1,721,051 research outputs found
Challenges in load balance due to renewable energy sources penetration: The possible role of energy storage technologies relative to the Italian case
Full text linkWith the rapid growth of the electricity produced by RES (renewable energy sources), especially those highly variable and unprogrammable (e.g. wind and solar power), the need of energy system flexibility increases significantly. Since RES currently represent a significant fraction of the power supply, their variable nature poses challenges to power grid operation, such as RES curtail and loss in global efficiency of thermoelectric plants, since they are often operated at part-load as fluctuating back-up power. In particular, thermoelectric plants recently moved their role from base-load power to fluctuating back-up power. Such a cycling operation represents a less obvious effect of grid flexibility requirement due to RES penetration. Main effect is the increment of both energetic costs, due to reduced efficiency operation, and wear-and-tear costs. This aspect is deeply analysed in reference to the Italian electricity generation mix in the period 2008-2012. Moreover, the possible coupling of energy storage systems with thermoelectric plants is highlighted as an alternative solution respect to retrofitting of existing plants
Model predictive control application for a battery energy storage system in a wind power plant
No full textLately, high penetration of intermittent renewable energy sources into power systems requires, besides efficient technologies employment, developing adequate control strategies to improve their performance. Given that their operation flexibility is constrained by short timeframe of foresight, energy storage systems represent an attractive solution that can mitigate the natural variability of renewable power plants electricity output, providing therefore enhanced quality of supply. The nonlinearity and uncertainty governing wind energy conversion systems, which have the widest range of variation regarding their output, entail implementing appropriate control. This paper presents a simulation model for an application of model predictive control on managing the exploitation of a battery energy storage system in a wind energy power plant, aiming to overcome the inherent variability of the natural resource. The model used for simulation consists of a variable pitch wind turbine driving a permanent magnet synchronous generator, a high voltage battery and a power converter as generation/storage subsystem and a load fed by it. Simulations were performed using Matlab/Simulink programming environment and aimed to determine the structure of the controller regarding the number and nature of the signals (measured and not measured disturbances and outputs; manipulated variables) employed for control purposes. The results obtained show a stable behavior of the proposed configuration
Variability assessment of renewable energy sources based on power generation recordings
No full textReliability of renewable energy generation forecast became particularly important since its share denotes a constant growth in the global energy mix and the uncertainty of supply continuity resulting from this rises. Given the numerous geographic and meteorological factors that greatly influence the results of a more general probabilistic determination, an accurate prospect is hardly possible when enlarging the territory or the time span. Moreover, power systems disturbances and load variation, also unpredictable, overlap the inherent intermittency of renewable energy based plants electricity output, further complicating to obtain a satisfactory estimates. This paper aims to assess the variation trend of wind energy, photovoltaic, biomass and hydro energy based on momentary recording of power generation and demand for the last decade in Romania. First, the multiple variables influencing the recorded power generated by each source were identified and coefficient matrices determined by regression, for each day. Forwards, the cumulative probability of achieving a certain renewable energy share in meeting electricity demand for selected days is calculated after fitting the most suitable distribution. Results are presented for the minimum and maximum average electricity demand days, considered to be representatives in terms of system loading. Using the most recent registrations of system's electricity generation and demand, for 2017, the assessments are estimated dependences are evaluated. Available data processing and computational algorithms were developed in Matlab programming environment
Sustainable water-energy innovations for higher comfort of living in remote and rural areas from developing countries: From seawater to hydrogen through reversible Solid Oxide Cells
No full textAccess to affordable renewable energy and clean water are among the most prominent challenges humankind faces to ensure a non-discriminatory comfort of living. Innovation in system engineering meets with new energy carriers, enabling synergistic effects defined as “sector-coupling”. For instance, hydrogen and Reversible Solid Oxide Cells (rSOCs) are innovative technologies that yield multiple valuable effects. This paper evaluates the impact of such technology in novel PV-hybrid storage mini-grids with close access to seawater, achieving simultaneous renewable energy storage and seawater desalination thereby. The novel mini-grid operation is simulated in archetypal rural communities from developing countries (Sub-Saharan Africa) for 365 days of operation. The study encompasses three development scenarios in agreement with sustainability policies in force. The analysis of results allows finding the fittest mini-grid asset to achieve techno-economic optimization. A trade-off solution is identified with a critical reading of results in a future perspective: the Levelized Cost Of Electricity (LCOE) for a system with at least 70% renewables penetration is in the range of 0.29–0.43 €/kWh, while the rSOC runs with the only energy storage task. Moreover, the availability of seawater pushes LCOE below 0.20 €/kWh since it is also possible to benefit from the desalination function. This result aligns with the most economic mini-grid asset that can be implemented while embedding a significant energy performance increase
Assessment of additional aging on electric vehicles batteries in the framework of vehicle to building services
No full textThe energy transition implies a progressive loss in grids inertia. Energy storage systems can contribute to enhance the flexibility of electric systems, even if their penetration in the grid at the European level currently amounts to only a few percentage points of the overall generation capacity. In this framework, the use of electric vehicles (EVs) as multiple decentralized mobile energy storage when interconnected to a bidirectional charging column for performing Vehicle-to-X services is widely proposed. In this work, as pioneering approach, the additional aging of 50-kWh BEVs and 10-kWh PHEV batteries performing Vehicle-to-Building (V2B) operation is experimentally assessed in reference to a grid-connected renewable Micro-Grid (MG). A MG dynamic model including suitable stochastic real-time power management is developed to minimize i) the instantaneous grid power exchange and, ii) the PHEV power fluctuations. Simulations outcomes provide batteries State of Charge evolutions, subsequently implemented in the design of experiment to perform accelerated aging tests. Four 18,650 NMC Li-ion cells are tested over 9 equivalent years of operation. This allows to quantify the V2B additional degradation for the investigated case study. As results, State of Health (SoH) value achieves 84.8 % for the PHEV battery (compared to 95.8 % when V2B is not performed), while it stands at 92.9 % for the BEV (slightly lower than 95 % SoH for V2B absence). These outcomes could contribute to pave the way in the awareness of V2B impact on renewable-based Micro-Grids, while reducing stressful conditions on PHEV batteries that could yield to faster degradation
Economics of innovative high capacity-to-power energy storage technologies pointing at 100% renewable micro-grids
No full textIntermittency and unpredictability of variable renewable energy sources, as well as the mismatch between generation and users’ demand, are the major hurdles to overcome looking at 100% renewable grids. Energy storage (ES) technologies are the answer to this question, yet high market costs are still compared to market parity. For the possibility to decouple capacity and power, hence tailoring the energy storage features according to the main functions required, the solutions investigated are based on Vanadium Redox Flow Batteries (VRFBs) and Reversible Solid Oxide Cells (rSOC). In low interconnected micro-grids, the decoupled sizing of capacity and power is an essential feature to attain higher cost-effectiveness. Current metrics for the economics of renewable energy storage fail to a large extent in assessing the value of stored energy, especially when the power source is scarcely predictable. This paper presents improved techno-economic metrics to compare high capacity-to-power ES technologies for renewable-based micro-grids. The new metrics synthetically translates energy efficiency and quality of system integration into monetary terms, going beyond the classic definition of Levelized Cost of Electricity (LCOE). Then, they provide a tool to understand where the main causes of payback deferral stand. For the case-study analysed, different storage assets (VRFB, rSOC and hybrid rSOC) for installations in households featuring 25 kWh bulk capacity and 1.5 kW discharging power are evaluated. The LCOE is equal to 0.438€‧kWh−1, 0.739€‧kWh−1 and 0.769€‧kWh−1 for VRFB, rSOC and hybrid rSOC respectively. Yet, considering the unit of stored energy, the hybrid rSOC storage system is more convenient than the basic rSOC (2.05€‧kWh−1 versus 2.61€‧kWh−1), but far less cheap than VRFBs (0.560€‧kWh−1)
13X Ex-Cu zeolite performance characterization towards H2S removal for biogas use in molten carbonate fuel cells
No full textA 13X zeolite modified with Cu ions (13X Ex-Cu) by means of an innovative technique was employed as adsorbent for H2S removal from biogas, to obtain a desulfurized fuel suitable for molten carbonate fuel cell systems. Sorbent performance was characterized over a wide range of operating conditions typical of biogas mixtures (high H2S content - 200 and 1000 ppmv; CH4 (60%)/CO2 (40%) matrices) and compared to several conventional sorbents. A sensitivity performance analysis was conducted, varying parameters as space velocity, reactor temperature, gas matrix composition and particles size, finalized to identify the optimal conditions for the studied application.
13X Ex-Cu zeolite showed high potentiality for H2S uptake, specifically lowering space velocity, increasing reactor temperature and in presence of high methane concentration in the gas mixture, with adsorption capacity of 40 mg/g under specific and optimized conditions. By means of B.E.T. and XRD analyses, it was demonstrated that the obtained enhanced performance is due to the presence of a large amount of Cu2+ ions, guaranteed by the innovative synthesis procedure, able to realize an efficient physical-chemical adsorption mechanism
Study of the carbonation-calcination reaction applied to the hydrogen production from syngas
No full textIn the last years the interest in hydrogen as an energy carrier is significantly increased both for vehicle fuelling and stationary energy production by fuel cells. The benefits of a hydrogen energy policy are the reduction of the greenhouse effect and the centralization of the emission sources. Moreover, an improvement to the environmental benefits can be achieved if hydrogen is produced from renewable sources, as biomass.
The present study relates the development of an innovative system for hydrogen production and CO(2) capture starting from syngas. The plant is based on the carbonation and calcination reactions for CO(2) absorption and desorption, respectively. In the carbonation reactor also steam methane reforming and CO-shift take place to enhance the hydrogen production. By means of a thermodynamic analysis, the system has been optimized in terms of the amount of the hydrogen produced and its purity. Different syngas compositions have been tested. The results confirm the effectiveness of the system proposed, which provides 99% H(2) purity and zero CO(2) emission in the case of the syngas derived from Battelle Columbus Laboratories gasifier
Assessment Analysis of BEV/PHEV Recharge in a Residential Micro-Grid Based on Renewable Generation
No full textTo limit the climate change, a strong evolution on stationary renewable power production and transport sector is needed. More than 34 million of Battery Electric Vehicles (BEVs) and 13 million of Plug-in Electric Vehicles (PHEV) are expected to circulate in Europe by 2030. This negatively affects distribution lines during BEV/PHEV charge, especially in densely populated areas. A possible solution to enhance BEV/PHEV penetration without impact on grid stability is represented by Micro-Grids (MGs), including renewable production, local loads, and energy storage. In this work, a residential MG composed by a Photovoltaic (PV) power generation system, a local load including BEV/PHEV charge, and a Li-ion battery energy storage system is implemented to assess and compare the impact on grid energy independence introducing BEV and PHEV charging load. Four different scenarios are simulated, considering either BEV or PHEV charge, varying the installed PV power (i.e., 3 kWp and 6 kWp) and Li-ion battery nominal capacity (10–20 kWh). The results demonstrate that, in a MG integrating 6 kWp PV and 20 kWh battery, BEV and PHEV can be daily charged by PV energy for 23% and 68% respectively. Hence, enhancing PV installed power and energy storage capacity in the future residential MGs will be needed to avoid stability issues on distribution feeders, in the view of massive BEV penetration for pursuing the limit to global warming
Electrochemical Impedance Spectroscopy study on ammonia-fed Solid Oxide Fuel Cells
Full text linkThe use of ammonia as a fuel is one of the promising pathways to decarbonize the energy sector. When ammonia is converted into power in the so-called "Ammonia-to-Power", the most interesting technology is the Solid Oxide Fuel Cell (SOFC) that can operate directly with ammonia and reach high performance in terms of efficiency. SOFCs are a high-efficiency and, potentially, low-cost technology, but still suffer from degradation issues related to internal losses. An innovative experimental technique to evaluate losses evolution caused by degradation is electrical impedance spectroscopy (EIS), followed by measurement data post-processing through the Distribution of Relaxation Times (DRT) analysis. In this study, a single SOFC is studied with a combined EIS and DRT methodology, when operating with a gas mixture of hydrogen, nitrogen and ammonia. The results identify the contribution to DRT of fuel dilution and the internal ammonia decomposition reaction
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