Energy Utilization System Research Articles

Economic Value Estimation of Biogas Utilization in Public Wastewater Treatment Plants of the Republic of Korea

This paper presents economic value estimation of improved biogas utilization systems of public wastewater treatment plants in Republic of Korea. Since a large amount of biogas produced at digestion facilities is being wasted as a by-product, the biogas energy utilization system needs to be enhanced. In this paper, three operating options able to utilize the produced biogas are proposed, and then their monetary benefits are estimated by means of net present value calculation. Real operational data from the public wastewater treatment plant located in Sejong city, Republic of Korea, is used to reflect a variation of the rated daily gas production and its concentration according to the weather and seasons, resulting in calculating more reliable results. Additionally, to minimize the estimation errors due to uncertainties of the gas concentration and the gas selling price, a Monte Carlo simulation considering the variation of critical input data is carried out. As a result, the proposed approach can lead to better decisions in selecting the suitable biogas utilization system by forecasting the ranges of possible economic values.

Techno-economic and thermodynamic analysis of solid oxide fuel cell combined heat and power integrated with biomass gasification and solar assisted carbon capture and energy utilization system

A new system involving biomass gasification (BioG) with solid oxide fuel cell (SOFC) in combined heat and power (CHP) manner is evaluated. The aim of this system is to efficiently utilize biomass, while solar-assisted solid oxide electrolyzer cell (SOEC) methanation exploits CO2 from the system exhaust. CO2 and H2O are co-electrolyzed to form syngas, followed by four step methanation to produce synthetic natural gas. The energy system is thoroughly assessed using energy, exergy, exergoeconomic, and environmental assessments. The BioG-SOFC-CHP overall energy and exergy efficiencies reach up to 59 % and 44.7 %, respectively. Additionally, the SOEC-methanation subsystem achieved overall energy and exergy efficiencies of 78.5 % and 73.8 %, respectively. BioG showed the largest exergy destruction of 78.34 kW compared to 12.3 kW for SOFC. In SOEC-methanation subsystem, heater 2 has the largest exergy destruction of 98.93 kW. The economic analysis showed that the methane selling price of 18 $/GJ and the electricity tariff of 0.13 $/kW, which are nearly identical to the market price, resulting in a payback period of 10 years. Exergoeconomic analysis showed cost rate of SOFC power generation and methane production of 0.05225$/kWh and 29.5$/GJ, respectively. The BioG-SOFC-CHP provided low CO2 emission of about 0.13–0.166 t/GJ, which indicates its low environmental impact.

Utilization of Cold Energy from LNG Regasification Process: A Review of Current Trends

Liquified natural gas (LNG) is a clean primary energy source that is growing in popularity due to the distance between natural gas (NG)-producing countries and importing countries. The large amount of cold energy stored in LNG presents an opportunity for sustainable technologies to recover and utilize this energy. This can enhance the energy efficiency of LNG regasification terminals and the economic viability of the LNG supply chain. The energy stored in LNG in the form of low temperatures is referred to as cold energy. When LNG is regasified, or converted back into its gaseous form, this cold energy is released. This process involves heating the LNG, which causes it to vaporize and release its stored energy. The current state-of-the-art techniques for LNG cold energy utilization, including power generation, air separation, traditional desalination, and cryogenics carbon dioxide (CO2) capture are discussed in this review. While most of the current LNG cold energy utilization systems are presented, potential future applications are also discussed. The commercialization of sustainable technologies, such as improvement strategies for LNG cold energy utilization, is becoming increasingly important in the energy industry.

Performance modeling and analysis of a PVT-HP system with the roll-bond plate as the evaporator during winter conditions

In recent years, PVT (Photovoltaic thermal) has attracted extensive attention in social production and daily lives. As a new technology with low-carbon output, environmental protection and energy saving features, the development of PVT will have great application prospects. Buildings need heating in winter, air-conditioning in summer, and, electricity and domestic hot water supply throughout the year. In the face of the diversified energy supply needs of buildings, the existing photothermal and photovoltaic technologies (irrespective of the photoelectric or photothermal conversion efficiency of modules, or the form of single-function module structures and solar energy utilization systems) are unable to meet the requirements of various energy uses of buildings. There are issues too, such as the large footprint of modules. To this end, this paper starts from the perspective of further improving the comprehensive utilization efficiency of solar energy and meeting the requirements of various energy uses in buildings. The authors adopted a combination of experiment and simulation to evaluate the performance of the PVT-HP (Heat pump) system in this study. The PVT-HP system is set up in Dalian and only runs for a short period of time to get necessary operation data. The simulation model uses a self-built PVT module and verifies its accuracy of the model through its operation date. With the proven PVT-HP model, the authors carried out a dynamic simulation and an economic analysis of the operation of the PVT-HP in winter. The operation performance, supply and demand matching, cost and economic payback period of the PVT-HP system were calculated, and the adaptability analysis for different regions are given. Finally, the nominal power of the PVT-HP system was found to be about 2.4 kW per group, the coefficient of performance (COP) in winter was about 4.32, the total winter heating capacity of the system in Dalian reached 6016 MJ, and the power production reached 168 kWh (which can offset 43 % of the total winter power consumption). The system heating performance was good for all regions, and its payback period in Dalian was found to be 6.53 years; the regional adaptability and economy were found to be ideal.

A comprehensive evaluation of wind-PV-salt cavern-hydrogen energy storage and utilization system: A case study in Qianjiang salt cavern, China

With global energy consumption increasing year by year, the industrial sectors of the world’s countries have never been more urgent in achieving carbon reduction. Renewable energy plays a crucial role in the industrial decarbonization process. As the most mature renewable energy technology, wind and photovoltaic power generation have made significant progress in recent years. However, the intermittent characteristics hinder the efficient use of renewable energy. Existing research provides sufficient support for the flexible scheduling of large-scale renewable energy. Hence, this paper proposes a combined energy system composed of wind power-photovoltaic-energy storage salt cavern with hydrogen as the energy scheduling carrier. The system mainly realizes energy conversion through electrolytic water equipment and fuel cells. Then, Qianjiang City, Hubei Province, is taken as the analysis object, and the working conditions of each component in the system are optimized with the help of an improved particle swarm optimization algorithm. According to the results, the system’s contribution to the energy system is discussed, and the system's economy and carbon reduction effect is studied. The analysis proves that the improved particle swarm optimization algorithm has a stronger solving ability. The combined energy system can effectively improve the economy and renewable energy utilization rate, meet the regional electricity demand, and significantly reduce carbon emissions. The economic analysis of the system shows that the operation and maintenance cost of hydrogen storage salt caverns accounts for the largest proportion of the total cost, about 60 %. Compared with several existing large-scale energy storage technologies, it is found that the energy efficiency of the whole system is only about 40 % due to the limitation of technology maturity. Nevertheless, the flexibility of the hydrogen storage system layout is relatively high. The required underground space volume is only equivalent to 1/6 and 1/2 of pumped storage and compressed air storage with the same scheduling capacity. The system will provide a theoretical support for the optimization of energy pattern and layout.

Performance analysis of a fuel cells integrated system utilizing Liquified Natural Gas as fuel for a green shipping target

In this study, a system integrating Solid Oxide Fuel Cells (SOFC) fueled by Liquefied Natural Gas (LNG) for marine vessels is proposed and analyzed. The system comprises Proton Exchange Membrane Fuel Cells (PEMFC), Organic Rankine Cycle (ORC), Gas Turbine (GT), Steam Rankine Cycle (SRC), and Waste Heat Boiler (WHB) combined with the SOFC system to enhance power generation and system performance. The PEMFC is particularly important for maritime applications, compensating for the disadvantage of the SOFC in terms of starting and response time according to the vessel's demand. The CO2 capture system designated in this proposal not only helps to comply with international regulations and standards on emission control but also reduces the power consumption requirement for traditional CO2 capture. To simulate and optimize the system's design, the Aspen HYSYS V12.1 process modelling software is employed. The thermodynamic models and equations for this proposed system are based on the first and second laws of thermodynamics. The exergy destruction equations and calculations for the main components are established and estimated to optimize the system's design and operation. The predicted performance of the proposed system is 68.76% for energy efficiency and 33.58% for exergy efficiency. The combined system for cold energy utilization and waste heat recovery generates more than 2100.42 kW equivalent, representing 35.6% of the total system generation. The results of the analysis indicate that when the current density is increased from 930 to 1930 A/m2, performance of system experience a reduction of 33.18% and 16.2% for the energy and exergy efficiencies, respectively.

Design study on the integrated utilization system of medium temperature waste heat and LNG vaporization cold energy for 200000 DWT LNG-powered vessels

The study object for this work is a 215000 ton very large crude carrier ? liquefied natural gas ? powered vessel, intending to integrate the use of medium temperature flue gas waste heat from the exhaust turbine and cold energy from liquefied natural gas vaporization. It proposes a Rankine cycle power generating system with a two stage booster and three stage lateral nesting following the principle of ?temperature matching, stepped utilization?, taking into account real demands and circumstances of the vessel. The study shows that in this tonnage vessel, through the design and optimization of the stepped utilization scheme, the cold energy released during the vaporization of liquefied natural gas fuel from the ME-GI host machine and the medium temperature waste heat from the exhaust turbine can be fully utilized, and the system structure is tight and simple. After the non-azeotropic mixed working media was optimized and the operational parameters were optimized using genetic algorithm, the system designed in this paper can reach 54.61% exergy efficiency and 187.83 kW net output of power generation. The annual income of the final designed system can reach CNY 1, 133, 240. The capital recovery cycle is expected to be 5.06 years if the system is put into operation.

Hierarchical microporous superhydrophobic surfaces with nanostructures enhancing vapor condensation heat transfer

A new hierarchical superhydrophobic surface with micropores and nanoblades (MN SHS) is proposed to strengthen the jumping ability of droplets and maintain the high-efficiency droplet jumping condensation at the larger subcoolings. The results demonstrate that the jumping frequency and the proportion of multidroplets merging (n ≥ 8) on the MN SHS are higher than those on the nanostructured superhydrophobic surfaces (Nano SHS). Moreover, the maximum diameter of condensate droplets is only 150 μm, which is approximately 50% smaller compared to the Nano SHS. Spontaneous jumping of condensate droplets is observed on the 40PPI MN SHS (PPI: the average number of pores per inch.) at a subcooling of 16 K; while the droplet jumping condensation occurs at a maximum of 5 K on the Nano SHS. As the subcooling ranges from 5 K to 16 K, the heat transfer coefficient of MN SHS is increased by at least 26.4% compared to the Nano SHS. In addition, lattice Boltzmann model is adopted to simulate the self-propelled jumping behaviors on different structured surfaces. The energy conversion efficiency of drops on the MN SHS is higher compared to that on the Nano SHS. This work will contribute to the potential development of dropwise condensation in energy utilization, petrochemical engineering, thermoelectric cooling and aerospace thermal management systems.

Integrated Regenerative Braking Energy Utilization System for Multi-Substations in Electrified Railways

This article proposes an integrated regenerative braking energy utilization system (RBEUS) to improve regenerative braking energy (RBE) utilization in electrified railways. The proposed RBEUS uses a traction substation energy storage system and two sectioning post converters to achieve coordinated RBE utilization in three consecutive traction substations via power-sharing and storage, and the power quality can also be improved. A hierarchically coordinated control strategy is developed based on the operation principle to provide real-time power management and control for the RBEUS. In the system layer, a centralized power management strategy is designed for operation mode management and active power command generation. It uses a sequential quadratic programming-based algorithm to solve the objective function to achieve optimal RBE utilization under different operation modes. In the converter layer, local controllers of the RBEUS enable converters to respond to the active power commands from the system layer and reactive power commands generated by themself for power flow control. The effectiveness of the proposed RBEUS is comprehensively verified by using a hardware-in-the-loop experiment. Besides, a comparison analysis of the proposed RBEUS and literature methods is conducted to testify the superiority of the RBEUS. The feasibility of RBEUS implementation is also discussed from fault protection and economy.

Theoretical analysis on energy saving of cold energy utilization system for a liquid hydrogen heavy-duty truck

• Model of on-board liquid hydrogen cold energy utilization system is established. • Energy saving effect of cold energy utilization system is illustrated. • Three system states corresponding to different energy saving features are defined. • Annual energy saving under C-WTVC in four typical cities across China are analyzed. In this paper, a model of a novel on-board cold energy utilization system for a liquid hydrogen (LH 2 ) heavy-duty fuel cell truck is established to evaluate the energy saving effect comprehensively compared to the original LH 2 system without cold energy utilization. The cold energy is used for cooling the inlet air of compressor and the coolant of the accessories cooling system through a two-stage vaporizer to reduce the parasitic power. The related influencing factors, such as ambient temperature and fuel cell stack load are taken into consideration. In addition, the effect of cold energy distribution ratio, which is closely related to the design of two-stage LH 2 vaporizer, is also analyzed. The system is divided into three states corresponding to different energy saving features under these influencing factors. The simulation results show that the total parasitic power consumption can be saved by up to 15% under steady state. Based on that, the annual energy saving of this system in heavy-duty fuel cell truck is simulated under Chinese-World Transient Vehicle Cycle (C-WTVC) in four typical cities across China. It is found that annual energy saving can be realized even in extremely cold areas like Harbin (126.6°E, 45.8°N) and annual average saving energy could reach 9∼15% in different cities.

Pyroelectric based energy harvesting devices: hybrid structures and applications

Waste-heat management and harvesting have demonstrated significant potential in enhancing the efficiency of conventional energy utilization systems.

Self-assembly of MXene-decorated stearic acid/ionic liquid phase change material emulsion for effective photo-thermal conversion and storage

As a typical latent functionally thermal fluid with large energy storage capacity and good liquidity, phase change material emulsion (PCME) plays a broad and important role in solar energy utilization. However, the high-temperature instability and supercooling problems of PCME limit its practical application. The ionic liquid (IL)-based PCME allows for the possibility of being used as a heat transfer fluid (HTF) under more extreme temperature conditions. In this work, stearic acid (SA)/IL PCME, prepared by one-step self-assembly of MXene nanosheets at the SA/IL interface, can effectively absorb and convert solar energy into thermal energy. Furthermore, MXene-decorated SA/IL PCMEs have good high-temperature stability, little supercooling degree (0.9–3.1 °C), and large energy storage capacity. The maximum apparent specific heat capacity and average absorbance of the MXene-decorated SA/IL PCME are 4.5 and 303.1 times higher than those of IL, respectively. Under 2 sun irradiation, the 0.05–20 wt% MXene-decorated SA/IL PCME achieves high photo-thermal conversion efficiencies (91.3% at 68.9 °C, 39.4% at 115.1 °C) due to its large energy storage capacity and excellent optical absorption property. The simple interfacial self-assembly provides a promising strategy to prepare high-performance SA/IL PCME used as a novel HTF for medium-temperature solar energy utilization systems.

Sustainable Seawater Desalination and Energy Management: Mechanisms, Strategies, and the Way Forward.

Solar-driven desalination systems have been recognized as an effective technology to address the water crisis. Recently, evaporators prepared based on advanced manufacturing technologies have emerged as a promising tool in enhancing ocean energy utilization. In this review, we discussed the thermal conversion, energy flow, salt deposition mechanisms, and design strategies for solar-driven desalination systems, and explored how to improve the desalination performance and energy use efficiency of the systems through advanced manufacturing technologies. In future perspectives, we determined the feasibility of coupling solar-driven solar desalination systems with multi-stage energy utilization systems and emerging artificial intelligence technologies, for which conclusions are given and new directions for future desalination system development are envisioned. Finally, exciting opportunities and challenges in the face of basic research and practical implementation are discussed, providing promising solutions and blueprints for green and novel desalination technologies while achieving sustainable development.

Multifactor optimization of medium and deep U-type borehole heat exchanger design using Taguchi method

The medium and deep U-type borehole heat exchanger (MDUBHE) coupled with ground source heat pump systems has recently received extensive attention as a novel closed-loop geothermal energy utilization system. The heat extraction performance of MDUBHE is impacted by multiple factors, while previous studies mainly concentrate on the impacts of single short-term factors. Therefore, long-term multifactor optimization is a great need to improve the heat extraction performance of MDUBHE. In this paper, six impact factors of buried depth, horizontal pipe length, flow rate, inlet temperature, geothermal gradient, and ground thermal conductivity are selected through sensitivity analyses. The Taguchi method is creatively applied to optimize the multiple impact factors of MDUBHE. The percentage contribution of each impact factor on the evaluation parameters QL-a, COP-a, and Rd-15 is quantified using Analysis of Variance. The results indicate that the geothermal gradient has the highest impact on the average per meter heat transfer rate QL-a, with a percentage contribution of 39.21%. The inlet temperature has the highest percentage contribution of 29.77% for COP-a. The ground thermal conductivity is the main impact factor for the average heat loss rate Rd-15 with a percentage contribution of 80.75%. Comprehensively considering the evaluation parameters with same weights, the ground thermal conductivity has the most significant influence on the heat extraction performance of MDUBHE, with a percentage contribution of 46.15%. This study could provide theoretical guidance and technical support for the design and promotion of MDUBHE.

Multi‐stage cold energy recovery/utilization: A 10 MW class cold store with liquefied natural gas

AbstractIn coastal cities, a large amount of cold energy is released into the nearby seawater during the process of regasification of liquefied natural gas (LNG) at the receiving terminal, and meanwhile, a large amount of exported and/or imported foods need to be frozen by bulk cold energy near the sea. In this paper, a new multistage cold energy recovery/utilization system is investigated to link the LNG cold energy directly to supply the coastal cold store. This design uses a realistic case in Ningbo LNG receiving station in China, and for the very first time considers how to utilize the LNG cold energy in an efficient manner regarding the technical, economic, and environmental benefits. A three‐stage LNG cold energy utilization system is designed and evaluated by considering different temperatures, pressures, and heat exchange parameters. Compared to conventional electric‐driven cold stores, the proposed multistage cold energy recovery/utilization system has a much cheaper capital cost during the initial investment stage, and also avoids the utility power consumption during the daily operation period. In the case study, from Ningbo LNG receiving station to a 10 MW class cold store, the proposed multienergy system can save the energy of 20.05 kilotons of standard coal, and the carbon emission reduction is up to 1.49 × 108 kg per year.

Special Issue on Challenges for Power Electronics Converters

Power electronics technology is playing an increasingly important role in modern energy utilization systems [...]

Multi-energy coordination control method of power system connected to microgrid of combined cooling, heating and power

The problems of energy shortage and ecological destruction are becoming increasingly serious. As a comprehensive energy utilization system, cogeneration system has gradually become a research hotspot. In order to improve the basic frequency stability and reduce the operation cost, this paper presents a multi-energy coordinated control method for CHP micro-grid. Firstly, the topology of CCHP system is analyzed. On this basis, this paper constructs a CCHP power system including micro turbine (MT) and air conditioning (AC). Secondly, a multi-component composite energy storage method for power system is proposed. Different types of energy storage devices than a single way of energy storage has better performance, to achieve multi-complementary. Finally, in the construction of power system collaborative control model, this paper constructs power system collaborative control model based on load storage optimization idea of source network. Experimental results show that the proposed control method has strong fundamental frequency stability and low operating cost, and has certain application value.

Thermodynamic analysis and optimization of a multi-stage Rankine cycle power system combining with hydrate energy storage for liquefied natural gas cold energy utilization

Natural gas (NG) as a primary energy source plays an important in industrial systems. Natural gas generally needs to be converted into liquified natural gas (LNG) during transportation and stored at a low temperature (around-162 °C), which contains a large amount of cold energy that can be used. The discharge of cold energy into the ocean or atmosphere will cause not only energy waste but also environmental pollution. In order to recover LNG cold energy more efficiently, a novel LNG cold energy utilization system integrating Organic Rankine cycle (ORC), transcritical CO2 cycle (TRCC), CO2 energy storage and seawater ice-making cycle and combustion power system is proposed and investigated in this study. Energy analysis and exergy analysis were studied in details. The exergy efficiency and net electric generation (NEG) were analyzed and optimized using the optimizer in Aspen HYSYS. The results reveal that, exergy loss ratio of combustion power system and CO2 energy storage system are relatively larger than that of other subsystems. In addition, The ORC performance of six working fluids was analyzed. The NEG of R290 and R1270 as working fluid of ORC is significantly higher than that of the other four working fluids. Under the condition of basic process simulation, the NEG of ORC and TRCC is 223.7 kW and 216.4 kW, respectively. The total exergy efficiency reaches 39.01 %. After parameter optimization in the optimizer, the total NEG of ORC and TRCC increases by 6.9 % from 440.1 kW to 470.6 kW and the exergy efficiency can reach 39.8 %.

Utilization of light energy and photodynamic therapy based on thylakoid membranes

<p indent="0mm">The thylakoid membrane, which contains photosynthetic pigments, lipids and proteins, is the main site where the photosynthetic light reaction of green plants, eukaryotic algae and cyanobacteria occurs. Water photolysis and photosynthetic electron transport are two core processes of the light reaction. The former is responsible for converting photons into electrons, and the latter then condenses the energy from the high-potential electrons into energy carriers such as adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide phosphate (NADPH). Due to the electron transport and energy conversion properties of the light reaction, thylakoid membrane can be used in biophotoelectrochemical and biophotoelectrocatalytic systems. Biophotoelectrochemical systems refer to direct or indirect extraction of electrons from the photosynthetic electron transfer chain (PETC) of the thylakoid membrane and transfer the electrons into an external electrode, eventually converting light energy into electric current. Biophotoelectrocatalytic systems refer to the use of ATP and NADPH generated in the light reaction of the thylakoid membrane to drive a series of ATP- or NADPH-dependent biocatalytic reactions. These thylakoid membrane-based light energy utilization systems are featured with material renewability and environmental compatibility. In addition, they show higher energy efficiency than that of the whole photosynthetic-cell systems. Furthermore, thylakoid membranes also hold clear advantages over sub-cellular photosystems, including retention of photosynthetic complexes in their natural environment and relatively simple and fast procedures for their extraction and purification. For biophotoelectrochemical systems, scientists have optimized the electron transfer between the thylakoid membrane and electrode, for example by developing different immobilization methods, or modifying electrode surface with redox polymers and nanomaterials. As an effective platform for cofactor regeneration, the thylakoid membrane-based biophotoelectrocatalytic systems have been used to drive the enzymatic synthesis of poly(3-hydroxybutyrate) (PHB) from acetate, as well as CO₂ fixation through a synthetic crotonyl-coenzyme A (CoA)/ethylmalonyl-CoA/hydroxybutyryl-CoA (CETCH) cycle. In addition to light energy utilization, thylakoid membranes can also be used in photodynamic therapy (PDT) of tumors. Firstly, the photosensitizer porphyrin in the chlorophyll molecules can produce singlet oxygen (¹O₂) from O₂ under visible light irradiation, which in turn kills the tumor cells. Secondly, the photosynthetic oxygen evolution of thylakoid membrane can rapidly supply O₂ <italic>in situ</italic>. Moreover, thylakoid membranes contain abundant catalase, which catalyzes the decomposition of H₂O₂ into O₂, thus further increasing the supply of O₂. This paper summarizes recent progress in the research of thylakoid membranes in these three fields, focusing on the application forms and underlying mechanisms. Moreover, the difficulties and challenges in the application of thylakoid membrane are discussed, and future research directions are prospected. Specifically, developing protective structures such as hydrogels or artificial vesicles to address the issue of short half-life of isolated thylakoid membranes will be crucial. In light of their ingenious energy conversion characteristics and amenability for potential commercialization, thylakoid membrane-based biotechnological systems will have a bright future in the fields of bioenergy, biocatalysis and biomedicine.

Green smart grid predictive analysis to integrate sustainable energy of emerging V2G in smart city technologies

In recent years, the volume of data has grown exponentially. Big data analytic platforms for the smart grid have enormous potential since they play an essential role in the decision-making process and help to prevent disasters or instabilities in the grid. Vehicle to Grid (V2G) technology has become a buzzword in the industry. It is posited as a forthcoming technology to be grasped in a distant, ultimately green, and future. However, this view is now being challenged as V2G is being deployed at a large scale. The severe challenges of rapid population growth, ecological pollution, and energy deficiency have encouraged the design of smart grids and electric transport systems, especially electric vehicles containing central energy utilization systems in a smart city. This paper proposes a robust and distributed approach to balance supply and demand. This study have constructed a unique framework to manage the ambiguous performances of vehicles and supplied energy resources in a smart city. Furthermore, it analyze the influence of network topology by evaluating the strength of solid network motifs using predictive analysis for the whole system.