Primary Reserve Research Articles

Improving the efficiency of acidic eluents for elution of Scandium from Lewatit® VP OC 1026 and TP 272 solvent impregnated ion exchange resins

Scandium is a strategic element with exceptional applications however, its widespread application has been limited mainly due to its high price which itself originates from lack of enriched primary reserves. Mineralized waste materials and mine tailings collected from various mining activities often contain low amounts of Sc and rare earth elements (REE), along with much higher levels of contaminants such as Si, Fe and Al. Ion exchange resins, especially phosphorus containing solvent impregnated ones, show extremely high selectivity for quantitative adsorption of Sc from pregnant leach solutions. However, efficient and economical elution of Sc from these types of resins is still a challenge. In this study, a series of water miscible organic solvents including methanol, ethanol, 1-propanol, 2-propanol and acetone are explored with sulfuric acid in elution of Sc at room temperature (25 °C). With the proposed binary solvent system in this study, 98% of the adsorbed Sc was eluted from VP OC 1026 (impregnated with D2EHPA) with 4 M H2SO4 in 50 vol.% 1-propanol while negligible amount of Sc could be recovered with 2 M H2SO4 even at high temperatures. Also, exceeding 97% of the loaded Sc on TP 272 (impregnated with Cyanex 272) could be successfully eluted with 6 M H2SO4 containing 50 vol.% 2-Propanol. Nevertheless, the elution efficiency of Sc from TP 272 was notably constrained, falling below 20 %, when 2 M H2SO4 was employed as the eluent. The added organic solvents also significantly increased the performance of H2SO4 in elution of Sc from the resins in columns. The addition of just 10 vol.% 2-propanol to 2 M H2SO4 led to significant increase in the elution of Sc from TP 272. The maximum concentration of Sc in the eluted fractions increased by over threefold, going from 167.0 mg/L to 532.6 mg/L, when compared to using 2 M H2SO4 under similar elution conditions.

ტრიფინის პარადოქსი ოცდამეერთე საუკუნეში

This article presents a fresh perspective on the Triffin Paradox, a concept introduced by economist Robert Triffin in the mid-20th century that continues to have a significant impact on global financial systems and policies. Despite the passage of time and the evolution of the economy, the fundamental principles of the Triffin Paradox remain relevant in today's financial discussions. The paper provides a thorough analysis of the ongoing relevance of the Triffin Paradox in the modern global economy. It draws upon historical context, theoretical frameworks, and empirical evidence to shed light on how the paradox continues to manifest itself in the current financial landscape. Specifically, it explores how the dominance of the U.S. dollar as the world's primary reserve currency perpetuates structural imbalances and systemic vulnerabilities, echoing the concerns raised by Triffin. Moreover, the paper delves into the implications of the Triffin Paradox for various stakeholders, including policymakers and central banks. It examines the challenges posed by the pursuit of domestic monetary policy objectives in an interconnected world, where the stability of the global financial system relies heavily on the stability of the reserve currency issuer. Additionally, the paper explores potential strategies for mitigating the risks associated with the Triffin Paradox and fostering a more sustainable international monetary order. By integrating insights from economics, finance, and international relations, this paper contributes to a deeper understanding of the Triffin Paradox and its enduring significance in shaping contemporary financial dynamics. It emphasizes the need for policymakers and stakeholders to address the inherent structural tensions in the global monetary system, with the goal of promoting financial stability, economic resilience, and inclusive prosperity worldwide.

"Proud, brave, and tough": women in the Canadian combat arms.

Canada's defence policy, Strong, Secure, Engaged, emphasizes the importance of leveraging Canada's diversity to strengthen the Canadian Armed Forces. Currently, women in the Canadian military are underrepresented across most elements and occupations, especially in the combat arms occupations, including among officers and non-commissioned personnel in combat units such as infantry, armored corps, artillery, and combat engineering. Research suggests that the benefits associated with the inclusion of women in combat arms occupations include an increase in collective intelligence, operational effectiveness, task cohesion, and diversity. This article explores the gender gap in the Canadian combat arms by examining the findings from two recent qualitative research studies on the perceptions of women in the Regular Force and Primary Reserve. The authors analyze female military personnel's perceptions of women serving in the combat arms, and the ways to increase their inclusion in the military. The key findings reveal the following themes on women's perceptions of servicewomen in the combat arms: great job for those who want it; challenging environment (e.g., working within a masculinized culture, necessary toughness, tokenism and the "pink list," being treated differently, and family loyalty); unique challenges faced by women in combat roles; combat takes a toll on women's mental and physical health; and benefits of women's participation in multinational operations. The discussion highlights the need to increase diversity, equity, and inclusion, promote a culture change that fosters greater inclusion of women in the combat arms, and increase operational effectiveness through training and policies.

Understanding the role of storage reserve mobilization during seed germination and initial seedling growth in species of the genus Carapa

A physiological and metabolic database for various species of Amazonian plants is crucial to the species selection and sustainable utilization of their diversity. We hypothesized that understanding the mobilization of Carapa seed reserves and water uptake during germination could provide insights into the physiological behavior and propagation to differentiate species of the same genus. Given this, the mobilization mechanisms of primary reserves, water uptake, and enzymatic activities in seeds of two species of Carapa (C. guianensis and C. vasquezii) were investigated. The lipid content was high in both species, with a value of 63.7±4.7% for C. guianensis and 55±1.5% for C. vasquezii. C. guianensis showed higher values for the other evaluated reserves. The protein profile highlights a band between 15 and 25 kDa in C. guianensis. As for the enzymatic activities investigated (lipase, amylase, protease, acid phosphatase), C. guianensis showed greater activity for most of them, except for acid phosphatase. Overall, the species showed different metabolic strategies and dynamics regarding the water uptake and use of reserves. Our findings indicate that distinct metabolic pathways are employed during the germination and initial seedling growth stages of two Carapa species. This trait can potentially guide the use and preservation of these species.

Thermal energy storage integration for increased flexibility of a power plant with post-combustion CO2 capture

Flexible operation of thermal power plants will become increasingly relevant in the coming years. This work evaluates the effect of integrating a steam accumulator into a 598 MW supercritical coal-fired power plant with moving bed temperature-swing adsorption CO2 capture. Charging the accumulator with reheat steam from the turbine train can reduce the net power output by up to 1.4 % (8.2 MW) for around 200 min. Small charging flow rates are recommended to maximize the final pressure of the accumulator. Covering the sorbent regeneration duty and meeting the demand of two feedwater heaters were considered as alternatives for discharging of the accumulator. Thermal storage discharging was found to give relative power plant load increases between 1.7 and 11.2 % (10.2–66.9 MW) for up to 37.5 min, which exceeds the requirement for primary reserve. Increases in the electrical energy output of 10.5–11 MWh were achieved. The flexibility modes studied in this work are compatible with high CO2 recovery rates.

Unveiling the Thirst: Revealing the Water Requirements of Gujrat's Thriving Crops using CROPWAT 8.0

Water plays an essential role in agriculture, serving as a primary reserve that directly impacts crop production and food security. Water conservation is critical for sustainable agriculture and the well-being of communities and ecosystems, chiefly due to the increasing global demand and rising water dearth concerns. The water needs of crops and irrigation scheduling in the district Gujrat, Pakistan, are currently missing enough information. Therefore, this study was conducted to determine the crop water requirements and establish irrigation schedules for the major crops in district Gujrat, Pakistan. The crop water requirement (CWR) and irrigation schedules were determined by CROPWAT 8.0 by using the input climate data obtained from the POWER-NASA website from 1991-2020. Other than climatic data, crops (wheat, rice, sugarcane, and maize) and soil information were added from CROPWAT 8.0 pre-existing data. The crop planting dates were estimated by Ayub Agriculture Research Institute (AARI). The gross and net crop water requirements are 624.3 mm and 491.3 mm for wheat, 1805.2 mm and 1768.3 mm for rice, 4135.1 mm and 3537.2 mm for sugarcane, and 1203.5 mm and 1051.4 mm for maize. The deployment of CROPWAT 8.0 proves to be valuable in precisely assessing crop water requirements and computing irrigation scheduling. The study's outcomes show the potential to boost food production and aid in well-organized water reserve management.

Understanding the Crystal Chemistry of Phosphate Cathode Materials

Thermal batteries are primary reserve batteries that can achieve high power output in a short period of time by melting an insulating salt electrolyte with a pyrotechnic heat source and converting it into a highly conductive eutectic salt electrolyte. The thermal battery exhibits no self-discharge before activation, and the initial capacity of the thermal battery is maintained after long-term storage. Thermal batteries are an attractive option for emergency power supplies in aircraft, ejector seats, space landings and helicopters due to their outstanding robustness, high reliability, and long-term storage properties.FeS2 or CoS2 are the most common cathode materials for thermal batteries.1 However, their high cost and relatively low discharge voltage makes it desirable to find new materials that have higher voltage discharges, higher specific capacities, low cost and that are environmentally friendly. Polyanion cathode materials have attracted much attention in the field of both Li-ion and Na-ion batteries,2–4 as they can be regarded as low-cost materials and environmentally friendly. However, to the best of our knowledge, there have been no studies on polyanion cathode materials for thermal batteries. These materials are formed by tetrahedral units (XO4)n- (X = P, S, Si or B) bonded to MO6 polyhedra (M = transition metal). The tetrahedral anion presents a very strong covalent bond between X-O, giving rise to higher voltages versus Li+/Li or Na+/Na via the inductive effect and their very stable framework and open structure facilitates ion diffusion. Thus, polyanion materials present high structural stability and enable the tuning of the operating potential, making them an excellent choice for developing new cathode materials for thermal batteries. Here we report some of our latest work on the synthesis, structure and electrochemistry of polyanionic cathode materials for thermal batteries. 1 R. Li, W. Guo and Y. Qian, Front. Chem., 2022, in press, doi: 10.3389/fchem.2022.832972 2 Z. Gong and Y. Yang, Energy Environ. Sci., 2011, 4, 3223–3242. 3 C. Masquelier and L. Croguennec, Chem. Rev., 2013, 113, 6552–6591. 4 Q. Ni, Y. Bai, F. Wu and C. Wu, Adv. Sci., 2017, 4, 1600275.

Primary frequency control by fuzzy-based participation controller for plug-in electric vehicles

ABSTRACT The increasing penetration level of electric vehicles (EVs) shows that they will enter into the category of distributed energy sources in the near future. Major upgradation is required in the conventional power system to handle upcoming challenges due to electrification in the transportation sector and generate opportunities for the power system. The energy storage capability of batteries and advancement in fast switching converters enable EVs to support the grid with different ancillary services, e.g. primary frequency control (PFC). However, an effective charging strategy/controller is required to support the grid with PFC without violating constraints from grid and EVs. This paper proposes a novel fuzzy-based controller to decide EV’s availability for PFC with an optimized participation level considering different operational modes and EV charging demand. The controller computes the participation level of EVs based on real-time inputs from EVs, magnitude of frequency deviation and availability of primary reserve. The Spanish power system model has been employed to show the proposed controller’s efficacy and compare it with other recently reported controllers. The MATLAB/Simulink platform has been used to perform frequency and power response analysis for four different defined cases. Results show that EVs with the proposed fuzzy-based controller can effectively support the grid with PFC service without violating the grid’s and EV’s limits.

A prototype recuperated supercritical co2 cycle: Part-load and dynamic assessment

High efficiency, flexibility and competitive capital costs make supercritical CO2 (sCO2) systems a promising technology for renewable power generation in a low carbon energy scenario. Recently, innovative supercritical systems have been studied in the literature and proposed by DOE-NETL (STEP project) and by a few projects in the EU Horizon 2020 (H2020) program aiming to demonstrate supercritical CO2 Brayton power plants, promising superior techno-economic features than steam cycles particularly at high temperatures.The H2020 SOLARSCO2OL project, which started in 2020, is building the first European MW-scale sCO2 demonstration plant and has been specifically tailored for Concentrating Solar Power (CSP) applications. After a detailed explanation of the modelling approach for steady and unsteady cycle simulations, this paper presents the off-design and dynamic analysis of such plant layout, which is based on a simply recuperated sCO2 cycle. The entire system model has been developed in TRANSEO environment. The part-load analysis ranged from 50% of nominal up to a 105% peak load, discussing the impact on compressor and turbine operating conditions. Full operational envelop has been determined considering cycle main constraints, such as maximum turbine inlet temperature and minimum pressure at compressor inlet.The off-design performance analysis highlights the most relevant relationships among the main part-load regulating parameters, namely molten salt mass flow rate, CO2 mass flow rate, total CO2 mass in the loop, and shaft line speed. The results show specific features of different control approaches, discussing the pros and cons of each solution, considering also its upscale towards commercial applications. In particular, the analysis shows that at 51% of load an efficiency decrease of 20% is expected. Finally, the dynamic characterization of the closed loop shows the relatively fast responsiveness of the plant to compressor speed variations, causing quick changes in CO2 mass flow rate, together with longer time scale phenomena related to the plant heat exchangers. In this respect, sCO2 plants demonstrate to have the potential to provide primary reserve for the electrical grid, as far as thermal stresses on main plant components are kept under acceptable limits.

Modeling the impact of nickel recycling from batteries on nickel demand during vehicle electrification in China from 2010 to 2050

China is promoting the production and use of electric vehicles (EVs) to achieve carbon neutrality. However, the shift will drive higher demand and tighter supply of nickel in China. We develop a stock–driven bottom–up dynamic substance flow analysis (SFA) model to simulate the demand trends of various EVs under 3 scenarios, the flow of nickel under 9 scenarios and the amount of recoverable nickel under 27 scenarios in China's EV industry from 2010 to 2050. The results indicate that China's current production capacity and primary reserves of nickel cannot meet the growing nickel demand, especially under the High EVs–LNCT scenarios, and closed–loop nickel recovery from EV batteries can effectively alleviate the demand–supply contradiction. In different scenarios, the annual recycling nickel could cover between 67.7 % and 96.6 % of the demand for EV batteries in 2050, and between 37.9 % and 58.1 % in terms of the cumulative quantity by 2050. When the low nickel battery technology is adopted and the recovery efficiency is rapidly improved, the recovered nickel would meet the demand for EV batteries to the highest degree. Therefore, sufficient attention should be paid to low–nickel battery technology and efficient recycling of spent EV batteries, which is of great significance to ensure the development of EV industry and the availability of nickel in China.

A system-level thermal-electrochemical coupled model for evaluating the activation process of thermal batteries

As the primary reserve batteries widely used in military domain, the intricate thermal-electrochemical behaviors and tiny time scale of the activation process make the development of thermal batteries a pain-stacking work, as lacking of the precise model to guide the design process. In this study, a system-level thermal-electrochemical model for evaluating the main technical indexes of LiSi/FeS2 thermal batteries during activation stage is built, which comprehensively considers the main physical and chemical processes such as combustion, heat transfer, phase change, ion transport, voltage variation and so on. The activation characteristics of two types of 5-cell thermal batteries are predicted by this model, and the activation voltages of the two batteries are tested to validate the model. The model possesses the high precision with error less than 5 % by comparing the simulation results of activation voltage with that of experiment results. Specifically, the model reveals that the instantaneous temperature of pyrotechnic pellet after combustion is around 1570 K, and the electrolyte becomes molten and its internal resistance sharply decreases to mΩ level when the temperature reaches its melting point. The variation process of activation voltage is mainly dominated by the geometry size of cell stack and the thickness ratio of pyrotechnic pellet to single cell, besides, the activation time can be considered to be the peak value time of activation voltage. Fuse strip has important effects on the activation process of thermal batteries, especially in the rapid increase period of activation voltage, and the heat transfer is the time-limited step of the activation process. The difference of internal resistance between the unactivated state and activated state of thermal batteries can reach 12 orders of magnitude. These results indicate that our model can perform well in evaluating the activation process of thermal batteries and guiding the optimal design.

Al2O3 nanoparticles modified the FeS2 cathode to boost the interface wettability and electrochemical performance for thermal batteries

Thermal batteries are widely employed as the primary reserve batteries due to their high energy density and long shelf lifespan. FeS2 is the most studied and promising cathode material of thermal batteries at present because of its abundant stock and superior electrochemical performance. However, the FeS2 cathode is limited by low discharge capacity, big polarization, and security issues during discharge process. Herein, the improved electrochemical performance is achieved by increasing the interface wettability between cathode and electrolyte, in which the FeS2 cathode has modified by Al2O3 (FeS2@Al2O3) nanoparticles. The good wettability of the solid-liquid interface suppresses the overflow of electrolytes, and the discharge capacity of thermal batteries by using FeS2@Al2O3 cathode is 341.3 mAh·g−1, which is higher than that of pure FeS2 cathode (319.7 mAh·g−1). Significantly, this work provides a novel idea for modifying cathode material for comprehensive performance and safe thermal batteries in practical engineering applications.

Metabolic reserves of diapausing western cherry fruit fly (Diptera: Tephritidae) pupae in relation to chill duration and post-chill rearing conditions.

How different macronutrients are utilized at various stages of pupal diapause and the effects of winter length on nutrient reserves remain poorly studied for most insects. Western cherry fruit fly, Rhagoletis indifferens (Diptera: Tephritidae), is a specialist on cherries in higher latitudes or elevations in western North America that exhibits a obligate pupal diapause requiring chilling before adult development can occur. We determined the relationship between metabolic reserves and diapause status in R. indifferens pupae, testing the hypotheses that lipids are the primary reserves utilized during diapause and that long periods of warmth deplete these reserves more than periods of cold. Effects of 0- to 20-week durations at 3°C and subsequent exposure to 23°C and 16:8 L:D (warm rearing conditions) for 0 to 7 weeks on lipid, protein, soluble carbohydrates, and glycogen reserves of R. indifferens pupae were determined. During diapause, lipid reserves were the primary source of energy utilized by R. indifferens, while protein and soluble carbohydrates levels were stable throughout diapause and thus less utilized. At post-diapause, glycogen levels fluctuated the most, indicating that lipid reserves were utilized to produce glycogen to support metabolism for adult fly development. Unchilled pupae did not deplete lipid reserves, unlike chilled pupae, likely because unchilled pupae remained in diapause. Rhagoletis indifferens may have evolved a nutrient utilization strategy typical of rigid diapausing insects in higher latitude environments.

Estimation of Internal Rate of Return for Battery Storage Systems with Parallel Revenue Streams: Cycle-Cost vs. Multi-Objective Optimisation Approach

This paper assesses the profitability of battery storage systems (BSS) by focusing on the internal rate of return (IRR) as a profitability measure which offers advantages over other frequently used measures, most notably the net present value (NPV). Furthermore, this study proposes a multi-objective optimisation (MOO) approach to IRR estimation instead of relying on the simple linear optimisation and compares the results to the popular linear optimisation with battery cycle-cost penalty. The analysis is conducted under perfect foresight conditions by considering multiple revenue streams: arbitrage trading in the day-ahead and intraday markets, peak shaving, participating in the primary reserves market, and from photovoltaic (PV) power-generation unit. Data are collected for the German power market for 2017 and 2021. The results show that MOO approach yields similar IRR estimates to the cycle-cost model in 2017. However, higher market volatility and increased electricity prices in 2021 resulted in tangible differences. The analysis shows that, if such conditions are coupled with a low battery capacity price, the MOO method significantly outperforms the cycle-cost model. The effects of battery calendar lifetime and state of charge which decrease profitability are also considered. Nevertheless, a noticeable rise in profitability in 2021 relative to 2017 could provide enough compensation to address the issue of relatively poor viability track record.

Bidding a Battery on Electricity Markets and Minimizing Battery Aging Costs: A Reinforcement Learning Approach

Battery storage is emerging as a key component of intelligent green electricitiy systems. The battery is monetized through market participation, which usually involves bidding. Bidding is a multi-objective optimization problem, involving targets such as maximizing market compensation and minimizing penalties for failing to provide the service and costs for battery aging. In this article, battery participation is investigated on primary frequency reserve markets. Reinforcement learning is applied for the optimization. In previous research, only simplified formulations of battery aging have been used in the reinforcement learning formulation, so it is unclear how the optimizer would perform with a real battery. In this article, a physics-based battery aging model is used to assess the aging. The contribution of this article is a methodology involving a realistic battery simulation to assess the performance of the trained RL agent with respect to battery aging in order to inform the selection of the weighting of the aging term in the RL reward formula. The RL agent performs day-ahead bidding on the Finnish Frequency Containment Reserves for Normal Operation market, with the objective of maximizing market compensation, minimizing market penalties and minimizing aging costs.

Comparative small-signal evaluation of advanced grid-forming control techniques

This paper presents the small-signal modelling and analysis of the most recent grid-forming control techniques, namely the matching control (MC) and the dispatchable virtual oscillator (dVOC). These are compared to more classical SME techniques such as synchronverters (SV) and voltage-controlled virtual synchronous machines (VCVSM) under different grid conditions. In addition to studying the time-domain response (inertial behaviour, steady-state operation point, etc.), a thorough evaluation of the dominant eigenvalues of each control is carried out by obtaining the participation factors and the sensitivity to physical and control parameter variations. Simulation results are obtained for a grid-forming converter connected to a dynamic grid model that emulates different properties of low-inertia power systems—e.g. primary reserve, inertial strength, coupling strength, etc. Besides, hardware-in-the-loop experimental results are presented to validate the analysis.

Multi-stage resilience scheduling of electricity-gas integrated energy system with multi-level decentralized reserve

Extreme events pose threats to secure and consistent supply of electricity-gas integrated energy system (EGIES), and adequate resilience is essential for improving risk defense abilities. Considering the constraints of power distribution network (PDN) and natural gas system (NGS), a multi-stage strategy integrating multi-level decentralized reserve is proposed for resilience enhancement in EGIES. Storages of multi-area community integrated energy systems (CIESs) serve as the secondary reserve while the primary reserve, i.e., independent electric power/natural gas system, fails to meet reserve requirements. Furthermore, the thermal storage of building air on the consumption side is taken as the tertiary reserve, so as to obtain a better emergency response effect. The scheduling framework consists of reserve calculation, economic scheduling, and fault restoration. On the basis of multi-area reserve calculation, day-ahead economic scheduling is conducted, maintaining adequate reserve with consideration of decentralized reserve constraints; thus, high-priority demands can be recovered in case of supply disruptions. In addition, the flexible topology of PDN is utilized to facilitate the restored loads by optimal islanding partition. Via conic relaxation conversion, the original nonconvex model is tracked into a unified mixed-integer second-order cone programming (MISOCP) formulation, which can be effectively and accurately solved. Finally, numerical study on a modified IEEE 33-bus test system and a modified 7-node gas system connecting multiple community integrated energy systems shows the effectiveness of the proposed resilience strategy.

Sustainable valorization of semiconductor industry tantalum scrap using non-hazardous HF substitute lixiviant

Global tantalum production from mines averages 1800 tons per year and hardly increases, but demand for tantalum in the electronics industry consistently increasing. Globally, 50% of total tantalum produced is being used for tantalum capacitors manufacturing, almost all demand from various industries is mainly met by primary resources only. Tantalum production and supply predominantly dominated by Congo and Rwanda which accounts for > 50%, add disadvantages for the strategic and economic competitiveness of other nations. To address the monopoly dominated by Congo and Rwanda, and the disparity of tantalum primary reserve, exploitation of secondary resources can alternatively address the drawbacks of primary resource distribution. Currently, hardly < 1% of tantalum getting recycled, and the poor recycling rate of tantalum is mainly contributed by the lack of efficient and sustainable valorization technology for recycling tantalum-bearing scraps like electronic capacitors and semiconductor industry tantalum scrap. In the current investigation, a sustainable tantalum extraction process from scrap dominated by hydrometallurgical route has been developed. Tantalum scrap which is passive to leach for tantalum recovery was calcinated for oxidation of TaN content and followed by tantalum has been leached using a mixture of NaF and HCl, a specially developed novel lixiviant for the purpose as an HF substituent. Calcination process parameter like temperature and time requirement for oxidation was optimized varying one parameter at a time. Then, the efficient leaching condition was optimized for quantitative leaching of tantalum. The process can achieve 99.99% efficient leaching, the process can successfully be applied for feasible industrial-scale tantalum scrap recycling. The HF substituent lixiviant can add advantages to overcome occupational and industrial operation safety challenges associated with HF lixiviant. The reported valorization process can be a sustainable tantalum recycling process that simultaneously can address UNO sustainable development goal, WEEE directive, and UNEP E-Waste Management goal.

Dynamic wake analysis of a wind turbine providing frequency support services

The participation of wind farms in providing ancillary services is an asset for the power system and one way to maintain a strong grid with the increasing penetration of renewable energy sources. Research has shown this to be feasible for wind farms by using efficient prediction and sophisticated control systems. In some parts of the world, strict grid codes are already being implemented that require wind farms to provide ancillary services. Moreover, the primary reserve market in Europe is moving towards shorter procurement periods, providing wind farms an opportunity to more efficiently optimise their resources based on short term forecasts. It can however be challenging for the wind farms to efficiently participate in grid frequency support services, especially for primary reserve services. The reason behind this is the requirement of quick activation and deactivation of power reserve margin for services such as Frequency Containment Reserve (FCR) and Fast Frequency Response (FFR). A full activation of the contracted reserve is required within seconds of a grid frequency dip. A sudden change in wind turbine dynamics is expected to have an impact on the wake behind the wind turbine. The wake effect within a wind farm is taken into thorough consideration in its design process. The effect on the wake due to the wind turbines participating in fast response ancillary services however, remains unexplored. This is a matter of greater concern for wind farms with a high capacity density. To this end, the main contribution of this article is to observe the effect of ancillary service based control system on the wake effect of a wind turbine. Additionally, the capability of developed wind turbines controllers to follow primary reserve services are also tested. FFR and FCR services are tested for a range of frequency designs, these include both synthetic and actual grid frequencies. The synthetic frequency profiles are designed to replicate both fast and slow frequency variations in order to analyse the impact on wake behaviour. The simulations are performed for low and high wind speed including constant as well as turbulent winds.

Reserve-Constrained Unit Commitment Considering Adjustable-Speed Pumped-Storage Hydropower and Its Economic Effect in Korean Power System

The Korean government has declared the goal of net-zero-carbon emissions with a focus on renewable energy expansion. However, a high proportion of baseload generators and an increasing proportion of variable renewable energy (VRE) may cause problems in the power system operation owing to the low cycling capability of baseload generators and variability of VRE. To maintain system reliability, the government is planning to construct pumped-storage hydropower (PSH) plants, which can provide flexibility to the system. This study evaluated the operating cost savings obtained by different types of PSH: the adjustable-speed PSH (AS-PSH) and fixed-speed PSH (FS-PSH), based on the duck-curve phenomenon and the increase in spinning reserve requirement. In this study, the reserve-constrained unit commitment was formulated using a mixed-integer-programming considering the operational characteristics of AS-PSH and conventional generators. To consider the duck-shaped net-load environment, the projected VRE output data were calculated through physical models of wind turbines and photovoltaic modules. The operating costs for the non-PSH, FS-PSH, and AS-PSH construction scenarios were KRW 43,129.38, 40,038.44, and 34,030.46, respectively. The main factor that derived this difference was determined to be the primary reserve of AS-PSH’s pumping mode.