Energy Storage Mode Research Articles

Commercial grid scaling of Energy Bags for underwater compressed air energy storage

Large-scale ability to store surplus energy for use during periods of high demand is a formidable asset in reducing the energy cost, improving electric grid reliability and addressing climate change. An Energy Bag is a fabric balloon-like vessel anchored to a sea- or lakebed for the purpose of storing surplus energy in the form of compressed air. This mode of energy storage is attractive because the passive pressure force of the deep-water environment takes on the significant role of pressure vessel structure to maintain pressurization of the air stored within the Energy Bag. Upon further investigation, it becomes evident that particular attention must be given to the storage volume and pressure required to satisfy requirements economically for commercial grid-scale development of this novel technology. This paper provides an introduction to the benefits and prerequisites pertaining to commercial scale energy storage capacity as related to Energy Bag structure, volume and deployment depth.

Probe on Questions and Mode of Renewable Resource Development and Utilization on Small Islands

Aiming at small islands location limits and the established power grid characteristics, the paper analyses some practical problems to be dealt with when renewable resource is utilized. Combined with the characteristics of small islands, the paper puts forward the new mode without energy storage devices, and designs a renewable resource application system driven directly by photovoltaic devices, emphatically analyses the key technology of no energy storage mode. The new mode effectively resolves the battle neck problem of traditional off-net mode.

Switching of Microwave Radiation Storage and Output Modes in Superconducting Resonance-Cavity Compressors with an Interference Switch

UDC 621.37 We propose a commutator for the interference switch of microwave electromagnetic radiation on the basis of a waveguide H-junction made as a cavity with tunable parameters, which is connected to one arm of this junction. The superconducting version of a microwave compressor with such a switch is analyzed. The conditions of effective switch operation in the mode of electromagnetic energy storage and its fast output in the case of controllable manipulation of the Q-factor and resonant frequency of the switching cavity are determined. Estimates of the output parameters of the superconducting compression system are presented for storing- and switching-cavity Q-factors of about 5 · 10 8 . The possibility of increasing the radiated power in such a compression system by 40–60 dB for output microwave pulses with durations of about 5–10 ns is demonstrated. Variants of practical implementation of the system are considered.

Energy reserves of Southern Ocean copepods: Triacylglycerols with unusually long-chain monounsaturated fatty acids

Two of the dominant Southern Ocean copepods, Calanus simillimus and Calanus propinquus, are known for their lipid storage via triacylglycerols indicating year-round activity, as opposed to diapausing species, which accumulate wax esters. We studied the lipid and fatty acid compositions of C. simillimus (CV stages) with focus on its ability to produce unusually long-chain monounsaturated fatty acids. Besides the biosynthesis of high-energy fatty acids with 20 and 22 carbon atoms, the occurrence of fatty acids with 24 carbon atoms accounting for up to 15% of total fatty acids is intriguing. Their double bond positions were unequivocally determined as (n−9), (n−11) and (n−13) by DMOX derivatisation. The dominant isomer was 24:1(n−11) contributing up to 8% to the total fatty acids. The major fatty acids were the isomers 22:1(n−11) and (n−9) averaging 20% and 10%, respectively. A re-evaluation of fatty acid data of C. propinquus also revealed 24:1 fatty acids exhibiting on average 5% with (n−11) and (n−9) as main isomers. The principal fatty acids were also 22:1(n−11) and (n−9), but in contrast to C. simillimus both fatty acids occurred in equally high amounts of about 20%. The de novo biosynthesis of these long-chain monounsaturated fatty acids generally represents a very efficient energy storage mode. Chain elongation to 22 and even to 24 carbon atoms in C. propinquus and further optimised by C. simillimus yields high-energy compounds for these triacylglycerol-storing copepods. Biosynthetic pathways for the fatty acids are proposed and discussed in view of the well-adapted life cycle strategies of the two species, which have to cope with a pronounced seasonal food supply in the Southern Ocean.

A Two-level Energy Storage System for Wind Energy Systems

Abstract Wind power outputs fluctuate with the changing of wind speed. The use of energy storage equipment is considered a reasonable solution to suppress wind power fluctuations. An energy storage mode may have its disadvantages over the others, for example, capacity limits, dynamic response, higher prices or shorter lifetime. Moreover, wind power fluctuations are present at different frequencies, to demand the energy storage to offer power support in different time ranges. To improve the performance, in this paper, a combined energy storage mode is discussed to meet the short-term and long-term energy storage requirement for wind power. Short-term energy storage is designed to meet the fast-changing power, using such as super capacitors. Long-term energy is designed to meet the large-scale capacity requirement using Li-ion battery or Vanadium Redox Battery (VRB). By analyzing the actual data of wind power outputs, the capacities of the two kinds of energy storage means are given as an example of the method.

Numerical Modeling of Alternate Melting and Solidification

A finite-volume model is used to analyze alternate melting and solidification, which is the fundamental operational mode of latent thermal energy storage (LTES) systems. The simulated cases include: (1) melting of tin with natural convection, (2) alternate melting and solidification of sodium nitrate, and (3) cyclic phase change of gallium. For each case, temporal evolution of the heat transfer rate and liquid fraction is presented. In addition, snapshots of phase interface, temperature, pressure, and liquid velocity distributions are presented. The implications of the modeling results are discussed.

Numerical Simulation & Experimental Research of Heat Charging Process of Cylindrical Units with PCM of Al-Si Alloy

Phase change thermal storage used metal as phase change material (PCM) is an important mode of solar thermal energy storage. In this paper, the heat charging processes of solar heating units were simulated under three kinds of heating flux 100,150 and 200kW/m2 at the bottom face respectively, while the thickness of heat receiving layer at the bottom was in 5, 10 and 15mm. Al-Si alloy was selected as PCM used in the cylindrical body of the units which were in the size of φ1000×1000mm. The change of temperature and solid-liquid phase change interface of Al-Si alloy were analyzed to find out the suitable absorber thickness of thermal energy storage units which can run safety under the condition of temperature 700~900K and heat flux 100~200kW/m2, such as the application of solar thermal energy storage unit in high temperature solar thermal power stations. In the last a test system was built up and the experimental result was close to the simulation value of a unit in the size of φ300×1000×10mm.

The Thermodynamic Significance of Order Parameters During Glass Relaxation

The thermodynamic state of a glass is often described in terms of a number of order parameters, each of which evolves toward its equilibrium value during glass relaxation. The problem comes in identifying these order parameters and determining their physical significance. The authors argue that the order parameters in a glass can be defined in terms of a set of configurational temperatures, each corresponding to a particular mode of energy storage. The evolution of glass properties can then be calculated using a coupled set of rate equations describing the relaxation of the configurational temperatures toward their equilibrium values, viz., the reservoir temperature. The authors illustrate the concept of configurational temperatures by considering the free energy of mixing in alkali borate and silicate glasses.

Performance enhancement of a subcooled cold storage air conditioning system

This article experimentally investigates the enhancement of thermal performance for an air conditioning system utilizing a cold storage unit as a subcooler. The cold storage unit is composed of an energy storage tank, liquid-side heat exchanger, suction-side heat exchanger and energy storage material (ESM), water. When the cooling load is lower than the nominal cooling capacity of the system, the cold storage unit can store extra cold energy of the system to subcool the condenser outlet refrigerant. Hence, both the cooling capacity and coefficient of performance (COP) of the system will be increased. This experiment tests the two operation modes: subcooled mode with energy storage and non-subcooled mode without energy storage. The results show that for fixed cooling loads at 3.05 kW, 3.5 kW and 3.95 kW, the COP of the subcooled mode are 16.0%, 15.6% and 14.1% higher than those of the non-subcooled mode, respectively. In the varied cooling load experiments, the COP of the subcooled cold storage air conditioning system is 15.3% higher than the conventional system.

Simplified Voltage-Sag Filler for Line-Interactive Uninterruptible Power Supplies

There are three types of static uninterruptible power supplies (UPSs): passive standby, line interactive, and double conversion. The last one protects the load against all types of line disturbances, but it is the most expensive and the one with the lowest efficiency. On the other hand, passive-standby and line-interactive UPSs have higher efficiency and lower cost, but they show an important drawback: a switching time from normal to stored-energy mode. As a consequence, there is a notch in the UPS output voltage during this switching time. In a previous paper, the authors proposed a method for filling these voltage notches with a sinusoidal waveform generated by a switch-mode converter. In this one, a simplified notch filler is proposed. It consists of two capacitors, one charged with positive voltage and the other with negative voltage. If the fault occurs in the positive period, the positive-charged capacitor is connected to the load. This connection is then modulated in order to obtain a sinusoidal waveform at the load. In the negative period, the other capacitor is used in the same way.

THE FROZEN FLOW AND THE EQUILIBRIUM LIMITS IN A POLYATOMIC GAS WITH RELAXATION EFFECTS

A traveling waves analysis for a polyatomic gas with n internal energy storage modes is performed. In both the frozen flow and the equilibrium limit the existence and qualitative behavior of traveling waves are investigated. Methods from geometric singular perturbation theory are used to study these limits.

A highly-advanced solar house with solar thermal and sky radiation cooling

A unique energy-independent house (‘HARBEMAN house’; HARmony BEtween Man And Nature) incorporating solar thermal, underground coolers, sky radiation cooling, photovoltaic electricity generation and rain-water collection was built in Sendai (latitude; 38° 17′00″ north and longitude; 140° 50′14″ east), Japan during July, 1996. The average solar energy received on a horizontal surface there in January is 7900 kJ/m2/day. This paper reports the experimental results since September 1996 to date. The annual variations of water temperature in the underground main tank, heating /cooling/domestic hot water demands, collected and emitted heats by solar collector and sky radiator, were measured. The paper also clarifies the method of computer simulation results for the HARBEMAN house and its results compared with the annual experimental data. The proposed HARBEMAN house, which meets almost all its energy demands, including space heating and cooling, domestic hot water, electricity generated by photovoltaic cell and rainwater for standard Japanese homes. The proposed system has two operational modes: (i) a long-term thermal energy storage mode extending from September to March and (ii) a long-term cool storage mode extending from April to August. The system is intended to utilize as little energy as possible to collect and emit the heat. This paper also clarifies the primary energy consumption, the external costs (externalities) and the means for the reduction of carbon-dioxide (CO2) emissions. The primary-energy consumption and carbon-dioxide emissions of the proposed house are only one-tenth of those of the conventional standard house. Moreover, the thermal performance of this house will be compared with the results of the IEA solar low-energy house TASK 13. Finally, this paper validates the external costs of this house, which have been intensively discussed in recent years in European countries. The present energy-sufficient house will be attempting in 21st century to reduce carbon dioxide emissions, which will be one of the key factors for mitigating global warming.

On the thermomechanics of shape memory wires

The thermomechanical behavior of a shape memory wire is modeled based on a theory that takes cognizance of the fact that the body can possess multiple natural configurations [1]. The constitutive equations are developed by first constructing the form of the Helmholtz potential (based on different modes of energy storage), and dissipation mechanisms. The internal energy includes contributions from the strain energy, the latent energy, the interfacial energy and thermal energy. The entropy of the system includes the"entropy jump" associated with the phase transition.¶The role of the rate of mechanical dissipation as a mechanism for entropy generation and its importance in describing the hysteretic behavior is brought out by considering the difference between hysteretic and non-hysteretic (dissipation-less) behavior.¶Finally, simple linear or quadratic forms are assumed for the various constitutive functions and the full shape memory response is modeled. A procedure for the determination of the constants is also indicated and the constants for two systems (CuZnAl and NiTi) are calculated from published experimental data (see [2, 3]). The predictions of the theory show remarkable agreement with the experimental data. However, some of the results predicted by the theory are different from the experimental results reported in Huo and Muller [2] We discuss some of the issues regarding this discrepancy and show that there appears to be some internal inconsistency between the experimental data reported in Figure 6 and Figure 9 of Huo and Muller [2] (provided they represent the same sample).

Electronically conducting polymers and activated carbon: Electrode materials in supercapacitor technology

Supercapacitors are now attracting much attention as battery‐complementary devices for applications requiring high operating power levels, such as in electric vehicle technology. Two types of supercapacitors with different modes of energy storage are currently under study: the double‐layer, and the redox. Electronically conducting polymers represent an interesting class of electro‐active materials for redox supercapacitors and can be applied in different configurations. Performance data for new and conventional devices are presented and compared to those of a double‐layer capacitor with activated carbon electrodes.

Multicomponent vapor transport model for viscous, transitional, and molecular flow

A multicomponent vacuum flow and vapor transport model for a long outgassing tube has been developed and verified experimentally. The model includes advective and diffusive vapor transport processes for a wide range of gas flow, from viscous to molecular. Existing single component approaches to the separation of vacuum flow into molecular and viscous fractions have been extended to include multicomponent transport with partial advection and interdiffusion. A set of nonlinear partial differential equations describing vacuum flow and transport in a tube are derived and solved with an iterative numerical scheme. Comparison of model simulations with laboratory measurements of vapor transport in a long vacuum sampling tube showed that the model accurately represents the process of interdiffusion in all flow regimes. Advection was accurately simulated by the model for all vapor components in fully viscous flow. Partial advection and tube limited diffusion in the transition flow range were also well simulated by the model for an argon–air mixture, while benzene–air and 1,1,1-trichloroethane–air mixtures showed slightly less than predicted partial advection. Reduced advection with these latter compounds may be due to the many energy storage modes available to the multiatomic molecules, which result in less momentum transfer than would be predicted by methods that assume fully elastic collisions between molecules.

Flex Cycle Combustor Development and Demonstration

An innovative, “flex-cycle” combustion system has been developed for the Garrett Model 400-1 Integrated Power Unit (IPU), a 425 shp (317 kW) gas turbine engine designed for use on future fighter aircraft. Demonstration of this system required real-time transient operation of the combustor in a full-scale test rig. The transient testing was unique, having been performed with an electronic control, which modulated all combustor operating parameters according to programmed engine component maps, drag curves, fuel schedules, and selected ambient test conditions. The axially injected annular combustor is capable of engine starts in two seconds, as well as producing 200 shp (149 kW) for emergency use at all altitudes up to 50,000 ft (15,240 m). The combustion system is capable of switching operation from the emergency power stored energy (SE) mode to the normal-air breathing (NAB) auxiliary power mode without loss of engine power. The flex-cycle combustor supplies emergency power in the SE mode with a temperature rise of 2200°F (1222°C) and in the NAB mode with a temperature rise of 1600°F (889°C). Specific features that make these requirements possible include air-assisted simplex airblast fuel atomizers with integral check valves, and effusion-cooled combustor liner walls. This paper describes the flex-cycle combustion system design, test methods used, and significant test results. Steady-state performance, in both the SE and NAB operating modes, and real-time transient test results are discussed. The transient testing included rapid starts as well as transitions from the SE to NAB operating regimes.

Tidal power in Canada

This presentation examines the tidal power resource of Canada and its utilization. The topics of the presentation include target development sites for the Bay of Fundy, cost benefit analysis, comparison of sites and modes of energy storage, cost reduction, environmental effects, and an analysis of the overall feasibility of tidal power development in the Bay of Fundy.

Energy characteristics of a short-pulse S-band industrial linac

The time-averaged and time-dependent energy spectra of an S-band, standing-wave industrial linac with direct injection are examined during steady-state and stored-energy mode operation. The effective fill-time for the structure under heavy beam-loading conditions is found to be significantly shorter than that predicted from an unloaded structure.

On the birth of spark channels

The breakdown stage of a spark discharge in air is analyzed. This short duration stage (< 1 μs) has been divided into two phases. In the first, the electrical energy is introduced in a constant volume process. In the second, a sudden expansion occurs which is associated with the generation of a shock wave. The thermodynamic properties of the plasma were calculated by using concepts of statistical thermodynamics, in which molecular dissociation, ionization (up to the 3rd ionization) and the various modes of energy storage in a molecule were considered. The transport coefficients (thermal and electrical conductivities) were evaluated from molecular theory, as modified for partially ionized gas. The plasma conditions at the end of the second phase are expressed in terms of the breakdown energy and the maximum temperature of the plasma. The initial conditions for the arc stage have therefore been established. It is shown that owing to the drastic changes in the gas composition at high temperatures, the relationship between the input energy and the plasma temperature and its dimensions is quite complicated. The total thermal energy of the kernel at the end of the breakdown stage, as predicted by a simple model, was found to be four times higher than predicted by the present rigorous model.

Optimizing the efficiency and stored energy in quasi-three-level lasers

A model is developed for calculating the pumping efficiency of quasi-three-level lasers operated in the energy storage mode. The model is specifically applied to room temperature 1.03- mu m Yb:YAG lasers and predicts that diode-pumped Yb:YAG lasers can be at least as efficient as diode-pumped Nd:YAG lasers provided that the pump intensity is sufficiently high. The effect of amplified spontaneous emission (ASE) is also investigated to find the relation between activator ion concentration and the ASE-limited stored energy in active mirror gain elements. >