Periodic Reporting for period 1 - IMPRESS (Integrated Modular Power Conversion for Renewable Energy Systems with Storage)
Okres sprawozdawczy: 2019-10-01 do 2021-09-30
The European Union’s (EU) renewable energy directive requires that at least 32% of its total energy needs must be supplied using renewables by 2030. The potential benefit of this directive is the reduction in greenhouse gas emissions and EUs decreased dependence on fossil fuel that often comes from foreign nations. To diminish dependency on external energy sources by using the local renewable energy resources to meet the energy demand in the EU is an important step. Such distributed power generation initiative will help stimulate the economy of the EU cities, lower the cost of energy, increase the renewable energy industries and provide energy security. This creates a strong need for energy sources that are spread across the city or a certain region yet well integrated with the main power grid.
The action investigates existing preeminent topologies for Distributed Renewable Energy Source with Storage (DRESS) and proposes a novel optimized arrangement for such integrated energy systems. An optimized control algorithm for the effective operation of the sources, PV and battery, within the modules integrated into the ac grid will be studied. Energy-efficient algorithms for the optimized operation of DRESS will be proposed considering various modes of operation. The existing performance monitoring and diagnostic methods in the modular inverters will be studied and a robust diagnostic method for integrated battery and PV unit will be developed to increase the availability of DRESS. The final application of this action will be to produce applicable robust distributed local energy systems using PV and storage to maximize energy generation and increase availability.
The action investigates existing preeminent topologies for Distributed Renewable Energy Source with Storage (DRESS) and proposes a novel optimized arrangement for such integrated energy systems. An optimized control algorithm for the effective operation of the sources, PV and battery, within the modules integrated into the ac grid will be studied. Energy-efficient algorithms for the optimized operation of DRESS will be proposed considering various modes of operation. The existing performance monitoring and diagnostic methods in the modular inverters will be studied and a robust diagnostic method for integrated battery and PV unit will be developed to increase the availability of DRESS. The final application of this action will be to produce applicable robust distributed local energy systems using PV and storage to maximize energy generation and increase availability.
In work package 1, the action has investigated the control of modular converters with a PV panel connected to each module. It is shown that the converter is capable of Maximum Power Point Tracking (MPPT) on each PV panel without the need for any additional hardware such as a dc-dc converter which is typically used for MPPT. On the PV panel level, the Levelized Cost of Energy (LCOE) and energy yield are studied when the Lithium-ion battery is integrated. In the traditional system the need for an additional power converter for battery energy management results in increased LCOE. Despite high performance, it is seen that such a system may not be economical. Therefore, a solution with high efficiency and lower LCOE is desired despite higher capital expenditure.
In work package 2, the action has investigated innovative ways of integrating PV panel and battery pack such that the need for the additional dc-dc converter is eliminated. Such a solution not only results in high efficiency in the range of 99-99.6% but the reduced cost due to the elimination of dc-dc converters leads to a reduction in LCOE. The aim of doing so is to achieve a scalable, high-efficiency integrated PV-battery solution with decreased LCOE compared to traditional solutions in the market despite higher CAPEX. At the same time, it is observed that the performance of the battery is also enhanced due to the inherent pulsation current through the battery cells.
In work package 3, the action has studied the close interaction between the pulsating current through the battery due to the new configuration. It was initially thought that the pulsed current produced by the proposed solution would improve the battery charging performance. However, this was not found to be true. Through experiment, it was observed that the degradation of the lithium-ion battery in case of pulsed current charging was lower when compared to the traditional charging method (constant current - constant voltage. The proposed solution inherently generated pulsed current. The improvement in the lifetime of the battery was higher than 20% and for the specific case, a 50% higher cycle life was observed for NMC batteries. Such an extension in the lifetime of the battery will prove to benefit applications such as photovoltaic systems in bringing the LCOE lower than the current state-of-the-art systems with Lithium-ion battery storage.
In work package 2, the action has investigated innovative ways of integrating PV panel and battery pack such that the need for the additional dc-dc converter is eliminated. Such a solution not only results in high efficiency in the range of 99-99.6% but the reduced cost due to the elimination of dc-dc converters leads to a reduction in LCOE. The aim of doing so is to achieve a scalable, high-efficiency integrated PV-battery solution with decreased LCOE compared to traditional solutions in the market despite higher CAPEX. At the same time, it is observed that the performance of the battery is also enhanced due to the inherent pulsation current through the battery cells.
In work package 3, the action has studied the close interaction between the pulsating current through the battery due to the new configuration. It was initially thought that the pulsed current produced by the proposed solution would improve the battery charging performance. However, this was not found to be true. Through experiment, it was observed that the degradation of the lithium-ion battery in case of pulsed current charging was lower when compared to the traditional charging method (constant current - constant voltage. The proposed solution inherently generated pulsed current. The improvement in the lifetime of the battery was higher than 20% and for the specific case, a 50% higher cycle life was observed for NMC batteries. Such an extension in the lifetime of the battery will prove to benefit applications such as photovoltaic systems in bringing the LCOE lower than the current state-of-the-art systems with Lithium-ion battery storage.
The proposed PV-battery solution eliminates the need for a dc-dc converter which is necessary for the current state-of-the-art power systems. The cell level control of the battery allows it to operate as a variable voltage source that can be precisely controlled. This solution acts as a converter as well as a battery management solution with active balancing. The expected result at the end of the project is a robust solution for localized power harvesting and storage solution. The action aims at validating a PV-battery solution that is scalable and can be conveniently used in residential and commercial PV power plants, electric vehicles, and in other applications such as space, maritime, etc. The large-scale adoption of the proposed solution has a high value in terms of achieving carbon neutrality. Furthermore, the cell level control of the battery unit allows monitoring the performance and aging of each cell. Resulting in reduced remanufacturing cost of the battery unit for second-life usage which leads to an improved circular economy.