With the fast growth of renewable energy sources (RES), more and more uncertainties are involved and influencing the stable operation of power systems. Controlled islanding is the last measure to ...prevent power system blackouts, thus this paper aims to propose a novel model of system separation based on Online Coherency Identification and Adjustable Robust Optimization Programming (OCI-AROP) for minimizing load shedding considering the uncertainties of RES. First, Fuzzy C-Means (FCM) clustering method with F -statistics is utilized to identify the coherent generator groups with the frequency data measured by Phasor Measurement Units (PMUs). Then, the OCI-AROP model considering coherent group constraints, connectivity constraints and robustness constraints about RES are presented. Finally, the case studies on IEEE-39 bus system and WECC-179 bus system are employed to demonstrate the effectiveness of the proposed OCI-AROP model, and comparisons among the OCI-AROP model and the other models are also given to show its superiority.
The Canary Islands power systems face environmental, economic, and social sustainability challenges. They heavily rely on imported fossil fuel for electricity generation; this leads to an increase in ...the Cost of Electricity (COE) and CO2 emission; a reduction can be made by utilizing more renewable energy sources (RES). This paper presents a comprehensive techno-economic assessment of increasing the RES utilization in Tenerife and Gran Canaria. Results illustrate that the least-cost RES penetration in each island exceeds 60% compared to 18.8% and 15.5% today. This implies a potential 58% reduction in CO2 emission intensity. The additional RES integration decreases the COE by 23.0% and 25.3% in Tenerife and Gran Canaria, respectively. The impact of imposing CO2 emission penalties is explored, results show a slight increase in the optimal RES capacity. Electrical Interconnection between both islands is also investigated, it is found to increase the optimal aggregate RES penetration beyond 70%, reduce COE by 30.3% and lower CO2 emission by 70%, compared to the current situation. Finally, the results obtained can support decision-makers to establish policies to help transform the energy system in islands into a more sustainable and reliable system using RES, energy storage, and energy exchange between islands.
•The paper investigates increasing RES penetration in the Canary archipelago.•The COE is decreased in Tenerife and Gran Canaria even at high RES penetrations >70%.•Electrical interconnection improves the utilization of resources in both islands.•The optimal COE for interconnection is lower by 30% compared current situation.•CO2 emission are reduced by 70% with interconnection and 59% without interconnection.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study examines the impact of energy consumption and usage of fossil sources (e.g., oil, gas, coal), nuclear energy, and renewable energy on carbon dioxide (CO2) emission by considering the ...significance of the environmental degradation for countries as well as people. In this context, the top five countries that produce more than 50% of total CO2 in the world are examined. Besides, yearly data from 1965 to 2019 is used. Moreover, multivariate adaptive regression splines is applied for empirical analysis. The results indicate that (i) coefficients of determination (R2) of the best prediction models for the countries are above 99% that provide reliable results; (ii) energy consumption, coal consumption, nuclear energy, and renewable energy usage have an effect on the CO2 emission in some of these countries whereas not effective in some others; (iii) coal, oil, and natural gas consumption are the most significant indicators for the CO2 emission generally; (iv) the effects of the variables change according to different thresholds. Therefore, following a straightforward general approach for the countries in decreasing environmental degradation cannot be helpful. The results highlight the adverse effects of fossil fuels for the CO2 emission in high carbon producing countries. Policy proposals are also discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the modern scenario of smart-grids, the concept of virtual power plant (VPP) is undoubtedly a cornerstone for the smooth integration of renewable energy sources into existing energy systems with a ...high penetration level. A VPP is the aggregation of decentralized medium-scale power sources, including photovoltaic and wind power plants, combined heat and power units, as well as demand-responsive loads and storage systems, with a twofold objective. On one hand, VPP relieves the stability and dispatchability problems on the external smart grid since it can be operated on an individual basis, appearing as a single system on the whole. On the other hand, VPP improves flexibility coming from all the networked units and enable traders to enhance forecasting and trading programs of renewable energies. This paper proposes a novel distributed decentralized prediction method for the management of VPPs. The novelty of the proposed technique is to effectively combine the concepts of neural networks and machine learning with a distributed architecture that is suitable for the aggregation purposes of the VPP.
Thermal district networks are effective solutions to substitute fossil fuels with renewable energy sources for heating and cooling. Moreover, thermal networking of buildings allows energy efficiency ...to be further increased. The waste heat from cooling can be reused for heating in thermal district systems. Because of bidirectional energy flows between prosumers, thermal networks require new hydraulic concepts. In this work, we present a novel network topology for simultaneous heating and cooling: the reservoir network. The reservoir network is robust in operation due to hydraulic decoupling of transfer stations, integrates heat sources and heat sinks at various temperature levels and is flexible in terms of network expansion.
We used Modelica simulations to compare the new single-pipe reservoir network to a basecase double-pipe network, taking yearly demand profiles of different building types for heating and cooling. The electric energy consumed by the heat pumps and circulations pumps differs between the reservoir and base case networks by less than 1%. However, if the reservoir network is operated with constant instead of variable mass flow rate, the total electrical consumption can increase by 48% compared to the base case. As with any other network topology, the design and control of such networks is crucial to achieving energy efficient operation.
Investment costs for piping and trenching depend on the district layout and dimensioning of the network. If a ring layout is applied in a district, the reservoir network with its single-pipe configuration is more economical than other topologies. For a linear layout, the piping costs are slightly higher for the reservoir network than for the base case because of larger pipe diameters.
•Networks for simultaneous heating and cooling are a key technology to decarbonize cities and their suburbs.•The reservoir network enables simultaneous heating and cooling.•The reservoir network is more robust in operation than other typical network topologies.•The reservoir network enables modular network expansion.•The reservoir network potentially decreases piping and trenching costs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Energy management strategy is proposed for a hybrid pumped hydro-battery storage.•Optimal system sizing and sensitivity analysis are carried out.•Hybrid storage has electricity cost ...3.5 times lower compared to single storage.•Hybrid storage reduces curtailment by 290% compared to single storage.•Hybrid storage has smaller upper reservoir hence greater applicability potential.
The development of energy storage systems paves the way towards a high integration of renewable energy sources in the electricity generation sector. Considering above, this paper introduces a new energy management strategy to efficiently coordinate a hybrid energy storage system based on pumped hydro storage (long term bulk storage) with batteries (short term, more flexible). For the purpose of this analysis, hourly time series of irradiation, wind speed, temperature and real measured load (characteristic for farmstead) covering one year were gathered for the selected site in Algeria. The optimal size of the system is determined based on a multi-objective optimization using a grey wolf optimizer implemented in MATLAB software. The results indicate that the hybrid storage system enables achieving higher reliability at lower cost in comparison to a system with single storage technology. The use of hybrid storage also reduces the curtailment of renewable generation. Further findings reveal that the cost of an optimal energy supply system with 97.5% reliability is 0.162 €/kWh, 0.207 €/kWh and 1.462 €/kWh for hybrid storage, battery and pumped storage, respectively. However, sensitivity analysis shows that the optimal hybrid storage configuration is less resilient when changes in irradiation/temperature/load are considered. This indicates that special actions (upscale of installed power) must be undertaken to avoid lower performance of hybrid storage systems. In summary, the hybrid storage system seems to be better sized for consideration in optimized solar/wind conditions, but by avoiding oversizing they are less resilient to future potential changes in renewable energy availability.
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GEOZS, IJS, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Using Jansky Very Large Array data obtained from high-resolution observations at 5.5 GHz at multiple epochs in 2014 and 2019, we have detected a population of radio variables and transients in the ...radio-bright zone at the Galactic center. With observations covering a sky area of 180 arcmin2 at an angular resolution of 0 4, we report new detections of 110 Galactic center compact radio (GCCR) sources with a size of <1″. The flux densities of GCCR sources exceed 70 Jy, with at least 10 significance. Among these sources, 82 are variable or transient and 28 are nonvariable. About 10% of them are expected to be extragalactic background sources. We discuss the possible astrophysical nature of the detected sources. As compared to the Galactic disk (GD) population of normal pulsars (NPs) and millisecond pulsars (MSPs), a majority (80%) of the GCCR sources appear to fall within the high flux density tail of the pulsar distribution, as extrapolated from a sample of NPs in the GD. However, MSPs extrapolated from the GD population are too weak to have contributed significantly to the GCCR population that has been detected. We also cross-correlated the GCCR sources with X-ray sources in Chandra X-ray catalogs and found that 42 GCCR sources have candidate X-ray counterparts. Most of the GCCR sources having X-ray counterparts are likely to be associated with unresolved or slightly resolved radio jets launched from X-ray binaries with a compact object, either a black hole or a neutron star.
Achieving greenhouse gas reduction targets requires an increased share of renewable energy sources in todays energy systems. The spatial and temporal mismatch between electricity supply and consumers ...demand arising from fluctuating renewable electricity generation can be overcome by energy transport and storage. Here, one option is the Power-to-Gas concept. With this, hydrogen is produced by water electrolysis and can then be flexibly distributed and stored throughout the energy system. In this study, an optimization model is proposed that represents such an energy system as multiple interconnected nodes and which considers the systems time-dependent characteristics in terms of the integration of typical days and their chronological order. This methodology is applied to determine the cost-optimal design and operation of future energy systems for Power-to-Gas scenarios in Germany. In these scenarios, hydrogen is supplied to mobility and industry. Onshore wind turbines and hydrogen pipelines and underground storage facilities are considered for generation, transmission and storage. For all scenarios, a hydrogen cost below the current hydrogen retail price of 9.5 Euro/kg at German fueling stations is obtained. Additionally, the value of hydrogen storage in salt caverns is investigated by prohibiting their construction during optimization, which results in a cost increase of 1.5 Euro/kg.
•Energy system optimization model with a novel temporal discretization approach.•Multi-regional, hourly resolved Power-to-Gas scenarios are investigated.•Hydrogen costs stay below the current hydrogen fueling retail price in Germany.•Hydrogen storage in salt caverns is used as a seasonal storage option.•Salt caverns are of economic importance in Power-to-Gas scenarios.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
New techniques and approaches are constantly being introduced to analyze and enhance the transient stability of renewable energy-source-dominated power systems. This review article extensively ...discusses recent papers that have proposed novel and innovative techniques for analyzing and enhancing the renewable source-dominated power system’s transient stability. The inherent low-inertia characteristics of renewable energy sources combined with fast-acting power electronic devices pose new challenges in power systems. Different stability concerns exist for grid-following and subsequent grid-forming converter/inverter connections to power grids; hence, distinct solutions for enhancing the transient stability have been devised for each. Moreover, the fundamental concepts and characteristics of converter/inverter topologies are briefly discussed in this study. Recent discussions and reviews of analysis and enhancement techniques in transient stability could lead to new ways to solve problems in power systems that rely primarily on renewable energy sources.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this paper, a new configuration security framework is developed for reliability and resiliency improvement of distribution networks by the coordination of the securityconstraint unit commitment ...(SCUC) and mobile marine power sources (MMPSs) under both post-disaster and normal restoration operations. It is assumed that a MMPS contains nondispatchable distributed generators (DGs), e.g., photovoltaics (PV), as well as dispatchable DGs, e.g., gas turbines and diesel generators. A mixed-integer linear programming model is formulated for coordinating MMPSs and SCUC under both normal and extreme conditions (e.g., natural disasters, cyber and physical attacks). To better characterize the uncertainties in renewable generation and electric load, a deep learning gated recurrent unit is adopted to forecast the PV power output. The proposed model is tested on the IEEE 69-bus distribution network to validate the effectiveness and merits of MMPSs. Results show that the reliability and resiliency could be enhanced by using MMPSs within the network.
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