Search

Pumped thermal energy storage (PTES) technology offers numerous advantages as a novel form of physical energy storage. However, there needs to be a more dynamic analysis of PTES systems. This paper proposes a dynamic simulation model of the PTES system using a multi-physics domain modeling method to investigate the dynamic response of key system parameters during the system's start-up and variable operating conditions. Additionally, the impact of equipment parameters on system characteristics was analyzed. Furthermore, a comparative analysis was conducted to assess the variation in system characteristics when considering the different working medium properties. The results show that the system cavity volume should be selected as 5 m3, and the initial pressure of the system during the charge/discharge period should be selected as 2.1 MPa and 3.8 MPa, respectively. The system runs to the design operating conditions during the start-up process in about 1400 s. In the process of variable operation conditions, the power load in the charge/discharge period can be increased or reduced from the rated value by gas filling or venting, and the system characteristics change accordingly. The simulation model and research findings will offer theoretical insights for optimizing the design of the PTES system. • A dynamic simulation physical model of the PTES system was proposed. • The dynamic changes in system characteristics were analyzed. • The TES tank's thermal inertia and heat management of the PTES system were analyzed. • The effects of main equipment parameters on system characteristics were analyzed. • System characteristics were compared when using different gas properties. [ABSTRACT FROM AUTHOR]

This study presents the modelling and dynamic simulation of a high penetration wind diesel power system (WDPS) consisting of a diesel generator (DG), a wind turbine generator (WTG), consumer load, dump load and a battery energy storage system (BESS). First the WDPS architecture and the models of the WDPS components are described. The WDPS is simulated in wind-only (WO) mode where the DG is not running and the WTG supply active power and in wind-diesel (WD) mode where both DG and WTG supply power. The simulation results are given showing graphs of the main electric variables in the WDPS (system frequency and voltage and active power in each component) and main battery variables (current, voltage and state of charge). The results in the WO mode show how the BESS, under the command of a proportional-integral-derivative (PID) controller, supplies/stores active power to regulate the isolated system frequency. The WD control enables the BESS to smooth the load and wind power variations, so that the isolated system power quality is improved. Also it is shown in the WD mode a peak shaving application where the control orders the BESS to supply active power temporarily to support system frequency in a DG overload situation. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel dynamic model for thermocline thermal energy storage systems is presented. [•] Adaptive grid technique used. [•] Accuracy is improved while using an order of magnitude fewer states and equations. [•] Effects of numerical diffusion are minimized. [•] Model more accurate under temperature (and density) inversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermochemical heat storage using Ca(OH) 2 /CaO in a fluidized bed reactor was modeled. • Variable renewable energy fluctuation can be absorbed by using steam as fluidizing gas. • The energy efficiencies for nitrogen were higher than that for steam. • The simulated data agreed with the experimental data, albeit not perfectly. A simplified dynamic model of a Ca(OH) 2 /CaO–containing fluidized bed reactor was developed by combining a continuously stirred tank reactor model in the solid phase with a series of continuously stirred tank reactors in the gas phase for mass transport. The heat supplied to the thermochemical heat storage system was allowed to fluctuate to evaluate the absorption of variable renewable energy fluctuation. In addition, the performance of the fluidized bed was assessed using nitrogen or steam as the fluidizing gas. For nitrogen, the fluctuation of bed temperature increased with the increasing time step of heat change. The bed temperature was affected by the magnitude of the fluctuation of the supplied heat more strongly for nitrogen than for steam, mainly because the rate of dehydration under these conditions was more strongly dependent on temperature than in the case of steam. The thermochemical heat storage efficiency (calculated by considering reaction heat) and energy storage efficiency (calculated by considering reaction heat and sensible heat) equaled 14.1% and 34.1% for steam and 29.9% and 62.7% for nitrogen, respectively. The differences between the efficiencies for steam and nitrogen were ascribed to the latent heat of H 2 O. Sensitivity analysis showed that both efficiencies increased with increasing heat supply because of the concomitant decrease in the time required to heat the system to the reaction temperature. During this time, thermochemical heat storage did not occur, which resulted in lower efficiency. Therefore, the fluctuation from variable renewable energy can be absorbed by using thermochemical heat storage. [ABSTRACT FROM AUTHOR]

Biomass combined heat and power plants (CHPPs) can operate target-specifically because of their controllability while supporting decarbonization in district heating. The transition from the German Renewable Energies Act funding, which has promoted biomass CHPPs but is now about to expire, to direct marketing, is a major economic challenge for many biomass-heating grids. To successfully accomplish it, the flexible operation of biomass CHPPs, compared to the previous baseline-operation, is becoming an increasingly important requirement if participation in the electricity markets is to remain profitable. This paper presents a techno-economic assessment of flexible CHPP operation in a modeled district heating system with a CHPP, a peak load boiler and a thermal heat storage. The simulation model compares two cases - a natural gas and a wood-chip gasifier CHPP. The analysis of the results investigates the parameters that need to be adapted to make biomass-fired CHPP heating grids more efficient compared to fossil-fired CHPP heating grids in a flexible operating scenario. It highlights the technical and economic superiority of a fossil-fired CHPP in flexible operation in comparison to the wood gasifier system. The introduction of a CO 2 -tax on natural gas as a fuel, currently under discussion in Germany, would increase the competitiveness of the wood gasifier. • Simulation model of a district heating system. • Model units are wood or natural CHP plant, peakload boiler and heat storage. • Three scenarios for CHP plant dispatch under consideration of electricity prices. • Focus on dynamic differences of the CHP plant operation strategy. • Results show limitations in operational flexibility of the wood gas CHP plant. [ABSTRACT FROM AUTHOR]

To overcome non-programmability issues that limit the market penetration of renewable energies, the use of thermal energy storage has become more and more significant in several applications where there is a need for decoupling between energy supply and demand. The aim of this paper is to present a multi-node physics-based model for the simulation of stratified thermal energy storage, which allows the required level of detail in temperature vertical distribution to be varied simply by choosing the number of nodes and their relative dimensions. Thanks to the chosen causality structure, this model can be implemented into a library of components for the dynamic simulation of smart energy systems. Hence, unlike most of the solutions proposed in the literature, thermal energy storage can be considered not only as a stand-alone component, but also as an important part of a more complex system. Moreover, the model behavior has been analyzed with reference to the experimental results from the literature. The results make it possible to conclude that the model is able to accurately predict the temperature distribution within a stratified storage tank typically used in a district heating network with limitations when dealing with small storage volumes and high flow rates. [ABSTRACT FROM AUTHOR]