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Solar energy, wind energy etc. are the main sustainable energy sources used around the world. These sustainable energy sources are used in day-to-day life in various forms for numerous purposes. One of the highly used sustainable energy sources is the solar energy which with the help of photovoltaic (PV) cells can be made use for the generation of electrical power. However, these sources generate less voltage values and thus it requires a high gain converter. In this paper, a modified Luo with flyback DC to DC converter is presented that assures high voltage gain, single switch, less stress across the components and less ripple current. Furthermore, the simulations along with the hardware prototype for the presented converter is carried out and presented in this paper.

The contribution of solar photovoltaic (PV) in the electrical power sector is increasing expeditiously. Recent interest in the integration of solar PV into the grid raises concerns about the synchronization technique. Continuous research has successfully replaced the small stand-alone system with a grid-tied PV system. A grid-tied PV system is popular due to the abundance of solar light and advanced power electronics techniques. This paper helps to provide a basic conceptual framework to develop a superior grid-tied system. Synchronization is a crucial problem in grid-tied inverters operation and control research indicates that frequency, phase, and amplitude of voltage are the most crucial parameters that need to be measured and controlled for grid-tied application. This paper presents the state of the art of various synchronization methods for both single-phase and three-phase units. A phase-locked loop (PLL) is a popular grid synchronization approach, which needs to sustain power system oscillations as its vulnerability influences the produced reference signal. Traditional PLL catches the frequency and phase through feedback loop-filter (LF) to improve steady-state capability during adverse grid conditions. The review paper focuses on the power stages architecture of PV fed grid synchronization along with a comparison of various PLL techniques based on their merits and demerits. This paper will be the one-stop reference for the researchers in the area of PV-fed grid.

Energy harvesting in the railway industry has great potential for many applications. Energy harvesters can provide electrical power for track-side, on-board, and infrastructure instruments, including health monitoring sensors, signaling, switches, and safety equipment. Due to the rapidly growing trend of the railway network, a considerable number of instrumentations need to be located in inaccessible, remote, and harsh locations where providing the energy through cable is almost impossible. In these cases, self-powered sensors and distributed power generators can be used based on energy harvesting techniques. High-intensity sound and vibration levels in the railway environment prove them to be promising sources of energy for self-powered devices. This paper aims to provide a comprehensive review on the railway sound and vibration energy harvesting, from the beginning to the most state-of-the-art. This paper addresses different energy harvesting resources for the railway environment, diverse methods of energy harvesting and their advantages and drawbacks, and at the end, energy harvesting applications in the railway industry. Different models and prototypes of energy harvesters are introduced and compared. Finally, the potential applications of railway energy harvesting are addressed, and future challenges and trends are discussed. The scheme of the present paper is designed in a way to provide readers the most significant principles that need to be considered in the design of railway energy harvesters.

Life Cycle Climate Performance (LCCP) is a widely accepted metric to evaluate the carbon footprint of air conditioning (AC) systems “from cradle to grave.” This paper: (1) reviews the invention and evolution of LCCP, including a comprehensive timeline and bibliography; (2) documents the successful application of LCCP in the replacement of HFC-410A with HFC-32 in room air conditioners; (3) compares the conceptual frameworks and the operational approaches; and 4) reflects on the drawbacks of current LCCP research and points out possible future work. The major policy-relevant findings are: 1. The indirect emissions caused by energy consumption is 70 to 80 percent of the LCCP of AC systems in most countries but will decline in importance as electric power supply shifts rapidly from fossil fuel to renewable energy sources, which have near-zero carbon intensity; 2. The embodied greenhouse gas (GHG) emissions in refrigerant manufacture are, in most cases, negligible but the physical and chemical properties are crucial for system optimization for low carbon footprint; 3. The LCCP metric can be used for multiple purposes such as refrigerant selection and AC system architecture optimization; and 4. Data limitations in material manufacturing and the carbon intensity of electric power are the most significant challenges. Finally, this paper describes a variety of methods to fill in data gaps, including the correction factor method, the data-driven method, and the database searching method. The next-generation LCCP will be an enhanced evaluation process considering local climate, heat islands, and local power supply characteristics.

This paper reviews and compares the main doubly-fed induction generator (DFIG) models for stability assessment in the literature by PSCAD/EMTDC simulation. The main contribution of the paper is a detailed study on small- signal admittance-based modeling of DFIGs for stability analysis. A complete DFIG model characterized from a 2x2 admittance-based transfer matrix is proposed which has frequency coupling between positive and negative sequences resulting from considering the PLL and the DC capacitor. In addition, two simplified DFIG models in the literature are derived from the complete model and discussed. The models are applied to stability analysis using the generalized Nyquist criterion and the positive-mode-damping stability criterion. The predictions are validated for several mechanical speeds and short-circuit ratios by PSCAD/EMTDC time-domain simulation. The study shows the need to apply the complete model to accurately assess subsynchronous stability, as significant differences from simplified models may occur at low frequencies.

Producción Científica, The widespread use of devices based on power electronics and other nonlinear loads has led to an increase in harmonic distortion that affects the quality of power systems. Therefore, the correct measurement of harmonic and interharmonic content is necessary. The International Electrotechnical Commission (IEC) standards define the concepts of spectral and time grouping required for such measurements. This paper demonstrates that the procedures defined in the IEC standards are not sufficiently accurate when several close interharmonic tones interact due to the lack of stability of the values that the Discrete Fourier Transform obtains in each sampling window, and to the inaccuracy in the measurement of interharmonic groups and rates when using the Hanning window. This paper proposes novel solutions based on time aggregation and the use of other groupings and alternative windows. The results obtained are compared with the results produced by applying the rectangular window indicated in the standards, using sensitivity analysis varying one of the tones and using experimental results measuring the output signals of frequency inverters driving induction motors. The proposed method achieves greater accuracy and stability in the measurement of spectral groupings and their related distortion rates in signals with abundant and dispersed interharmonic content.

The propensity to utilization of inexpensive, clean and distributed energy resources in the today's power systems structure are expanding due to various economic, political and sociological reasons. However, the power generated by these resources is extremely unpredictable, which is called uncertainty and exceptionally fluctuated drastically that is known as variability, during the operation epoch. So, exposure to these two features is great significance and value. This problem is known as the power system flexibility in the literature of electrical power system studies. Promoting flexibility in the system is too expensive and can be evaluated in different time frames. This paper studies the power system flexibility with the presence of uncertainty and variability of demand and supply side resources in a planning timeframe. This paper proposed an improved method for demand response uncertainty modeling with Z-number. This method is a hybrid possibilistic and probabilistic process. Furthermore, this paper applied an approved method for renewable generation uncertainty modeling with Monte Carlo. The scrutinies show, the most cost-effective way to consider the flexibility is planning timeframe, so this study proposed a novel paradigm for Flexibility-Constrained Integrated resource planning in presence of high penetration uncertain and variable demand-side and supply-side resources namely as FCIRPU/V-DSRs. The simulations are implemented with the proposed FCIRPU/V-DSRs methodology on a test system. The results show that this innovative framework provides a significant improvement in the power system flexibility at an inferior cost than other investigated methods.

The static var compensator (SVC) is one of the devices that has been widely used for reactive compensation to improve the capacity and flexibility of power transfer in the electrical power system. However, the SVC changes the voltages and currents of the power network to which it is connected. Consequently, the measured impedance can be changed and affect protection relays operation based on this characteristic. Several papers have been published about the SVC effects on distance protection applied in transmission lines (TL). However, it is not widely known the impact of SVC on the transient behavior of generators, such as protection against loss of excitation (LOE) in synchronous machines connected to TL with SVC. In this sense, based on the modeling of a test electrical power system in the PSCAD/EMTDC simulation environment, the assessment of the effects of SVC on the behavior of the ANSI 40 protection function for the conditions of the total LOE and partial LOE since these events can cause the synchronous machine to operate in conditions above the rated ones. In addition, this paper presents a testbed that allows performing secondary tests in physical relays when simulated signals are applied to perform protection studies in the presence of SVC in power systems.

Carbon foot print is latest hot discussion and all the countries are started the initiation to minimize it. One of the main carbon emission industries is thermal electrical power generating company. For the social welfare the emission has to minimize to maximum extend. The electrical power generation company as well needs to minimize the generation cost for the better operation. Minimizing carbon foot print and minimal power generation cost are opposite to each other. When the optimization focused to minimize the generation cost it lead to increase the carbon foot print and vice versa. This paper addresses the constraint the optimization problem which needs the objective of reducing both emission and generation cost. Electrical power generating cost of thermal power plant is nonlinear and non-convex in nature. Likewise the emission produced by the thermal power plant is complex mathematical problem. Intelligent algorithms are best suitable to solve these types of practical problems. In this paper hybrid of firefly algorithm and differential evolution technique is adopted to find the constrained emission minimization and cost minimization. Firefly algorithm works based on brightness, attractiveness and movement and there is no mutation process. Differential evolution technique has better mutation process and hence this mutation operation of differential evolution technique is introduced with firefly algorithm for the hybrid operation and to get better result. The research work is aimed to reduce the carbon foot print as well the generation cost of the power system.

As a developing nation with its increasing energy demands, Fiji is in the process of introducing renewables to generate green power to minimize its reliance on fossil fuels and to minimize greenhouse emissions. The paper focuses on green power generation with the available renewables. The overview deals with their prospective users and therefore the challenges to those sources within the view of the local context. Photovoltaic standalone systems connect peoples of remote areas with the rest of the country to upgrade their living standard. Power generating authority along with the Ministry of Energy of Fiji are actively involved in evaluating and incorporating these potentials for power generation. Hydropower, bioenergy, solar energy and wind power are the prominent renewables on which Fiji's future power generation would be based. The share of renewable energies in the urban power generation in the calendar year 2019 was about 53% (561.96 million units). 55.9% of the Fijian population lives in rural areas and settlements. The photovoltaic standalone system through the solar home system (SHS) project and mini-hydroelectric-grids have been introduced to electrify these areas. Photovoltaic grid-connected systems are being introduced in the urban population to increase green energy proportion in the country's electricity power generation. Photovoltaic road lights are being planned to replace conventional road lights. The emission of carbon dioxide by the power sector has been gradually reducing since 1993. In 2015, 1925 million metric tonnes of carbon dioxide was emitted which was 21% less than that of 2005. The Government of Fiji is committed to utilize natural renewable energy resources available and generate 99% green electrical power by 2030. This paper sets a benchmark for other pacific island nations in realizing the success that renewables are achieving in the isolated populations of Fiji.

Power transformers are most imperative and critical element in electrical power system grid. To have a consistent electricity supply it is obligatory to give substantial attention for upkeep of the transformer. To capitalize on the lifespan and reliability of transformers, it is significant to be aware of the ageing and damage of any internal as well as external parts such as winding, core, tap changer, bushings etc. of power transformers. Condition monitoring is a significant protagonist in asset performance management approach and right diagnosis will provide the indication of probable faults that may occur and means to get rid of it. For accurate measurements of failure chances and to estimate residual life of power transformers, industry standards have defined certain methods in order to associate outcomes from several routines, type and special tests. This paper covers a comprehensive review on established tests as a part of chemical, electrical and miscellaneous incipient faults such as dissolved gas analysis, oil testing methods, sweep frequency response analysis, recovery voltage method, partial discharge, infrared thermograph test, turns ratio test, dielectric dissipation factor, transformer winding resistance, core to ground test, and insulation resistance calculation. It also contemplates the practices extensively helpful for measuring the health index, lifecycle enhancement, condition-based assessment and probability of failures. This paper summarizes a comprehensive assortment of methods extracted from industry and academic resources and distinguishes internal faults in an integrated structure with inclusion of health index formulation and interpretation for lifecycle prediction and possible suggestions to improve the asset condition. Index Terms- Power Transformer, Incipient Faults, Condition Based Assessment, Health Index, Failure Analysis.

Transitioning the energy sector to zero or net-zero emission of greenhouse gasses (GHG) and substantially reducing other pollutants is a massive, costly, and long-term effort. The typical starting point and centerpiece of energy decarbonization is the electric power sector. The sector is a large direct GHG emitter. It already has many technological, non-carbon emitting alternatives that are rapidly declining in capital and operating costs and improving in performance, making electricity the least expensive and accessible energy carrier to decarbonize. This paper explores what the modeling community should do to inform this transition. The underpinning premise of this paper is that policymakers genuinely want to be informed from the modeling community about their range of options, their ability to achieve various objectives, and possible unintended outcomes. Since the goal of the modeling community is to help inform policymaking, it is important that they hear the needs of policymakers, be it economic, technological, or social goals.

The Africa Continental Free Trade Area presents an opportunity for the creation of a single continental electricity market in Africa. This market has the potential to promote the efficient development of electricity infrastructure and symbiotic electricity trading between members of Africa's five regional electric power pools. A framework is proposed to harness the opportunities presented by the African Continental Free Trade Area through the coordination of technical and commercial endeavors of the regional power pools in Africa. This includes fostering sharing mechanisms of best practices that support the development of national and international institutions, harmonizing regulations and grid codes, and promoting electricity trading opportunities that will catalyze the development of inter-regional infrastructure projects. In this paper, the authors propose a bilateral contract market that aligns with and complements the existing regional power pools without encumbering them with unnecessary bureaucracy. The paper's policy recommendations are designed to promote proactive adoption and compliance with the recommended best practices, market rules and regulations by market participants, motivated by their self-interests.

The recent seismic events that occurred in South Korea have increased the interest in the re-evaluation of the seismic capacity of nuclear power plant (NPP) equipment, which is often conservatively estimated. To date, various approaches—including the Bayesian method proposed by the United States (US) Electric Power Research Institute —have been developed to quantify the seismic capacity of NPP equipment. Among these, the Bayesian approach has advantages in accounting for both prior knowledge and new information to update the probabilistic distribution of seismic capacity. However, data availability and region-specific issues exist in applying this Bayesian approach to Korean NPP equipment. Therefore, this paper proposes to construct an earthquake experience database by combining available earthquake records at Korean NPP sites and the general location of equipment within NPPs. Also, for the better representation of the seismic demand of Korean earthquake datasets, which have distinct seismic characteristics from those of the US at a high-frequency range, a broadband frequency range optimization is suggested. The proposed data construction and seismic demand optimization method for seismic capacity re-evaluation are demonstrated and tested on a 480 V motor control center of a South Korea NPP.

Spacecraft operation in ultra-low Earth orbits (150–250 km) can provide advantages for carrying out traditional tasks. At the same time, the long-term maintenance of spacecraft in such orbits requires the delivery of a propellant supply from the Earth to compensate the aerodynamic drag. An increase in the lifetime can be achieved with air-breathing electric propulsion (ABEP) using outboard atmospheric gases as a propellant. To ensure ABEP operation, it is necessary to provide the required electric power supply and density of ionized gas. At the same time, lowering the orbit altitude or extension of solar arrays is accompanied by a rise in aerodynamic drag, the required thrust to compensate it and, therefore, the required power supply. In this paper the problem of integrated optimization of the trajectories and layout parameters of spacecraft by the criterion of the ABEP power consumption at the fixed spacecraft volume is considered. Variations in the density and composition of the atmosphere and the periods of shading of the spacecraft are taken into account. An analytical solution is obtained depending on generalized parameters that combine such characteristics as the specific power of solar arrays, total thruster efficiency and aerodynamic drag coefficient. The dependencies of the orbit characteristics enabling the long-term maintenance of spacecraft with ABEP on the generalized parameters are determined.

This paper investigates the integration of the fractional-order capacitor on electrical power systems to improve system performance. The system performance problem in this exploration is reducing the losses and improving the voltage profile. For decades, capacitor installation is having a great effect on compensating system reactive power which affects system performance and quality. The novelty in the proposed work is to integrate the fractional capacitor to the power systems as a distributed generator. The study compares the classical capacitor implementation versus the fractional capacitor as a suggested new technology. Due to the complexity of the study to obtain optimal size, parameter, and location of the proposed technologies, Marine predator as a meta-heuristic optimization technique is employed. The proposed methodology can be divided into two parts; a single objective function to study the losses minimization and the voltage improvement individually and the second part is the multi-objective single representation problem to find the optimal solution for both two targets, the losses reduction, and the voltage profile improvement. The proposed fractional capacitor implementation is assimilated to standard IEEE 69 radial system.

Desiccant dehumidification systems are thermally regenerated systems that can be used either as standalone or as complementary additives for conventional cooling systems. One of their best competitive qualities is the potential to utilize low-grade heat sources for the regeneration process, thus decreasing electrical power consumption and scaling back the emissions of greenhouse gasses. However, up till now, desiccant dehumidification systems saw limited practical applications, due to their relatively high capital costs and low efficiency. To enhance the commercial competitiveness of desiccant dehumidification systems and expand their fairly tiny niche market, it was necessary to improve the system's performance and reliability and reduce their costs. A detailed discussion of the current designs configurations and the main differences between them may help future researchers to come up with novel, innovative designs, to overcome the system's drawbacks and make them actual viable alternative competitors in the dehumidification market. Consequently, this paper presents and analyzes the development of those configurations in the following three main aspects: packed bed, fluidized bed, and rotating desiccant wheel.

Historically, energy constraints have limited the spatial range, endurance and capabilities of ocean observation systems. Recently developed wave energy conversion technologies have the potential to help overcome these limitations by providing co-located and persistent power generation for ocean observations, enabling new opportunities for ocean research. In this paper, we develop the first techno-economic model for wave-powered ocean observation systems and use the model to study system characteristics and cost drivers. Our model utilizes time-domain simulation and optimization to identify cost-optimal system characteristics and to estimate capital and operational costs. Using our model, we evaluate the use of wave energy to power a 200 W ocean observation system deployed for five years at five unique geographic locations. We found that, depending on the geographic location, cost-optimal wave energy powered systems require an ≈ 0.5–3 kW wave energy converter and an ≈ 15-50 kWh battery. The corresponding range of power system costs over the deployment duration is between $110,800 and $673,200. We build on these results by performing a sensitivity analysis of key model parameters and identifying the potential economic impact of future technology advancements. Overall, our results indicate that characteristics of the geographic location, power system durability, and electrical power demand are key drivers of power system economics for ocean observing.

The need of world electricity production is growing at an increasing rate and because of its limited supply, it cannot completely be met by ordinary energy framework. The use of hybrid systems by renewable electricity sources for energy generation has also created considerations in general. There is no one source of renewables ready to continuously load electricity, and hybrid systems are thus a key solution. Renewable energy is produced by inexhaustible reserves, usually refilled on a human scale, such as sun, wind, hydro, mainstay, biomass, etc. In four core areas, renewable energy often provides energy: electricity, air and water heating/cooling, transport, and rural (stand-alone and network) energy services. In comparison with other sources, renewable power sources have reserves in large geographical regions amassed in a small number of countries. Rapid organization of renewable energy sources and energy conservation brings enormous energy stability, ecological change relief and financial benefits. Hybrid systems (PV-Biomass) are used in different regions to provide electricity to overcome discontinuity and transition in solar and wind power. This paper discusses the techno-economic feasibility analysis of solar biomass system in the Ludhiana district of Punjab.

A blood collection monitor is a device used during the blood collection process to provide a shaking moment to the blood being received from the donor thereby mixing the blood homogeneous with the anticoagulants in the blood bag. The shaking moment and anticoagulants prevent blood coagulation. The amount of blood to be collected varies from donor to donor which ranges from 350 ml to 450 ml. The existing electronic blood collection monitors being used in hospitals and laboratories include not only mechanical but also an electric mechanism that provides oscillations to a blood bag, quantify the blood amount and measure the flow of blood. However, the dependency of these devices on external electric power sources limits its application in rural areas as well as large-scale donation camps. The present study offers a mechanical blood collection monitor which does not require any external power for its functioning and thereby overcomes the drawbacks of the conventional device. The present paper offers the design considerations and systematic study of the proposed mechanical blood collection monitor. Additionally, the linkage mechanism and associated gear train were analysed using ANSYS and ADAMS which further opens up the ways to study the variations in kinetic energy and torquing moment.

This paper reports an experimental study on power consumption of PolyJet 3D printing. Controllable variables studied are location of samples on the build platform and volume of printed samples. The measured output is “Power Efficiency”: electrical power consumed per unit volume (cubic millimeter) of printed samples. Power Efficiency values are determined by dividing the product of consumed wattage and total print time by total volume of samples. Samples of different volumes are placed at different locations on the build platform. The results show that Power Efficiency is higher when samples are arranged along the X axis than when they are arranged along the Y axis.

Solar energy is a non-depleting source of energy where one hour of solar energy reaching on earth’s surface is enough to meet the world’s demand for a year. In present scenario people need electric power every single minute. Solar energy can be easily generated using photovoltaic panels for any type of purposes i.e., domestic or industrial. It is also very efficient and clean energy system. A lot of researches are going on solar energy to make it more efficient so that maximum energy can be drawn from sunlight. Conversion of solar energy to electrical energy includes a number of converters according to its use. One major issue related to a converter is with respect to switching losses, on state losses and sometimes complex gate circuits. Primarily from few years a lot of emphasis is given to reduce the number of switches in a converter circuit. Nine Switch Converters are a major leap in the world-changing scenario towards the converters that are being employed to the various systems, due to its various advantages which include fewer switching devices than usual, less switching losses and high-power quality. In this paper, a Photovoltaic solar array is used as a source along with a Nine-Switch converter to power a separate three-phase load. The voltage generated by the Photovoltaic solar array is regulated using a dc-dc boost converter whose output is supplied to the input of the nine-switch converter that will ultimately power the loads. The gating signals for the nine-switch converter employs the space vector modulation technique, as space vector modulation has a number of advantages when compared to other modulation techniques which includes less harmonics, higher modulation index etc. A MATLAB simulation is included to show the performance of the system.

With the growing importance of renewable energy generating resources around the world, the government is working towards expanding the share of renewable energy to 20% of total power generation considering the limitation of coal-fired and nuclear generation by 2030 in South Korea. However, the growing number of wind generating resources being connected to the electrical power system presents a challenge for transmission grid planning to increase the penetration of wind power while maintaining high levels of reliability and security of the electrical power system. In this paper, we propose a probabilistic power output model of wind generating resources for network congestion management. We use the historical data from the wind farms located on Jeju Island in South Korea to fit the Weibull distribution and implement Monte Carlo simulations. The simulation results, which represent network congestion with probabilistic values, are applied to the empirically modeled power grid of Jeju Island and a steady-state security evaluation is performed. The proposed probabilistic approach will be a key role to reduce the risk of over-investment in power transmission facilities compared to the deterministic approach to develop the generation mix scenarios with high wind power penetrations.

This paper continues discussion on financial viability and design optimisation of biomass-fired Organic Rankine Cycle (ORC) Combined Heat and Power (CHP) systems. It examines influence of such decision variables as ORC system rated electric power output, architecture and working fluid. The considered ORC system structures are simple, regenerative and regenerative cycle with split heat exchanger. Eight working fluids are considered, namely: MM, MDM, MD2M, D4, D5, toluene, ethylbenzene, and cyclohexane. The system was modelled and simulated using Ebsilon® Professional software. Sample project is assessed in terms of power generation efficiency, Primary Energy Savings (PES), and financial indicators, such as Net Present Value (NPV) and Internal Rate of Return (IRR). Results revealed considerable differences in optimal power output. The optimal value of the ORC generator power output in terms of NPV is within the range from 1000 to 2600 kW depending on the system configuration and the working fluid. In terms of IRR the optimal rated power is between 750 and 1400 kW. The highest values of nominal rated power output have been obtained for ethylbenzene. What is more, the economic indicators get higher values for hydrocarbons than for silicone oils, which are nowadays widely used in biomass fired ORC systems.

Excessive consumption of fossil fuels has led to depletion of reserves and environmental crises. Therefore, turning to clean energy sources is essential. However, these energy sources are intermittent in nature and have problems meeting long-term energy demand. The option suggested by the researchers is to use hybrid energy systems. The aim of this paper is provide the conceptual configuration of a novel energy cycle based on clean energy resources. The novel energy cycle is composed of a wind turbine, solar photovoltaic field (PV), an alkaline fuel cell (AFC), a Stirling engine and an electrolyzer. Solar PV and wind turbine convert solar light energy and wind kinetic energy into electricity, respectively. Then, the generated electricity is fed to water electrolyzer. The electrolyzer decomposes water into oxygen and hydrogen gases by receiving electrical power. So the fuel cell inlets are provided. Next, the AFC converts the chemical energy contained in hydrogen into electricity during electrochemical reactions with by-product (heat). The purpose of the introduced cycle is to generate electricity and hydrogen fuel. The relationships defined for the components of the proposed cycle are novel and is examined for the first time. Results showed that the output of the introduced cycle is 10.5 kW of electricity and its electrical efficiency is 56.9%. In addition, the electrolyzer uses 9.9 kW of electricity to produce 221.3 grams per hour of hydrogen fuel. The share of the Stirling engine in the output power of the cycle is 9.85% (1033.7 W) which is obtained from the dissipated heat of the fuel cell. In addition, wind turbine is capable of generating an average of 4.1 kW of electricity. However, 238.6 kW of cycle exergy is destroyed. Two different scenarios are presented for solar field design.

Hybrid parabolic trough concentrators were considered as the basis of co-generation systems, which mainly based on the Simultaneous production of thermal and electrical energy. In this paper, a thermal model of two cogeneration systems consisting parabolic trough collector, combined with a cylindrical thermoelectric generator was presented. The collector of the present configurations forms an annular channel between the inner side of absorber tube and upper surface of tubular thermoelectric generator. A heat transfer fluid (Therminol VP1 or hot water) is passed along the annular channel using a pump with low consumption, which mainly energized by the produced power from the tubular thermoelectric generator. Also, the heat transfer fluid (Therminol VP1 or Hot water) temperature is mainly based on the temperature adjustment principle, where the heat transfer fluid flow rate is adjusted according to sun irradiation to keep the heat transfer fluid temperature at 400 °C for Therminol VP1 or at 95 °C in the case of water. To examine the effects of solar concentration ratio and sun irradiation on the thermal and electrical performance of the hybrid system, a set of nonlinear equations were developed and coded in MATLAB software (R2015a). The power output and electrical efficiency of the tubular thermoelectric generator, the overall efficiency and net power as well as hot water storage of the hybrid systems were separately presented and discussed for all three solar concentration ratios and ten sun irradiation values. To validate the predicted results of the numerical model, two available research works have been used. The comparison of results obtained with results of the exact solution indicates a good agreement. The novel integration technique shows major improvements in thermal and electrical performance of both hybrid systems. As a results, the overall efficiency of the first hybrid system (Here, Therminol VP1 serves as a heat transfer fluid) reached to 70.550% corresponding to 306.5826 L/Day of Therminol VP1 at 400 °C and about 585 W of additional power. These values in the case of water serves as a heat transfer fluid up to 76.913%, 1058.467 L/D of hot water at 95 °C and 97.032 W of additional electrical power, respectively.

© 2022 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ The use of the electrical energy storage (EES) plays an important role in the transition of energy generation towards renewable energy sources (RESs). An effective sizing of EES systems is very important in order to cope with the volatility of RESs and to ensure a reliable energy supply. The present paper provides a methodology which helps to determine the minimum required EES size for conceiving a fully standalone system. Its approach is based on the evaluation of the energy balance for a given design period, and it can also be applied for sizing the EES system in grid-connected applications. The methodology was validated using measurement data obtained from two different systems corresponding to: a) a near-zero energy building with local generation sources, and b) a large-scale battery energy storage system (BESS) installed in a factory and used for peak-shaving. The obtained results confirmed the effectiveness of the proposed methodology by estimating the required size of the EES system. A good correlation was found between the estimated and the installed BESS size in the considered systems. The deviation between real and estimated BESS capacities was found to be less than 5%. Peer Reviewed Objectius de Desenvolupament Sostenible::13 - Acció per al Clima Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant

There is a trend that traffic unbalance in electric power communication networks is becoming more and more prominent because of the increasing communication demand from the development of the energy Internet. To reduce transmission risk and improve network’s reliability and throughput, it is necessary to optimize the routes of communication services with traffic and risk balance strategies. In this paper, a risk and traffic-based routing algorithm for electric power communication services is proposed. We first establish a risk balance strategy with service importance and link availability, then proposes a traffic balance scheme considering bandwidth on links and traffic-processing capability of nodes. Based on traffic characteristics and service risk, the proposed algorithm considers the traffic flow and risk value of the link synthetically and designs a corresponding routing strategy by introducing the balance factor. Numerical results obtained in a real electric power communication environment demonstrate that the algorithm can reduce both the blocking probability and the service risk simultaneously, which achieves the balance between traffic and risk and obtain the optimal performance of electric power communication network.

With the development of human societies, new industries and needs are being formed which supplying their power and energy consumption, requires the development of equipment and infrastructure in the field of power generation and transmission. An example of these industries are seawater desalination (SWD) units. In addition, increasing attention to air pollution has led to the proliferation of electric vehicles (EVs) or the use of hydrogen as a zero emission fuel. Energy hubs (EHs) can benefit from advantages such as optimal use of installation capacity and environmental potential by accepting to provide other needs along with common requirements such as electricity, cooling, and heating. In this case, EH is able to increase its flexibility by converting energy into the desired product and storing it in a different form as of electrical or thermal energy. In this paper, EH utilizes a SWD with Reverse Osmosis (RO) technology as a flexible load and an Organic Rankine Cycle (ORC) as a new technology for generating electrical power by means of thermal power. In addition, for better interact with available EVs, one parking lot and a Battery Swapping Station (BSS) are introduced. The Electrolyser uses the electrical power to supply the required amount of hydrogen, and the hydrogen tank in addition to fuel cell (FC) help to balance the production and consumption of hydrogen. In order to model the existing uncertainties, scenario generation method as well as information gap decision theory (IGDT) method have been used. The efficacy of the proposed model is evaluated on a smart commercial building in Qeshm Island, which is located a few kilometers off the southern coast of Iran.

Riding a road vehicle involves only 10- 16 % of the fuel energy to overcome the resistance from friction and air drag, while the rest contributes to a massive ecological and economic damage. From an energy balance point of view, a great amount of energy is dissipated as vibrations at the shock absorbers level. In this paper, a hydraulic regenerative shock absorber, able to recover and convert the vibration energy caused by road profiles is designed and manufactured by exploiting off-the-shelf components to reduce R&D costs, and its overall maximum efficiency is measured. The prototype is composed of a twin tube electronically controlled shock absorber and of an electro-hydraulic unit (also called regenerative valve) rigidly connected to it. The main relations ruling the dynamics of a regenerative damper are discussed and the main features of the regenerative valve are designed to comply with size, performance, and safety requirements. Parametric relations are illustrated and properly managed to justify the choice of a dedicated electric motor. Performances are assessed through simulations and experimental tests, while reliability is confirmed through a thermal analysis that reveals no thermal issues. The prototype reaches a maximum overall harvesting efficiency of 11.7 % for an intermediate value of the external electric load at a 500 mm / s rod speed and a maximum electric power in output of 75 W for a high external electric load at 1000 mm / s rod speed. Efficiency is strongly hindered at low values of rod speed because of predominant friction effects. It is also demonstrated the possibility to modify the damping curve by varying the electrical characteristics of the circuit connected to the electric machine. The compact design of the RSA, with a mass of only 5.8 kg , allows its installation into the suspension of a B-class SUV with a minimum impact on the current damper structure.

This paper introduces a new multigeneration gas turbine-supercritical carbon dioxide combined power cycle integrated with a solar-powered carbon capturing system to produce electricity, cooling effect, freshwater, and ammonium bicarbonate. This multigeneration system is analyzed using the first and second laws of thermodynamics to assess the system performance. The results of this analysis show that this integrated system is able to produce ammonium bicarbonate at a rate of 1.30 kg s−1, while producing 2,280 kW of electric power. The overall energy and exergy efficiencies of this integrated system are found to be 22.3%, and 11.9%, respectively. Then, some parametric studies are conducted to observe how this integrated system behaves under different operating conditions. One finding is that the solar irradiance affects the overall energy and exergy efficiencies considerably. Also, changing the isentropic efficiencies of the turbines in the system has more significant effects on the net electric power production than changing the isentropic efficiencies of the compressors.

The smart-grid has requirements of flexible automation, efficiency, reliability, resiliency and scalability. These are necessitated by the increasing penetration of power-electronics converters that interface distributed renewable energy systems which energize the fast-evolving electric power network. Microgrids (MGs) have been identified as modular grids with the potential to effectively satisfy these characteristics when enhanced with advanced control capabilities. Model predictive control (MPC) facilitates the multivariable control of power electronic systems while accommodating physical constraints without the necessity for a cascaded structure. These features result in fast control dynamic response and good performance for systems involving non-linearities. This paper is a survey of the recent advances in MPC-based converters in MGs. Schemes for the primary control of MG parameters are presented. We also present opportunities for the MPC converter control of autonomous MGs (power quality and inertia enhancement), and transportation electrification. Finally, we demonstrate MPC’s capabilities through hardware-in-the-loop (HiL) results for a proposed adaptive MPC scheme for grid-forming converters.

This paper presents characteristics of heat accumulation system operation in one of the Polish combined heat and power (CHP) plants. The heat source cooperating with this installation is cogeneration units consisting of gas engines with a total heat output of 8 MWt and total electrical power of 8 MWe. The total thermal capacity of the non-pressure hot water accumulator is 75 MWh. An important issue in the case of hot water tanks is thermal stratification caused by the difference in density between higher-temperature water, located at the top of the hot water storage tank and colder water at its bottom. The article presents the results of numerical analysis based on the axial-symmetric model of a hot water tank using Ansys Fluent R19.2 software. Simulations with the Computational Fluid Dynamics (CFD) method were carried out for the process of charging the heat accumulator lasting 10 h. The effect of mesh density on the results obtained was analysed. The results were compared with the measurement data from the CHP plant. Heat losses from the hot water tank were taken into account and the density characteristics of the heat flux lost to the environment were presented.

Solar thermal air-Brayton cycle system stands out among distributed power systems with high reliability, compactness, low cost and little water consumption, but its operation is affected by the availability and stability of solar energy. Thermal energy storage (TES) is necessary for dispatchable power generation and stable operation of solar thermal air-Brayton systems, but there are insufficient studies on the integrated TES-solar air-Brayton cycle system. In this paper, a honeycomb ceramic TES was designed for a 10 kW-scale solar air-Brayton cycle system based on the steady state off-design cycle analysis. The TES presented high efficiencies in the charging and discharging experimental tests, which were 79.6% and 76.5%, respectively. The air leakage between the ceramic modules was founded to affect the outlet air temperature and module temperature. Besides, a one-dimensional transient TES model was developed and validated. A feasible stand-alone operation strategy for the system was finally simulated based on the transient system model, which showed that constant output electric power (∼12 kW) and extended power generation duration of 3 h could be realized by integrating the TES. This work contributes to the design and modeling of TES for solar air-Brayton cycle systems as well as the system operation strategy analysis.

Biomass-fuelled Combined Heat and Power Generation (CHP) systems can efficiently convert chemical energy contained in biomass into electricity and heat. Currently there is a large number of abandoned forests and biomass of agroforestry origin that is not being used. The use of residual biomass as a source of energy in CHP systems is presented as a particularly attractive alternative for energy obtention. This paper presents the results of a biomass boiler coupled to an Organic Rankine Cycle (ORC). Three residual biomasses, named pruning vine, pruning kiwi and gorse have been selected due to their potentiality and availability in the Galicia-North Portugal Euroregion. For this purpose, micro-cogeneration tests at bench scale were performed, based fundamentally on varying dissipation conditions in the low-grade temperature range (below 100 °C). Micro-cogeneration performance was assessed based on the electrical power and efficiency obtained, along with the global efficiency achieved (electrical plus thermal). Combustion measurements comprised gaseous emissions analyses and determination of the efficiency of the process. Micro-cogeneration results obtained show that differences in temperature between the hot and the cold source have a significant influence. The higher the temperature difference, the higher the electrical power and efficiency, as well as the higher global performance obtained, with values close to the maximum of the ORC employed (i.e 4 kWe, 9% and 96% respectively). Thus, the technical feasibility of the system to simultaneously obtain heat and electricity from low grade heat sources in small-scale applications was demonstrated. Regarding to combustion, parameters regulated by European emission standards are under the limits using the biofuels (residual biomasses) studied. Thereby, the suitability of those biomasses in thermochemical valorization processes was demostrated.

Looped travelling-wave thermoacoustic electric generator (LTTAEG) can transform thermal energy to electric power using thermoacoustic effect. Based on our previous effort on multi-stage LTTAEG with side-branched and dual-opposed linear alternators (LAs) as acoustic-to-electric transducers, for a higher output electric power and thermal-to-electric efficiency, a 4-stage LTTAEG is studied numerically and experimentally in this paper. In the simulation, the performance of 4-stage looped thermoacoustic heat engine is investigated based on linear thermoacoustic theory while the performance of dual-opposed LA is studied based on a novel network model. A new coupling algorithm between the 4-stage looped TAHE and dual-opposed LA is also proposed. In experiment, with 6 MPa pressurized helium as working gas, 650 °C and 25 °C heating and cooling temperatures. A highest electric power of 6.1 kW with thermal-to-electric efficiency of 15.86% and a highest thermal-to-electric efficiency of 19.64% with electric power of 4.37 kW is obtained when the electric capacitance connected to the LA is 17 μF and the electric resistance is 40 Ω and 75 Ω, respectively. Due to the high oscillating pressure in the system, some nonlinear phenomena have caused the simulation results deviated from the experimental results, especially in acoustic power and electric power, which should be investigated and considered in the future study.

Although freshwater is necessary for the well-being of humankind, increasing population growth and limited resources lead to a serious crisis to supply freshwater. Since the Earth is surrounded by seawater, desalination based on electrical power is introduced as a promising technology to provide freshwater. It is well documented that the connection of remote areas that usually do not have access to freshwater into the electricity grid is not affordable and eco-friendly. Hence, the efforts to design and construct high reliability, cost-effective, and eco-friendly stand-alone hybrid renewable energy system in remote areas. In line with this, this paper describes a novel energy management system for the optimized operation of a stand-alone hybrid energy system based on photovoltaic panels, wind turbines, batteries, and diesel generator. For this purpose, a multi-objective optimization problem is formulated by combining three objective functions, i.e., minimum the total life cycle cost as well as environmental impacts on human health and ecosystems and the maximum system reliability that can conflict with each. To solve the multi-objective optimization problem, a division algorithm is proposed that is more flexible and faster compared with conventional algorithms such as genetic algorithm. In order to show the proposed framework, a real case study in Larak Island, Iran, with appropriate solar and wind is considered. The effectiveness of the applied approach compared with optimization results of genetic algorithm and the artificial bee swarm optimization algorithm that was previously used successfully to solve optimization problems related to desalination integrated with the renewable energy system. The optimization is performed based on different diesel fuel price amounts (0.2, 0.5, and 1 $/liter). It is seen that at fuel price set to 0.2 and 0.5 $/liter, the seawater reverses osmosis desalination/photovoltaic/diesel generator/battery is the most cost-effective energy system, and when fuel price is 1 $/liter, the seawater reverses osmosis desalination/photovoltaic/wind turbine/diesel generator/battery is the most cost-effective hybrid system. While at fuel price set to 0.2, 0.5, and 1 $/liter, the seawater reverse osmosis desalination /photovoltaic/wind turbine/diesel generator/battery is the most eco-friendly. Finally, the results of this study show proposed algorithm is faster and more accurate (100 iterations, 98.36% accuracy) than the genetic algorithm (1000 iterations, 83.03% accuracy) and the artificial bee swarm optimization (300 iterations, 95.49% accuracy).

One of the aims of the modernization of the existing road lighting installations is to improve their energy efficiency. EN 13,201–5 standard introduces energy performance indicators for road lighting installations which only take into account active power. Real installations of road lighting do not only experience active power flow, but also reactive power and distortion power flows. This is due to the non-linear current-voltage characteristics of luminaires. Moreover, the use of LED technology has changed the power factor of a luminaire from inductive to capacitive. The paper proposes the introduction of new energy performance indicators: the reactive power density indicator DQ, the annual reactive energy consumption indicator DEQ, the distortion power density indicator DH and the annual distortion energy consumption indicator DEH. The energy performance indicator DP and the new DQ and DH indicators can be presented as coordinates in the Cartesian space in the form of a vector which is interpreted as an indicator of the total energy performance. The use of the proposed indicators in the road lighting design will enable the selection of the best lighting design variant in terms of the electrical power quality, especially if the compared luminaires have a similar or identical active power.

The transition towards a decarbonised electrical power system has consequences for the operation of Anaerobic Digestion (AD) providing an incentive to respond to the dynamic demand for electricity. Therefore, dynamic models to predict and control the AD process are of interest. A large number of models of AD exist, however, none seems fit for routine use in industry, being either too simple and inaccurate, or too complex. Consequently, the aim of this paper is to develop a new moderately complex dynamic model for process design and operational control of AD for intra-day on-demand electricity generation. The model interprets AD as three irreversible first order chemical reactions in series. The periodic nature of the usual feeding regime is used to develop a new general chemical kinetic analysis for a well-mixed tank subject to periodic feeding that is also industry friendly and fit for purpose with AD. The use of the model for AD is validated with eight datasets for different experimental conditions each mimicking demand-driven biogas production from sewage sludge obtained at pilot scale (0.05 m3). The model is accurate in predicting the biogas production rate, and the significant operational parameters of the process. The periodic version of the model performs generally better than a dynamic version that performs a bespoke mass balance at each feed and integrates the modelling equations until the next feed. It is concluded that the periodic model is fit for the purpose of predicting the operational parameters needed for dynamic biogas production and on-demand electricity generation.

This paper aims to propose a comprehensive energy management system (CEMS) to simultaneously enhance the resilience of microgrids (MGs) and distribution network (DN) in a multi-microgrid (MMG) system against unexpected events. It also develops a reliability evaluation framework for the reliability evaluation of MMG distribution systems. In this regard, the proposed CEMS includes two main strategies: (1) networked operation mode (NOM), attributed to the cooperation of independent sub-sections (MGs/DN) in fault-affected portions. Here, each MG must exchange power with the DN and other MGs (may be islanded simultaneously) by participating in peer-to-peer (P2P) energy sharing to enhance resilience and reliability of the whole network, and (2) individual operation mode (IOM), comprising the grid-connected, optional islanding, fully forced islanding, and partial islanding modes for different operational requirements of MGs. Thus, the required information of an outage is identified. A suitable decentralized strategy based on the proposed CEMS and the novel adaptive problem formulation are initially used to operate such systems under different operating conditions. The NOM and IOM together assure the survivability of the whole system during the emergency periods and maintain reliable electric power supply for consumers while guaranteeing system stability indicators and ensuring operating costs of MGs. To substantiate these claims, we use different case studies to demonstrate the efficiency of the proposed CEMS based on a modified reliability test system.

Coordinated operation of Coupled Electric Power and District Heating Networks (CEPDHNs) brings advantages as e.g., the district heating networks can provide flexibility to the electric power network, and the entire system operation can be further decarbonized through heat pumps and electric boilers using electricity from renewable energy sources. Still, today CEPDHNs are often not operated in a coordinated way causing a lack of efficiency. This paper shows, how efficient resource allocation is achieved by determining the power exchange between both networks over an aggregated market. We introduce a welfare-optimizing, market-based operation for a CEPDHN that satisfies operational constraints and considers network losses. The objective is to integrate uniform pricing market-clearing and operational constraints into one approach, in order to obtain high incentive compatibility for the market participants while preventing high uplift costs from redispatch. For this, we use a hybrid market model mainly based on uniform marginal pricing and additionally utilize pay-as-bid pricing for a fraction of the allocated bids and offers. We perform a case study with a real CEPDHN to validate the functionality of the developed approach. The results show that our solution leads to efficient resource allocation while maintaining safe network operation and preventing uplift costs due to redispatch.

Greenhouse gas emissions from the burning of fossil fuels are one of the main causes of anthropogenic climate change. Large-scale deployment of renewable energy can play an immense role in transforming the global energy system and mitigating the emissions. This paper describes the development of a novel framework called MArket Penetration ModeLing of Renewable Energy Technologies in Electric Power Sector (MAPLET-PS). MAPLET-PS assesses the impacts of policy measures such as carbon price and financial incentives on the adoption of renewable energy technologies. The framework was used to develop a case study for the electric power sector of Alberta, a fossil-dominated province in Western Canada. The results show that implementing a carbon price on fossil fuel electric power sources and incentives for renewable energy, along with the phase-out of coal-fired electricity generation, can mitigate 29% of Alberta's electricity sector 2020 GHG emissions by 2050 and reduce GHG emissions from 46.5 Mt of CO2 eq. in 2020 to 23.6 and 29.1 Mt of CO2 eq. per year in 2030 and 2050, respectively, in Alberta. Moreover, these changes can increase the share of renewable energies from 12.5% in 2018 to 30% in 2050. These rates can be achieved by implementing a carbon price along with a 1000 $ incentive per kW new capacity development and 70 $ incentive per MWh electric power generation from renewable sources, from 2021 to 2025, primarily from wind turbines.

Distributed generation (DG) is a promising solution to climate change problems related to rapidly increasing electric power consumption. However, the increasing penetration of DG units poses challenges in enhancing the distribution network reliability owing to their intermittent nature. This paper proposes an integrated voltage control and maintenance insurance planning model for power system reliability under uncertainties in demand loads and active power output of DG units. Voltage control is executed to solve the power quality issue by optimally coordinating the reactive power outputs of the DG units and the active power outputs of storage batteries (SBs). A maintenance insurance scheme is applied to ensure the operating conditions of DG units and SBs in a continuous manner without unexpected interruptions. The reliability indices represented by the voltage deviation cost and expected interruption cost are employed in the proposed planning model to minimize the total power system cost. The decisions include the number and location of DG units and SBs, the reactive and active power of DG units and SBs, respectively, as well as the preventive maintenance cycle and insurance coverage level. A robust fuzzy programming model based on type-2 fuzzy numbers is proposed to obtain the optimal solution in the planning horizon. The application of the proposed model is examined using an empirical case study. The results indicated that the voltage control and maintenance insurance can aid in enhancing the distribution network reliability by reducing the related cost by approximately 26.09%.

Supercritical carbon dioxide (sCO2) cycle is suitable for high temperature heat source, but introduces challenging in absorbing moderate/low temperature flue gas energy for coal fired power plant. Here, we explore the effect of flue gas cooler (FGC) and overlap energy utilization (OEU) on sCO2 cycle. FGC and OEU extract moderate temperature flue gas energy by a splitting CO2 flow rate from the cycle and a combined cycle, respectively. Recompression cycle plus reheating (RC + RH) and tri-compression cycle plus reheating (TC + RH) are two basic cycle types for coal fired power plant. A thermodynamics model coupling with thermal–hydraulic characteristic is developed. The analysis is performed for a 100 MW rated power capacity. For RC + RH, we show that OEU yields an electric power efficiency increment of 0.13% compared to FGC, which is caused by smaller pressure drops in boiler components when using OEU. Even though TC + RH introduces difficulty in absorbing moderate/low temperature flue gas energy, OEU still can decrease outlet flue gas temperature (Tfg,ex) to 126 °C, which is acceptable. However, FGC achieves a higher Tfg,ex of 172.6 °C by a pinch temperature difference limit of 30 °C, which deteriorates boiler efficiency thus it is not acceptable. We conclude that OEU is better than FGC, no matter for RC + RH or TC + RH. The double-channel-tail-flue concept is proposed to not only increase thermal efficiency of the system, but also elevate boiler efficiency. This paper presents an important clue to design thermodynamics cycle for small capacity coal fired power plant, which is expected to have fast response with respect to load variations.

A new concept of bifacial PV/PCM (BIF-PV/PCM) system with sandwiched thermal energy storage enclosure has been investigated that possesses 1.21 times power output density and 7.39 times total energy utilization density per unit land area compared to the conventional PV system. Based on the melting morphology and thermo-electric performance of the initially rectangular PCM enclosure, an optimized bifurcated non-rectangular design of the enclosure is proposed to enhance the incident radiation utilization ability by 87% more than a simple one PV/PCM system. Enhanced utilization of solar radiation manifests into 105% more melting compared to conventional PV/PCM system. With the strategic mirror reflection and bypassing the solar radiation towards the rear PV panel and strategic design of PCM enclosure to aid convection-driven melting, electric power output has been increased significantly (about 77%) compared to similar conventional PV/PCM system. The study revealed that overall system efficiency could approach about 74% if suitable strategies are adopted, as demonstrated in this paper. Results are discussed in terms of energy utilization efficiency, exergy efficiency, power conversion efficiency, tracking melting front morphology, and its effect on heat transfer characteristics, etc. This investigation has been carried out with the help of an experimentally calibrated numerical model that accurately mimics the melting morphology of PCM and other heat transfer characteristics of the system. The findings of this study would help design and develop a more efficient BIF-PV/PCM system to meet exponentially increasing energy needs.

Heat pump technology can effectively reduce the energy consumption and environmental pollution caused by coal-fired heating. However, commonly used heat pump heating systems have poor performance in low temperature environments, making it challenging to meet the heating demand in cold regions. In this paper, the performance of an electrically driven free-piston Stirling heat pump is studied based on SAGE software. The numerical simulation results show that the 2409 W heating capacity can be obtained with the input electric power of 1 kW, heating temperature of 40 °C and ambient temperature of −20 °C. The overall coefficient of performance reaches 2.41 with corresponding relative Carnot efficiency of 46.2%. In addition, the operation characteristics of this heat pump system under different temperature conditions are investigated in detail. With the constant difference between heating and ambient temperatures, this heat pump can operate efficiently in different temperature ranges. With the increase of temperature difference, the available energy loss in the whole system decreases, leading to the improvement of relative Carnot efficiency. These results show the strong adaptability of the free-piston Stirling heat pump system to different working temperatures.

The use of wind power, a pollution-free and renewable form of energy, to generate electricity has attracted increasing attention. However, intermittent electricity generation resulting from the random nature of wind speed poses challenges to the safety and stability of electric power grids when wind power is integrated into grids on large scales. Therefore, accurate forecasting of wind speed and wind power (WS/WP) has gradually taken on a key role in reducing wind power fluctuations in system dispatch planning. With the development of artificial intelligence technologies, especially deep learning, increasing numbers of deep learning-based models are being considered for WS/WP forecasting due to their superior ability to deal with complex nonlinear problems. This paper comprehensively reviews the various deep learning technologies being used in WS/WP forecasting, including the stages of data processing, feature extraction, and relationship learning. The forecasting performance of some popular models is tested and compared using two real-world wind datasets. In this review, three challenges to accurate WS/WP forecasting under complex conditions are identified, namely, data uncertainties, incomplete features, and intricate nonlinear relationships. Moreover, future research directions are summarized as a guide to improve the accuracy of WS/WP forecasts.

An innovative integrated Swiss-roll-combustor/Stirling-hot-end component is proposed in this paper. A power generation system in conjunction with a Stirling engine is also built around the component and tested. The Stirling engine is a compact-size, unpressurized, γ-type engine that uses air as working gas. The Swiss-roll combustor is laden with small catalytic beads to decrease the ignition temperature and improve combustion efficiency. Experiments respectively burning dimethyl ether and syngas were conducted to better understand the potential of the system on tapping into green biomass energy. The marriage between the Swiss-roll combustor and the Stirling engine’s hot end offers many advantages as follows: The structural support from the spiral-channel wall in the Swiss-roll combustor enables the bottom wall of the Stirling engine to be made very thin, which improves the rate of heat transfer from the heat source to the engine significantly. Meanwhile, the system inherits those advantageous features in combustion from the Swiss-roll combustor, including a broader range of fuel/air ratio, higher combustion efficiency, and higher efficiency in harvesting the heat of flue gas. Compared to the predecessor of the present engine, the incorporation of the proposed component is proven to improve engine’s performance remarkably. In the experiment of burning dimethyl ether, the system produced 18.7 W of electric power and achieved 2.4% thermal to electric efficiency under a temperature difference of 254 °C. Such performance is remarkable among atmospheric-pressure Stirling engines. The proposed component has accomplished its design goal and would hopefully inspire new ideas for the development of green-energy Stirling-engine power generation systems in the future.

This paper proposes a novel PEMFC-based combined cooling, heating and power (CCHP) system with independent control of refrigeration and dehumidification, which is used in data centers with strict requirements on temperature and humidity. The effects of operating parameters of PEMFC (current density, hydrogen and oxygen pressure) and refrigeration system (hot water distribution ratio, mass flow of cooling water and chilled water) on the 4E (energy, exergy, economy and environment) are investigated. Meanwhile, multiobjective optimization of the above parameters is carried out. The results show that a high inlet pressure is beneficial to improve system efficiency and reduce annual greenhouse gas (GHG) emissions. An increase in the chilled water mass flow increases system efficiency and reduces annual GHG emissions, while an increase in the cooling water mass flow yields the opposite results. Moreover, an increase in the proportion of hot water entering the adsorption chiller causes system efficiency and the annual GHG reduction to initially decrease and then increase. Compared with the unoptimized system, the energy efficiency, exergy efficiency, system cost, GHG emission reduction, electric power, cooling power, heating power and dehumidification rate of the system increase by 5.5%, 0.77%, 10%, 21.27%, 12.87%, 5.37%, 45.73% and 1.53%, respectively.

Advancements of power electronic technologies result in significant improvement in efficiency of power delivery to applications that consume or feed electrical energy to a grid. A transformer is an integral part of the power delivery process. Transformers used for power delivery must be efficient, compact and of low cost, and more importantly, they should be compatible with the connected source such as a power inverter. For a desired power density, the transformer design involves optimization of its electrical and magnetic circuits permitted by the thermal limits of core and copper. The limit of the magnetic circuit is indirectly linked to the winding design. Better use of core influences the design of the electrical circuit as well. Therefore, proper choice of core material and geometry is very important design consideration. This article reviews the domain of soft magnetic materials suitable for handling large electrical power from grid frequency to high-frequency applications. The paper covers different examples and elaborates the role of a transformer for one specific application. Review of transformer design considerations used in different applications, which are categorized based on their load characteristics, is a novelty of this work.