Autonomous Island Research Articles

Pumps as turbines for pumped hydro energy storage systems - A small-size case study

Pumped Hydro Energy Storage (PHES) technology has been used since early 1890s and is, nowadays, a consolidated and commercially mature technology. PHES systems allow energy to be stored by pumping water from a lower-to a higher-level reservoir. Subsequently, this energy can be released through a turbine placed in a penstock, which connects the two reservoirs, to produce energy. Although these plants have historically been employed at large power scales (in the order of hundreds of MW), in recent years, micro- and small-scale plants are becoming more interesting, due to their possibility of being integrated with renewable energy systems (RES) used in autonomous island grids. Capital costs associated with hydraulic machines used in PHES systems represent the most critical economic factor, which can be mitigated by using commercial centrifugal pumps in reverse mode (Pumps as Turbines, PATs) in place of small hydro turbines. These expected economic benefits must be weighed in each specific case study, with some drawbacks related to the use of PATs, mainly associated to a lower round-trip efficiency with respect to specifically designed pumps and turbines.In this work, a small-scale PHES plant has been studied coupled to an existent photovoltaic system for the integration in the electric grid of a small island in Southern Italy. Two different PHES outlines have been compared based on techno-economic considerations. The former is a typical PHES system composed of both pumps and a turbine, while the latter uses only an array of parallel pumps which work also in reverse mode. The analysis demonstrates the feasibility of integrating a photovoltaic and PHES plant, which results in a lower cost of electricity production, while PHES performance in the PAT-based outline results penalized by the lower efficiency of PATs with respect to the hydraulic turbine.

Dimensioning of Reactive Power Compensation in an Autonomous Island System

In this paper, a method for sizing the reactive power compensation in a non-interconnected island power system is presented and applied to determine the necessary inductive reactive power compensation for the autonomous power system of Rhodes Island, Greece. The Rhodes power system is often confronted with an excess of reactive power, as a result—inter alia—of underground high-voltage (HV) cable lines and distributed generation penetration. Reactive power compensation is typically a local issue in power systems, usually aiming at maintaining an acceptable voltage profile on specific transmission segments, e.g., long underground or submarine cables. In autonomous systems, however, where network lengths are relatively short, reactive power compensation is meant to address the overall reactive power equilibrium of the system. The proposed method follows a three-step approach. First, power flow analysis is conducted to determine the size of the maximum compensation that may be necessary, i.e., the compensation size that practically allows unit commitment to be conducted without being constrained by reactive power considerations. Then, a unit commitment and economic dispatch model is executed over the course of a year to determine the optimal compensation size, using the output of the power flow analysis to formulate reactive power balance constraints. Finally, the results of the economic optimization are assessed in terms of dynamic security to verify the feasibility of the optimal solution.

Active and Reactive Power Droop Controller Design for Reliable and Optimal Control of Renewable-Based Micro-Grid

Technical concerns about micro-grid dynamics, particularly in autonomous (island) mode necessitate revision of current paradigms in control of energy systems. Advanced control techniques are imperative segments for micro-grid realization. In general, micro-grids and the integration of distributed energy resources (DER) units introduce a number of operational challenges that required to be addressed in the control design and protection systems such that the reliability and stability levels are not affected significantly and subsequently ensured that the distributed generations (DGs) potential benefits are wholly harnessed. In this paper, the micro-grid coordination strategy was investigated by simply analysing the present micro-grid situation and various control strategies. More so, active-reactive power (P/Q) and droop controller based on proportional-integral (PI) and model predictive control (MPC) were designed to control the inverter output of the micro-sources. A micro-grid model, which has two photovoltaic (PV) and one wind turbine (WT) blocks, were built in MATLAB/Simulink to simulate the following three cases in this study. The three cases are as follows, the switching of operation mode between the grid connected and islanded mode, increasing and decreasing of loads in islanded mode and the disconnection of one PV system at a certain time in islanded mode. Therefore, through the simulation analyses, the MPC controller utilized in this micro-grid as compared to the PI controller, achieved desirable efficiency of the inverter’s power control and shared the load power effectively.

Planning of Aegean Archipelago Interconnections to the Continental Power System of Greece

This paper presents the results of a thorough planning investigation carried out by the Transmission System Operator (TSO) and the Distribution Network Operator (DNO) in Greece in order to study the interconnections of the Aegean Islands with the mainland power system. The feasibility of interconnecting islands is based on the need for a reliable power supply to isolated and autonomous islands, reducing the operating costs of the power generation system through the withdrawal of high-cost oil-fired generating units, and the further ability to increase renewable energy source (RES) penetration in the country’s energy mix, according to directions imposed by the National Energy and Climate Plan. Among the alternative topologies and interconnection technologies considered, the final selection of the interconnection scheme selected for inclusion in the development plans of TSO and DNO was based on their detailed comparative evaluation, considering financial and other technical criteria.

Principles of sustainable development of the autonomous island territories of the Gulf of Peter the Great

This article explores the prerequisites for sustainable development of island territories of the Gulf of Peter the Great that retained their autonomy from continental Vladivostok – AskoldIsland, Popov Island, Reyneke Island, Rikord Island, Putyanin Island. A brief overview is provided on the development of islands in prerevolutionary and Soviet period, as well as at the turn of the XX – XXI centuries. It is noted, that the initial period of islands territorial development (late XIX – early XX centuries) is characterized with sustainable natural resource management based on consideration of the local landscape, natural and climatic conditions. Computer modeling of the annual course of wind and insolation regime of island territories is conducted for elaboration of the advanced models of sustainable natural resource management. This allowed determining comfort and discomfort landscape areas of the indicated islands for the three main seasons – winter, spring-summer, and summer. Typical terrain contributes to localization of the comfort and discomfort zones. At the same time, comfort and discomfort zone would be specific for each of the three seasons, which should be considered in arranging various types of recreation activities. Based on the results of studying the peculiarities of socioeconomic development of the islands and their landscape-climatic specificity, the author highlights three groups of islands and suggests models of sustainable development for each group: 1) Model of full-scale economic-recreational development with restoration of the collapsed ecological framework  (Popov Island and Putyanin Island); 2) Model of autonomous development with restoration of the collapsed ecological framework (Reyneke Islan); 3) Model of economical development (Askold Island, Rikord Island). The author develops the schemes of territorial development of the islands, and suggests projects on formation of sustainable environment of rural localities and tourist routs.

Silk Road archipelagos: Islands of the Belt and Road Initiative

The concept behind the Belt and Road Initiative (BRI; formerly ‘One Belt, One Road’) began to take shape in 2013. Since then, this Chinese-led project has become a major plank in China’s foreign relations. The BRI has grown from its basis as a vision of interregional connectivity into a truly global system, encompassing places—including many island states, territories, and cities—from the South Pacific to the Arctic, from East Africa to the Caribbean, from the Indian Ocean to the Mediterranean. Islands and archipelagos are particularly prominent in the BRI’s constituent 21st-Century Maritime Silk Road (MSR) and Polar Silk Road or Ice Silk Road projects, but little scholarly attention has been paid to how the BRI relates to islands per se. This special section of Island Studies Journal includes nine papers on islands and the BRI, concerning such diverse topics as geopolitics, international law and territorial disputes, sustainability and climate change adaptation, international relations of autonomous island territories, development of outer island communities, tourism and trade, and relational understandings of archipelagic networks. Taken together, these papers present both opportunities and risks, challenges and ways forward for the BRI and how this project may impact both China and island and archipelago states and territories.

Ethnozoological practices in Rodrigues island of the Mascarene archipelago

Ethnopharmacological relevanceRodrigues, is an autonomous island that forms part of the Republic of Mauritius. It is a component of the Mascarene archipelago alongside Mauritius and Reunion island. Despite their relative geographical proximity, each island has its own unique biodiversity and indigenous knowledge. Nonetheless, there is no documentation of the use of animal-based remedies (ABR) in Rodrigues. This study was therefore designed to gather and compare primary traditional knowledge on the different ABR used by Rodriguans.Aim of the study: To collect, analyse, document, compare, and disseminate the use of ABR against common human ailments in Rodrigues island. MethodsData was collected following interviews from key informants (n = 150). Primary data collected in the present study was compared with those reported from the nearest island, Mauritius. Three quantitative indices including (i) the frequency of citation, (ii) the similarity ratio and the percentage of shared uses among the two islands and (iii) new uses and percentage of new uses recorded in Rodrigues for each animal species mentioned were calculated. ResultsA total of 32 animal species belonging to 13 taxonomic groups among which 55% were vertebrates and 45% invertebrates were reported to treat 38 different ailment conditions. Altogether, 73 distinct medicinal preparations employing 22 different animal parts and by-products were concocted from the different animal species reported. Most used animal parts were meat (21%) followed by the whole body (14%). The preparations were either administered orally (78%) or topically (22%). Interestingly, resources such as the Rodriguan bat (Pteropus rodricensis) and honey are unique to the island and have never been studied before. Pteropus rodricensis is an endangered species while Carcharodon carcharias is a vulnerable one. The shared medicinal uses of the species among the 2 islands ranged from 0 to 50% with the most similar uses (50%) being for Columba livia and Donax Spp. respectively. The proportion of new uses of animal species recorded in Rodrigues was higher (NUR ≥ 30%) for Panulirus penicillatus, Ovis aries, Gallus gallus domesticus, Scutigera coleoptrata, Apis mellifera, Bos taurus and Capra aegagrus hircus. ConclusionRodriguans were found to possess valuable knowledge on a plethora of ABR. It is believed that the present documentation will serve to record and present this vanishing knowledge to the scientific community before it is further eroded from the island. Given the dearth of primary published information on zootherapeutic practices in Rodrigues, this study opens new avenues for biomedicine development in an attempt to develop alternative therapies or complement existing ones.

Islanding strategy for restoring electric power supply by means of electric vehicle idle power against cold load pickup

This study presents a new method of forming emergency-responsive autonomous islands for restoring electric power supply using an electric vehicle (EV) idle power against the so-called cold load pickup (CLPU). Two stepwise discretisation methodologies are firstly proposed, which are used to discretise arbitrarily given cold-load models and aggregate discretised EV discharge models, respectively. Then, under the framework of mixed-integer linear programming, a methodology of forming particular responsive restoration islands is built, which aims to maximise the recovered energy of interrupted end-users given discretised CLPU and EV discharge models. Comparative analyses via the proposed method against existing algorithms are conducted on both a partial IEEE RBTS-BUS6 test feeder and a practical feeder. Specifically, the conducted analyses investigate the impacts of the CLPU on energy restoration and the assistance performance of discharge power from EV's on boosting the capability of responsive restoration islands to restore the interruption. Moreover, an especial relationship is studied, between the utilisation rate of total discharge power of an EV parking lot and the rate of restored energy concerning the total lost energy.

A Methodology for Determination and Definition of Key Performance Indicators for Smart Grids Development in Island Energy Systems

There is a growing interest over the last decades in the field of autonomous island grids that is driven mainly by climate reasons. The common objective among the members of the European Union (EU) is the increase of Renewable Energy Sources (RES) penetration in the energy mixture, as well as turning the grid into a smart grid. Consequently, more and more state-of-the-art solutions are being proposed for the electricity generation and the optimization of the energy system management, taking advantage of innovations in all energy related sectors. The evaluation of all available solutions requires quantitative assessment, through the adoption of representative Key Performance Indicators (KPIs) for the projects that are related to smart grid development in isolated energy systems, providing the relevant stakeholders with a useful comparison among the proposed solutions. The evaluation approach that is described in this paper emphasizes the role of the various stakeholder groups who face the proposed solutions by different points of view. Apart from the domains of interest that are also observed in previous approaches, the proposed list also contains a set of legal KPIs, since the regulatory framework can either represent a serious barrier or grant a strong incentive for the implementation of state-of-the-art energy technology and grid management solutions in different countries.

Sizing of a solar–geothermal hybrid power plant in remote island electrical network

The rapid increase of world energy demand over the past decades has led to an extensive exploitation of the planet’s natural resources. Given that the population growth will continue for the next decades, there is an urgent need for a switch to Renewable Energy Sources (RES). One of the promising solutions to the energy problem is the geothermal energy which consists of stored energy in the earth in the form of water or steam at high pressure and temperature. Countries located in seismic zones possess a high geothermal potential due to their position at destructive and constructive plate margins. Greece is one of the countries with a remarkable potential in geothermal energy of medium and high enthalpy fields. Interest in the exploitation of geothermal fields for electricity generation is mainly focused on non-interconnected Greek islands, where energy is produced from oil-based generators with high energy cost and low-quality electricity, mainly during the summer months which is a period of high energy demand. In this respect, the present study investigates the possibility of combining a geothermal power plant with a concentrated solar array to provide energy to an autonomous island grid. Since the productivity of geothermal fields is gradually decreasing over the years, the combination of solar with geothermal energy source aims to the extension of the productive lifetime of the field, achieved by reheating the geothermal fluid during reinjection to the injection well. The thermal energy, generated by concentrated solar collectors, increases the temperature of the geothermal brine and reduces the energy degradation of the field. In this study, the energy efficiency of different reheat values are studied in order to achieve the combination of a geothermal power plant and a concentrated solar field that can meet specific targets for lifetime energy production. According to the results, the proposed installation can merely contribute to the energy autonomy of the island grid during periods of low demand and provide energy security in periods of high energy consumption.

Faroe Islands: Towards 100% R.E.S. penetration

The Faroe Islands complex consists of 18 islands. The total energy demand is based on imported oil (93%). Electricity needs account for around 10% of the total energy consumption, with 51% covered from wind and hydro in 2016.Annual average wind velocities above 10 m/s and annual rainfalls higher than 3000 mm are measured in several sites. The annual incident solar irradiation on horizontal plane is around 780 kWh/m2. Wind and rain tend to be less in summer, posing a challenge for 100% energy needs cover.This article investigates the perspectives for 100% Renewable Energy Sources (RES) penetration in Faroe, including heating and transportation energy consumptions. Two wind/photovoltaic parks and Pumped Hydro Storage (PHS) systems are investigated for two autonomous systems, the main grid comprising 11 interconnected islands and the autonomous island of Suðuroy, accounting for 10% of the population. Wind potential maps are developed and the PHSs are sited on digitized land terrain. The systems' operation is numerically simulated, aiming at the optimization of the dimensioning. Real demand and RES data are employed. It is shown that RES annual penetration higher than 90% can be approached with RES – storage power plants absolutely technically and economically feasible.

Pumped energy storage system technology and its AC–DC interface topology, modelling and control analysis: a review

Pumped-storage hydropower plants can contribute to a better integration of intermittent renewable energy and to balance generation and demand in real time by providing rapid response generation. The utilisation of variable-speed pump-turbine units with a doubly fed induction machine is being progressively applied due to its overall efficiency and high level of operating flexibility. This study presents state-of-the-art pumped energy storage system technology and its AC–DC interface topology, modelling, simulation and control analysis. It also provides information on the existing global capacities, technological development, topologies and control strategies of the pumped-storage system. This report also outlines the analysis of dynamic performances of the system. It also attempts to recommend the future works in this area. This study concludes that pumped storage is the most suitable technology for small autonomous island grids and massive energy storage, where the energy efficiency of pumped storage varies in practice. Around the world, the size of the pumped-storage plant mostly lies in the range of a small size to 3060 MW. The back-to-back voltage source converter topology is mostly conducted due to its significant features. Due to its imperative features, the vector control strategy is widely used. The pumped-storage plant is dedicated to power management and stability regulation of grid and isolated power systems.

A hybrid power plant towards 100% energy autonomy for the island of Sifnos, Greece. Perspectives created from energy cooperatives

The article presents the technical - economic details of a hybrid power plant, towards 100% electricity production for the autonomous island of Sifnos, Greece, following the initiative of the Sifnos Island Cooperative (SIC) to claim the island's energy independence and a sustainable future for the local community.In the case of Sifnos, energy independency is achievable given the high wind potential and the availability of an appropriate site for the installation of a seawater Pumped Hydro Storage system. Despite the low power demand (annual peak demand 6.5 MW), pumped storage remains the optimum energy storage technology, with a set-up specific cost of 30 €/kWh of storage capacity. The project's economic feasibility is ensured with a selling electricity total price of 0.29 €/kWh, given the production specific cost (0.34 €/kWh) of the existing thermal power plant.The hybrid power plant anticipates to constitute the kernel of the SIC objectives for a general social and economic development for the local community. This can be approached with the re-investment of the project's profits for the development of essential technical infrastructure and the exploitation of the electricity production surplus, combined with energy saving or smart-grid techniques, to foster new professional activities.

Economic and Environmental Considerations for Zero-emission Transport and Thermal Energy Generation on an Energy Autonomous Island

The high cost and environmental impact of fossil-fuel energy generation in remote regions can make renewable energy applications more competitive than business-as-usual scenarios. Furthermore, energy and transport are two of the main sectors that significantly contribute to global greenhouse gas emissions. This paper focuses on the generation of thermal energy and the transport sector of a fossil fuel-based energy independent island in Greece. We evaluate (1) technologies for fully renewable thermal energy generation using building-specific solar thermal systems and (2) the replacement of the vehicle fleet of the island with electric and hydrogen-fueled vehicles. The analysis, based on economic and environmental criteria, shows that although solar thermal decreases greenhouse gases by 83%, when compared to the current diesel-based situation, it only becomes economically attractive with subsidy scenarios equal to or higher than 50%. However, in the transport sector, the sum of fuel and maintenance costs of fuel-cell and electric vehicles is found to be 45% lower than that of the current fleet, due to their approximately seven times lower fuel cost. Lastly, it will take approximately six years of use of the new vehicles to balance out the emissions of their manufacturing phase.

PHAROS: An Integrated Planning Tool for Meeting the Energy and Water Needs of Remote Islands using RES-based Hybrid Solutions

There is a significant number of Greek islands in the Aegean Sea that still meet their electricity demand on the basis of the local autonomous thermal power stations, using considerable amounts of imported oil. In addition, many of these islands suffer from water scarcity, covering their potable water needs with water imports at extremely high costs. Under the framework of PHAROS research project, and in an effort to support energy and water self-sufficiency, an integrated software tool has been developed for the optimal planning of hybrid renewable energy systems (HRES), capable of investigating the energy balance of autonomous island regions. In this context, a planning methodology for HRES combined with a sizing algorithm for desalination plants were devised and integrated in the advanced software tool named Energy System Analysis (ESA). ESA enables the detailed analysis of systems that include components such as wind, PV and desalination plants, energy storage devices and diesel engines. To this end, the long-lasting problems of the Aegean Sea islands, mainly stemming from their state of remoteness and isolation, require the examination of long-term energy strategies, which ESA can support in an efficient manner. In this context, the current work provides a short presentation of the ESA tool main features, using two discrete case studies that correspond to a North and a South Aegean Sea island respectively.

A Hybrid RES Distributed Generation System for Autonomous Islands: A DER-CAM and Storage-Based Economic and Optimal Dispatch Analysis

The possibility of replacing the existing autonomous thermal power plants by Distributed Energy Resources (DER) based on renewable energy sources (RES), along with the appropriate energy storage technologies in order to deal with the major problems that autonomous islands usually face was investigated. A case study of a small Greek island, which is confronted by various energy and water shortages, was studied for assessing the feasibility of DER deployment. The main objectives investigated were cost minimization, CO2 emissions minimization and DER reliability maximization. The DER-CAM (Distributed Energy Resources Customer Adoption Model) decision support tool was used for the multi-objective analysis conducted, which proposes a set of optimal solutions defining the appropriate Distributed Generation (DG) technologies, the capacities of storage and other technologies and the optimal dispatch of the DG system. A mutual beneficial solution, for all stakeholders, was proposed indicating the scope for developing such systems for all islands facing the same problems.

Generation scheduling in non-interconnected islands with high RES penetration

In this paper, the generation scheduling problem for autonomous island systems with significant penetration of non-dispatchable Renewable Energy Source (RES) generation is investigated, proposing a unit commitment-economic dispatch (UC-ED) model which is fully compatible with the provisions of the regulatory framework currently applicable to the Greek non-interconnected island (NII) systems. Two UC-ED model variants are presented and comparatively assessed, in order to illustrate the impact of various system parameters (technical characteristics of the thermal units, reserve requirements, etc.) on the expected operating profile of the NII system. A detailed UC-ED model is first proposed, which takes into account the reserve requirements at different time scales (primary, secondary and tertiary reserves) and respective capabilities of generating units. An alternative, simplified UC-ED model is also presented, formulated on the basis of aggregate spinning reserves, to cater for uncertainties in the actual reserve capabilities of existing thermal units. The developed UC-ED models are applied to an existing NII system to evaluate their performance and results obtained on an annual basis.

Augmenting corporate R&D with networked micro innovation teams

Continuous innovation is key to a company's growth. The current models for corporate research and development are not suited for evaluating small scale emerging technology and trends. Networked micro innovation teams fill that gap and augment corporate R&D expenditure but using employee volunteers to identify and evaluate innovative concepts. These teams provide competitive advantages to the companies which develop them. The basic structure of corporate research and development has not changed despite radical changes in how ideas and technologies emerge in the market [1]. There is ample opportunity for companies to create internal innovation teams which evaluate emerging technologies and trends at a smaller scale than is practical with the traditional R&D departments. There are few studies among the legion about R&D which consider very small, or micro, innovations. Technology now enables a different approach to identifying and testing opportunities at a drastically smaller, cheaper scale than. In the past, innovative R&D departments have created autonomous islands free from bureaucracy or traditional management in order to address specific goals. Lockheed Martin's skunk work [2] and Alphabet's X lab (formerly Google[x]) are examples of innovation incubators outside the formal R&D process [3]. Creating separate laboratories which operate under separate rules can be useful pursuing auditions goals and for time and capital intensive projects, however, even these looser structures are overkill for the needs of some projects. To fill this gap, companies should create micro innovation teams which function as a network of local, decentralized teams. For example, buying an Oculus rift to explore its capabilities is an act too small for either a traditional or skunk works-style corporate R&D department. Yet, there are many opportunities for open innovation available to companies if they have the ability to conduct rapid and small-scale experimentation.

An integrated stochastic multi-regional long-term energy planning model incorporating autonomous power systems and demand response

The power sector faces a rapid transformation worldwide from a dominant fossil-fueled towards a low carbon electricity generation mix. Renewable energy technologies (RES) are steadily becoming a greater part of the global energy mix, in particular in regions that have put in place policies and measures to promote their utilization. This paper presents an optimization-based approach to address the generation expansion planning (GEP) problem of a large-scale, central power system in a highly uncertain and volatile electricity industry environment. A multi-regional, multi-period linear mixed-integer linear programming (MILP) model is presented, combining optimization techniques with a Monte Carlo (MCA) method and demand response concepts. The optimization goal concerns the minimization of the total discounted cost by determining optimal power capacity additions per time interval and region, and the power generation mix per technology and time period. The model is evaluated on the Greek power system (GPS), taking also into consideration the scheduled interconnection of the mainland power system with those of selected autonomous islands (Cyclades and Crete), and aims at providing full insight into the composition of the long-term energy roadmap at a national level.

Overlapping community identification approach in online social networks

Online social networks have become embedded in our everyday lives so much that we cannot ignore it. One specific area of increased interest in social networks is that of detecting overlapping communities: instead of considering online communities as autonomous islands acting independently, communities are more like sprawling cities bleeding into each other. The assumption that online communities behave more like complex networks creates new challenges, specifically in the area of size and complexity. Algorithms for detecting these overlapping communities need to be fast and accurate. This research proposes method for detecting non-overlapping communities by using a CNM algorithm, which in turn allows us to extrapolate the overlapping networks. In addition, an improved index for closeness centrality is given to classify overlapping nodes. The methods used in this research demonstrate a high classification accuracy in detecting overlapping communities, with a time complexity of O(n2).