the hydraulic pressure of the hydraulic cylinder of the brake. The numerical control of the frictional braking force is realized, and the braking force control strategy can be realized with the braking control system. The experimental results show that the system improves the s...

Effect of HRT and external resistances on power generation of sidestream microbial fuel cell with CNT-coated SSM anode treating actual fermentation filtrate of municipal sludge

A microbial fuel cell (MFC) with multiwall carbon nanotube (CNT) coated stainless steel mesh (SSM) coated anode (S-MFC) was operated with a filtrate generated by the fermentation of municipal primary sludge. The S-MFC's maximum power density (MPD: 69.8–164.9 W/m3) and energy recovery (ER: 0.15–0.60 kWh/kgCOD) were 7–21 times higher than those (3.8–27.3 W/m3 and 0.01–0.11 kWh/kgCOD) of MFC with a graphite felt as an anode (G-MFC). The microbial communities of S- and G-MFCs varied slightly depending on the electrode material. Chloroflexi (23.5%) was dominant in S-MFC, and Proteobacteria (25.3%) in G-MFC. Fermenting bacteria such as Rhodanobacter lindaniclasticus and Anaerolineaceae bacterium were dominated by continuous non-electrochemically active bacteria invasion because the actual fermentation filtrate was directly utilized as the substrate. Nevertheless, the CNT-coated SSM anode and the fermentation filtrate of primary sludge improved the power generation in MFC, which demonstrates the significant potential of this sidestream process for sludge treatment.

Energy demand and carbon footprint of treating household food waste compared to its prevention

The majority of household food waste in the EU is sent to landfill or incinerated; a slowly-increasing fraction is collected separately and utilised for anaerobic digestion (AD) or in-vessel composting (IVC). This study evaluates life cycle environmental impacts of these four options to identify the most sustainable alternatives. The results are compared to waste prevention, inclusive of upstream supply-chain impacts. The results suggest that AD has the lowest, net-negative carbon footprint of –40 kg CO2 eq. per tonne of waste treated and the highest life cycle energy recovery efficiency of 12% with respect to the total primary energy recovered. If all of the heat can be utilised, then both AD and incineration can achieve maximum energy recovery efficiencies of around 25%. Waste landfilling has the highest carbon footprint at 193 kg CO2 eq./t and a recovery efficiency of 3% through the combustion of landfill gas. IVC, credited for the production of fertiliser, has a carbon footprint of 80 kg CO2 eq./t and it has the lowest recovery efficiency at 1%. Under the best conditions, the greatest CO2 eq. savings are achieved by the incineration of food waste, with a net-negative carbon footprint of –221 kg CO2 eq./t. However, this is eclipsed by the 2,800–3,100 t CO2 eq. that can be avoided by preventing the avoidable and potentially avoidable food waste. Thus, while unavoidable food waste may be best treated via AD or incineration, the savings are negligible compared to the benefits of waste prevention. Therefore, food waste may be used within a circular economy to reclaim a limited amount of resources, but it should not be considered an alternative to prevention.

Temperature Disturbance Management in a Heat Exchanger Network for Maximum Energy Recovery Considering Economic Analysis

The design of heat exchanger networks (HEN) in the process industry has largely focused on minimisation of operating and capital costs using techniques such as pinch analysis or mathematical modelling. Aspects of operability and flexibility, including issues of disturbances affecting downstream processes during the operation of highly integrated HEN, still need development. This work presents a methodology to manage temperature disturbances in a HEN design to achieve maximum heat recovery, considering the impact of supply temperature fluctuations on utility consumption, heat exchanger sizing, bypass placement and economic performance. Key observations have been made and new heuristics are proposed to guide heat exchanger sizing to consider disturbances and bypass placement for cases above and below the HEN pinch point. Application of the methodology on two case studies shows that the impact of supply temperature fluctuations on downstream heat exchangers can be reduced through instant propagation of the disturbances to heaters or coolers. Where possible, the disturbances have been capitalised upon for additional heat recovery using the pinch analysis plus-minus principle as a guide. Results of the case study show that the HEN with maximum HE area yields economic savings of up to 15% per year relative to the HEN with a nominal HE area.

Synergistic bio-oil production from hydrothermal co-liquefaction of Spirulina platensis and α-Cellulose

Hydrothermal liquefaction (HTL) is a promising technology for the conversion of wet biomass into liquid fuels. In this study, the hydrothermal co-liquefaction (HTCL) of Spirulina platensis and α-Cellulose for bio-oil production was investigated. The bio-oil yield of HTCL was increased significantly by blending α-Cellulose with low-lipid content microalgae of Spirulina platensis in the absence of any catalysts supplementary which reduces the processing cost. The results showed that bio-oil productivity was increased drastically up to 40.33 wt % (28.53 wt % with pure Spirulina platensis and 14.47 wt % with pure α-Cellulose), with a positive synergistic effect (SE) of 16 wt % during the HTCL process. The composition of synthesized bio-oil was analyzed by GC-MS which revealed that HTCL of Spirulina platensis and α-Cellulose are to decrease of its heterocyclic compounds, increased esters and hydrocarbons contents than HTL of pure Spirulina platensis or α-Cellulose. The possible reaction pathways were derived by synthesized bio-oil composition. The maximum energy recovery rate 82% was obtained on HTCL process. The study concluded that, HTCL process is more favorable for the economic concern due to high convention of bio-oil efficiency.

Dual-stage chemical looping of microalgae for methanol production with negative-carbon emission

Abstract As the world is transitioning towards a low-carbon economy, it is becoming important to develop ways to reduce carbon dioxide (CO2) emissions. Chemical looping, a low carbon technology for the industry, is considered as a potential breakthrough technology and a viable option for efficient fuel conversion and carbon capture and storage, with the successful completion of pilot plant trials in the USA. The conversion of captured CO2 to methanol can be considered a promising method for significantly reducing CO2 emissions, while the produced methanol can be used as a convenient energy carrier for hydrogen storage. This study focuses on a process of converting microalgae, a potential fuel feedstock, into methanol by utilizing CO2 generated within the process. The specific focus lies on the conversion of the microalgae into methanol through dual-stage chemical looping and efficient process integration with maximum energy recovery. Aspen Plus® was used to simulate the facility producing 42 mt (metric tons) methanol/h using 60.1 mt/h CO2 and 8.2 mt/h H2. The process was divided into four-module operations: drying, chemical looping gasification, syngas chemical looping, and methanol synthesis. The energy efficiency of this process is around 45–51% which is comparative with the concentrated CO2-based methanol and typical biomass-based syngas to methanol processes. Because the separated CO2 obtained via chemical looping is utilized for methanol synthesis, the carbon-negative value is attained.

A new braking strategy based on motor characteristics and vehicle dynamics for unmanned electric vehicles

Traditionally, vehicle braking generally follows the driver's braking intention. It is impossible for the driver to work out the optimal braking trajectory. However, unmanned vehicle can decide when to brake and how to brake. In this paper, we propose a braking scheme for unmanned electric vehicles. It adopts different braking control strategy according to different braking conditions. When the situation is urgent, the vehicle adopts emergency braking. Otherwise, the vehicle adopts normal braking. In the case of normal braking, the vehicle can automatically set the optimal braking trajectory. The setting of the braking trajectory is based on the characteristics of the motor and vehicle states. When the vehicle follows the set braking trajectory, the electric vehicles can obtain the maximum braking energy recovery. The simulation results show that the proposed braking method is able to achieve the maximum braking energy recovery in the case of normal braking.

OPTIMIZATION OF ENERGY UTILITIES CONSUMPTION IN THE AQUEOUS SODIUM HYDROXIDE SOLUTION EVAPORATION

The paper proposes the retrofit design of a three-unit evaporator for evaporating of aqueous sodium hydroxide solution in order to increase its concentration. The retrofit assumes the creation of a heat exchange equipment network that has to implement heat recovery of the process streams of the evaporator. The design was carried out with the pinch-analysis methods. The treshhold problem (demand for hot utilities only) was identified by shifting the composite curves and the treshhold temperature difference 11,7 °С was found. Problem definition, like a pinch problem, was made with the choice of minimum temperature difference DTmin = 12 °С in heat exchange equipment. The design of the heat exchangers network that realizes the minimum consumption of external utilities and maximum energy recovery was created, and the network optimization with energy relaxation was carried out. Modern plate heat exchangers as heat exchange equipment were chosen and calculated. The economic evaluation of the design was conducted. The payback period will be about two months.

Biohythane production from sugarcane bagasse and water hyacinth: A way towards promising green energy production

The present study embarks the concept of developing continuous biohythane (biohydrogen followed by biomethane) production from renewable energy sources. Combination of sugarcane bagasse and water hyacinth were used to reduce the use of costly chemicals for fermentation process. The lignin content of sugarcane bagasse was reduced using alkaline hydrogen peroxide pretreatment. The maximum lignin reduction of 89 ± 3% (w/w) was observed at 50 °C and 150 min pretreatment time. Scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy analysis were performed to confirm the lignin removal after pretreatment. Further, the influence of the hydraulic retention time on two stage biohythane production was studied by using combination of pretreated sugarcane bagasse and water hyacinth (1:2 ratio) (soluble COD, 30 ± 2 g/L) in continuous stirrer tank bioreactor. The suitable hydraulic retention time for biohydrogen and biomethane production were found to be 8 h and 10 d, respectively, which gave the maximum hydrogen and methane yield of 303 mL/g COD and 142 mL/g COD, respectively. The continuous biohythane production process increased the overall substrate conversion efficiency up to 86% with the maximum gaseous energy recovery of 8.97 kJ/g COD.

A Control Algorithm for the Novel Regenerative–Mechanical Coupled Brake System with by-Wire Based on Multidisciplinary Design Optimization for an Electric Vehicle

Current regenerative braking systems in electric vehicles have several problems, such as complex structures, too many control parameters, and inconsistent braking responses. To solve these problems, a control algorithm with multidisciplinary design optimization (MDO) is proposed based on the novel regenerative–mechanical coupled brake-by-wire system. A dynamic model of the novel regenerative braking system was established to analyze the mechanism of coupled braking and propose a braking torque distribution strategy. To realize a better balance between the optimum braking stability and the maximum regenerative energy recovery based on the braking torque distribution strategy and sample points, the MDO mathematical model was developed to optimize the control parameters with the collaborative optimization algorithm. The finite sample points comprising the vehicle speed, battery state-of-charge, and braking severity were obtained through an optimal Latin hypercube design and represent the overall design space. A network was established based on the sample points and the optimization results. Using this network, the in-depth characteristics of the sample points and the optimization results were obtained through supervised learning to develop the control algorithm for vehicle braking. A simulation was performed using the normal braking condition, and the simulation results demonstrated that the control algorithm has higher control precision than conventional methods and better real-time performance than online optimization.

Anaerobic and photocatalytic treatments of post-hydrothermal liquefaction wastewater using H2O2

Hydrothermal liquefaction (HTL) of cyanobacteria is a promising process for energy generation. However, post-HTL wastewater (PHWW) contains high amounts of organic matter and toxic compounds. This study investigated photocatalysis and anaerobic digestion (AD) for the treatment of PHWW from Spirulina conversion. H2O2 was used as an external oxidant in the photocatalysis or as a pretreatment in the AD process. The effect of different concentrations of H2O2 was evaluated. Greater CH4 production and higher COD reduction were observed when pre-treated PHWW was used. In the photocatalytic treatment, color and COD reduction reached 93.1% and 23.4%, respectively, with the addition of H2O2. When a combination of the oxidative pretreatment and AD was applied, a maximum energy recovery of 66.7% was reached, while the photocatalysis reached a maximum of 61.5%. Use of the best conditions with proper dilutions resulted in higher growths of the Spirulina cultivation compared to that with conventional algal media.

Theoretical Study and Experimental Validation of a Hydrostatic Transmission Control for a City Bus Hybrid Driveline with Kinetic Energy Storage

A city bus with hybrid drive system was studied for its performance. The driveline under consideration consists of two alternative energy sources—an internal combustion engine (ICE) and kinetic energy storage (KES)—a hydrostatic transmission (HST), a drive axle and corresponding gears. A generalized law for HST control is obtained that satisfies kinematic and torque requirements for the alternative energy sources and the different modes of operation of the bus. A test stand was developed for validation of the chosen control strategy and for the energy flow simulations through the HST. The estimated maximum energy recovery potential is around 20–25%.

Hydrothermal liquefaction of Chlorella vulgaris: Effect of reaction temperature and time on energy recovery and nutrient recovery

Hydrothermal liquefaction of Chlorella vulgaris feedstock containing 80% (w/w) water was conducted in a batch reactor as a function of temperature (300, 325 and 350°C) and reaction times (5, 10 and 30min). The biocrude yield, elemental composition and higher heating value obtained for various reaction conditions helped to predict the optimum conditions for maximizing energy recovery. To optimize the recovery of inorganic nutrients, we further investigated the effect of reaction conditions on the ammonium (NH4+), phosphate (PO43−), nitrate (NO3−) and nitrite (NO2−) concentrations in the aqueous phase. A maximum energy recovery of 78% was obtained at 350°C and 5min, with a high energy density of 34.3MJ/kg and lower contents of oxygen. For the recovery of inorganic nutrients, shorter reaction times achieved higher phosphorus recovery, with maximum recovery being 53% at 350°C and 5min. Our results indicate that the reaction condition of 350°C for 5min was optimal for maximizing energy recovery with improved quality, at the same time achieving a high phosphorus recovery.

Power-assist control of a human–electric hybrid bicycle with energy regeneration and cruise control

In this article, we propose three different controllers for the human–electric hybrid bicycle. The main objective of the controller is to ensure power-assist, cruise control and regenerative braking whenever possible. Power-assist controller is designed without torque sensor, cruise controller is designed to keep constant speed and the regenerative braking controller is designed to save the energy while braking. Proportion-assisted power method is implemented using the pedaling torque estimated by disturbance observer. Cruise control is achieved using the estimated speed from the hall sensor rather than using actual speed sensor. Single switch regenerative braking method is applied to yield maximum energy recovery during braking. It is noted that the performance similar to torque sensor–based proportion-assisted power is achieved using torque sensorless approach. All of the proposed controllers are implemented experimentally in the experimental setup, and their results are presented.

The energy and economic target optimization of a naphtha production unit by implementing energy pinch technology

In this paper, energy pinch analysis is implemented on the Naphtha Production Unit as an operating process plant. It endeavors to approach the current system to the maximum energy recovery (MER) design by providing several scenarios in the heat exchangers network. Furthermore, the economic analysis considering the initial investment and operating costs of the system was conducted in each scenarios to achieve a cost-effective system. The results obtained just from the pinch analysis optimization technique, indicate that reducing the heating and cooling loads do not reduce the total costs. Therefore, two objective optimization of minimization of the levelized cost of product (LCOP) as well as maximization of the overall energy performance of the system are concerned to find out the optimal scenario of the energy network layout. Here, retrofit of the maximum energy recovery design is performed to represent the energetical and economical optimal layout.

Maximum Energy Recovery in Electric Vehicle through Regenerative Braking System

Maximum Energy Recovery in Electric Vehicle through Regenerative Braking System