Ahmad Zahedi

Bio: Ahmad Zahedi is an academic researcher from James Cook University. The author has contributed to research in topics: Photovoltaic system & Grid parity. The author has an hindex of 17, co-authored 93 publications receiving 1385 citations. Previous affiliations of Ahmad Zahedi include Monash University, Clayton campus & Monash University.

Review of control strategies for voltage regulation of the smart distribution network with high penetration of renewable distributed generation

Abstract: Integration of renewable energy sources (RES) into traditional power system is one of the most viable technologies to meet the ever increasing energy demand efficiently. But, this technology arises a lot of challenges which are necessary to be taken care of for smooth operation of the network. Voltage regulation is the most significant technical challenge that tends to limit the amount of penetration of renewable distribution generators (DGs) into the distribution network. This paper attempts to present a detailed review of the control strategies that are being utilized to mitigate voltage regulation challenges when increased amount of renewable DGs are connected within the distribution network. This study analyses the direct impacts of increased accommodation of renewable DGs on the distribution network operation and evaluates current research status of voltage control strategies. Then qualitative analysis is performed for all kinds of voltage control approaches involving their pros and cons for the first time. The objective of this contribution is to present the latest research status of distribution system voltage control strategies with highly penetrated renewable DGs and a brief review of different control methodologies.

Maximizing solar PV energy penetration using energy storage technology

Abstract: Many countries around the world are considering using solar energy technologies in their future energy planning. The intermittency and unpredictability nature of solar power generation, which can influence the power quality and reliability of the power grid especially at large-scale solar energy systems, constitute a drawback for use of solar technology. Precise research and investigations are needed to overcome this weakness helping solar power be used in power network in large scale. The variation in sun radiation may lead to over-production of electricity from solar PV generators at one time, and lack of production to satisfy the energy demand at another time. As a result, solar PV systems demonstrate a low-level of reliability in power systems. However, an energy storage technology would play a significant role in increasing the reliability of solar power generation systems. The objectives of this study are: firstly to review the issues in relation to grid-integration of solar PV systems, secondly, to review a range of storage devices that could technically and economically be used in association with solar PV energy in order to increase the solar energy penetration level with appropriate reliability in weak electric systems, and finally to present a model for solar PV system combined with battery and super-capacitor.

A review of drivers, benefits, and challenges in integrating renewable energy sources into electricity grid

Abstract: Since the global warming and climate change are recognized as real concerns, attention of power system planners and operators, energy policy makers and regulators as well as developers around the world including Australia is focused on using alternative and low emission energy technologies for electric power production. Renewable energy and energy efficient technologies have many advantages including reducing climate change, increasing sustainability in power sector, and increasing security of power supply. This paper presents an overview on both current electricity grid and future grid. Experts believe that in future more distributed generation (DG) will be integrated into the low to medium electricity grid. This paper will also review the key drivers in relation to integration of increased DG technologies in general and the renewable energy-distributed generation (RE-DG) technologies in particular, into the electric power system and the opportunities and challenges linked to these technologies. This paper also reviews possible connection location of RE-DG into the grid and its impact on system voltage.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

A global review of energy consumption, CO2 emissions and policy in the residential sector (with an overview of the top ten CO2 emitting countries)

Abstract: Climate change and global warming as the main human societies’ threats are fundamentally associated with energy consumption and GHG emissions. The residential sector, representing 27% and 17% of global energy consumption and CO2 emissions, respectively, has a considerable role to mitigate global climate change. Ten countries, including China, the US, India, Russia, Japan, Germany, South Korea, Canada, Iran, and the UK, account for two-thirds of global CO2 emissions. Thus, these countries’ residential energy consumption and GHG emissions have direct, significant effects on the world environment. The aim of this paper is to review the status and current trends of energy consumption, CO2 emissions and energy policies in the residential sector, both globally and in those ten countries. It was found that global residential energy consumption grew by 14% from 2000 to 2011. Most of this increase has occurred in developing countries, where population, urbanization and economic growth have been the main driving factors. Among the ten studied countries, all of the developed ones have shown a promising trend of reduction in CO2 emissions, apart from the US and Japan, which showed a 4% rise. Globally, the residential energy market is dominated by traditional biomass (40% of the total) followed by electricity (21%) and natural gas (20%), but the total proportion of fossil fuels has decreased over the past decade. Energy policy plays a significant role in controlling energy consumption. Different energy policies, such as building energy codes, incentives, energy labels have been employed by countries. Those policies can be successful if they are enhanced by making them mandatory, targeting net-zero energy building, and increasing public awareness about new technologies. However, developing countries, such as China, India and Iran, still encounter with considerable growth in GHG emissions and energy consumption, which are mostly related to the absence of strong, efficient policy.

Redox flow batteries for the storage of renewable energy: A review

Abstract: The need for grid-connected energy storage systems will grow worldwide in the next future due to the expansion of intermittent renewable energy sources and the inherent request for services of power quality and energy management. Electrochemical storage systems will be a solution of choice in many applications because of their localization flexibility, efficiency, scalability, and other appealing features. Among them redox flow batteries (RFBs) exhibit very high potential for several reasons, including power/energy independent sizing, high efficiency, room temperature operation, and extremely long charge/discharge cycle life. RFB technologies make use of different metal ion couples as reacting species. The best-researched and already commercially exploited types are all-vanadium redox batteries, but several research programs on other redox couples are underway in a number of countries. These programs aim at achieving major improvements resulting in more compact and cheaper systems, which can take the technology to a real breakthrough in stationary grid-connected applications.

Battery energy storage system size determination in renewable energy systems: A review

Abstract: Renewable energy, such as hydro power, photovoltaics and wind turbines, has become the most widely applied solutions for addressing issues associated with oil depletion, increasing energy demand and anthropogenic global warming. Solar and wind energy are strongly dependent on weather resources with intermittent and fluctuating features. To filter these variabilities, battery energy storage systems have been broadly accepted as one of the potential solutions, with advantages such as fast response capability, sustained power delivery, and geographical independence. During the implementation of battery energy storage systems, one of the most crucial issues is to optimally determine the size of the battery for balancing the trade-off between the technical improvements brought by the battery and the additional overall cost. Numerous studies have been performed to optimise battery sizing for different renewable energy systems using a range of criteria and methods. This paper provides a comprehensive review of battery sizing criteria, methods and its applications in various renewable energy systems. The applications for storage systems have been categorised based on the specific renewable energy system that the battery storage will be a part. This is in contrast to previous studies where the battery sizing approaches were either arranged as an optimised component in renewable systems or only accounted for one category of renewable system. By taking this approach, it becomes clear that the critical metrics for battery sizing, and by extension the most suitable method for determining battery size, are determined by the type of renewable energy system application, as well as its size. This has important implications for the design process as the renewable energy system application will drive the battery energy storage system sizing methodology chosen.