Peak Load Power Research Articles

Research on interruptible load supply curve simulation based on industrial classification

Recently, with the adjustment of industrial structure, peak power load is getting sharper in China. Interruptible Load Management (ILM) enables power system to gain deterministic access to Interruptible Load (IL) provided by power consumers, which can use a more economical way to ensure real-time balance and safe operation of power system. This paper proposes a simulation method of interruptible load supply curve of lager industrial power consumers based on industrial classification, which can predict capacity of interruptible load that lager industrial power consumers are willing to provide under different interruptible load prices. An example towards a China’s eastern province shows that, if government wants to acquire interruptible load capacity of 10 million kW, the interruptible price should be priced higher than 0.7 RMB/kWh.

Research on Optical Energy Storage System Based on Rule Logic Control

Photovoltaic energy storage system is composed of photovoltaic power generation, energy storage battery, load and power grid, it has researched on different modes of bi-directional DC/AC converter, taking into account a variety of photovoltaic output fluctuations, energy storage battery charging and discharging management, load increasing and decreasing, etc. Aiming at the energy management strategy, using DC bus voltage fluctuation as the basis of energy layer mobilization, the power balance control based on regular control is proposed. Compared with the DC bus voltage level energy management, the power tracking accuracy is further improved and energy loss is reduced. Finally, through MATLAB/Simulink being in off/connected model and the charging/discharging model, the effectiveness of the energy control strategy was verified separately by simulation. The simulation results show that: the proposed control strategy can improve the power tracking accuracy and reduce the energy loss of the system; the proposed strategy guarantees the bidirectional exchange of system energy and maintains the power balance in the network, the DC bus voltage is stable, and the energy storage battery achieves smooth power output and peak load shifting.

A Two-Layer Optimization Model for Energy Storage Configuration in the Distribution Network

The large-scale access of electric vehicles will aggravate the peak-to-valley load difference of the distribution network, and the intermittent power generation of high-penetration renewable energy also threatens the safe operation of the distribution network. Energy storage is widely used in the fields of power peak load shifting and access of renewable energy. This paper proposes a two-level optimization model that considers both planning and operation of energy storage system. At the planning level, a method for the location and capacity of energy storage is proposed based on the economics of the distribution network. At the operation level, a scheduling strategy applying to different seasonal scenarios is proposed to achieve the best effect of peak load shifting. The simulated annealing particle swarm algorithm with good convergence performance is used to solve the model. Finally, the performance and economic benefits of the model are demonstrated through simulation research.

SOLPS-ITER drift modelling of ITER burning plasmas with narrow near-SOL heat flux channels

Abstract SOLPS-ITER code simulations with fluid drifts activated are used to examine the consequences for divertor performance, under burning plasma conditions, of a reduction in scrape-off layer (SOL) cross-field transport such that the outboard midplane SOL parallel heat flux width, λq is reduced to the very low values predicted by the experimental scaling in [T. Eich et al., Nucl. Fusion 53 (2013) 093031] for high plasma current operation on ITER. The decrease of λq from the standard value (~3.5 mm) used in the ITER SOLPS modeling database, to λq ~ 1–2 mm expected from the scaling, leads to a strong narrowing of the operational window in terms of divertor heat loading limits. To maintain similar levels of sub-divertor neutral pressure, pn (one of the key divertor operational parameters) as those obtained with standard transport, higher levels of neon impurity seeding are required when transport is reduced, yielding higher Zeff at the upstream separatrix and requiring further integrated modelling to assess the impact on confinement. The simulations also demonstrate that the strong increase in in-out target peak power loading asymmetry at low pn seen for standard transport when drifts are switched on in the code is preserved, and in fact worsens, for low transport. This significantly reduces margins for power handling control at lower pn if heat flux channels will be narrow on ITER.

Estimating synthetic load profile based on student behavior using fuzzyinference system for demand side management application

This paper proposes a novel approach of estimating synthetic load profiles based on the electrical usage behavior using the fuzzy inference system (FIS) for demand side management (DSM). In practice, DSM is utilized to change the pattern of electrical energy consumed by end-users to modify the load profile by manipulating the price of the electricity. This study focuses on the energy consumption consumed by students who are paying electricity bills indirectly. Therefore, the effectiveness of conventional DSM methods on this user requires further investigation. In this study, the FIS estimates the synthetic load profile based on the student?s behavior profile. Then, three DSM techniques: load clipping, load shifting, and load conservation, are applied to the electrical usage behavior model. The FIS estimates the synthetic load profile based on the modified electrical usage behavior model with these DSM techniques. From this estimation, the synthetic load profiles are analyzed and compared to evaluate the effectiveness of the DSM methods on the students. The result shows that the FIS estimates the synthetic load profile satisfactorily. Also, load conservation is the most effective technique in reducing the peak load profile and power consumption for this type of user. Conclusively, the result implies that the proposed methodology can be used to evaluate the effectiveness of the DSM method to reshape the load profile.

Capacity Design and Cost Analysis of Converged Renewable Energy Resources by Considering Base Load Conditions in Residential and Industrial Areas

In this paper, a design technique for constructing a renewable-energy-based power system based on a customer’s power load is proposed. The proposed design technique adopts a second renewable energy power source in charge of the base load and is an improved method of the referenced studies with one type of renewable energy power source. In this proposed method, fuel cells are adopted as the base power source, and PV (photovoltaic) power generation and an ESS (energy storage system) are adopted as the power generation sources that supply the middle-load and peak-load power. When the fuel cell is applied as a base power source through the method designed in this study, a cost reduction of approximately 30.03% is expected, compared to a system that does not use a base power source. In addition, the criteria for securing a system’s power supply stability and the economics when fuel cells are adopted are analyzed in terms of the system’s installation cost.

A coherent strategy for peak load shaving using energy storage systems

Abstract In recent years, balance of power supply and demand as control and smoothing of peak load demand has been one of the major concerns of utilities. Hence, peak load shaving is a preferred approach to cut peak load and smooth the load curve. This paper presents a novel and fast algorithm to evaluate optimal capacity of energy storage system within charge/discharge intervals for peak load shaving in a distribution network. This method is based on reshaping of aggregated load profile (historical load profile), which observed from the main distribution substation to calculate required BESS size by simple and fast mathematical procedures. A case study of 22-bus model is analyzed in MATLAB® environment to determine optimal location of the selected BESS. Main contribution of this paper is (ⅰ) to find the optimal size (capacity and power) of BESS, (ⅱ) determine the optimal location of BESS, and (ⅲ) propose the BESS control strategy and scheduling for optimum operation. Different scenarios including the baseline case (without BESS), centralized BESS, and centralized BESS with PV are considered to reduce peak load demand and power losses, as well as to improve voltage profile during peak load hours. Simulation results indicate that all cases of BESS installation can significantly improve the operation of the distribution network. Simulation results highlight centralized BESS and PV as a compelling case to shave demand peak. All told, findings indicate the effectiveness of the proposed algorithm for peak load shaving by giving optimum location and sizing of BESS.

Impurity transport and divertor retention in Ar and N seeded SOLPS 5.0 simulations for ASDEX Upgrade

Impurity seeding will be an important tool to reduce the peak power loads and temperatures at the divertor targets in future tokamak devices. To improve the physics understanding and provide predictive capabilities for the impact of impurities on the plasma, different impurity species have to be investigated and compared to each other. For this purpose SOLPS 5.0 simulations of argon (Ar) and nitrogen (N) seeded H-mode plasmas for ASDEX Upgrade have been performed. The (purely numerical) investigations extend previous studies dedicated to impurity transport and to the divertor impurity retention. An analysis of mixed Ar and N impurity seeding reveals that a trade-off between pedestal top temperature drop and fuel dilution can be achieved by an adjustment of the impurity mixture. Due to the impact of the impurities on the temperatures, the impurity seeding reduces the main ion ionization rates in the divertor regions, and therefore, the ion particle sources. Accordingly, this modification of the particle sources results in a main ion background flow inversion at higher seeding levels, which also strongly affects the impurity flow patterns. This mechanism explains a modification of the impurity density distribution at higher seeding levels, where Ar impurities are observed to be redistributed from the outer to the inner divertor. A less pronounced effect is observed for N, which can be explained by the radiation efficiency. The divertor impurity retention is determined by the relative positions of the ionization front of the neutral impurities and the impurity stagnation point. The impact of impurity seeding on the stagnation point position is studied in detail for the first time. Under the investigated conditions, decreasing the target temperature (i.e. increasing impurity seeding) always results in a reduction of the divertor impurity retention. This is a critical result making power exhaust even more challenging.

Design and Implementation of DC Pulsed Power Supply Employing Self-Excited Induction Generators and Flywheels for Toroidal Field Coils of a Tokamak Device, PLATO

Tokamak devices with non-superconducting coils must be equipped with pulsed power supplies employing energy storage system when the devices cannot receive electricity from power grids directly. Flywheel energy storage system (FESS) for the coil power supplies have been used only in large or middle-sized tokamak devices since they employed synchronous motor generators (SMGs), which have difficulty in downsizing and maintenance. In our previous research, FESS with induction motor generators (IMGs) utilizing self-excited phenomena was developed. In this paper, using two novel concepts of multiple IMGs and installing a multistage converter, both of design flexibility and coil current ripple reductions are realized. As an experimental result, a peak load power of 778 kW and an electric energy supply of 408 kJ to the dummy coil were achieved using a toroidal field coil power supply (TFCPS) of a tokamak device, PLATO.

Thermodynamic analysis of hybrid adiabatic compressed air energy storage system and biomass gasification storage (A-CAES + BMGS) power system

A thermodynamic analysis of a power system consisting of adiabatic compressed air energy storage and biomass gasification energy storage power system in a hybrid mode for simultaneous production of electricity and warm water for use domestically is presented in this paper. The hybrid system is designed to meet peak load power demand of 1.3 MW from a blend of 1 MW adiabatic compressed air energy storage system powered by electricity and 0.3 MW rated dual fuel (syngas + diesel) powered engine. The syngas fuel used in the dual fuel engine is supplied by a downdraft biomass gasification system whose wood feed is supplied by a hot air dryer system operated by waste thermal energy recuperated from the system. The performance of the overall system is assessed with total system efficiency, electrical efficiency, effective electrical and exergy efficiency as metrics. In addition, the performance of the sub-components of the system is appraised using exergy destruction and exergy efficiency. The overall energy and exergy efficiency of the system is found to be approximately 38% and 29%, respectively. The electrical and effective electrical efficiency, are 30 and 34%, respectively. The exergy efficiency of the sub-system components are 61.38, 21.47, 5.76, 89.17 and 86.12% for the biomass gasifier, dual fuel engine, hot air dryer, air compressor and air expander, respectively. It is found that the destroyed exergy in the components of the hybrid system is the uppermost in the biomass gasifier, then the DFE and the AE in that order. The minimum destroyed exergy occurs in the hot air dryer. The system has a primary energy savings ratio 10 which means it cannot be deployed as a CHP system under the EU criteria.

Efficient and rigorous evaluation of fast particle losses in non-axisymmetric tokamak plasmas

We present an analysis scheme called loss-map analysis that quantitatively connects the fast ion transport in 3D magnetic field to the underlying transport mechanisms. The loss-map analysis is generally applicable, but here its use is demonstrated by applying it to study alpha particle losses in the ITER baseline scenario and ICRH losses in the reduced-field scenarios. This demonstration addresses the issues raised by the earlier ITER fast ion confinement studies. The focus is in the analysis scheme itself which aids in interpreting and confirming the results of orbit-following simulations by providing a way to connect observed losses to known fast ion transport processes. The loss maps can also be used to estimate fast ion losses directly from the magnetic field structure, thus providing a fast alternative to orbit-following simulations. Furthermore, the loss maps connect the particle birth position in the phase space to the wall region where it is lost. This can be used to optimize marker initialization in simulations that estimate peak power loads or FILD signals, thus reducing the required computational time which otherwise might be prohibitive.

Multi‐objective optimisation method for coordinating battery storage systems, photovoltaic inverters and tap changers

The many well-established advantages of distributed generation (DG) make their usage in active distribution networks prevalent. However, uncontrolled operation of DG units can negatively interfere with the performance of other equipment, such as tap-changers, in addition to resulting in sub-optimal usage of their potential. Thus, adequate scheduling/control of DG units is critical for operators of the distribution system to avoid those adverse effects. A linearised model of a multi-objective method for coordinating the operation of photovoltaics, battery storage systems, and tap-changers is proposed. Three objective functions are defined for simultaneously enhancing voltage profile, minimising power losses, and reducing peak load power. The formulated multi-objective problem is solved by means of the epsilon-constraint technique. A novel decision-making methodology is offered to find the Pareto optimality and select the preferred solution. To assess to proposed model's performance, it is tested using 33-bus IEEE test system. Consequently, tap-changers suffer lessened stress, the batteries state-of-charge is kept within adequate limits, and the DG units operation is at higher efficiency. The obtained results verify the effectiveness of this approach.

Viability of Seasonal Natural Gas Storage in the Saudi Energy System

Saudi Arabia expects to double its natural gas production within the next decade. This increased domestic supply is expected to meet the demand for gas from Saudi Arabia’s industrial development and, most importantly, to displace liquid fuels in its electricity sector. Given the strong seasonal variability of the latter, underground gas storage (UGS) can help ensure the availability of gas to meet peak power load. In this vein, we assess the geologic and economic viability of UGS in Saudi Arabia under different scenarios: with and without LNG imports allowed, and under low and high domestic gas production. Depleted oil fields or aquifers are best suited for gas storage in the Kingdom. Using a model of the country’s energy system, we show that in the case of high gas production, storage capacity would be built to bypass the transport limit for gas for use in electricity generation in the summer. In the low production case, gas storage would facilitate optimal gas use among sectors throughout the year. The net present gain – defined as the discounted sum of the annual differences in benefits and costs – is used to determine the economic viability of gas storage.

Increasing Revenue of Nuclear Power Plants With Thermal Storage

AbstractIntroducing large amounts of electricity produced from variable renewable energy sources such as wind and solar decreases wholesale electricity price while increasing the volatility of the market. These conditions drive the need for peak-load power generation, while regulation requirements fuel the push for flexible power generation. The increase of variable renewable energy in the market share, along with falling natural gas prices, makes nuclear power plants less competitive. Thermal storage is being considered to increase the nuclear power plant revenue. Thermal storage increases the flexibility of the nuclear plant system without sacrificing its efficiency. There are multiple opportunities to increase the nuclear power plant revenue, including increased capacity payments, arbitrage, and ancillary services. An economic analysis was performed to investigate the revenue increase of the system with thermal storage. The investment cost was assessed, and net present value was evaluated for the considered scenarios. Two system designs were considered in the analysis: a thermal storage system using the existing power conversion infrastructure and an integrated design with thermal storage fully incorporated into the reactor system design. The preliminary analysis showed that introducing a thermal storage system is profitable for some scenarios considered. Profitability depends significantly on the storage size, output flexibility, share of variable renewable energy, and market characteristics.

On the role of hydrogen radiation absorption in divertor plasma detachment

Transition to the detached divertor regime that allows lowering the peak power loads on the divertor targets to a tolerable level requires low plasma temperature Te ~ 1 eV and high plasma density ne ~ 1021 m−3 in front of the target. Under such conditions, radiation trapping of the Lyman lines of hydrogen isotopes becomes important. It can influence both energy balance and the ionization/recombination rates significantly. Nevertheless, opacity is typically neglected in the 2D edge transport codes used to study the divertor plasma detachment. We report on the first in-depth investigation of radiation opacity effects on transition to detachment. Simulations are performed with the SOLPS 4.3 code package using a DIII-D size tokamak as a particular example. It is found that in pure hydrogen plasma suppression of the neutral hydrogen radiation loss due to the photon absorption makes reaching the detached plasma regime more difficult. A significantly higher average separatrix plasma pressure is required to reach a similar degree of detachment. Adding plasma impurities compensates for the reduced neutral radiation and offsets the effect of opacity. In a carbon device, where the impurity source is due to erosion of the divertor components and is strongly connected to the edge plasma density, the absorbed fraction of the hydrogen radiation is easily compensated with the increasing carbon radiation loss. However, nowadays, in the more relevant case of the full-metal wall and seeded impurity with the feedback-controlled content, the increase of the edge plasma density alone is insufficient to compensate for trapping of the hydrogen radiation. In this case, achievement of the desired degree of detachment requires higher average separatrix plasma pressure or seeded impurity content than those obtained from the transparent plasma model.

SAVING RESOURCES IN THE CONSTRUCTION OF HYDROELECTRIC POWER PLANTS

The article describes run-of-the-river hydroelectric power plants. The authors specify the importance of performing technical and economic calculations in justifying the large-sized units of the water-supplying channel of a run-of-the-river hydroelectric power plant: turbine pits and suction (discharge) pipes. The study shows that the amount of construction work and the total cost of building a hydroelectric power plant depend on the size of these water supply units. The research objective is to analyze the validity of establishing the main dimensions of the suction pipes for modern technical and economic conditions. The researchers use the discounted income method. The calculations are performed for a hydroelectric power plant with an elbow suction pipe. The analysis of how the operating conditions of a hydroelectric power plant influence the savings of construction resources is carried out. The analysis shows that saving construction resources by reducing the length of the suction pipe is justified if the hydroelectric power plamt is designed to work only at peak power loads. For hydroelectric power plants operating at semi-peak or base power loads, the additional construction costs would be appropriate if leading to the decrease in pressure loss and to the increase in electricity generation.

Multi-objective optimization model predictive dispatch precooling and ceiling fans in office buildings under different summer weather conditions

In summer, a ceiling fan has a tremendous potential to cool rooms, resulting in energy saving and a peak load reduction. During the critical peak pricing (CPP) period of the electricity, one method to attain substantial energy cost saving is to turn off the heating, ventilating and air conditioning (HVAC) system, but this may result in overheating. Fortunately, precooling and ceiling fans can be used to reduce the feeling of hot sensation. Therefore, the best control strategy for an HVAC system and ceiling fans is to maximize energy cost saving without much thermal comfort sacrifice. This paper presents a multi-objective optimization model predictive control (MO-MPC) of precooling temperature setpoint and ceiling fan speed. The proposed MO-MPC integrates an optimization engine, Dakota, and a detailed energy simulation tool, EnergyPlus, to determine the optimal control strategies considering the energy cost and thermal comfort simultaneously. A sub-program of substituting EnergyPlus with decision tree regression models for building climate prediction is deployed. If the calculation time is too long to achieve real-time control, this sub-program can be adopted to accelerate the calculation. In this study, the proposed MO-MPC framework is applied to a small and large building in four different cities with different CPPs. For a summer day, compared with the baseline cases of no precooling and no ceiling fan, the optimal strategies for the small building achieve energy cost savings between 10.3% and 33.3% and a peak power load decrease from 44.0% to 51.9%. Without precooling but with a ceiling fan control, on a particular summer day, for the large building case in Shanghai, 7.4% energy saving is achieved. The optimal control of the precooling temperature and ceiling fans result in a 14.4% energy cost saving. By using the decision tree regression models instead of EnergyPlus, the calculation time of the big office reduces from about 10 hours 40 minutes to 24.4 minutes.

A Novel Thermal Energy Storage System in Smart Building Based on Phase Change Material

This paper presents a novel phase change material based thermal energy storage system (PCMTESS) that is suitable for smart building energy management, together with its corresponding thermal-electric combined two-stage dispatching strategy. Benefiting from the phase change materials’ thermal characteristic of absorbing or releasing a significant amount of heat at a constant temperature, this thermal energy storage system is endowed with a high capacity and a relatively stable thermal state during its charge/discharge process. To evaluate the thermal performance of the PCMTESS, which is integrated as a part of building wallboard, a detailed analytic thermodynamic building model is proposed that considers the influence of the forced air convection and the external environments, such as solar radiation. Furthermore, a two-stage electric-thermal combined dispatching scheme is designed to minimize the electricity consumption expenditure and power fluctuation on the premise of maintaining a comfortable indoor temperature. Simulation studies on a smart building indicate that the proposed thermal energy storage system is a feasible and economical solution for solving peak load shaving and power fluctuation.

A 1-mW Class-AB Amplifier With −101 dB THD+N for High-Fidelity 16 $\Omega$ Headphones in 65-nm CMOS

A low-power class-AB amplifier for high-fidelity headphones is presented. The linearity of a class-AB amplifier strongly depends on the loop gain over the audio band and voltage swing. In this paper, a cascode-driven mesh technique limits the number of high-swing nodes in the output stage, thereby preserving the loop gain of the preceding gain stages. A frequency compensation scheme is proposed that extends the unity-gain bandwidth (UGB) and increases the loop gain at 20 kHz. Combining these two techniques, the amplifier achieves −101.4-dB total harmonic distortion plus noise (THD+N) over the full audio band, the lowest ever reported nonlinearity among sub-milliwatt CMOS class-AB amplifiers. The amplifier delivers 51.2-mW peak power to a $16\Omega \|0.33$ -nF load while consuming 0.97 mW of total static power. It has UGB of 12.3 MHz and SNR of 108 dB. These results are consistent when measured over eight test chips. Compared to the recent prior art, the amplifier exhibits >12 dB better linearity and >14-dB dynamic range. This results in 2.5 $\times $ improvement in figure of merit (FOM = Peak Load Power/(Quiescent Power $\times $ THD+N[%])). It occupies 0.16 mm 2 in a standard 65-nm CMOS.

Multi-objective planning for the allocation of PV-BESS integrated open UPQC for peak load shaving of radial distribution networks

Abstract This paper presents a multi-objective planning approach for the optimal allocation of PV-BESS integrated open UPQC (PV-BESS-UPQC-O) for peak load shaving of radial distribution networks. The open UPQC (UPQC-O) is a custom power device which consists of series and shunt inverters. It is designed to provide reactive power compensation and to mitigate some power quality problems. The UPQC-O is integrated with BESS to inject active power to the network during peak hour for peak load shaving. The charging of BESS is to be done using PV panel. A multi-objective optimization problem is formulated, in which maximization of peak load shaving, minimization of cost of placement of PV-BESS-UPQC-O, and minimization of total power loss during peak load demand with the placement of PV-BESS-UPQC-O are the objective functions. The limits on bus voltage magnitude, line current flow, and PV capacity are the constraints of this optimization problem. The Pareto-based multi-objective particle swarm optimization (MOPSO) is used to simultaneously optimize these objectives so as to obtain a set of Pareto-approximation solutions. From this set, a distribution network owner can choose a solution depending upon its desired level of peak load shaving, power loss, and capital expenditure budget.