Diffusion Of Renewable Energy Sources Research Articles

Application of cascaded neural network for prediction of voltage stability margin in a solar and wind integrated power system

Voltage stability is a paramount concern in the management of renewable-rich power systems. As the diffusion of renewable energy sources continues to increase, accurately estimating voltage stability margins becomes essential. This paper addresses the critical need for effective voltage stability margin estimation and presents a novel approach to predict the same on the solar and wind integrated power system. A new machine learning methodology is developed based on the cascaded neural network (CNN). The proposed CNN methodology effectively estimates the loadability margin in a renewable-rich power system under normal operating conditions, varied loading directions, and various contingency situations. The results of CNN are compared with different machine learning techniques and tested in the IEEE 30 bus system and IEEE 118 bus system under various operational circumstances. The results illustrate the efficiency of the suggested method for online assessment of a power system's Voltage Stability Margin. The proposed approach gives real-time insights into voltage stability margins by leveraging the power of data and powerful algorithms, allowing grid operators to proactively manage and optimize renewable energy integration while ensuring grid dependability and stability.

Digitalization in the Renewable Energy Sector

This study explored the association between renewable energy uptake and digitalization in the sector by reviewing relevant literature (published 2010–2022), with the aim of identifying the existing utilization of digital technologies within the sector, challenges to adoption, and future prospects. Different search engines (SCOPUS, Web of Science, and Google Scholar) were used to locate relevant papers and documents. The results revealed the high significance of digital technologies in supporting the renewable energy sector, with high costs and security risks representing the key challenges. Most papers reviewed had a positive outlook, but recommended further research and development for effective energy transition and resilient infrastructure. The current drivers of the integration of digital technologies to support the diffusion of renewable energy sources appear to extend beyond energy demand and involve many aspects of sustainability and sustainable development. Compared with previous reviews, this work has unique scope and novelty since it considers the bigger picture of the coupling between digitalization and the renewable energy sector, with a greater focus on critical areas in these two interconnected bodies that need to be addressed. The relatively small sample of relevant papers (69 from 836 hits) located in the literature review confirms the need for more research covering the subject in greater depth.

Convergence in renewable energy sources diffusion worldwide

The diffusion of renewable energy sources (RES) is a fundamental objective of the worldwide policy actions for sustainable development, at the UN level with the sustainable development goals (SDG) recommendations, to ensure access to affordable, reliable, sustainable and modern energy for all (SDG 7). Also, primary attention to RES has been given at the EU level with the new Green Deal and the new objectives of the Next Generation EU after the Covid pandemic, and at the level of national Governments worldwide. So far, there has not been an analysis of the RES convergence process across countries worldwide, given that the issue of climate change is a global externality. Previous analyses have focused on specific regions, such as EU, OECD, provinces of China. This paper fills this gap, providing new evidence on the convergence process of RES for the 176 countries that account for more than 98% of the world population, from 1990 to 2018. A common panel data set has been used to take into account countries’ specific effects. Several socio-economics and political variables are introduced to test conditional convergence such as openness to trade, developments in financial markets, income distribution, level of education. The results of this new contribution reveal that there is evidence of sigma-absolute and conditional beta-convergence process for several groups of countries. Moreover, the conditional convergence analysis shows that spatial spillover effects exert rich and complex impact on convergence speed. Finally, we provide policy recommendations, highlighting that the decarbonization target in 2050 needs additional mobilization of public and private resources to pursue a common, convergence path worldwide.

Convergence in renewable energy sources diffusion worldwide: First results

The diffusion of renewable energy sources (RES) is a fundamental objective of the worldwide policy actions for sustainable development, at the UN level with the sustainable development goals (SDG) recommendations, to ensure access to affordable, reliable, sustainable and modern energy for all (SDG 7). Also, primary attention to RES has been given at the EU level with the new Green Deal and the new objectives of the Next Generation EU after the Covid pandemic, and at the level of national Governments worldwide. So far, there has not been an analysis of the RES convergence process across countries worldwide, given that the issue of climate change is a global externality. Previous analyses have focused on specific regions, such as EU, OECD, provinces of China. This paper fills this gap providing new evidence on the convergence process of RES for 176 countries that account for more than 98% of the world population, from 1990 to 2015. A common panel data set has been used taking into account countries’ specific effects. Several socio-economics and political variables are introduced to test conditional convergence such as openness to trade, developments of financial markets, income distribution, level of education. The results of this new contribution reveal that there is evidence of sigma- absolute and conditional beta-convergence process for several groups of countries. Moreover, the conditional convergence analysis shows that spatial spillover effects exert rich and complex impact on convergence speed. Finally, to provide policy recommendations, we simulate alternative scenarios to assess when the target levels of RES can be reached worldwide.

Impact of feed-in tariffs on electricity consumption

The diffusion of renewable energy sources is an important policy issue for all countries. In particular, feed-in tariffs (FITs) are a major policy instrument used to diffuse renewable energy sources in developed countries. A few recent studies have found a rebound effect from the installation of solar photovoltaic (PV) systems. However, consumer behavior in relation to electricity consumption following the installation of solar PV systems is largely unknown. In particular, previous studies do not effectively reveal the FIT effect on electricity consumption. Therefore, we set up a model to measure this effect and conduct empirical analysis to confirm the theoretical contribution of the improved model. Our estimation results based on the matching method show that the FIT scheme increases the consumption of electricity purchased from electricity companies if the FIT rate exceeds the electricity price. This finding is important for better understanding the true cost-benefit of FITs.

Techno-economic impact of collective self-consumption on different energy-related investments for a condominium

Energy Communities (ECs) are gaining a key role in supporting the transition towards a low carbon economy in EU, since they combine the promotion of efficient energy practices with an expected positive social impact. Legislators are resorting to the concept of collective self-consumption as a tool to favor the electrification of energy needs and the diffusion of renewable energy sources. This work presents the first results in this field of the ENERGYNIUS project, co-funded by Regione Emilia-Romagna, focusing on the economic feasibility of investment decisions that would increase energy efficiency and renewables’ penetration in the household sector. To this purpose, a mathematical model has been developed, featuring an hourly time step definition of the internal and external energy exchanges and an accurate modelling of the electricity billing. It has been applied to an Italian condominium case study where the energy requirements of the inhabitants – in terms of electricity, heating, cooling and private transportation – have been considered. Thanks to the model, it is possible to compare increasing levels of electrification (e.g., photovoltaic panels, heat pumps, electric vehicles and batteries) and assess the benefits of collective selfconsumption on the condominium cash flows and environment (fossil CO2 emissions).

Intelligent management of hybrid energy systems for techno-economic performances maximisation

The great diffusion of renewable energy sources in the latest decades led to a pervasive diffusion of hybrid energy systems (HESs), in which several sources of energy are combined to fulfil the user demand. As the number of HES sources and related hardware components raise, the number of interconnections between these latter increases more than proportionately. Such condition determines high HES complexity, that can be exploited to achieve greater overall efficiency. This research deals with the HES designed to meet the electricity load required by a single user. Furthermore, the considered HESs leverage single or multiple components in charge of electricity production (e.g. PV module, wind turbine, etc.) a battery energy storage system (BES) and a connection with the national grid that allows the electricity purchase and sale processes. A two-step approach is proposed to deal firstly with the HES sizing, by exploiting an iterative method to identify the optimal size of each energy component. The second step consists in the energy flows management, i.e. the hourly dispatching between the HES components. Indeed, two different strategies are proposed to intelligently manage the hourly electricity flows. On the one hand, the proposed heuristic algorithm (HA) aims to minimize the purchased energy from grid imposing a constant dispatching of the electricity flows according to the amount of produced energy, the state of charge of the BES and the user request. On the other hand, a mixed integer linear programming (MILP) model leverages the short-time forecasts of environmental parameters, energy tariffs, and load request to optimise in real-time the electricity trade process from an economic point of view. The overall approach, including the comparison between the HA and the MILP, has been tested and validated on several case studies, concerning specific HES architectures, a range of European countries, both domestic and non-domestic users as well as multiple values of energy request. The results justify the HES installation in all the considered case studies, leading to an economic saving greater than 35% compared to electricity purchase from grid uniquely. However, the MILP adoption for the management of energy flows is recommended only for HESs fuelled by multiple energy sources.

Improved Efficiency Management Strategy for Battery-Based Energy Storage Systems

Battery-based energy storage systems are forecasted to have a rapid diffusion in the next future, because they can support the diffusion of renewable energy sources and can offer interesting ancillary services for the distribution grid. Consequently, energy management strategies for batteries and inverters present in storage systems will play a fundamental role in order to guarantee effective energy transfer processes between storage systems and the grid. This paper proposes an efficient management strategy which allows maximizing the overall energy efficiency of grid-connected storage systems taking into account the actual relationship between the efficiency and the charging/discharging power of the storage system. The effectiveness of the strategy is as shown by analysis results, the proposed strategy can allow a remarkable efficiency increase compared with strategies which are not aimed at the efficiency optimization.

Perceived barriers to invest in renewable energy sources in the Cretan hotel industry

ABSTRACTThe paper aims to describe which barriers are encountered within the hotel sector with regards to implementing the use of renewable energy sources (RES) taking into account their expenses on energy as well as annual profits. The empirical analysis is based on binary logistic regression models employing data that influence hoteliers’ decision for investing in RES. Results support that hoteliers consider economic, institutional and human-related factors as barriers for investing on RES. Policy-makers should consider that perceived barriers towards adopting RES differ between hotels with differing financial and energy performances. These variations are very important to consider in order to effectively address the barriers preventing the diffusion of renewable energy sources so as to reduce the impact of the hotel industry in environmental degradation attributed to energy consumption.

Performance analysis of the deflector integrated cross axis wind turbine

Wind turbines in the context of integration in an urban environment are considered as one of the most promising technologies for the efficient diffusion of renewable energy sources. However, situations such as low wind velocity, highly turbulent and skewed wind flow conditions are commonly encountered in this environment. This misaligned flow could affect the horizontal axis wind turbine performance. The vertical axis wind turbine (VAWT) is more suitable to operate under these unfavorable conditions. Nevertheless, the conventional VAWT has low efficiency and poor self-starting characteristics. Therefore, a novel design of deflector integrated cross axis wind turbine (CAWT) is proposed. Tests were carried out to harness wind energy from both the horizontal and vertical components of the skewed flow induced by the deflectors. A semi-empirical approach was also developed to analyse the performance of the CAWT. The aerodynamic behaviour of the CAWT was determined by combining the blade element momentum (BEM) model and double multiple streamtube theory (DMST). The approach showed notable agreement between the experimental and theoretical results (9.8%–14.2% difference). In conclusion, the findings from the experiment and the model showed that the concept has very good potential in the renewable energy industry.

Comparative Analysis of Topologies to Integrate Photovoltaic Sources in the Feeder Stations of AC Railways

The increasing diffusion of renewable energy sources in the power systems is likely to extend in the near future to the power supply of railways. This paper compares the technical and economic benefits of several configurations with power electronics converters for the integration of photovoltaic (PV) sources into the railway power supply systems. For each of these configurations, a design methodology is proposed for selecting the ratings of the railway power supply components. The requirements for the phase imbalance on the feeding transmission line are assumed in accordance with current regulatory standards and, wherever necessary, phase balancers are added. The design methodology is applied to the power supply of a high-speed railway and the configurations under study are numerically compared based on their technical feasibility and economic cost, using the generation capacity of the PV source as an independent variable. The analysis demonstrates that with a progressive integration of PV sources into railway systems, the configurations with power converters supplying the overhead lines could become more beneficial than more classical solutions where the overhead line is supplied via a transformer.

Forecasting the RES generation in developed and developing countries: a dynamic factor model approach

In this study, we investigate the path toward cleaner generation systems based on the forecast of renewable production diffusion in developing and developed countries. We analyze the factors that affect investments in RES generation and are able to explain the mid-term diffusion of renewable energy sources. This empirical analysis is performed on a large dataset of 129 countries and 32 variables that are observed during 1995–2011. Because of the large number of variables and their high degree of collinearity, the first step of the analysis was implementing a Dynamic Factor Analysis to extract factors that explain the majority of the variation of the original variables. In the second step, we determine the key factors that promote RES investments by using a panel regression model. Then, model estimates are used to determine out-of sample predictions. The results of the empirical analysis are separated into developed and developing countries according to the World Bank income classification. All the countries increase their share of RES generation in the next year but with different growth rates. Developing countries invest less than developed countries and prefer traditional generation sources. In developing countries, investments are enhanced by international financial aid. Conversely, developed countries demonstrate greater environmental awareness and, in many cases, incentivize the diffusion of green generation. However, certain developed countries prefer to invest less in renewable energies because they are tied to an economic system that is based on fossil fuels.

Energy Storage Operation for Voltage Control in Distribution Networks: A Receding Horizon Approach

The widespread diffusion of renewable energy sources and low carbon technologies in distribution electricity grids calls for counteracting overvoltage and undervoltage arising in low voltage (LV) feeders, where peaks of load demand and distributed generation are typically not aligned in time. In this context, deployment of energy storage systems (ESSs) in appropriately selected nodes of the network is recognized as a viable approach to tackle the problem. This paper proposes a voltage control scheme based on a receding horizon approach to operate the ESSs installed in an LV network. The essential feature of the approach lies in the very limited information needed to predict possible voltage problems, and to compute the storage control policy making it possible to counteract them in advance. The procedure is successfully applied to an Italian LV network, featuring demand and generation profiles, which cause overvoltage and undervoltage in the absence of voltage control.

The evaluation of renewable energy policies across EU countries and US states: An econometric approach

Renewable energy policies are implemented to promote the diffusion of renewable energy sources within the market. However, their effectiveness on renewable electricity capacity remains subject to uncertainty. This paper addresses what renewable policy instruments are effective ways to increase capacity of renewable energy sources. This study employs a 1990–2008 panel dataset to conduct an econometric analysis of policy instruments, namely, feed-in tariffs, quotas, tenders and tax incentives, in promoting renewable energy deployment in 27 EU countries and 50 US states. The results suggest that renewable energy policy instruments play a significant role in encouraging renewable energy sources, but their effectiveness differs by the type of renewable energy policy instruments. Findings reveal that feed-in tariffs, tenders and tax incentives are effective mechanisms for stimulating deployment capacity of renewable energy sources for electricity, while the other commonly used policy instrument – quota – is not.

“Team Play” between Renewable Energy Sources and Vehicle Fleet to Decrease Air Pollution

The reduction of air pollutants for the purpose of maintaining or improving air quality across the globe is a fundamental concern to which all modern governments are allocating varying amounts of attention and resources. The successful amelioration of air pollution requires strategic investments in the commercialization and adoption of “clean energy technologies” by both private and public entities, the conversion of contemporary houses to “smart houses”, the diffusion of Renewable Energy Sources (RES) including photovoltaic systems (PV), wind farms, and different forms of bioenergy, and the integration of electric-powered vehicles. In concert with these ideas, this paper aims to discuss the possibility of undertaking a feasibility study in two countries Canada and Italy concerning the integration of electric vehicles (EVs) and electric motorcycles (EMs). The proposed feasibility study would seek to assess the prospect of replacing the current vehicle fleets in these two countries with EVs in a manner that utilizes renewable energy sources and, thus, does not generate new toxic emissions. In conclusion, this study demonstrated that a pronounced introduction and distribution of RES, EVs, and EMs can operate as a great opportunity for both the environment and the capacities and needs of energy production. Today, the EV is not widespread. With this contribution, it is shown how EVs can be well integrated with renewable energy. Therefore, it is the duty of governments to implement policy strategies, in order to spread them across more territory.

Time Series Properties of the Renewable Energy Diffusion Process: Implications for Energy Policy Design and Assessment

Confronted by increasingly tight budgets and a broad range of alternative options, policy makers need empirical methods to evaluate the effectiveness of policies aimed at supporting the diffusion of renewable energy sources (RES). Rigorous empirical studies of renewable energy policy effectiveness have typically relied on panel data models to identify the most effective mechanisms. A common characteristic of some of these studies, which has important econometric implications, is that they assume that the contribution of RES to total electricity generation will be stationary around a mean. This paper reviews such assumptions and rigorously tests the time series properties of the contribution of RES in the energy mix for the presence of a unit root. To that end, we use both individual and panel unit root tests to determine whether the series exhibit non-stationary behavior at the country level as well as for the panel as a whole. The analysis, applied to a panel of 19 OECD countries over the period 1990-2012, provides strong evidence that the time series of the renewable share of electricity output are not stationary in 17 of the 19 countries examined. This finding has important implications for energy policy assessment and energy policy making, which are discussed in the paper.

Enhanced Ir-Ru-Ox Electro-Catalysts for Oxygen Evolution in Proton Exchange Membrane Water Electrolysis

Interest in water electrolysis has recently increased with the large diffusion of renewable energy sources and the perspective to produce hydrogen with a very low environmental impact [1-2]. In this regard, hydrogen appears a promising energy carrier that can be produced by cost-effective electrolysis of water using renewable energy sources and it can be used to store energy in grid-balancing services. A challenging problem to the development of such process is the substantial energy loss associated with the oxygen evolution during electrochemical water splitting. High surface area nanostructured (2-10 nm) IrRu-oxide electro-catalysts can substantially reduce this loss allowing to achieve efficient hydrogen production. IrOx and Ir0.7Ru0.3Ox nanosized materials of similar crystallite size (mean size 5 nm) were prepared for application as oxygen evolution electro-catalysts in solid polymer membrane water electrolysers (PEMWEs). The physico-chemical properties of the catalysts were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) and X-ray-Photoelectron Spectroscopy (XPS). Particular efforts were addressed to tailor the crystallographic characteristics and the surface properties. The electrochemical properties were investigated in an electrolysis cell, based on Nafion 115 and 30% Pt/C as cathode catalyst, by using linear sweep voltammetry, electrochemical impedance spectroscopy and Tafel curves. The Ir0.7Ru0.3Ox-based electro-catalyst showed a performance of 3.2 A cm-2 at 1.85 V at 90°C which corresponds to a voltage gain of 0.1 V as compared to the IrOx catalyst at the same current density. A similar Tafel slope with a decrease of charge transfer resistance for IrRuOx compared to IrOx would indicate the same mechanism for these materials and higher intrinsic activity for the mixed oxide. The present study indicates that Ir0.7Ru0.3Oxcan be an excellent electro-catalyst for the oxygen evolution in PEM-based water electrolysis provided that structure, morphology and surface characteristics are properly tailored. Acknowledgements The authors acknowledge the financial support of the EU through the FCH JU Electrohypem Project. ‘‘The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2010-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement Electrohypem n 300081.’’ References Siracusano, S.; Van Dijk, N.; Payne-Johnson, E.; Baglio, V.; Aricò, A.S.; Applied Catalysis B: Environmental, 2015, 164:488. DOI:10.1016/j.apcatb.2014.09.005 Aricò, A.S., Siracusano, S., Briguglio, N., Baglio, V., Di Blasi, A., Antonucci, V. Journal of Applied Electrochemistry, 2013, 43:107. DOI: 10.1007/s10800-012-0490-5

Identifying barriers in the diffusion of renewable energy sources

Rapid diffusion of renewable energy sources (RES) in the electricity power sector is crucial if the EU wants to fulfill its 2050 CO2 reduction commitments. For this reason, identifying and alleviating all barriers that hinder the development of RES is necessary to the successful deployment of these technologies. This paper discusses the main barriers in the diffusion of wind and photovoltaic (PV) solar power in the Greek electricity sector by drawing on the literature of technological innovation systems and system functions. Furthermore, we provide an explanation of the different diffusion rates between the two technologies. Inadequate financial resources, low grid capacity, delays in the issuance of building permits, opposition from local communities to the construction of wind farms and the lack of a stable institutional framework are among the most important barriers that inhibit the diffusion of the wind and PV solar power. The nature of the barriers identified in this study calls for policy intervention.

Development of a Geographical Information System (GIS) for the Integration of Solar Energy in the Energy Planning of a Wide Area

Energy planning has become one of the most powerful tools for urban planning even if several constraints, (i.e., aesthetic, archaeological, landscape) and technological (low diffusion of Renewable Energy Sources, RES) reduce its spreading. An efficient and sustainable urban planning process should be based on detailed energy issues, such as: (i) the effective energetic characteristics and needs of the area like urban density and energy consumption, (ii) the integration of different RES and (iii) the diffusion of high efficiency technologies for energy production like cogeneration and district heating. The above-mentioned energetic issues and constraints must be constantly updated, in order to evaluate the consequences on environment and landscape due to new distributed generation technologies. Moreover, energy strategies and policies must be adapted to the actual evolution of the area. In this paper the authors present a Geographical Information Database System (GIS DB) based on: (i) the availability of land use (Land Capability Classification, LCC) to evaluate the productive potential; (ii) the estimation of residential energy consumptions (e.g., electricity), (iii) the integration of RES. The GIS DB model has been experimented in a wide area of Central Italy, considering exclusively the solar energy source for energy generation.

Influence of the heat storage size on the plant performance in a Smart User case study

The increasing diffusion of renewable energy sources are posing new challenges to the power grid due to their intrinsic unpredictability causing poor power quality, line congestion and unreliable and unsecure grid operations. In the future, power grid operators may require to the customers/producers a prescribed exchange profile, leading to a diffusion of storage systems or prime movers (especially small combined heat and power for distributed resources) able to balance renewable sources fluctuations. In this latter case, one of the major issue is the efficient use of the heat co-generated: the adoption of thermal storages appears to be necessary. In this paper, the energy performance of a Smart User, i.e. a dwelling with renewable energy sources, a combined cooling, heat, and power system, and heat and cooling back-up generators, is estimated by means of a purposely developed TRNSYS unsteady model. A virtual stand-alone operating condition is imposed for the analysed building as an arbitrary profile of power exchange with the grid. The balancing of renewable sources fluctuations imposes a non-negligible part of the heat from the prime mover to be wasted and a sensible consumption for auxiliary devices (i.e. the auxiliary boiler and the compression chiller). By applying a thermal storage, and increasing its capacity, the fraction of heat wasted and the supply from other devices is remarkably changed, showing different plant performance and efficiencies. The Smart User primary energy consumptions of the different configurations are compared to several options, showing appreciable differences in the performance.