Søren Juhl Andreasen

Accelerated Lifetime Testing Methodology for Lifetime Estimation of Lithium-Ion Batteries Used in Augmented Wind Power Plants

The development of lifetime estimation models for Lithium-ion battery cells, which are working under highly variable mission profiles characteristic for wind power plant applications, requires a lot of expenditures and time resources. Therefore, batteries have to be tested under accelerated lifetime aging conditions. This paper presents a three-stage methodology used for accelerated lifetime testing of Lithium-ion batteries. The results obtained at the end of the accelerated aging process were used for the parameterization of a performance-degradation lifetime model, which is able to predict both the capacity fade and the power capability decrease of the selected Lithium-ion battery cells. In the proposed methodology both calendar and cycling lifetime tests were considered since both components are influencing the lifetime of Lithium-ion batteries. Furthermore, the proposed methodology was validated by running a verification stage of the lifetime model, where Lithium-ion battery cells were tested at normal operating conditions using an application specific mission profile.

Y-Source Boost DC/DC Converter for Distributed Generation

This paper introduces a versatile Y-source boost dc/dc converter intended for distributed power generation, where high gain is often demanded. The proposed converter uses a Y-source impedance network realized with a tightly coupled three-winding inductor for high voltage boosting that is presently unmatched by existing impedance networks. The proposed converter also has more variables for tuning the required gain and, hence, more degrees of freedom for meeting design constraints. These capabilities have been demonstrated by mathematical derivation and experimental testing. For the experiments, a 300-W prototype has been built in the laboratory using silicon carbide devices for better efficiency. The prototype has been tested with a regulated power supply, before operating it with a high-temperature proton-exchange-membrane fuel cell. Results obtained confirm the practicality and performance of the proposed converter.

Evaluation of Fuel-Cell Range Extender Impact on Hybrid Electrical Vehicle Performance

The use of electric vehicles (EVs) is advantageous because of zero emission, but their market penetration is limited by one disadvantage, i.e., energy storage. Battery EVs (BEVs) have a limited range, and their batteries take a long time to charge, compared with the time it takes to refuel the tank of a vehicle with an internal combustion engine (ICE). Fuel cells (FCs) can be added to an EV as an additional energy source. These are faster to refill and will therefore facilitate the transition from vehicles running on fossil fuel to electricity. Different EV setups with FC strategies are presented and compared. The results of the setups are presented by range, efficiency, and price. These show the negative effect on the range when purpose-designed setups are driven above the design requirement as the range drops considerably. The simulations also showed the necessity of good FC control when driving in start/stop city cycles. Simulations with the New European Driving Cycle (NEDC) showed that efficiency fell by at least 15% for the FC hybrid EV (FCHEV) when compared with BEVs.

Datasheet-based modeling of Li-Ion batteries

Researchers and developers use battery models in order to predict the performance of batteries depending on external and internal conditions, such as temperature, C-rate, Depth-of-Discharge (DoD) or State-of-Health (SoH). Most battery models proposed in the literature require specific laboratory test for parameterization, therefore a great majority do not represent an appropriate and feasible solution. In this paper three easy-to-follow equivalent circuit modeling methods based only on information contained in a commercial Li-Ion cell manufacturers datasheet are presented and validated at steady state, comparing simulation results and manufacturers curves. Laboratory results are included in order to demonstrate the accuracy of parameters estimation. Results of each method are presented, compared and discussed for a Kokam SLPB 120216216 53Ah Li-Ion cell.

A comparative study of lithium ion to lead acid batteries for use in UPS applications

Uninterruptible power supply (UPS) systems have incorporated in their structure an electrochemical battery which allows for smooth power supply when a power failure occurs. In general, UPS systems are based on lead acid batteries; mainly a valve regulated lead acid (VRLA) battery. Recently, lithium ion batteries are getting more and more attention for their use in the back-up power systems and UPSs, because of their superior characteristics, which include increased safety and higher gravimetric and volumetric energy densities. This fact allows them to be smaller in size and weight less than VRLA batteries, which are currently used in UPS applications. The main purpose of this paper is to analyze how Li-ion batteries can become a useful alternative to present VRLA. In this study, three different electrochemical battery technologies were investigated; two of the most appealing Li-ion chemistries, lithium iron phosphate (LFP) and lithium titanate oxide (LTO) were compared with lead acid batteries, in terms of their basics characteristics (e.g. capacity, internal resistance) and their dependence on the operating conditions.

Short term energy storage for grid support in wind power applications

The penetration of wind power into the power system has been increasing in the recent years. Therefore, a lot of concerns related to the reliable operation of the power system have been addressed. An attractive solution to minimize the limitations faced by the wind power grid integration, and thus to increase the power system stability and the energy quality, is to integrate energy storage devices into wind power plants. This paper gives an overview of the state-of-the-art short-term energy storage devices and presents several applications which can be provided by the energy storage device - wind power plant combined system. Moreover, two methods for estimating the remaining useful lifetime of the energy storage devices are presented.

Performance Degradation Tests of Phosphoric Acid Doped Polybenzimidazole Membrane Based High Temperature Polymer Electrolyte Membrane Fuel Cells

Degradation tests of two phosphoric acid (PA) doped polybenzimidazole (PBI) membrane based high temperature polymer electrolyte membrane (HT-PEM) fuel cells were reported in this paper to investigate the effects of start/stop and the presence of methanol in the fuel to the performance degradation. Continuous tests with H2 and simulated reformate which was composed of H2, water steam and methanol as the fuel were performed on both single cells. 12-h-startup/12-h-shutdown dynamic tests were performed on the first single cell with pure dry H2 as the fuel and on the second single cell with simulated reformate as the fuel. Along with the tests electrochemical techniques such as polarization curves and electrochemical impedance spectroscopy (EIS) were employed to study the degradation mechanisms of the fuel cells. Both single cells showed an increase in the performance in the H2 continuous tests, because of a decrease in the oxygen reduction reaction (ORR) kinetic resistance probably due to the redistribution of PA between the membrane and electrodes. EIS measurement of first fuel cell during the start/stop test showed that the mass transfer resistance and ohmic resistance increased which can be attributed to the corrosion of carbon support in the catalyst layer and degradation of the PBI membrane. During the continuous test with simulated reformate as the fuel the ORR kinetic resistance and mass transfer resistance of both single cells increased. The performance of the second single cell experienced a slight decrease during the start/stop test with simulated reformate as the fuel. [DOI: 10.1115/1.4029081]

Potential Usage of Thermoelectric Devicesin a High-Temperature Polymer ElectrolyteMembrane (PEM) Fuel Cell System: Two Case Studies

Methanol-fueled, high-temperature polymer electrolyte membrane fuel cell (HTPEMFC) power systems are promising as the next generation of vehicle engines, efficient and environmentally friendly. Currently, their performance still needs to be improved, and they still rely on a large Li-ion battery for system startup. In this article, to handle these two issues, the potential of thermoelectric (TE) devices applied in a HTPEMFC power system has been preliminarily evaluated. First, right after the fuel cell stack or the methanol reformer, thermoelectric generators (TEGs) are embedded inside a gas–liquid heat exchanger to form a heat recovery subsystem jointly for electricity production. It is calculated that the recovered power can increase the system efficiency and mitigate the dependence on Li-ion battery during system startup. To improve the TEG subsystem performance, a finite-difference model is then employed and two main parameters are identified. Second, TE coolers are integrated into the methanol steam reformer to regulate heat fluxes herein and improve the system dynamic performance. Similar modification is also done on the evaporator to improve its dynamic performance as well as to reduce the heat loss during system startup. The results demonstrate that the TE-assisted heat flux regulation and heat-loss reduction can also effectively help solve the abovementioned two issues. The preliminary analysis in this article shows that a TE device application inside HTPEMFC power systems is of great value and worthy of further study.

An Advanced HIL Simulation Battery Model for Battery Management System Testing

Developers and manufacturers of battery management systems (BMSs) require extensive testing of controller Hardware (HW) and Software (SW), such as analog front-end and performance of generated control code. In comparison with the tests conducted on real batteries, tests conducted on a state-of-the-art hardware-in-the-loop (HIL) simulator can be more cost and time effective, easier to reproduce, and safer beyond the normal range of operation, especially at early stages in the development process or during fault insertion. In this paper, an HIL simulation battery model is developed for purposes of BMS testing on a commercial HIL simulator. A multicell electrothermal Li-ion battery (LIB) model is integrated in a system-level simulation. Then, the LIB system model is converted to C code and run in real time with the HIL simulator. Finally, in order to demonstrate the capabilities of the setup, experimental results of BMS tests over a certain set of exemplary cases are shown.

Multi-Objective Control of Balancing Systems for Li-Ion Battery Packs: A Paradigm Shift?

While a great number of battery balancing circuit topologies have been proposed, the unique control objective typically pursued is equalization of single cell charge. However, a balancing circuit could offer potentially more control features, especially with topologies able to provide bidirectional power flow control. This has not been explored yet in literature or at least not with enough thoroughness. Thus, in addition to charge balancing, up to three more objectives could be pursued simultaneously. Firstly, virtual resistance control, in order to provide dynamic compensation for variations in terminal cell voltage. Secondly, thermal management, to achieve a more uniform temperature distribution within a battery pack. Third, on-board diagnosis or fault detection tools, e.g. to perform characterization tests or to identify and even isolate problematic cells. In this paper, this issue is discussed and evaluated for a battery pack made up of 48 large format Li-Ion cells in series in a e-mobility application. Simulation results demonstrate the technical feasibility of this newly defined concept.