Degradation of Supercapacitors (SC) is quantified by accelerated ageing tests. Energy cycling tests and calendar life tests are used since they address the real operating modes. The periodic characterization is used to analyse evolution of the SC parameters as a whole, and its Helmholtz and diffusion capacitances. These parameters are determined before the ageing tests and during 3 × 105 cycles of both 75% and 100% energy cycling, respectively. Precise evaluation of the capacitance and Equivalent Series Resistance (ESR) is based on fitting the experimental data by an exponential function of voltage vs. time. The ESR increases linearly with the number (No) of cycles for both 75% and 100% energy cycling, whereas a super-linear increase of ESR vs. time of cycling is observed for the 100% energy cycling. A decrease of capacitance in time had been evaluated for 2000 hours of ageing of SC. A relative change of capacitance is ΔC/C0 = 16% for the 75% energy cycling test and ΔC/C0 = 20% for the 100% energy cycling test at temperature 25°C, while ΔC/C0 = 6% for the calendar test at temperature 22°C for a voltage bias V = 1.0 Vop. The energy cycling causes a greater decrease of capacitance in comparison with the calendar test; such results may be a consequence of increasing the temperature due to the Joule heat created in the SC structure. The charge/discharge current value is the same for both 75% and 100% energy cycling tests, so it is the Joule heat created on both the equivalent series resistance and time-dependent diffuse resistance that should be the source of degradation of the SC structure. The diffuse resistance reaches a value of up to 30Ω within each 75% energy cycle and up to about 43Ω within each 100% energy cycle.
A developed method and measurement setup for measurement of noise generated in a supercapacitor is presented. The requirements for noise data recording are considered and correlated with working modes of supercapacitors. An example of results of low-frequency noise measurements in commercially available supercapacitors are presented. The ability of flicker noise measurements suggests that they can be used to assess quality of tested supercapacitors.
In this paper a measurement system for determination of supercapacitor equivalent parameters is proposed. Specific properties of materials used for supercapacitor construction require some advanced tools and measurement procedures to be applied during tests. The measurement system allows to measure values of equivalent parameters by both the DC and AC method whilst keeping appropriate time criteria required by this type of devices. Furthermore, in this paper the most relevant properties and measurement capabilities of the proposed system are described as well as some exemplary values of the supercapacitor equivalent parameters measured experimentally are presented.
The paper presents a laboratory prototype of the three-phase transformer less voltage outages compensator with an energy storage based on high voltage supercapacitors. The system described is able to protect an isolated grid e.g. in industry against short voltage interruptions, dips and sags. An idea of a control method as well as a Digital controller has been presented, too.
Solar energy is widely available in nature and electricity can be easily extracted using solar PV cells. A fuel cell being reliable and environment friendly becomes a good choice for the backup so as to compensate for continuously varying solar irradiation. This paper presents simple control schemes for power management of the DC microgrid consisting of PV modules and fuel cell as energy sources and a hydrogen electrolyzer system for storing the excess power generated. The supercapacitor bank is used as a short term energy storage device for providing the energy buffer whenever sudden fluctuations occur in the input power and the load demand. A new power control strategy is developed for a hydrogen storage system. The performance of the system is assessed with and without the supercapacitor bank and the results are compared. A comparative study of the voltage regulation of the microgrid is presented with the controller of the supercapacitor bank, realized using a traditional PI controller and an intelligent fuzzy logic controller.
This paper proposes four different cost-effective configurations of a hybrid energy storage system (HESS) in an electric city bus. A comparison is presented between a battery powered bus (battery bus) and supercapacitor powered bus in two configurations in terms of initial and operational costs. The lithium iron phosphate (LFP) battery type was used in the battery bus and three of the hybrids. In the first hybrid the battery module was the same size as in the battery bus, in the second it was half the size and in the third it was one third the size. The fourth hybrid used a lithium nickel manganese cobalt oxide (NMC) battery type with the same energy as the LFP battery module in the battery bus. The model of LFP battery degradation is used in the calculation of its lifetime range and operational costs. For the NMC battery and supercapacitor, the manufacturers’ data have been adopted. The results show that it is profitable to use HESS in an electric city bus from both the producer and consumer point of view. The reduction of battery size and added supercapacitor module generates up to a 36% reduction of the initial energy storage system (ESS) price and up to a 29% reduction of operational costs when compared to the battery ESS. By using an NMC battery type in HESS, it is possible to reduce operational costs by up to 50% compared to an LFP battery ESS.