다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

A review of computer tools for analysing the integration of renewable energy into various energy systems

Large-scale deployment of intermittent renewable energy (namely wind energy and solar PV) may entail new challenges in power systems and more volatility in power prices in liberalized electricity markets. Energy storage can diminish this imbalance, relieving the grid congestion, and promoting distributed generation. The economic implications of grid-scale electrical energy storage technologies are however obscure for the experts, power grid operators, regulators, and power producers. A meticulous techno-economic or cost-benefit analysis of electricity storage systems requires consistent, updated cost data and a holistic cost analysis framework. To this end, this study critically examines the existing literature in the analysis of life cycle costs of utility-scale electricity storage systems, providing an updated database for the cost elements (capital costs, operational and maintenance costs, and replacement costs). Moreover, life cycle costs and levelized cost of electricity delivered by electrical energy storage is analyzed, employing Monte Carlo method to consider uncertainties. The examined energy storage technologies include pumped hydropower storage, compressed air energy storage (CAES), flywheel, electrochemical batteries (e.g. lead–acid, NaS, Li-ion, and Ni–Cd), flow batteries (e.g. vanadium-redox), superconducting magnetic energy storage, supercapacitors, and hydrogen energy storage (power to gas technologies). The results illustrate the economy of different storage systems for three main applications: bulk energy storage, T&D support services, and frequency regulation.

Electrical energy storage systems: A comparative life cycle cost analysis

This paper reviews water electrolysis technologies for hydrogen production and also surveys the state of the art of water electrolysis integration with renewable energies. First, attention is paid to the thermodynamic and electrochemical processes to better understand how electrolysis cells work and how they can be combined to build big electrolysis modules. The electrolysis process and the characteristics, advantages, drawbacks, and challenges of the three main existing electrolysis technologies, namely alkaline, polymer electrolyte membrane, and solid oxide electrolyte, are then discussed. Current manufacturers and the main features of commercially available electrolyzers are extensively reviewed. Finally, the possible configurations allowing the integration of water electrolysis units with renewable energy sources in both autonomous and grid-connected systems are presented and some relevant demonstration projects are commented.

Hydrogen Production From Water Electrolysis: Current Status and Future Trends

This paper presents the latest comprehensive literature review of AC and DC microgrid (MG) systems in connection with distributed generation (DG) units using renewable energy sources (RESs), energy storage systems (ESS) and loads. A survey on the alternative DG units' configurations in the low voltage AC (LVAC) and DC (LVDC) distribution networks with several applications of microgrid systems in the viewpoint of the current and the future consumer equipments energy market is extensively discussed. Based on the economical, technical and environmental benefits of the renewable energy related DG units, a thorough comparison between the two types of microgrid systems is provided. The paper also investigates the feasibility, control and energy management strategies of the two microgrid systems relying on the most current research works. Finally, the generalized relay tripping currents are derived and the protection strategies in microgrid systems are addressed in detail. From this literature survey, it can be revealed that the AC and DC microgrid systems with multiconverter devices are intrinsically potential for the future energy systems to achieve reliability, efficiency and quality power supply.

AC-microgrids versus DC-microgrids with distributed energy resources: A review

Probabilistic Impact Assessment of Lightning Strikes on Power Systems Incorporating Lightning Protection Design and Asset Condition

This project is about the development and integration of a real-time network simulator in the laboratory using hardware in the loop (HIL) for the purpose of frequency regulation. Frequency regulation is done using the energy storage system (ESS) and a real-time network test bed developed in the smart energy laboratory in Newcastle University. An IEEE Test System was built in the OPAL-RT network simulator to mimic the power grid with renewable energy sources. The study demonstrates the viability of using an ESS to regulate the frequency under an increased penetration of renewable energy sources.

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Viability of using energy storage for frequency regulation on power grid

Guest Editorial: On the role of energy storage systems in the grid of the future: Selected papers from the 2019 UK Energy Storage Conference

High Voltage Direct Current (HVDC) interconnectors will help enable net-zero energy systems by transmitting renewable energy from where it is abundant to where it is needed. They may also contribute to balancing services, for which there will be increased demand due to the expanded fleet of renewable generation. However, increased and more flexible use of interconnectors, along with changes in generator locations as renewables displace fossil fuels, may lead to congestion on existing AC transmission systems. In this paper, a transmission network model is used to investigate whether power constraints will restrict the use of HVDC interconnectors for flexibility services. A method, demonstrated on the GB transmission network (which is expected to accommodate increased HVDC interconnector and renewable generation capacity as it transitions to net-zero), is presented which explores interconnector activity and identifies which AC network assets limit the capabilities of the HVDC interconnectors and how often. Results showed that the number of constraints met on the GB network, when the interconnectors were operating at all combinations of full import or full export, reduces in future years. Therefore, the current GB transmission network is suitable for effective use of the planned increased number of interconnectors. 

System stress with expanded use of interconnectors in the transition to net-zero

Mobile energy storage units are regarded as a critical flexibility resource in power distribution networks. In low-carbon energy systems, they can substitute mobile diesel generators as a back-up power source to small groups of customers after a widespread outage. In this context, this article presents a method for routing and dispatching of mobile storage units aimed at providing a resilient response to severe weather events combining multiple natural hazards in distribution grids. Focused on low voltage distribution network, it uses sources of information typically available in a smart grid and smart city context, such as geographic information systems, road surveillance systems, and smart meter data. Moreover, it represents the interdependence between power and transport infrastructures according to official transport analysis guidance, which determines average speed and travel times to the points of connection to out-of-service customers. The methodology is written as a mixed-integer programming formulation aimed at minimizing the energy not supplied over time subject to spatio-temporal and operating constraints. Furthermore, it is demonstrated in a realistic distribution network in the United Kingdom.

Phil Taylor

Papers

Probabilistic Impact Assessment of Lightning Strikes on Power Systems Incorporating Lightning Protection Design and Asset Condition

Viability of using energy storage for frequency regulation on power grid

Guest Editorial: On the role of energy storage systems in the grid of the future: Selected papers from the 2019 UK Energy Storage Conference

System stress with expanded use of interconnectors in the transition to net-zero

Routing and Dispatching of Mobile Storage Units for a Resilient Response to Severe Weather Events in Low Voltage Smart Grids