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Recently, multi-split air source heat pumps (ASHPs) have been used increasingly for space heating in cold winter. When it operates in frosting environment, periodic defrosting is necessary to maintain a high system performance. However, researches on its defrosting were few due to its high capital and complicated controls. To solve its fundamental problem of insufficient heat available during defrosting, a novel reverse-cycle defrosting (NRCD) method based on the phase change thermal storage has been developed. In this paper, comparative experiments using both standard reverse-cycle defrosting (SRCD) method and NRCD method were carried out on a multi-split ASHP unit with a phase change material heat exchanger (PCM-HE) acting as energy accumulator during heating operation and heat source during defrosting operation. Experimental results suggested that when using the NRCD method, the system performances, such as suction pressure and temperature, defrosting and heat-resumption durations, COP during defrosting operation can be effectively improved.

This paper is focused on contemporary posibilities of replacement diesel-powered railcars by accumulator powered railcars in regional railway traffic. In the first part of the paper, there are described advantages and disadvantages of this replacement. In the second part are presented the simulation counts and the simulation results of the drive of an accumulator powered railcar on the railway line Šumperk - Kouty nad Desnou. At the last part of this paper is shown the experimental accumulator powered railcar, which was built at University of Pardubice, and the energy research, that is realized with this railcar at railway line Mladějov na Moravě - Hřebeč.

This paper presents the experimental evaluation of two compact energy storage devices directed towards wind energy storage applications. The first is a compressed air energy storage (CAES) system with its low infrastructural cost, easy coupling with existing wind resources and high round-trip efficiency. The second system utilizes the harvesting of the work of buoyancy forces resulting from submerging styrofoam buoys in a liquid at times of abundant energy supply and harnessing energy back by allowing them to ascend when demand arises. While the systems considered here are compact in size, the results obtained on performance parameters such as efficiency of energy conversion and electrical output are sought to be generalized as a storage option for real offshore wind farms. The main challenges in designing larger systems are the heat generated due to air compression and the considerable friction drag affecting the buoys. Larger systems, however, have higher potential energy enabling them to operate at higher pressures and depths for the compressed air and the buoyancy systems, respectively. The proposed modular systems, composed of many cells of air cylinders or buoys are expected to decrease heat and friction losses intrinsic to large-scale systems while at the same time reducing infrastructure costs and transmission losses and enhance overall energy efficiency.

The Dual Hot-Gas Bypass Defrosting (DHBD) cycle is an effective defrosting method compared to a Reverse Cycle Defrosting (RCD) method to remove frost from the outdoor heat exchanger (HEX) of an air-to-air heat pump, especially the outdoor temperature is above 0 °C. However, the DHBD method has a drawback when the heat pump operates in cold outdoor environment, below 0 °C due to rapid decrease in refrigerant temperature followed by lower hot-gas bypass temperature. In order to overcome lower discharge temperature of compressor, a combined defrosting cycle with DHBD and the accumulator heating method is developed. An induction heater (IH) is adopted as the accumulator heater. The dynamic performance and defrosting time are compared between the conventional RCD method and the combined DHBD–IH method using a medium size air-to-air heat pump of 16 kW under the condition of −5 °C outdoor temperature. Due to the additional heater, the combined DHBD–IH method sustained higher discharge temperature of the compressor and reduced 15% of the defrosting time than that of the RCD method with nonstop indoor heating operation. The overall heating capacity of the DHBD–IH cycle including defrosting mode was 2.5 kW higher than that of the RCD cycle.

During a hypothetical severe accident in a nuclear reactor most of the radioactivity would be released from the damaged core and the broken primary circuit in the form of aerosols and chemical vapours and gases. However the effective radio-toxicity per unit release from the fuel depends both on the released mass and on the chemical form as well. The fission products release and transport in the circuit has been analysed for a Medium Break cold leg Loss Of Coolant Accident (MBLOCA) combined with the total loss of electric power supply (Station Black Out) for a reference PWR 1000 reactor using the severe accident integral code ASTECV1.3 rev2. A detailed description of the reactor model is given. Sensitivity analyses were performed in terms of break location and accumulator availability. The break location has an impact on the carrier gas temperature and in turn on the chemical speciation of the fission products. Also retention is influenced by the different flow pathways establishing in the circuit. The accumulator availability extends the duration of the core degradation process affecting the total production of hydrogen and the cumulative released mass of low, semi and highly volatile fission products. In agreement with the ASTEC equilibrium chemistry model, the Mo/Cs (Rb) molar ratio has the most influence on the fraction of iodine which can reach the containment in the gaseous or highly volatile form. Due to the surplus of Cs, the predicted dominant iodine species to the containment are CsI and its dimers. A 3–4% of iodine which reaches the break exists in gaseous (HI) and highly volatile metal-iodides (I 2 MoO 2 , SnI 2 , SnI 4 ) species.

An accumulator is an auxiliary component in a hydraulic system as it stores the energy and avoids the pump from running continuously through the system which can reduce the pumps life. The accumulator is also used as the power source in the hydraulic hybrid system to accelerate the vehicle. A common hydraulic system uses the hydraulic oil as their working medium, but there is an application using water due to the high accessibility and environmental concern. In this paper, an accumulator is developed by using weighing method to increase the pressure in the system. This system uses water as a medium to provide clean environment as well as safe for mobile purpose. The system includes electric motor, water pump, directional control valve, pressure control valve and motor hydraulic. The performance of the accumulator is obtained by measuring the ratio of output and input pressure. The source of electricity is varied by using an inverter to control the frequency and the power of the pump. From the experiment, the pressure output and flow rate decreased with the increasing of the loads on top of the accumulator, while the pressure loss increased with the number of load. The operational frequency is optimal at a low reading compared to a higher frequency.

Integrating energy storage system into wind system can mitigate the negative effects caused by the intermittent wind. In addition, the spectrum analysis of wind power implies that the hybrid energy storage system may have better performance on smoothing out the wind power fluctuations than the independent energy storage system. The main advantage of the hybrid energy storage system is the multi-response speeds. Also, the hybrid energy storage system often operates in the modes switch, partial load and frequent start/stop conditions. Thus, the dynamic behaviors of each devices and the assembly of hybrid energy storage system are important for the system operation and control system design. The design, off-design analysis and parametric analysis of a wind-hybrid energy storage system consisting an A-CAES (adiabatic compressed air energy storage) system and a FESS (flywheel energy storage system) based on spectrum analysis method are carried out in the previous paper (P Zhao et al., 2014). This paper will conduct a preliminary dynamic behaviors analysis of the proposed wind-hybrid energy storage system based on the dynamic models. The simulation results indicate that the total power of wind-hybrid energy storage system can fit the load requirement well, providing an efficient power management for wind power penetration.

There is considerable need for a mobile, reliable, efficient, and compact prime power supply for a host of applications, including directed energy and electrical grid backup among others. Electrochemical energy storage devices, which possess either high-power density or high-energy density, have been developed recently and are very applicable for use in these applications. The need for both high energy and high power, however, makes the design and implementation of such a prime power supply a nontrivial task. While lithium-ion batteries (LIBs) are available, which possess both high power and energy density, operation at high power reduces their cycle life, decreasing the reliability and increasing the cost of the system when replacement becomes necessary more frequently. One proposed method involves optimally combining high-energy batteries with high-power electric double layer capacitors (EDLCs) using actively controlled power electronics to regulate the current to and from each respective device. In such a scheme, energy can be slowly sourced to and from the batteries, while the capacitors are used to supply or accept the bulk of the current when the demand is high, especially during fast transients. This type of scheme should not only maximize the batteries' cycle life and ensure that both the energy and power required of the load(s) is always available, but will also increase the instantaneous power capabilities of the system, offering a well-rounded solution to sourcing steady and/or transient loads. When augmenting a fossil fuel generator with a hybrid energy storage module (HESM), the HESM has the ability to act as a high-energy reservoir that can harvest energy from the generator when the loads are in short periods of inactivity. This enables the generator to be continuously base loaded, thereby maintaining a high level of efficiency at all times, while theoretically maintaining the required power quality of the main ac bus. At the University of Texas at Arlington (UTA), an actively controlled, high-rate HESM has been constructed to evaluate its performance under the typical load condition presented by directed energy weapons. It has been assembled using LIBs, EDLCs, and commercial off-the-shelf power electronic converters. A discussion about the future of HESMs, the experimental setup at UTA, and the results obtained thus far will be presented here.

Liquid air energy storage (LAES) is a class of thermo-electric energy storage that utilises cryogenic or liquid air as the storage medium. The system is charged using an air liquefier and energy is recovered through a Rankine cycle using the stored liquid air as the working fluid. The recovery, storage and recycling of cold thermal energy released during discharge more than double the overall energy efficiency of the cycle. The demand on a storage plant in a grid support application is expected to be irregular and intermittent in response to fluctuating supply from intermittent renewable generators. This will complicate the storage of thermal energy and will mean the energy flow rates in the thermal store will vary from cycle to cycle and the state of charge of the store will also vary. This paper presents an analysis of the LAES cycle. The material and configuration of the cold thermal store is discussed in particular with reference to scale and measures to mitigate losses due to the irregular and intermittent duty cycle. The paper concludes with capital and levelised cost analysis of a reference 20 MW/80 MWh LAES plant and a comparison of the levelised cost with other storage technologies.

In this study, the performance of an R22 refrigeration system of 9.6 kW cooling capacity injecting vapor and liquid refrigerant to compressor inlet through accumulator is analyzed at high compression ratio experimentally. Results obtained in this study are compared and discussed for better performance of refrigeration system with respect to the injection type and ratio. In vapor injection, the COP decreased with increasing injection ratio while in the liquid injection, the COP increased up to 10% of injection ratio and decreased beyond that. Thus, the liquid injection up to 10% is recommended at high compression ratio in order to minimize the performance decrease and extend operating range of a refrigeration system. In addition, the subcooling for liquid injection could be considered as a proper parameter to control the injection for the reliable operation in the liquid injection case.

The recent Fukushima accident has resulted in an increased need for passive safety systems in upcoming advanced reactors. In order to enhance the global contribution and acceptability of nuclear energy, proven evidence is required to show that it is not only green but also safe, in case of extreme natural events. To achieve and establish this fact, we need to design, demonstrate and incorporate reliable ‘passive safety systems’ in our advanced reactor designs. In Nuclear Power Plants (NPPs), the use of passive safety systems such as accumulators, condensing and evaporative heat exchangers and gravity driven cooling systems provide enhanced safety and reliability. In addition, they eliminate the huge costs associated with the installation, maintenance and operation of active safety systems that require multiple pumps with independent and redundant electric power supplies. As a result, passive safety systems are preferred for numerous advanced reactor concepts. In current NPPs, passive safety systems which are not participating in day to day operation, are kept isolated, and require a signal and external energy source to open the valve. It is proposed to replace these valves by passive components and devices such as self-acting valves, rupture disks, etc. Some of these innovative passive valves, which do not require external power, have been recently designed, developed and tested at rated conditions. These valves are proposed to be used for various passive safety systems of an upcoming Nuclear Power Plant being designed by India. For example, the Hot Shutdown Passive Valves (HSPV), developed for the decay heat removal system keep the main heat transport system under hot conditions by passively sensing and controlling the system pressure. Another crucial and important valve which has been successfully developed is the Poison Injection Passive Valve (PIPV) for the Passive Poison Injection System. It not only provides higher reliability, but also ensures safe shutdown of the reactor in case of insider threats or malevolent acts in disabling active shutdown system of the reactor. Recently, an innovative valve called the Accumulator Isolation Passive Valve (AIPV) has been developed for the Emergency Core Cooling System (ECCS), which is engineered to mitigate the consequences of Loss of Coolant Accident (LOCA). During normal operation of the reactor, the pressurized accumulators (55 bar) are kept isolated from the reactor core (70 bar) by means of AIPVs. In case of a LOCA, these passive valves open when the main heat transport system pressure falls to a desired value. For prolonged cooling of the core, these passive valves regulate the discharge in a desired manner. These are non-standard, high pressure and high temperature valves, which are unavailable commercially and hence have to be indigenously designed and developed. This paper primarily deals with the design, development and testing of Accumulator Isolation Passive Valves (AIPV) proposed to be used in the ECCS. A 25 NB size AIPV has been designed and successfully tested at Integral Test Loop (ITL) under simulated reactor conditions. It is a self-acting, ANSI 600 rating valve, which requires no external energy (i.e., neither air nor electrical power). It not only provides passive isolation but also passively controls high pressure liquid discharge through it. The design concept of the valve, functional performance, in situ valve testing methodology and the test results at simulated conditions are discussed.

Due to the relatively high global warming potential value of R410A, a lot of effort has been devoted to the exploration of potential refrigerants to replace R410A in heat pump applications. Natural refrigerants with single-digit global warming potential values have not yet shown readiness. Therefore, some synthetic refrigerants with global warming potential values significantly lower than R410A, such as R32 and the R32-based blend D2Y60, are getting more attention. To evaluate the transient performance of these two drop-in low-global warming potential refrigerants, two dynamic heat pump models, based on different platforms, have been developed to simulate a heat pump cycle during both steady state and transient operations. Both models include an efficiency-based compressor model, two control volume-based heat exchanger models, a control volume-based valve model, a segmented pipe model and a lumped-capacitance accumulator model. In order to speed up the simulations, accelerated refrigerant property routine...

A large capacity and high-pressure piston water pump is often used as the power supply in a high-pressure water-jet propulsion system (HWPS). When the piston water pump works, some flow and pressure pulsation is generated and then creates large thrust pulsation and jet noise. In most cases, an accumulator charged constant pressure gas is always installed near the outlet of the water pump to absorb the flow and pressure pulsation. If the thrust of HWPS is required to alter, the rotation and output pressure of the water pump will change. So, the function of the accumulator absorbing flow pulsation and pressure pulsation will weaken. To solve this problem, an effective means that makes multiple accumulators which are charged different pressures to connect with the outlet chamber of the water pump is put forward in this paper. According to the structural pattern of water pump, working pressure range of HWPS and allowable value of pressure pulsation factor, some key parameters, could be worked out by optimal calculation method proposed first, such as the number of accumulators, volume and charged pressure of each accumulator. Finally, results of simulation and experiment revealed that three pairs of accumulators, whose parameters were optimally calculated from actual working conditions, could keep the pressure pulsation factor to about the allowable value all along when working pressure of HWPS varied over the range.

We consider an energy harvesting network where the transmitter harvests energy from nature, and the harvested energy can be saved in an imperfect battery which suffers from charging/ discharging inefficiency. In particular, when E units of energy is to be stored in the battery, only ηE units is saved and (1 - η)E is lost due to charging/discharging inefficiency, where 0 ≤ η ≤ 1 represents the storing efficiency. We determine the optimum offline transmit power schedule for such a system for single-user and broadcast channel models, for static and fading channels, with and without a finite battery size. We show that the optimum policy is a double-threshold policy: specifically, we store energy in the battery only when the harvested energy is above an upper threshold, and retrieve energy from the battery only when the harvested energy is below a lower threshold; when the harvested energy is in between these two thresholds, we use it in its entirety in the current slot. We show that the two thresholds remain constant unless the battery is depleted or full. We provide an algorithm to determine the sequence of optimum thresholds. For the case with fading, we develop a directional water-filling algorithm which has a double-threshold structure. Finally, we formulate the online problem using dynamic programming, and numerically observe that the online policy exhibits a double-threshold structure as well.

The article describes mathematical model of positive-displacement hydropercussion system of single-sided back action. The principal dynamic similarity criteria found are: the reduced ratio between areas of back-stroke chamber and gas chamber; the value proportional to the ratio between potential energy of accumulator and kinetic energy of hammer; the dimensionless lengths of back stroke and gas strut. Based on numerical calculations performed within a wide range of input parameters (similarity criteria), the author has plotted nomograms of isolines of the integral input characteristics and oscillograms of dynamic characteristics, which enables revealing basic mechanisms of behavior of the discussed system in the single-blow limit cycles. In the domain of practical significance parameters, the analytically estimated dimensionless pre-blow velocity should not be higher than 810 units.

SUMMARY This paper considers the day-ahead market with batteries and accumulators to level power generation. First, we model consumers with batteries, generators with batteries, and accumulators, all of whom strive to maximize their own profit. An optimal pricing algorithm based on dual decomposition and the steepest descent method is derived and shown to be stable. Finally, the effectiveness of the algorithm is demonstrated by means of numerical simulations which indicate that it achieves demand–supply balance. C⃝ 2015 Wiley Periodicals, Inc. Electr Eng Jpn, 191(4): 8–18, 2015; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22698

Summary This paper gives a broad overview of a plethora of energy storage technologies available on the large-scale complimented with their capabilities conducted by a thorough literature survey. According to the capability graphs generated, thermal energy storage, flow batteries, lithium ion, sodium sulphur, compressed air energy storage, and pumped hydro storage are suitable for large-scale storage in the order of 10's to 100's of MWh; metal air batteries have a high theoretical energy density equivalent to that of gasoline along with being cost efficient; compressed air energy storage has the lowest capital energy cost in comparison to other energy storage technologies; flywheels, super conducting magnetic storage, super capacitors, capacitors, and pumped hydro storage have very low energy density; compressed air energy storage, cryogenic energy storage, thermal energy storage, and batteries have relatively high energy density; high efficiencyin tandem with high energy density results in a cost efficient storage system; and power density pitted against energy density provides a clear demarcation between power and energy applications. This paper also provides a mathematical model for thermal energy storage as a battery. Furthermore, a comprehensive techno-economic evaluation of the various energy storage technologies would assist in the development of an energy storage technology roadmap. Copyright © 2015 John Wiley & Sons, Ltd.

The layout of a combined heat and power (cogeneration) plant based on renewable energy sources (RESs) and hydrogen electrochemical systems for the accumulation of energy via the direct and inverse conversion of the electrical energy from RESs into the chemical energy of hydrogen with the storage of the latter is described. Some efficient technical solutions on the use of electrochemical hydrogen systems in power engineering for the storage of energy with a cyclic energy conversion efficiency of more than 40% are proposed. It is shown that the storage of energy in the form of hydrogen is environmentally safe and considerably surpasses traditional accumulator batteries by its capacitance characteristics, being especially topical in the prolonged absence of energy supply from RESs, e.g., under the conditions of polar night and breathless weather. To provide the required heat consumption of an object during the peak period, it is proposed to burn some hydrogen in a boiler house.

Evaluations for possible using of superconducting materials in high power microwave generators based on the method of the resonant microwave compression were made. As an example the relationship between the power amplification factor and frequency was determined for superconducting rectangular cavities. Capabilities of superconducting cavities as energy accumulators were analyzed. Microwave power value required for feeding superconducting accumulator is estimated. Experimental results of storing and extracting the energy in superconducting cavities are presented.

Most of the cryogenic hydrogen apparatuses in the CSNS hydrogen system are non-standard equipment, and will be developed independently. This paper introduces the latest research progress. Manufacturing of the accumulator has been completed in February 2014. A prototype of the hydrogen-helium heat exchanger has been manufactured and tested for sealing. The manufacture of the cryogenic hydrogen heater and the ortho-para hydrogen convertor will be finished soon. These cryogenic devices will be integrated into the hydrogen cold box and the accumulator cold box. The engineering design of the cold boxes was completed, and the vessel of the hydrogen cold box has been manufactured.

Due to the costly short-term transients, frequency regulation, and load balancing, the electrical power grid faces an urgent need for large-scale energy storage. The long durability, high power and energy density, and low cost needed for stationary energy storage posing constant challenges for conventional battery technology inspire people to explore new kinds of energy storage technologies. Here, we assembled an aqueous rechargeable sodium ion battery by using NaMnO2 as a cathode material and NaTi2(PO4)3/C composites as anode materials in 2 M CH3COONa aqueous electrolyte. This battery system could work in a wide voltage range from 0.5 V to 1.8 V, giving an energy density of 30 W h kg−1 (based on the total mass of active materials) and could retain 75% of the initial capacity after 500 cycles at the 5 C rate. What is more, the earth-abundant precursors, environmental friendliness and inherent safety made this battery system particularly attractive for stationary energy storage applications.

The paper discusses a hydrogen circuit embedded in an Electric energy network. The circuit is instrumental for electrical energy storage whenever all the batteries (accumulators) within the network are charged, and a constant energy surplus exists in the network. The generated surplus energy is then converted to hydrogen, which is stored in a metal hydride storage case. At times of low energy status in the network, namely when the batteries are discharged and the applied generators (such as photovoltaic, wind, or microhydro power plants) cannot supply energy, a fuel cell is activated. The cell's operation principle is basically the reverse of that for an electrolytic cell (electrolyser), meaning that the cell consumes the hydrogen from the metal hydride storage to produce electric energy; this energy is subsequently stored in batteries (accumulators) connected to the smart grid. In the given context, the article aims to describe the relevant experiment and to present the algorithm to calculate energy efficiency, a most significant parameter of the entire hydrogen circuit.

Currently the improvement of stand-alone PV power systems characteristics, including increase of their service life is the actual direction of ground solar power development. The analysis of stand-alone PV power systems efficiency with the use of ultra capacitors is carried out by the means of mathematical modeling. The obtained data shows that the use of ultra capacitors as additional short-term energy storage devices in stand-alone PV power systems contributes to considerable increase of storage batteries lifetime and the total system operating time.

This paper presents the modeling and control for a novel Compressed Air Energy Storage (CAES) system for wind turbines. The system captures excess power prior to electricity generation so that electrical components can be downsized for demand instead of supply. Energy is stored in a high pressure dual chamber liquid-compressed air storage vessel. It takes advantage of the power density of hydraulics and the energy density of pneumatics in the “open accumulator” architecture. A liquid piston air compressor/expander is utilized to achieve near-isothermal compression/expansion for efficient operation. A cycle-average approach is used to model the dynamics of each component in the combined wind turbine and storage system. Standard torque control is used to capture the maximum power from wind through a hydraulic pump attached to the turbine rotor in the nacelle. To achieve both accumulator pressure regulation and generator power tracking, a nonlinear controller is designed based on an energy based Lyapunov function. The nonlinear controller is then modified to distribute the control effort between the hydraulic and pneumatic elements based on their bandwidth capabilities. As a result, liquid piston air compressor/expander will loosely maintain the accumulator pressure ratio, while the down-tower hydraulic pump/motor precisely tracks the desired generator power. This control scheme also allows the accumulator to function as a damper for the storage system by absorbing power disturbances from the hydraulic path generated by the wind gusts. A set of simulation case studies demonstrate the operation of the combined system when the nonlinear controller is utilized and illustrates how this system can be used for load leveling, downsizing electrical system and maximizing revenues.

The capacity of the primary energy source is the main parameter participating in a range of the electric vehicle (EV). The final choice of an appropriate structure of sources integrated into the vehicle can consist of one or a variety of energy sources/storages. This way increased effectiveness, thus an increase in driving range as well as regenerative braking energy, can be achieved. Energy storages for EV applications are rated on the basis of three parameters namely, specific energy, energy density and specific power. These are the key parameters taken into account in selecting appropriate energy sources. The article provides an analysis of collaboration of an ultracapacitor module with an accumulator battery.

This paper proposes the new hybrid energy storage system with the superconducting magnetic energy storage (SMES) and a lead-acid battery. The SMES is the most effective energy storage device due to its high power density, fast response, and high efficiency. However, its energy density is not higher than that of other batteries. Therefore, the proposed hybrid energy storage system combines these two energy storage devices. The optimal sizes of the SMES and battery are determined by considering the system cost, output power reference, and their proper efficiencies. Also, the new control algorithm is applied to share the charging and discharging powers effectively and therefore to manage the state-of-charge (SOC) in each energy storage device. Then, the performance of proposed hybrid energy storage system is evaluated on a residential photovoltaic (PV) system with respect to energy capacity, peak load leveling, and system efficiency.

The paper presents the operational results of a real life residential microgrid which includes six apartments, a 20 kWp photovoltaic plant, a solar based thermal energy plant, a geothermal heat pump, a thermal energy storage, in the form of a 1300 l water tank and two 5.8 kW h batteries supplying, each, a couple of apartments. Thanks to the thermal energy storage, the solar based thermal energy plant is able to satisfy the 100% of the hot water summer demand. Therefore the thermal energy storage represents a fundamental element in the management of the residential demand of thermal energy. It collects renewable thermal energy during day-time to release it during night-time, effectively shaving the peak of the thermal energy demand. The two electric storages, on the other hand, provide the hosted electrical subsystems with the ability to effectively increase the self-consumption of the local energy production, thus lowering the amount of energy surplus to be sold back to the grid, and increasing the self-sufficiency of the microgrid. For instance, the storage has supported self-consumption up to the 58.1% of local energy production with regard to the first battery, and up to the 63.5% with regard to the second one. Also, 3165 and 3365 yearly hours of fully autonomous activity have been recorded thanks to the first, and the second battery respectively. On the other hand, the yearly average efficiency amounts to 63.7%, and 65.3% respectively, for the first and second battery. In the second part of the paper we propose a computational framework to evaluate the overall performance of the microgrid system, while accounting different operating conditions and energy management policies. From this perspective, the framework acts as a useful modeling and design tool, to assess the opportunity of employing alternative energy management system topologies and strategies. Eight different configurations, with growing complexity, have been derived from the original system on purpose. The simulations, carried out based on real data related to one-year time period, have provided results showing that, the higher the integration level of electrical and thermal storage is, the higher degree of self-sufficiency can be achieved by the microgrid, and, in turn, the more consistent the yearly energy saving become. Nevertheless, despite the energy cost reduction achievable with the availability of storage systems in the Leaf House, their high investment cost made them not really profitable at the current price conditions for devices and energy purchase.

This paper carries on the simulation and optimization of hydraulic system, which focuses on the high energy consumption problem of large-scale blow molding machines. According to the characteristics of long work period and great fluctuation of flow demand, the paper designs the oil supplying system that can match the actuators’ hydraulic energy demand, introduces the working process of each component in the system, and analyzes the key technology of hydraulic system as well. The design and research avoids the shortcomings such as more components, complex debugging, discontinuous control and unstable operation, substantially reduces the installed capacity of variable pump and driving motor, and in the meantime, solves the impact problem of actuators effectively, which can make hydraulic system high efficiency, energy saving and run steadily.

This article presents the main results of researches on the liquid flow at the gas filled cavity inlet which can be used for design of innovative processes of internal surfaces cleaning for stagnant units and hydraulic cylinders. The researches have shown that the cavity filling with liquid is defined by the supply mainline response, the design of a hydro pneumatic accumulator and the cavity volume of the filled unit. Herewith, attainable time of the cavity filling has been changed from 0.5 to 1.5 sec, and the liquid flow rate at the cavity inlet varies from 150 to 200 m/sec, that considerably exceeds (8-10 times) the liquid flow rates in operating modes of the hydraulic drives.

With the increasing pressure of energy shortage, various technologies are being developed to meet the energy demand. Solar energy is one of the non conventional sources of energy widely used. Energy storage and renewable energy technologies have received more attention worldwide as economic progress as well as industrialization. One way to improve the efficiency is to store the energy during higher solar incidence and utilizing this stored energy during its lesser availability. Efficient storage technologies are required to store this energy to meet energy demand throughout day and night. Phase change materials (PCMs) are energy storage materials due to their characteristic of storing thermal energy by phase change and their ability to provide higher energy storage densities. Thermal energy storage (TES) research for seasonal storage is going towards thermo-chemical materials (TCM). However, nowadays, one of the promising methods is based on chemical reactions. Thermo-chemical materials using reversible chemical reaction principle are used to store energy. These materials are capable of storing solar thermal energy in one direction and to release it in another direction without heat losses, whenever energy is needed. In the present work, efficiency of solar still is improved with the aid of phase change materials. A wiper that pushes water to the collecting dish is also incorporated. Combined effect of PCMs and wiper enhances the efficiency and productivity.

Typical hydraulic systems with inertia executive components like hydraulic cylinders are generally low in damping and lack of stability. Adding DPD to systems is an easy and effectual method to solve these problems. The performance of a mechanical dynamic pressure feedback DPD applied in a common hydraulic system was simulated while the influences of the structure and system parameters on DPD and the system were analyzed. Further research on characteristic optimization was carried out by adding accumulators to DPD. It shows that the DPD can practically improve the system stability and contain the pressure impact. The accumulators should be set appropriately before the damping orifices and have a certain ability to absorb pressure impact.

Asecond compact accumulator is in use because a leakage occurred in the largewelded bellows of the original accumulatorin 2010. However, the present accumulator has the drawbacks, includinga lower pressure tolerance and large hysteresis duringexpansion and contraction, which can decrease the number of cycles to failure.In response, we developed new welded bellows with a pressuretolerance of 2.0 MPa and a hysteresis-free accumulator with a levelness accuracy of less than 1°.This accumulator has been confirmed through its commissioning to meet design requirements.

The configuration and working principle of hydraulic hybrid vehicle (HHV) based on the hydraulic transformer (HT) were described to extend its energy-regenerated potential. The approximate algorithm of basic elements for pipeline distributed parameter model was summarized to simplify the pipeline model calculation, and the various basic elements of this method were proven to be used in the practical application by comparison with the experimentally validated Zhao and Hullender model. The pressure pulsation characteristics between the HT and accumulator of the HHV by considering Zhao model, Hullender model, and original pipeline approximate model was analyzed to optimize the system structure design by the method of the mathematical model, which mainly includes the series accumulator and parallel accumulator, respectively. The simulation result shows that the series accumulator was better than the parallel accumulator in terms of pulsation damping of hydraulic transformer with considering the pipeline effect. The test-rig result shows that the theoretical analysis of the pulsation between the HT and accumulator with pipeline was very close to the measurement data of the experiment in the curve trend, where the theoretical analysis results of pulsation characteristic for HHV were appropriate and reasonable.

In this paper, a novel energy-saving control strategy is proposed for the accurate motion tracking of a hydraulic manipulator. To achieve independent pressure regulation for each chamber of the cylinder, as well as energy recovery during the back-and-forth movement of the cylinder, a hardware configuration with five low-cost programmable cartridge valves and an accumulator is developed to control the motion of the cylinder. Based on the hardware configuration, a novel multilevel control algorithm is proposed, which consists of the desired motion and pressure tracking control level (level I), the flow distribution level (level II), and the offside pressure profile planning level (level III). The proposed approach is theoretically shown to be able to minimize the energy consumption of the system while maintaining good motion tracking performance. Experimental studies confirm that the proposed strategy can indeed achieve both accurate motion tracking and minimum energy consumption simultaneously. Compared with the previous four-valve scheme and five-valve flow regeneration scheme without the use of accumulator by Liu and Yao, the proposed strategy has much less total energy consumption and equally good tracking performance.

In order to solve the process of fishing, hull has significant heave motion under the influence of marine environment, that caused towing tension instability and fishing low efficiency problems, proposed and developed based on the hydraulic cylinder and the accumulator between the energy conversion and PLC control of towing tension range controllable passive compensation device. According to its working principle, the passive compensation device of compensation system and control system was designed, using the hull heave motion as the control energy, hydraulic cylinder and accumulator combination as a compensation system, selects PLC224CPU and M235 expansion module as the control unit. Finally, the towing tension range change of compensation has carried on the simulation analysis, the simulation results show that the passive compensation device which can realize the adjustment and control of drag tension range, achieves the expected control effect.

It is developed a complex method for controlling the operation of the cogeneration system using such dynamic subsystems as: electric accumulator battery, heat electric accumulator; electric accumulator battery, heat pump, which uses a recover heat as a low-grade energy source, which changes as the production of energy and its consumption as a part of a cogeneration unit; biogas plant, heat pump, which uses the fermented wort as a low-potential power source, electric accumulator battery and heat electric accumulator. Predictive information obtaining for decision-making under conditions of not matching production and consumption of electric power and heat can reduce the cost of energy production and emissions of carbon dioxide by 15 %. Biogas saving, for example, by fermentation of 60.2 t/day with increasing marketability of raw biogas unit at 10-15 % is 49400 m3/year.

Soft drink cans filled with paraffin wax mixed with 5% w/w aluminum wool, obtained from disposable cans, doubled the thermal conductivity of cans filled only with paraffin wax. Thermal conductivity of the systems was determined by two ways: directly using a thermal conductivimeter, and indirectly based on temperature profiles and on the analytical solution of a cylinder. We designed, built and evaluated a heat exchanger for solar energy accumulation, composed by 48 disposable soft drink cans filled with a total of 9.5 kg of paraffin wax mixed with 5% w/w aluminum wool. In sunny days, the wax melted completely in 3 h. The accumulated energy of 3000 kJ, allowed increasing the temperature of 3.5 m3/h air flow rate from 20 to 40 °C during a period of 2 h. This application will allow extending the use of solar energy in drying processes or could be used as household calefaction system. The progress of the phase change front in time during the energy discharge period was simulated with COMSOL, whereas the effect of the number of cans and thermal conductivity of the paraffin wax on the air temperature increase was simulated with MATLAB.

The demand for, and consumption of, global energy is continually increasing across a world whose population will grow to nearly 9 billion people in the next couple of years. It is poised to continue its steady increase in the next several decades. The climate change and the decreasing availability of fossil fuels have hastened the development of satisfying sustainable and renewable energy technologies. Since electrical energy storage systems such as batteries and capacitors are considered as the most critical link between the ever-increasing renewable energy supply and demand, a lot of work has been done to improve their efficiency and performance. Further, the advancement of micro/ nano-electro-mechanical devices for telecommunication and biomedical applications initiates the demand for reliable lightweight electrical energy storage systems with small form factors. To fulfill all these requirements, the development of new materials with an exceptional specific surface area and excellent electrochemical properties has become the focus of much research effort. Electrical energy can be stored either chemically, for example, batteries, or physically, for example, capacitors. Chemically, the electrical energy is converted into chemical energy via Faradaic reduction and oxidation (redox) reactions. Although the energy conversion from electrical to chemical and vice versa is thermodynamically reversible in principle, in practice, such conversion often involves some degree of irreversibility due to the electrode−electrolyte interphase changes during the charging and discharging processes [1]. Therefore, the charge/discharge rates of batteries are very low and their lifecycle is limited to only several thousand cycles. However, depending on the types of batteries, they can have a very high gravimetric energy density of up to 200 Wh/kg [2].

In modern transport industry there is a tendency for electric vehicles with independent power supply to increase their amount, particularly it seems to appear in the fast development of electric cars. Nevertheless, there are still some flaws in electric vehicle drives to be improved. The element of an electric drive that limits the performance of the vehicle is almost always power supply. Li-Ion accumulators, which are most often chosen for this role, despite their good energy characteristics, have high impedance that causes great heat losses on the battery. Connecting a super capacitor, which has lower dc resistance, in-parallel with the accumulator can eliminate this drawback. In this work the study of the efficiency of energy transformation in induction motor electric drives has been conducted for both options of power supply: with supercapacitor and without it. The results of this study help to evaluate the benefits of using supercapacitor and to suggest the area of implementing supercapacitor in electric drives.

Renewable energy sourced from the sun, wind, waves or tides is clean and secure. Unfortunately, the energy that can be extracted from renewables and the demand for it varies both temporally and spatially. Therefore, energy storage is required to match generation with use. To date grid-scale energy storage has been limited by low energy densities, long-term performance degradation, low round-trip efficiencies or limited deployment locations. Although thermal storage has found uses these have been restricted to lower temperatures by thermal losses resulting in low energy densities and uneconomical electricity generation efficiency. In this paper an ultra-high temperature (1800 K) storage system is proposed where heat losses are minimised and recovered to make a higher storage temperature attractive, thus unlocking greater energy densities and efficiencies. Radiation dominates heat losses at ultra-high temperatures but can be minimised through the design of the storage medium container. However, even after energy is lost from storage, heat pumps in the store and charge cycles in addition to preheating during the extraction cycle can be used to recover a significant amount of heat. Collectively loss reduction and recovery techniques can lead to a storage system with a performance and utility that exceeds other energy storage methods Here the feasibility of the novel storage technique is demonstrated through thermodynamic and thermal analysis in each of the three key states of operation: charge, store and generation.

An optimally economical dispatch scheme for the operation of micro-grid is proposed in order to solve the micro-grid dispatch problems caused by large quantities of approved construction of micro-grid projects. And it analyzes the issue of a micro-grid system in micro-grid that whether the storage battery works or if there is a constraint between the micro-grid with the grid in switching power and thus calculates the power supply structure in each period and the total power supply cost per day as well as the average unit price of electricity purchase under these four different conditions by considering various cost and both the constraints of battery parameters and different rules in different durations. Then the utilization of renewable energy along with the produced influence of storage battery after adjustment is analyzed. The optimized dispatch model is established using the quantum-behaved particle swarm optimization and ultimately an optimized dispatch scheme with maximum economic benefits is determined for the significant improvement of economic benefits and better satisfaction for the requirements of real-time dispatch, which plays the role of peak load shifting of storage battery.

Electrification offers a great potential for commercial vehicles to significantly reduce energy consumption as well as CO2 and pollutant emissions during operation. The project eLift demonstrates the potential of the electrification of a special-purpose vehicle. A conventional diesel catering truck with hydraulic auxiliary lifting unit is to be replaced by a more efficient electrically driven truck. In this work, the potential for electrification of the catering truck is investigated and evaluated. According to the requirements of the system, alternative electrical components are selected which have a direct influence on the efficiency of electric vehicles. Subsequently, two different variants are created with different component combinations, the driving motor, the motor for the lifting system and the accumulator. The selected components are then inserted into an existing simulation model with the respective parameters. As a result, the total energy consumption is obtained for the system's typical tasks with respect to specific user application profiles. The results of both considered variants are compared with each another and evaluated against to the conventional diesel truck.

Phase Change Materials (PCMs) are utilized in different engineering fields, such as thermal storage of building structures, such as domestic hot water, heating and cooling systems, electronic products, drying technology, waste heat recovery, refrigeration and cold storage, and solar cookers. The biggest technological problems for the implementation of low and high temperatures PCM are the insufficient thermal conductivity of the available phase change materials, compatibility with the container material, cycling stability. In order to evaluate efficient and cost effective operation of thermal energy storage, different design concepts for PCM integration into heat exchanger/accumulator should be investigated. DOI: https://doi.org/10.3846/enviro.2017.270

Today, a lot of accumulator trains are introduced for saving the global environments. In the East Japan railway, a new battery powered railway vehicle called ACCUM on the non-electrified Oga line has been operated on March 4. ACCUM is provided AC-20kV energy from Oga substation. This substation has to possess earth fault protection system not to effect railway peripheral facilities and customers. However, it is necessary to considerate a special protection circuit because the substation has a short feeding circuit. Therefore this paper shows the earth fault protection system provided on Oga line.

The fluctuating nature of ocean waves requires the use of energy storage in wave energy systems to smooth output power. This is particularly true when a wave energy system connects to a remote, weak grid. The energy storage requirement will vary depending on the number of wave energy generators and storage placement within the collector system. This paper investigates the variation of storage size with location and numbers of WECs in a weak grid. The impact of temporal phase shift between waves is also studied.

We are studying a new scheme to produce very low emittance muon beams using a positron beam of about 45 GeV interacting on electrons on target. This is a challenging and innovative scheme that needs a full design study. One of the innovative topics to be investigated is the behaviour of the positron beam stored in a low emittance ring with a thin target, that is directly inserted in the ring chamber to produce muons. Muons will be immediately collected at the exit of the target and transported to two mu+ and mu- accumulator rings. We focus in this paper on the simulation of the e⁺ beam interacting with the target, its degradation in the 6-D phase space and the optimization of the e⁺ ring design mainly to maximize the energy acceptance. We will investigate the performances of this scheme, ring optics plus target system, comparing different multi-turn simulations., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark