Papers by Keyword: Energy Storage Density

Abstract: nanoand micro size Cu were employed separately and investigated comparatively. Different volume fraction of Cu was added into PVDF film in order to investigate the content of filler effect on the dielectric properties of polymer composites. XRD and SEM were used to analyze the crystalline phase and microstructure of the films. The results show that two sizes of Cu have the same peak features, and with the continuous increase of the content of Cu, it disperse better in PVDF. The dielectric constant (ε) of the composite containing 16 vol% micro-CCTO filler is 16 at 100 Hz and room temperature, and its dielectric loss (tanδ) is only 0.15, which is substantially better than others. Besides, for 18 vol% nanoCu/PVDF composite tanδ is 0.25 and ε is 18 at 100 Hz. Moreover, ε and tanδ of nanoCu/PVDF composite are both higher than those of micro-Cu/PVDF. Analysis shows that the composites with nanoCu have higher dielectric constants, which is mainly from the interfacial polarization.

Abstract: Conductive particle fillers could improve the dielectric properties of the polymer matrix. By solvent casting method, different volume fraction of nanosilver particles were added into the PVDF film to prepare Ag/PVDF composite film so as to increase the dielectric properties of the materials. SEM was used to analyze the microstructure of the films. SEM images show that nanoAg filler particles were uniformly distributed throughout the whole matrix of the composite films. Dielectric property tests show that with the increase of nanoAg content, the dielectric constants of the composites increase first and decrease later while the dielectric losses decrease first and increase later. In the case of the optimal 17vol% Ag content, the dielectric constant of the composite film is the highest (14.5 at 100 Hz) with lower dielectric loss, and the energy storage density is relatively high (0.340 J·cm⁻³).

Abstract: The absorption thermal energy storage (TES) system stores the energy in the form of potential energy of solution and is a promising technology for efficient energy transformation process. The performance of the absorption refrigeration system with integral storage for cooling applications using LiBr-H₂O as working pair under the condition without crystallization was analyzed on the basis of the first law of thermodynamics. Simulation was employed to determine the coefficient of performance (COP) and energy storage density (ESD) of the absorption TES system under different conditions such as the absorption temperature and storage temperature. The results show that the COP of the system is 0.7453 and ESD is 169.853 MJ/m³ under typical operation conditions in summer. A low absorption temperature yields both a higher COP and ESD. The solution heat exchanger could improve the COP of the system while has no effect on ESD. Results also showed that system has a good advantage when compared to other storage methods since it is do no need thermal insulation. The absorption TES may be considered as one of the promising thermal energy storage methods.

Abstract: The effect of Zr/Sn ratio on the dielectric and energy storage properties of lanthanum modified lead zirconate stannate titanate (PLZST) ceramics with compositions located near the boundary between antiferroelectric and ferroelectric phases was studied. Microstructural observation indicated that all the samples had a uniform morphology with pure perovskite phase and the average grain size reduced obviously with increasing Zr/Sn ratio. As the Zr/Sn ratio increased, the dielectric constant increased and the transition temperature T_m shifted to higher temperature. All the PLZST ceramics exhibited double hysteresis loops. The maximum polarization increased, while the switching field decreased when the Zr/Sn ratio increased. The variations of Zr/Sn ratio had little impact on remanent polarization. As a result, both charged energy density and discharged energy density increased with increasing Zr/Sn ratio. A high energy storage density of 1.75 J/cm³ was achieved in the PLZST ceramics with the Zr/Sn ratio of 82.5/7.5 at 9 kV/mm.

Abstract: Aiming to the key demands of cost, service life, environment and the time of energy storage in the energy storage technology of the distributed power generation of renewable resources, a novel compressed air green storage device based on the hydro-pneumatic conversion is put forward on the base of thermodynamics foundational principles. By the theoretical analysis for the energy cycle process of the storage device proposed, the corresponding calculation formulae are deduced for the energy storage efficiency and density under the condition of ideal gas, respectively. In addition, the changes of above index with pressure, compression ratio, and isentropic exponent are also researched. And the results show that the energy storage efficiency and density can be improved efficiently by controlling the energy conversion under the near isothermal condition so as to enhance the heat exchange capacity between the given energy storage device and its surrounding environment.

Abstract: Crystallization of a glass containing high dielectric performance components can be controlled in the nucleation and growth processes in order to meet the requirements of enabling the glass-ceramic dielectric composites to obtain the desired high electric energy storage densitiy. In this paper, the controlled crystallization technique was employed to synthesize glass-ceramic composites with addition of Gd2O3 in BaO-Na2O- Nb2O5- SiO2 glass system. The results show that both the dielectric constant and the breakdown strength of the glass-ceramic composites demonstrate an increasing tendency with the addition of Gd2O3 from 0 mol% to 7 mol% (relative to SiO2), being responsible for remarkable improvement of the energy storage density of the glass-ceramic composites from 1.7 J/cm3 to 4.7 J/cm3.

Abstract: The energy storage density of (1-x) BaTiO3 – x Ba(Mg1/3Nb2/3)O3 (x = 0, 0.1, 0.2, 0.3) ceramics was investigated. The microstructure of samples was characterized by scanning electron microscopy (SEM). The energy storage density was calculated from the P-E hysteresis loops measured at room temperature. Experimental results show that the energy storage density of 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramics is highest among all compositions. At 15.8kV/mm electric field, the energy storage density of the sample can reach up to 1.07J/cm3, which is about 1.5 times higher than pure BaTiO3. The improvement of the energy density can be due to two factors: one is the improved breakdown strength caused by the optimized microstructure, the other is the decreased remnant polarization. This result indicates that bulk 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramic has advantages compared with pure BaTiO3 ceramic for energy storage applications, and with further improvements in microstructure and reduction of sintering temperature, could be a good candidate for energy storage capacitors.