Energy Recovery Ratio Research Articles

Simulation of biocrude production from P. tricornutum, S. platensis, and C. vulgaris using Aspenplus®

Hydrothermal liquefaction (HTL) of biomass is performed at elevated pressure and temperature to avoid the drying process. This process is also suitable for the low grade biomass with higher moisture content. In this article, simulation of three types of microalgae species, such as Phaeodactylum tricornutum, Spirulina platensis, and Chlorella vulgaris, are performed using Aspen Plus®. Simulation conditions, for instance, temperature, proximate and ultimate analyses, feed rate, water content, component names, etc., are taken from the literatures. The results of microalgae are then compared at two different temperature conditions. The values, however, are not the same for all the materials due to the data availability from the literature. The highest calorific value is obtained from C. vulgaris; it is 37.27 MJ/kg at 621K, and the highest energy recovery and energy ratio are obtained from P. tricornutum; they are 88.78 % and 1.86, both at 648K respectively. The difference between experimental and simulated calorific values of different biocrudes are ranging from 2.7 % to 3.62 % at higher temperatures and from 4.68 % to 10.72 % at lower temperatures. Finally, it is found that the simulation results corroborate with the experimental results with minimal errors.

Wastewater treatment, hydrogen and energy recovery using electrochemical advanced oxidation

Electrochemical advanced oxidation processes (EAOPs) offer several advantages over conventional Advanced Oxidation Processes (AOPs) such as UV/H2O2 and H2O2/O3. This includes the absence of chemical additives and ease of control. However, high energy consumption hampers the industrial application of EAOPs. Currently, the hydrogen generated at the cathode is vented and wasted, because of its low gas purity and difficulty in collecting it. But it also underscores an opportunity where the reactor design can be improved to facilitate the collection of high-purity hydrogen for energy savings. In our study, The EAOPs reactor was designed with a proton exchange membrane (PEM) for hydrogen generation. The hydrogen at the cathode chamber is then supplied to a fuel cell to generate electricity. The energy efficiency of the EAOPs-fuel cell system is evaluated through the wastewater treatment performance and energy saving that fuel cells achieve. To optimize the EAOPs-fuel cell system, various operational conditions, including different anode types, salt concentrations, and target organic compounds, were examined to optimize the system. Our experimental results indicate that the EAOPs-fuel cell system exhibits energy-efficient performance across various operational conditions. Notably, the highest energy efficiency and recovery ratio were achieved when operating at 3 V with boron-doped diamond (BDD) as the anode. Furthermore, we investigated the impact of mass transfer on the system's energy efficiency, considering both the initial organic concentration and flow velocity. This study provided valuable insights into combining the effect of EAOPs and hydrogen fuel cells, contributing to the understanding and optimizing the oxidation performance. It also contributes to developing sustainable and cost-effective advanced oxidation technologies with wide-ranging water treatment applications.

Energy-recoverable landing strategy for small-scale jumping robots

Small-scale jumping robots widely employ the pause-and-leap locomotion strategy. They use elastic elements to enhance the jumping performance, which is promising for locomotion over rugged terrain. However, these robots typically lose a significant amount of mechanical energy during landing, which is initially accumulated for takeoff, resulting in wasted energy. Here, we propose a landing strategy that uses a jumping mechanism with controlled mono-stable or bi-stable characteristics to achieve the energy recoverable landing. By adjusting the jumping mechanism to an appropriate bi-stable state before landing, the robot’s extended leg retracts to its pre-jump configuration upon touchdown, enabling the recapture of mechanical energy within the springs. We develop analytical models for the touchdown collision and landing dynamics. A 165 g robot prototype is constructed, featuring integrated sensing, actuation, and computations. Both simulations and experiments are conducted to explore the effects of various factors on the landing behavior. Experiments demonstrate successful landings with energy recovery ratio exceeding 50% across different landing trajectories. This landing strategy holds significant potential for enhancing the locomotion efficiency of future small-scale jumping robots.

Simulative and experimental research on the heat exchanger for cold energy recovery of liquefied natural gas

Natural gas, a widely used energy source, is transported as liquefied natural gas (LNG). During the gasification of LNG, a large amount of cold energy is released, which can be recycled to achieve energy savings. An LNG cold energy heat-exchanger (shell-and-tube type) was designed to recover cold energy for application in 0 ℃ ammonia cold storage. To conduct a more intuitive and detailed study of the effects of the tube space and flow rate on each heat-exchange tube in a shell-and-tube heat exchanger, a double-pipe heat exchanger was designed and manufactured. Liquid nitrogen and a secondary refrigerant (antifreeze) was used as the cold and heat source, respectively. Owing to the effects of the tube space and refrigerant flow velocity on the heat transfer coefficient, simulations and experiments were conducted on the antifreeze velocity and tube space. The results showed that increasing the antifreeze flow velocity and reducing the tube space increased the amount of cold energy recovered. Based on the physical parameters of liquid nitrogen and LNG, the cold energy recovery ratio was 1.3. The predicted amount of cold energy recovered from LNG in double-pipe and shell-and-tube heat exchangers were determined by the cold energy recovery coefficient, cold energy recovery ratio, and number of heat-exchange tubes. The recovery of cold energy from LNG in a shell-and-tube heat exchanger was applied to cold storage, which can improve the cold storage performance by 36.8 %.

Intermittent mixing facilitates energy recovery and low carbon emissions from high-solids anaerobic co-digestion of food waste and sewage sludge

Mixing inside high-solids anaerobic co-digestion (HS-AcoD) is essential for process feasibility and economic sustainability. This study developed a proper energy assessment for a high solids anaerobic digestion-combined heat and power (AD-CHP) system to clarify the impact of mixing on methane production, energy recovery and carbon emission reduction during HS-AcoD of food waste (FW) and sewage sludge (SS). Results indicated that intermittent mixing enhanced methane production and shortened the lag phase compared with unmixing and continuous mixing. The modified Gompertz model yielded better fitting than the logistic and transfer function models via kinetic analysis. In the case of a scaled-up AD-CHP system, intermittent mixing with 15 min/h boosted energy output (2.14 × 103 kWh/tonne VS) at 21 d. Compared with continuous mixing, 15 min/h intermittent mixing at 13 d improved the energy recovery ratio from 31% to 45% and carbon emissions reduction from 0.25 t CO2/t VS to 0.35 t CO2/t VS. For a high availability of FW and SS in China, the AD-CHP system with intermittent mixing would have higher net energy output (128.4 × 109 kWh) and carbon emission reduction (15.3 million tonnes) by the full utilization of these biomasses. These results are expected to provide theoretical support for the high solids AD-CHP system in determining the optimal mixing strategy with maximum energy production for FW and SS disposal.

Extensive Analysis of a Reinvigorated Solar Water Heating System Using Low-Density Polyethylene Glazing

Solar energy is one of the most promising forms of alternative energy because it has no adverse effects on the environment and is entirely free. Converting solar energy into thermal energy is the most common and straightforward method; the efficiency of solar thermal conversion is approximately 70 percent. The intermittent nature of solar energy availability affects the performance of solar water heaters (SWH), which lowers the usefulness of solar energy in residential and commercial settings, particularly for water heating. Even at low temperatures, the performance of a collector can be improved by using low-density polyethylene (LDPE) glazing instead of traditional glass because it is less expensive and lighter than glass. Using a comprehensive experimental-simulative study, the Glass Solar water heater (glass SWH) and the low-density polyethylene solar water heater (LDPE SWH) are analyzed, examined, and compared in this work. These solar water heaters have galvanized iron (GI) as their absorber material. The SWHs were operated in a closed loop at a constant mass flow rate of 0.013 kg/s, and a 4E analysis (which stands for energy, exergy, economics, and efficiency recovery ratio) was carried out. This analysis included a look at the dynamic time, uncertainty, weight reduction, carbon footprint, and series connection. An LDPE SWH has an energy efficiency that is 5.57% and an exergy efficiency that is 3.2% higher than a glass SWH. The weight of the LDPE SWH is 32.56% lower than that of the glass SWH. Compared to the price of a conventional geyser, installing our SWH results in a cost savings of 40.9%, and monthly energy costs are reduced by an average of 25.5%. Compared to October, September has the quickest dynamic time to reach the desired temperature, while October has the most significant dynamic time. The efficiency recovery ratio (ERR) of a glass SWH is 0.0239% lower than that of an LDPE SWH. LDPE SWHs had a carbon credit worth INR 294.44 more than glass SWHs. The findings of these tests demonstrate that the LDPE SWH is a practical replacement for traditional means of heating water, such as SWHs and geysers.

Research on Adaptive Distribution Control Strategy of Braking Force for Pure Electric Vehicles

The actual driving conditions of electric vehicles (EVs) are complex and changeable. Limited by road adhesion conditions, it is necessary to give priority to ensuring safety, taking into account the energy recovery ratio of the vehicle during braking to obtain better braking quality. In this work, an electric vehicle with an EHB (electro-hydraulic braking) system whose braking force adaptive distribution control strategy is studied. Firstly, the vehicle dynamics model, including seven degrees of freedom, tire, drive motor, main reducer, battery pack, and braking system, was constructed, which is attributed to the vehicle configuration and braking system scheme. Second, based on curve I and ECE regulations, the adaptive braking force distribution control strategy was formulated by taking the maximum regenerative braking torque as the inflection point, the synchronous adhesion coefficient as the desired point, and the battery SOC, road adhesion coefficient, and braking strength as the threshold. Finally, the vehicle dynamics simulation model was built on the Matlab/Simulink platform, and the simulation results verified the feasibility of the proposed braking force adaptive allocation control strategy. The research shows that the adaptive distribution control strategy can better adapt to the complex and variable driving conditions of the vehicle by combining the inflection point and the desired point. The braking energy recovery ratios of the vehicle under the NEDC and NYCC cycle conditions on a high adhesion road are 52.62% and 47.45%. The braking force distribution curve is close to curve I under the low adhesion extreme road.

Catalytic hydrothermal deoxygenation of sugarcane bagasse for energy dense bio-oil and aqueous fraction acidogenesis for biohydrogen production

The study focuses on the effective conversion of sugarcane bagasse (SCB) by catalytic deoxygenation using various alkali and metal-based catalysts under N2 pressure employing water as solvent. The specific influence of catalyst over bio-crude yields (bio-oil and aqueous fraction) including energy recovery ratio was explored. The optimum catalytic condition (Ru/C) resulted in ∼ 70% of bio-crude and 28% of bio-oil with an improved HHV (31.6 MJ/kg) having 11.6% of aliphatic/aromatic hydrocarbons (C10–C20) which can be further upgraded to drop-in fuels. The biocrude composed of 44% of aqueous soluble organic fraction (HTL-AF). Further, the carbon-rich HTL-AF was valorized through acidogenic fermentation to yield biohydrogen (Bio-H2). The maximum bio-H2 production of 201 mL/g of TOC conversion (K2CO3 catalyst) was observed with 7.7 g/L of VFA. The SCB was valorized in a biorefinery design with the production of fuels and chemical intermediates in a circular chemistry approach.

Comparison of hydrogen production with the help of the plastic digesting organisms and by pyrolysis

Plastic waste collected from the landfills may be washed, shredded, digested by plastic-eating microorganisms centrifuged and sent back to the landfill. If the generated water should be electrolysed, in the case of processing 10% of the annually generated plastic waste, 24.2 Mt of plastic may be eliminated and 2.4 × 103 kWh of energy may be recovered with the energy recovery ratio of 0.8. This ratio would be 2 in the case of pyrolysis, indicating that pyrolysis may be 2.5 folds more efficient than the microbial process. Moreover, pyrolysis occurs at high temperatures and is much faster than the microbial process. If we can find a safe way to innoculate the dump sides with the plastic digesting microorganisms, hydrogen may be generated without the production of carbon dioxide and water; the plastic waste may be reduced in the long run.

Research on braking energy recovery technology of electric vehicle in underground coal mine based on road condition recognition technology

Electric explosion-proof trackless rubber-wheeled vehicles in coal mines usually use braking energy recovery technology to improve cruising range. In order to improve the efficiency of vehicle braking energy recovery and improve vehicle braking safety performance, this paper proposes a braking energy recovery control strategy for electric vehicles in coal mines based on road condition recognition. This strategy is based on the coal mine underground positioning technology, and adopts different braking energy recovery control strategies for different road conditions, while improving the braking energy recovery ratio of the vehicle, it ensures a good feeling of the brake pedal and ensures the safety performance of the vehicle braking. Finally, the feasibility of the control strategy is verified by simulation.

Hydrothermal liquefaction of sewage sludge into biocrude: Effect of aqueous phase recycling on energy recovery and pollution mitigation

Hydrothermal liquefaction (HTL) of sewage sludge is facing the challenges of low biocrude yield, a large number of intractable aqueous phase and heavy metals pollution. In this study, the aqueous phase produced by HTL was recycled as solvent with an aim to improve the biocrude yield and mitigate potential pollution. Results showed that the recycling of aqueous phase increased the biocrude yield from 17.9 to 30.5% and the energy recovery ratio from 40.3 to 61.7%. The recycling could increase the contents of Zn, Cu, Pb and Cr in solid residues by 2.7−3.0 times. It is worth emphasizing that the recycling reduced the COD of aqueous phase by 24.9%. However, the enhanced protein hydrolysis process reduced the calorific value of biocrude from 36.4 to 28.5 MJ/kg, and promoted the migration of the nitrogen to the aqueous phase, which was not environmentally favourable for the direct usage in diesel engines. Analysis showed that the ketones and the phenols in aqueous phase participated in HTL process as reactants, and the acids promoted the hydrolysis of protein in the sludge. Overall, the recycling of aqueous phase effectively improved the energy recovery and alleviated pollution of the sludge HTL.

Assessment of eco‐thermal sustainability potential of a cluster of low‐cost solar dryer designs based on exergetic sustainability indicators and earned carbon credit

This research aims to establish the interconnectivity between solar dryer designs and the exegetic-sustainability performance of solar dryers. This is to assist energy policymakers and fabricators to establish design standards and make the right choice for waste exergy management strategy for environmental sustainability. Therefore, in this study, the exergy-based sustainability indicators and earned carbon credit were used to assess and compare the performance of four different designs of solar dryers of equal collector capacity under the same external environmental conditions in the same town. In terms of better sustainability indicators that include high exergy efficiency, lower waste exergy emission, higher sustainability index and lower lack of productivity, solar dryer designs with single-pass triple air movement direction with inlet air powered by wind generator had the best indices for environmental sustainability. In contrast, the natural convection mix-mode solar dryer design had the lowest environmental effect factor and destruction coefficient while the indirect natural convection solar dryer had the highest energy recovery ratio based on exergy output from water evaporation. However, the mix-mode solar dryer powered by the wind generator earned the highest carbon credit. The exergy efficiency ranged from 19.09 to 52 % for the four cases, whereas the waste exergy ratio ranged from 0.52 to 0.81. The LOP value ranged from 2.95 to 19.96. Similarly, the sustainability index ranged from 1.28 to 2.5, the average environmental destruction coefficient varied from 3.96 to 20.96, the exergy recovery ratio for the four dryers varied from 0.001825 to 0.12405, and the earned carbon credit ranged from $442. 3 to $2630.5.

Self-Healing Properties of Asphalt Concrete with Calcium Alginate Capsules Containing Different Healing Agents.

Calcium alginate capsules encapsulating rejuvenator are a promising self-healing technology for asphalt pavement, but the effects of different healing agents on the self-healing performance of asphalt concrete has not been considered. In view of this, this paper aimed at exploring the effects of calcium alginate capsules containing different healing agents on the self-healing properties of asphalt concrete. Three types of capsules with sunflower oil, waste cooking oil and commercial rejuvenator were fabricated via the orifice-coagulation bath method and the interior structure, mechanical strength, thermal stability and oil content of the prepared capsules were characterized. The healing levels of asphalt mixtures with different capsules under different loading cycles and stress levels were evaluated. Furthermore, the saturates, aromatics, resins and asphaltenes (SARA) fractions and rheological property of extracted asphalt binder within test beams with different capsules after different loading conditions were assessed. The results indicated that all the three types of capsules meet the mechanical and thermal requirement of mixing and compaction of asphalt mixtures. The healing levels of test beams containing vegetable oil capsules were higher than that of waste cooking oil capsules and industrial rejuvenator capsules. The strength recovery ratio and fracture energy recovery ratio of test beams with vegetable oil capsules reached 82.8% and 96.6%, respectively, after 20,000 cycles of compressive loading at 1.4 MPa. The fracture energy recovery ratio of the waste cooking oil capsules also reached as high as 90%, indicating that waste cooking oil can be used as the healing agent of calcium alginate capsules to improve the self-healing property of asphalt mixture. This work provides a significant guide for the selection of healing agent for self-healing capsules in the future.

Investigation of a low-pressure flash evaporation desalination system powered by ocean thermal energy

To alleviate the consequences of the freshwater crisis and fully utilize marine resources in tropical coastal areas, this study presents a low-pressure flash evaporation desalination system driven by ocean thermal energy (OTE). Through gravity and atmospheric pressure, a natural vacuum can be formed in the evaporator, which achieves flash evaporation for warm surface seawater. Then, the vapour is condensed into freshwater via an inner coil condenser with flowing cold deep seawater. Using a water pump to fill the evaporator intermittently, the non-condensable gas accumulated in the desalination process can be thoroughly discharged. Based on the process of mass and heat transfer inside the system, a thermodynamic model was developed. Several performance evaluation indices, including water productivity, specific electrical energy consumption (SEEC) and recovery ratio (RR), were experimentally investigated under different parameters. The results indicate that productivity and SEEC are higher with increasing seawater flow rate and decreasing deep seawater temperature. Under a warm seawater temperature of 30 °C and a deep cold seawater temperature of 8 °C, the system obtained a maximum water productivity of 5.3 kg/h, and the corresponding SEEC and RR were 0.126 kWh/kg and 1.5%, respectively. Finally, compared with solar-driven desalination systems, the proposed OTE desalination system requires less energy consumption, which shows an attractive application prospect.

Shrimp waste-derived chitosan harvested microalgae for the production of high-quality biocrude through hydrothermal liquefaction

Microalgae harvesting is an expensive and energy-intensive process. The application of chitosan, a waste-derived natural flocculant, for microalgae harvesting and biocrude quality enhancement might overcome this challenge. This study explored the optimization of microalgae harvesting by shrimp waste-derived chitosan and the production of high-quality biocrude from the harvested biomass through hydrothermal liquefaction (HTL). The study suggested that more than 95% of the microalgal biomass were harvested at 17–26 mg/L of chitosan dosing with a mixing time and speed of more than 11 min and 75 rpm, respectively. The biocrude produced from chitosan harvested microalgae (CMA) showed higher yield (37.9%) and energy value (35.4 MJ/kg) than gravity harvested microalgae (GMA) (yield 28.2% and HHV 30.3 MJ/kg). In addition, CMA biocrude had higher °API gravity (18.4) and a higher percentage (66%) of lighter hydrocarbon fraction (<C20), which indicated high-quality crude properties. Finally, the higher energy recovery (85.2%) and lower energy consumption ratio (0.58) of CMA biocrude confirmed the net energy positivity system. In this context, the findings demonstrated that applying waste-derived flocculant (chitosan) for wastewater-grown microalgae harvesting and high-quality biocrude production would potentially lead to a sustainable algal biorefinery system.

Use of an alkaline catalyst with ethanol-water as a co-solvent in the hydrothermal liquefaction of the Korean native kenaf: An analysis of the light oil and heavy oil characteristics

Hydrothermal liquefaction of the Korean native kenaf, with ethanol–water as a co-solvent at 275–350 °C for 30 min with and without 1 wt% of the alkaline catalysts Ca(OH)2, Na2CO3, K2CO3, and KOH, was investigated to identify the effect of the alkaline catalyst addition on the characteristics of the light and heavy oil produced. Component, elemental, ICP-ASE, and GC-MS analyses were conducted to determine the characteristics of the light oil, heavy oil, and solid residue. The highest bio-crude oil yield of 61.81% at 275 °C was found using ethanol–water without an alkaline catalyst. The addition of alkaline catalysts prompted the decomposition of both the heavy oil and light oil fractions, and re-polymerization reactions were suppressed. In addition, there were increases in the area percentages of ketone and phenolics derived from holocellulose and monolignols, respectively. Calcium ion was mainly detected in the aqueous phase, while sodium and potassium existed as solids in the solid residue. The results show that the addition of a calcium-based alkaline catalyst in the hydrothermal liquefaction of kenaf can enhance the energy recovery ratio to 58% and calorific value to 32.27 MJ/kg of the light oil at 350 °C.

Vibration energy recovery system of vehicle suspension based on ultrasonic sensor

The current design of vibration energy recovery system for vehicle suspension does not analyze the vibration of the vehicle under different road conditions, resulting in the system's low energy recovery ratio, low recovery efficiency, and low energy utilization. Therefore, in this paper, the vibration energy recovery system of vehicle suspension based on ultrasonic sensors is proposed. The ultrasonic sensor is used to obtain the vibration information of the vehicle, and the vibration of the vehicle on the smooth and uneven roads is analyzed according to the obtained information. According to the analysis results, the design of the vibration energy recovery system for vehicle suspension is completed through four parts: the IGBT module, the control system, the direct thrust controller, and the energy management controller. The experimental results show that the system designed by the proposed method has a large energy recovery ratio, high recovery efficiency and high energy utilization rate.

Analysis of flow structure of tunnel fire based on modal decomposition

In order to study the large scale flow structure of fire smoke in tunnels, this paper uses the excellent ability of proper orthogonal decomposition for the first time to extract flow field structure, processes the flow field data obtained from numerical simulation, obtains the 2-D and 3-D large-scale flow structure of fire smoke in tunnels and analyzes it. The proper orthogonal decomposition of temperature and velocity pulsation field shows that the proportion of first-order modal energy in temperature field is much higher than that in velocity field, indicating that the flow structure of velocity field is more complex than that of temperature field. Through modal phase analysis and modal decomposition of 3-D flow field, the influence of mode on fire smoke flow is recognized, and the understanding of tunnel fire smoke flow structure is deepened. The low-order mode is closely related to smoke flow. The increase of fire power has little effect on the reconstruction of flow field, and the cross-section energy recovery ratio near the fire source is higher under the same fire power.

Numerical Study on Heat Transfer Efficiency of Regenerative Thermal Oxidizers with Three Canisters

The heat transfer efficiency of a regenerative thermal oxidizer with three canisters used for volatile organic compounds treatment was studied using numerical simulation methods. A one-dimensional model that took into account the variation of physical parameters with temperature was built. The results show that the preheating temperature and outlet temperature tend to be stable as the operation time is increased. The heat transfer efficiency of equipment was mainly evaluated by heat recovery efficiency and energy recovery ratio under steady state conditions, which was affected by the inlet gas flow and temperature, valve switch time, combustion temperature, materials and porosity of the regenerative medium, and packing height. With the increase in packing cross-sectional area and packing height, the increase in heat transfer efficiency leads to an increase in equipment cost. Simultaneously, the shorter the valve switch time and the higher the density of the regenerative medium battery also help to improve the heat transfer efficiency without blocking equipment. Unless the removal efficiency of volatile organic compound treatment is reduced, it is recommended to reduce the inlet and combustion temperatures.

Potentialities of thermal responsive polymer in forward osmosis (FO) process for water desalination

This work aims at assessing the technical feasibility and performances of the Forward Osmosis (FO), an emergent desalination process. Two FO processes with different draw solutions have been studied: the first one is based on Ammonium Bicarbonate (AB) and the second on poly (propylene glycol-ran-ethylene glycol) monobutyl ethers (PAGBs) with different molecular weight. The two solutes have different regeneration steps, but they adopt the same membrane separation process of the salt water. The comparison between the different processes is given in terms of recovery ratio, temperature and energy requirements. AB could be regenerated through column distillation at 99.63 °C and zeolite filter, while PAGBs could be regenerated at lower temperatures (77.2 – 83.6 °C) through gravity separation followed by a final step of nanofiltration. This study showed that PAGBs have great potential to desalinate water in an energy-efficient way, reaching minimum consumptions of 39.5 kWhth/m3 and 0.5 kWhel/m3, even if the water recovery is not so high (< 24%). On the contrary, AB has shown higher energy consumptions (> 3.51 kWhel/m3, > 442 kWhth/m3). Finally, a comparison based on energy consumptions and recovery ratio with the mature desalination technologies is provided, showing the potentialities of the process when low temperature heat is available.