Variable Renewable Sources Research Articles

Development of an optimization model for the feasibility analysis of hydrogen application as energy storage system in microgrids

Hydrogen can be used as an Energy Storage System (ESS) in a microgrid allowing to store surplus generation of variable renewable sources for later use. Research in the area mainly refers to the sizing of the components, however few studies evaluate the optimal technology selection and operation of microgrids using hydrogen as ESS. In this work, a model to determines optimal selection and to dispatch of Distributed Energy Resources (DER) allowing to evaluate the viability of hydrogen application as ESS in a microgrid is developed. The model is implemented in GAMS, using mixed integer linear programming, and applied in a hypothetical microgrid using as input data load profiles and commercial data available in literature. The results indicate the economical and environmental benefits of DER adoption, but the currently high investment costs make it infeasible to adopt hydrogen into a microgrid. However, when considering environmental costs and market prospects, the adoption of this technology became a good alternative, improving the energy management and reducing the total annual cost of the microgrid by 14.1%.

A Self-Balancing PSO-Tunned PI Controller for Integrating Parallel Converters with Variable Renewable Sources

This study aims to propose a system designed to fulfill the current and future energy requirements of commercial and domestic consumers. Recently, renewable energy generation methods obtained a higher priority in industrial applications to reduce and replace using hazardous fossil fuel-based energy generation methods. Conventional power generators generate AC voltage, which is incompatible with many modern appliances, requiring power conversion circuits. Power conversion circuits can make the overall system expensive and induce superfluous complexity in the system structure and control. In contrast, most renewable energy sources, such as photovoltaic and fuel cells, have inherent DC output voltage, and thus, the importance of DC systems inevitably surpasses the application of AC systems. In this framework, this paper focuses on the generation of multiple DC voltage levels. Three DC voltage levels were considered according to the IEC 60038 standard of the International Electrotechnical Commission. To generate multiple DC voltage levels, a parallel combination of power cells is used, where each power cell consists of a DC-DC converter. For adequate control, a particle swarm optimization tunned proportional integral (PSO-PI) controller applies. Three case studies evaluated the performance of the proposed system based on transient response and voltage ripples. For case study 1, the input and output conditions are kept constant; for case study 2, the input voltage is iterated, and the output load is kept constant; for case study 3, the input voltage is iterated, respectively the output load is also iterated with different load settings. In all case studies, the transient response is less than 0.15 s, and the voltage ripple is less than 5%. Keywords: DC-DC converters, power cells, renewable energy, particle swarm optimization, controller. https://doi.org/10.55463/issn.1674-2974.50.2.8

Method for determining the critical parameters of the sustainability of an energy system with integrated renewable energy sources

This paper proposes a method for modeling the regime of a power system with integrated variable renewable sources - wind power units and solar PV installations, the generation of which is continuously changing in accordance with the random variability of wind speed and solar radiation. Wind speed and solar radiation data were obtained for real regions in which a 240 MW wind farm and a 230 MW solar PV power plant are currently under construction. A method is proposed for calculating the value of the critical stress in the system for indefinitely changing wind speed and the level of its fluctuations, which determine the stochastic variability of the system regime. For each interval of change in wind speed, a set of probable modes of the system and the corresponding critical voltages in the network of the system are determined. The computational experiments were performed for the 30-node IEEE scheme.

Cluster-based stratified sampling for fast reliability evaluation of composite power systems based on sequential Monte Carlo simulation

An essential aspect in the operation and expansion of the electricity infrastructure is to ensure a reliable power supply, despite uncertainty (mainly caused by random failures, variability of renewable sources, and load growth). Reliability evaluation of composite power systems is a valuable tool for identifying possible deficiencies in operation. Power systems operation is becoming more variable and stochastic. Consequently, there is an urgent need to update the tools used to analyze their reliability. This article presents a novel method based on cluster-based stratified sampling (CBSS) and sequential Monte Carlo simulations (SMCS) to improve the reliability evaluation of composite power systems. Here, clustering algorithms are applied to reduce the number of observations required by traditional SMCS. The proposed approach is applied to RTS-79, RTS-96, and RTS-GMLC electrical networks to verify its accuracy and speed. The results obtained demonstrate that CBSS increase calculation speed in highly reliable networks, while preserving information on the probability distribution of the reliability indices.

Hydropower operation in future power grid with various renewable power integration

Hydropower generation may play an increasingly important role in the power grid under increasing contribution of variable renewable sources such as wind and solar. An improved understanding of the changes to hydropower dispatch under future higher VRE grid conditions reveals research gap that should be informed power grid planning and reservoir water releases policies considering multiple other water uses and varying hydrologic condition. This study aims to understand the role of hydropower in a changing power grid by employing a production cost model, PLEXOS, across future power system scenarios, planning horizons, and regions. We explore optimized hydropower dispatch to understand its potential role in minimizing the system cost and renewable curtailment. We also examine the sensitivity of hydropower revenue under various grid scenarios of the Eastern U.S. and hydrology conditions. Results indicate hydropower generation follows net load and compensates for the variability of solar and wind generation. Although energy prices are lower during some periods in the future grid scenarios, there is a potential for higher revenue for hydropower by providing both energy and ancillary services during times of stress. Further, hydropower revenue is sensitive to hydrology in the SERC region, which we considered as an example. The feasibility of hydropower dispatching with higher ramps between low and high hourly-capacity factors, as indicated in the optimization model, requires further study to consider other water use and ecology constraints.

Energy efficiency and conservation values in a variable renewable electricity system

To address climate change, most world energy systems must convert to carbon-free sources including variable sources such as solar and wind power. Currently there are few examples of such systems, and their economics are not well understood. In this study we consider how much energy efficiency and conservation are optimal in a system relying on variable renewable sources. Modeling a renewable electricity system for Mauritius, we demonstrate that marginal benefits of energy efficiency are greater than average costs of electricity, and that the value of energy conservation at specific times of limited electricity supply can be more than double the average cost of electricity production. This suggests important roles for energy efficiency and conservation in future renewable electricity systems.

Policy entry points for facilitating a transition towards a low-carbon electricity future

This study extends the ambit of the debate on electricity transition by specifically identifying possible policy entry points through which transformative and enduring changes can be made in the electricity and socio—economic systems to facilitate the transition process. Guided by the “essence” of the multi-level perspective — a prominent framework for the study of energy transition, four such entry points have been identified: 1) destabilising the dominant, fossil fuel-based electricity regime to create room for renewable technologies to break through; 2) reconfiguring the electricity regime, which encompasses technology, short-term operational practices and long-term planning processes, to improve flexibility for accommodating large outputs from variable renewable sources whilst maintaining supply security; 3) addressing the impact of coal power phase-out on coal mining regions in terms of economic development and jobs; and 4) facilitating a shift in transition governance towards a learning-based, reflexive process. Specific areas for policy interventions within each of these entry points have also been discussed in the paper.

Maximum Power Point Tracking Powered Solar PV Grid Integrated System Using DSTATCOM

Abstract: The energy crisis has arisen as a consequence of rapid depletion of fossil fuels and a growing awareness of the need of environmental preservation. As a result, scientists are attempting to develop new methods for harvesting renewable energy sources. Maintaining usage efficiency is essential for conserving resources for future generations. Due to the availability of renewable energy sources, the goal of this study is to explore, assess, and underline the importance of a PV system that is linked to the grid and as a consequence the description of PV systems in connection to grid regulation is examined. The micro grid concept decreases the number of reversals in a single AC or DC grid, making it easier to connect variable renewable AC and DC sources and loads to energy systems. Energy storage systems (ESS) are one way to improve the quality of a power supply while also assuring its stability. The distributed static synchronous compensator (D-STATCOM) is used to adjust if the AC network is unable to supply the power requirement. The suggested model was simulated in MATLAB R2020a simulink programme to see if it was feasible using an Intel core Pentium(R) dual core processor running at 2G.20GHz and 3GB RAM in a 64 bit configuration.

Energy Management Model for a Standalone Hybrid Microgrid through a Particle Swarm Optimization and Artificial Neural Networks Approach

Energy management systems are usually used to integrate different energy sources into a coordinated microgrid system. However, given the variability of renewable sources and the complexity of calculating renewable resource availability and managing energy, it is not easy to incorporate efficient energy management models in a microgrid. This work focuses on developing a methodology to incorporate optimized artificial networks into a self-adaptable energy management system to improve microgrids performance. The proposed model consists of a set of artificial neural networks organized into a cascade configuration. A Particle Swarm Optimization algorithm optimizes each artificial neural network; the proposed model aims to estimate and provide information to the energy management system. The model is implemented in MATLAB/Simulink environment and fed with experimental data. Correlation analysis of system variables between the different artificial neural networks is performed to validate the proposed model. Simulated tests are performed with scenarios using experimental data, and an analysis of the system's response is performed in terms of the root mean squared error and linear regression. The results showed that, compared to related works, the proposed model reduced errors by 59% and 56% for single and multiple-step prediction of energy parameter estimators. Regarding the fitness of the power estimator from the EMM for the test scenarios, an 0.1245 RMSE was obtained.

Assessment of variable solar- and grid electricity-driven power-to-hydrogen integration with direct iron ore reduction for low-carbon steel making

Power-to-gas (PtG) technologies offer a promising approach for decarbonization of energy-intensive industries, particular the iron and steel (I&S) sector, which depends on specific chemical feedstock and processes that are not currently directly electrifiable. However, PtG implementation faces challenges in the medium term related to the carbon footprint of electricity networks, decoupling process applications from variable renewable energy inputs, and economic feasibility. In this study, the design, energy, emissions, cost, and hourly operation of a power-to-hydrogen (PtH2)-based direct reduction of iron (DRI)-electric arc furnace (EAF) system, are investigated for solar energy-rich conditions in the near- to medium term (2030) with the intent to facilitate the deployment of low-carbon DRI-EAF steel making. A plant hourly operating and sizing methodology is developed based on PtH2 and use of renewable, low-cost solar photovoltaic (PV) electricity and H2 storage to counteract grid emissions and cost. The analysis approach is generically applicable to different solar-rich locations and other variable renewable electricity sources. For base-case system design/operating conditions, the emission intensity of the PtH2-I&S process is found to be abated from 890 to 567 kgCO2/tLS (∼36%), in absence of EAF scrap steel use, relative to the use of grid electricity only with no H2 storage, with a slight reduction in the levelized of cost steel (CLS) at 618 USD/tLS. Relative to conventional natural gas (NG)-DRI-EAF and blast/oxygen furnace (BF-BOF) processes, emission intensity is reduced by ∼43–60% and ∼53–74%, respectively. At off-base case PV and water electrolysis capacities, steel making emission intensity reductions of ∼40% relative to conventional NG DRI-EAF are achievable at normalized PV capacities, α = 3, relative to the plant nominal hourly electricity demand, and normalized electrolysis capacities, β ≥ 1.3, relative to the nominal hourly capacity requirement, while maintaining CLS within less than +25% of NG DRI-EAF. Based on the performance improvement and cost reduction potential for electrolysis and solar PV, the sub-space of normalized PV and electrolysis capacities yielding a ∼40% reduction in emission intensity within the above CLS limit would be significantly enlarged towards lower PV capacities (α ≥ 2) and electrolysis capacities (β ≥ 1.2).

Optimal techno-economic feasibility study of net-zero carbon emission microgrid integrating second-life battery energy storage system

With the increasing adoption of variable renewable sources (VRE) and the deployment of electric vehicles (EVs) in the market, the share of harmful carbon emissions is reducing continuously. Forming a microgrid (MG) is the best way to integrate renewable energy sources (RES) to make a low-carbon path for electrification. Second-life batteries (SLBs), derived from the first-life application of batteries used in EVs, are lower in price as compared to fresh EV batteries and have sufficient remaining capacity as energy storage for MG applications. Therefore, to show the techno-economic feasibility of SLBs, this paper shows a comparative study of MG consisting of photovoltaic (PV)/floating PV/wind/biogas with fresh Li-ion batteries (LIBs) and SLBs. This paper analyses 4 hybrid models with fresh LIBs in off-grid and grid-connected mode, and based on HOMER-Pro an optimal model is finalized for the Asian Institute of Technology (AIT), Pathumthani, Thailand. From, six different cases of fresh LIBs, the optimal case is also selected by considering the lowest net present cost (NPC) and cost of energy (COE). With the significant amount of reduction in NPC and COE, the grid-connected hybrid models are found to be more economically viable than the off-grid models. The grid-connected optimal hybrid model is further analyzed with SLBs where a range of cost multipliers (CMs) and energy throughputs are considered as the sensitivity parameters for SLBs. The results obtained from HOMER-Pro show that the grid-connected optimal model with SLBs reduces the NPC and COE by 36% and 35%, respectively, compared to the fresh LIBs. Hence, the optimal system shows the lowest NPC and COE as, 4,136,254$ and 0.0411$/kWh, respectively, with the SLBs.

Improvements to Modern Portfolio Theory based models applied to electricity systems

With the increase of the share of variable renewable energies in electricity systems, many studies were developed in order to determine their optimal technological and spatial mix. Modern Portfolio Theory (MPT) has been frequently applied in this context. However, some crucial aspects, important in energy planning, are not addressed by these analyses. We, therefore, propose several improvements and evaluate how each change in formulation impacts results. More specifically, we use generation cost instead of installed capacity as one of the objectives; we consider the correlation between demand and generation profiles; and we limit shortage risks via the inclusion of a CVaR measure. These modifications are presented in a formal model which is also applied to the case of Brazil. We found that, after including our proposed modifications, the resulting efficient frontier differs strongly from the one obtained in the original formulation. The main difference is that the new efficient frontier has a much shorter range of acceptable standard deviation values. Therefore, many of the portfolios obtained from the traditional formulation have a much higher probability of under-production, especially portfolios located at regions with standard deviation either too low or too high. Furthermore, we show that diversification plays an important role in smoothing output from portfolios of variable renewable sources.

Emergent landscapes of renewable energy storage: Considering just transitions in the Western United States

Governments, utilities, and energy companies are increasingly looking towards energy storage technologies to extend the availability of variable renewable power sources such as solar and wind. In this Perspective, we examine these fast-shifting developments by mapping and analyzing landscapes of renewable energy storage emerging across the Western United States. We focus on the rollout of several interrelated leading technologies: utility-scale lithium-ion batteries, supported by increasing regional lithium mining, and proposals for new pumped storage hydropower. Drawing on critical resource geography, we examine energy storage as both a component of renewable transition and as its own driver of landscape transformation, resource extraction, and conflict. By mapping and interpreting emerging Western landscapes, we show that leading energy storage technologies and the materials needed to make them can require extensive surficial land use and have significant regional water impacts, and that they are generating opposition from groups concerned about environmental degradation and (in)justice. We propose an agenda for future research on energy storage aimed at rendering its development more socio-ecologically beneficial and just.

Offshore Wind-to-Hydrogen Production Plant Integrated with an Innovative Hydro-Pneumatic Energy Storage Device

One of the main technical challenges of wind-to-hydrogen production plants is to couple intermittent and variable renewable power sources, such as wind turbines, with an electrolyser. Most hydrogen production concepts rely on electrical storage to smoothen the power input to the electrolyser. In this study, the use of a hydro-pneumatic energy storage system is proposed as an interface between the green, fluctuating electricity supply and the electrolyser. The performance of the proposed solution is analysed and compared to that of a conventional offshore wind-to-hydrogen production plant in order to identify potential advantages and drawbacks. The results of the simulations show that the FLASC energy storage system provides a stabilized, yet green power supply. Short-term fluctuations of the power input to the electrolyser can be avoided. A 70% reduction of the On/Off cycles can be obtained. Moreover, if compared to an offshore wind-to-hydrogen production plant with no storage there is no substantial difference in terms of hydrogen production observed over the analysed period of one year in spite of a 70% round-trip efficiency of the energy storage device.

Designing of a Feasible Low Pollutant Grid Integrated System for Steel Plant

This paper presents system architecture with low pollutant emission for application in Bhilai Steel Plant (BSP) located in Bhilai, Chhattisgarh, India. Chhattisgarh is very rich in terms of renewable resources like solar, wind and biomass. The availability of solar radiation in this region is significantly rich for any kind of solar generation options. The government provides widespread support for the use of renewable energy, particularly solar and wind which provide power without additional pollutants. These natural energy sources can be harnessed for electricity generation which depends upon the cost and efficiency of technology that is constantly improving to reduce the costs per kWh on the source. Solar energy utilization becomes complex due to supply and demand logic. Also, a backup generating capacity is required due to its intermittent nature, escalating the cost of the system with an increasing proportion of variable renewable sources. Many countries including India, have policies to support renewable to confer priority in the grid system by subsidizing them. The analysis is carried out by investigating the potential of solar energy and collecting data from BSP. In this paper, the existing system is modeled with one option of solar grid integrated system so as to have a low pollutant emission system, together with cost-saving. The existing system is taking power from the power plant(PP) and grid NTPC-SAIL Power Corporation Limited (NSPCL) whereas a solar grid integrated system is also modeled as an option for future energy sources.

Estimating the adequacy revenue considering long-term reliability in a renewable power system

The growing participation of variable renewable sources, with production costs close to zero, requires the review of electricity markets to guarantee security of supply. This work evaluates the dependence on additional revenue of different technologies that provide long-term reliability in a predominantly hydropower system, with model-based spot price, that considers generators variable production cost, and price cap. Using the future configuration of Brazilian Ten-Years Plan, each technology's revenue is estimated and then compared with investments required. Results demonstrate that, in systems with this market design, only technologies with a high dispatch factor can cover the investments solely with revenues from selling their production. For wind and solar plants, in 35% of scenarios, this income is sufficient to cover the investments. On the other hand, thermopower has more than 90% of scenarios where net income is nil, indicating that adequacy remuneration should cover investments. Battery storage and demand response are also analyzed. As the final income for a project will be given by the sum of different revenues, technologies that don't depend on a certain product may exercise market power and render ones that depend on that revenue infeasible, even if this solution isn't the most efficient for the system.

Modelling the efficiencyof power system with reserve capacity fromvariable renewable sources of energy

The paper considers modeling the efficiency of power system with integration large share of variable renewable sources of en-ergy with the account ofclimate conditions ofUkraine. The proposed methodology with its position between system planning and dispatch simulation contributes to the field of hybrid energy system models.The idea behind the methodallowshigh spatial and temporal resolution as well as the inclusion of the technical details of the power system and its dispatch.The novelty of this method is the usage ofa parametric approach is chosen to analyze different variable renewable sources of energyscenarios, precisely every possible its share and mix. This provides insights on the systematic effects of different resource mixes and may serve as a new ap-proach to the analysis of future power system development.The additional novelty aspect allows theoptimization of the design of the technical details of the power system with large variable renewable sourcessharesto have continuous improvementof its energy efficiency.The energy balance model generatoris well suited for the analysis of large share of variable renewable sources integration in the power system. The design of technical details of the power system with large variable renewable sourcesshares wasoptimized with the energy balancemodel.The results of numerical modelling demonstratedthat at 80% variable renewable sources of energy share, the overproductionis reduced to 20%, down from over 100 % without grid extensions.With it, the necessary wind and solar capacity decreases. Consequently, the possible achievable variable renewable sources of energy share areincreased, assuming the same technical potential. According to the results, a Ukrainian grid would allow to increase the possible variable renewable sources of energy share from 50% to 75%.

Which way to net zero? a comparative analysis of seven UK 2050 decarbonisation pathways

Since the UK’s Net Zero greenhouse gas emissions target was set in 2019, organisations across the energy systems community have released pathways on how we might get there – which end-use technologies are deployed across each sector of demand, how our fossil fuel-based energy supply would be transferred to low carbon vectors and to what extent society must change the way it demands energy services. This paper presents a comparative analysis between seven published Net Zero pathways for the UK energy system, collected from Energy Systems Catapult, National Grid ESO, Centre for Alternative Technology and the Climate Change Committee. The key findings reported are that (i) pathways that rely on less stringent behavioural changes require more ambitious technology development (and vice versa); (ii) electricity generation will increase by 51–160% to facilitate large-scale fuel-switching in heating and transport, the vast majority of which is likely to be generated from variable renewable sources; (iii) hydrogen is an important energy vector in meeting Net Zero for all pathways, providing 100–591 TWh annually by 2050, though the growth in demand is heavily dependent on the extent to which it is used in supplying heating and transport demand. This paper also presents a re-visited analysis of the potential renewable electricity generation resource in the UK. It was found that the resource for renewable electricity generation outstrips the UK’s projected 2050 electricity demand by a factor 12–20 depending on the pathway. As made clear in all seven pathways, large-scale deployment of flexibility and storage is required to match this abundant resource to our energy demand.

Review on Power Distribution Techniques in System Comprising of BESS

With regard to electrical energy sector, budgetary factors, power must be utilized as soon as possible once it is generated. Since storing large amounts of electrical energy is prohibitively expensive. Consequently, as energy storage substance have become mostly accessible, evenly distributed production is becoming more workable, especially with the Smart Grid concept. Distributed ESS (Energy Storage Systems) are gaining popularity. There is a diverse category of ESS namely, battery, thermal, mechanical, hydrogen and so on. But this paper investigates about the techniques used in Battery energy systems by several researchers to stabilize energy output and usage, these systems supplement variable renewable sources such as wind, tidal, and solar power.

The dependence of quantile power prices on supply from renewables

Understanding power prices dynamics is crucial for valuing flexibility assets such as storage or flexible consumption facilities that accommodate fluctuations in power supply from variable renewables. Owners of such assets need to know how extreme power prices can become in order to optimally manage (dis)charging or adjusting consumption volumes. We examine how to predict those high and low prices, being the different quantiles of the power price probability distribution function, and question how supply from variable renewable sources affect different quantile prices.The first contribution of our paper is that we apply quantile regressions in a panel data framework. This methodology acknowledges that day-ahead power markets’ data is structured as cross-sectional data and, as opposed to previous quantile regression techniques introduced in power markets, allows for simultaneous predictions for all hours during a delivery day. Day-ahead power prices for all 24 h in the next day are determined at the same moment, one day before delivery. The hourly data is therefore not a time-series, but a cross section. The second contribution is that we examine the interaction between demand and supply from variable renewable sources, instead of linear dependencies only.We find that lower and higher quantile prices are more heavily affected by variations in supply from variable renewable sources than centre quantile prices. This enables owners of flexibility assets to better manage their assets in anticipation of excess or scarce supply from renewable sources. By doing so, they increase the flexibility of power systems that face increasing installed capacity of variable renewable energy sources.