Short-term Storage Devices Research Articles

Stochastic Algorithms for Controller Optimization of Grid Tied Hybrid AC/DC Microgrid with Multiple Renewable Sources

—The hybrid AC/DC microgrid (MG) configuration is efficient as it reduces the need for multiple power conversions and hence losses. Therefore, this paper focuses on the study of grid assisted hybrid AC/DC MG comprising of solar PV and fuel cell (FC) systems on DC subgrid with supercapacitor (SC) as the short term storage device and wind energy conversion system (WECS) on the AC subgrid. A comprehensive study of the operation of MG is performed under varying system conditions in MATLAB/Simulink software. The real and reactive power (PQ) control scheme is used to regulate the DC bus voltage and power flow between the subgrids. Genetic algorithm (GA), artificial bee colony (ABC) optimization, particle swarm optimization (PSO) and the PSO with new update mechanism (PSOd) are used to compute the optimum gain values of proportional-integral (PI) controller in the PQ control scheme. The SC bank effectively reduces the power stress on the subgrids of the proposed hybrid MG system during intermittent conditions of load and generation. In addition, a comparative study of the heuristic optimization techniques is presented in detail. The ABC algorithm is found to arrive at the best results in determining the optimal gains of PI controller

The future role of Power-to-Gas in the energy transition: Regional and local techno-economic analyses in Baden-Württemberg

This paper analyses the potential of the Power-to-Gas (PtG) concept in Baden-Württemberg (BW), south west Germany. A macroeconomic analysis shows that a cost-covering operation of PtG for hydrogen production is first possible under our assumptions in 2030. Previous model-based analyses for Germany identified locations, mainly in north-west Germany, where these plants could achieve these full load hours and thus be economical in the future energy system by 2040. Importantly, although some short-term storage devices (batteries) are installed in BW in this scenario, no PtG plants are seen at the level of the transport network. A more detailed analysis for BW at the municipality level develops residual load profiles for individual 110 kV transformers and municipalities. A very large increase in the residual load profiles in the north-east of Baden-Württemberg by 2040 is encountered, suggesting a requirement for network strengthening and local storage, including PtG, in this area. Four very different and representative model regions are further analysed, whereby only Aalen, a region with large wind potentials in the north east of BW, is identified as having significant potentials for PtG by 2040 (between 69 and 155 MWel). The current restrictions for injecting hydrogen into the gas network (2–10% by volume) mean that these PtG plants would have to incorporate a methanation step in order to upgrade and feed in SNG. The generation of SNG on a local level is therefore expected to be an option by about 2040, if the development of renewable energy generation proceeds as quickly as expected in the current energy-political scenario explored here. The existing CO2 sources for methanation are not located in the vicinity of the expected PtG plants, so that a CO2 separation from the air and/or a liquefied transport could be most economical. Further work is required to consider the local energy infrastructure, especially electrical and gas distribution networks.

Power Control modeling and Simulation of Hybrid Power System for Building Microgrid Connected Application

In this paper, we propose to study the possibility of using a photovoltaic system combined with a high speed micro-turbine. This hybrid system can work as stand-alone system or grid connected system as it will be a part of a micro-grid. Initially, we propose Matlab/Simulink dynamic models of photovoltaic, micro turbine systems and supercapacitor. Then, we carry out a simulation comparison of the two systems, this is, with supercapacitor and without supercapacitor bank. We show that supercapacitor bank as short-term storage device was necessary to reduce the fast fluctuation of power in the case of sensitive loads. It is verified the simulation results of Matlab/Simulink based hybrid power system represent the effectiveness of the suggested hybrid power system.

Picture archive and communication systems implementation in a community medicine practice.

In order to gain experience with vendor-supplied picture archive and communication system (PACS) products, a Vantage PACS from Lockheed-Martin was installed in a Mayo community medicine practice in Rochester. This practice produces about 45,000 radiology examinations annually. The PACS includes central long- and short-term storage devices, 10 image display workstations, and a dedicated high-speed image distribution network. Digital images are produced using two Fuji computed radiography readers. Custom worklists were created to facilitate efficient system usage. Currently, all radiographic examinations for this practice are acquired digitally, and interpreted and distributed using the PACS. Remote softcopy interpretation via PACS has decreased the turnaround time for both routine and urgent examinations, and has allowed subspecialty interpretation or consultation for pediatric examinations. These results have significantly improved the radiology component of this community medicine practice.