Isolated Energy Systems Research Articles

Complementarity of electric vehicles and pumped-hydro as energy storage in small isolated energy systems: case of La Palma, Canary Islands

Isolated energy systems in archipelagos are characterized for having a great dependence on fossil sources due to isolation and territorial fragmentation. The island of La Palma is situated on the northwest of the Canary Islands, and its electric system is very small. Sustainability policies planned by local authorities are aimed to increase the share of renewable energies and the reduction of fossil energies. However, intermittence and the concentration of unmanageable renewable energies in few locations may hinder the operation of the system. In order to solve these problems, energy storage plays an essential role. The aim of this paper is to analyse the effects of the introduction of two possible alternatives as a way of energy storage: pumped hydro storage and electric vehicles. For this, we use a simulation model adapted to the features of La Palma, considering different scenarios. Results show that, in the most favourable scenario, the installation of an additional 25 MW from renewables (more than double the current power), supported by 20 MW of pumped hydro storage and a fleet of 3361 electric vehicles, would allow the current share of renewables to increase from 11% (in 2015) to 49%. Furthermore, this would mean a 26% reduction in CO2 emissions, 10% in costs of generated kWh and 19% in energy dependence.

Impact of solar and wind forecast uncertainties on demand response of isolated microgrids

A flexible load management may improve significantly the economic dispatch, especially for isolated energy systems with a significant share of renewables. For that purpose, renewable resources and load forecasts ought to be taken in account for optimal demand response programs.The present study uses solar forecast coupled with domestic hot water needs to anticipate the electric demand of solar thermal systems. On the other hand, wind electricity supply will take advantage of thermal storage of solar systems, using a demand response strategy based on genetic algorithms, for load optimization, in order to minimize overall operating costs. The methodology is applied to the isolated microgrid of Corvo Island, in Azores.Results show a 3% increase in the dispatch costs due to the forecasts uncertainty, when in presence of 8% of daily flexible loads. However, this impact is dissipated when solar thermal backup needs decrease, which is explained by the relevance of the wind forecast on the planning of the dispatch of flexible loads. Wind forecast uncertainties can impact in 2% in absorption of wind energy, varying with the forecast horizon considered, while the solar forecast uncertainties have more impact when the thermal energy storage is below the daily thermal demand.

Multi-Criteria Decision Support Methods for Renewable Energy Systems on Islands

Islands often are confronted with severe energy challenges especially those far from the main land which operate as isolated energy systems. In those cases electricity, the queen of the energy vectors shall be obtained from diversified sources to alleviate the burden of the dependence on fossil fuels. Thereby, the generation of electricity from renewable energy sources in combination with electricity storage becomes an irrecusably challenge in the nearby future. Often a variety of criteria can be applied to identify the suitability of technologies, whereas no ideal family of criteria has been defined in the literature. Hence, decision support for energy planning and management is required. This paper reviews the state-of-the-art of multi-criteria decision support methods applied to renewable energy and storage technologies. It will be analyzed where the current focus is placed on. The gaps of those analyzed studies will be evaluated and key aspects for future energy planning considerations for islands will be proposed. Finally, an outlook for a newly developed concept for island energy planning will be presented. Indeed, for most isolated islands renewable energy technologies in combination with storage devices are a desirable and valued solution for sustainable development.

Predictive Dispatch Across Time of Hybrid Isolated Power Systems

The paper proposes a methodology for the optimal dispatch of energy sources in hybrid and isolated energy systems. The proposed approach is based on the formulation and solution of a nonlinear discrete optimization problem aimed at optimizing input and output time trajectories for a set of combined generating and storage technologies. Loads and interruptible loads are among controlled variables, and are modeled according to their interruption costs. The approach is general enough to be applied to any hybrid system configuration and was developed having in mind the complex hybrid system architectures comprising several competing storage technologies (battery, pumping, and hydrogen). Test results are aimed at showing the feasibility of the proposed methodology, comparing optimal trajectories to suboptimal system behavior given by load-following strategies.

Managing Networked Hybrid-Energy Systems: a Predictive Dispatch Approach

Energy source management in networked enterprises is one of the crucial tasks of recent times: different energy requests as well as distribution among node-enterprise due to variety of production loads and duties exchanges may in fact bring to un-optimal energetic balance of the network. The idea of optimal balancing of energy sources within a set of nodes of an enterprise network, even though temporarily cooperating, by endeavoring a systemic perspective is the rationale of the present paper. A methodology for the optimal dispatch of energy sources in hybrid as well as isolated energy systems has been devised to this aim. The core of the methodology is based on the formulation and solution of a nonlinear discrete optimization problem aimed at optimizing input and output time trajectories for a set of combined power-generation and storage technologies. The proposed approach is general enough to be susceptible of implementation in any network of enterprises to optimize the energy dispatching.

Promotion of wind energy in isolated energy systems: the case of the Orites wind farm

With the establishment of the first wind farm on the island, Cyprus has made progress to satisfy the European Union’s 2020 renewable energy targets. Operational since September 2010, the 174 M€ Orites wind farm is currently the largest wind project in the Mediterranean region. In this article, the main characteristics of the project with regard to Cyprus’s national action plan for the promotion of renewable energy sources are presented. The socio-economic impacts of the project and its feasibility in the context of an isolated energy system are also examined. The results of a public survey to identify the attitudes of surrounding households and neighbouring cities towards the wind farm are presented. The assessment was based on face-to-face interviews conducted with 50 households from the surrounding communities and 100 interviewees from neighbouring cities. According to the survey, the public opinion on the wind farm was generally positive, and the majority of the respondents considered the wind farm to be acceptable as of no considerable environmental impact.

Maritime Superconductivity Perspectives

The present paper reports on the ongoing studies into the perspectives of maritime superconductivity (SC). Maritime applications follow a similar pattern as on-shore applications when it comes to performance if the competition is weak. For large scale applications like propulsion, power supply, and other machinery, the character of an isolated energy system onboard greatly influences the perspectives of maritime SC. The paper compares the energy chains of propulsion configurations and discusses the relations with energy carriers, storage, and conversions. It is shown that perspectives more or less follow the developments on all electric shipping: i.e., as for energy efficiency short range shipping and dynamic behavior favor SC technology; high-temperature superconducting engines may also be an improvement if electric propulsion is selected for other reasons than efficiency. High-temperature superconductor degaussing is promising, but demands adjustments. Maritime SC perspectives often depend on developments in other areas like fuels, conversions, and power electronics.

Wind power design in isolated energy systems: Impacts of daily wind patterns

Increasing levels of intermittent renewables, especially wind power, in energy systems require accurate temporal characterisation of the resources’ availability at seasonal, daily and hourly scales. This is crucial for isolated energy systems, where increasing wind power penetration is limited due to costly backup power generation requirements. In the case studies presented in this paper, the energy systems of two islands are simulated using a new methodology for synthetic wind speed scenarios including daily wind patterns. A trade-off analysis was conducted in terms of surplus wind power and renewables penetration rate, with the objective of supplying decision support on wind turbine placement. Results show that there may be a significant advantage in locating future wind parks on sites where wind speed patterns better match electricity demand patters, rather than just choosing a site with the highest mean wind speed, but only if the annual mean wind speed is still sufficiently high to make the investment economically feasible.

Design and optimization of isolated energy systems through pinch analysis

AbstractIsolated energy systems seem to be a promising option for electrifying remote locations where grid extension is not feasible or economical. Integration of battery bank as means of energy storage with different renewable energy systems can enhance the system reliability and its overall performance. Therefore, appropriate choices of generator sizes and the battery bank capacity are critical to the success of such renewable‐based isolated power systems. In this article, the tools of pinch analysis are extended to design isolated renewable energy systems. The importance of setting targets before design is highlighted for designing renewable‐based isolated energy systems. The system sizing through the grand composite curve (GCC) representation of stored energy is proposed in this article. The set of all feasible solutions, defined as the design space for the system, is graphically represented for in‐depth visualization. The relation between the design space approach for designing and optimizing an isolated energy system and the principles of pinch analysis have been established in this article. The GCC representation also provides opportunity to the system designer for strategic load growth without affecting the system size. Copyright © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.

The use of multiple criteria decision making methodologies for the promotion of RES through funding schemes in Cyprus, A review

In isolated energy systems with no indigenous sources of energy such as the one of the Republic of Cyprus, the renewable energy option is the only alternative to achieve energy independence. Though, the relative technological maturity of renewable energy sources and their satisfactory efficiencies, their implementation has not reached the expected levels in many regions. This situation is mainly due to the fact that the up-to-date efforts for their development have been underestimated and the parameters involved in drafting subsidy schemes are in some cases misinterpreted and not given the appropriate attention. Decision makers are faced with ongoing major energy challenges such as fossil fuel depletion, increasing demand, energy prices and thus the move towards a sustainable energy development is crucial and highly complicated. This paper investigates the use of MCDM methods and then implements the methods for three subsidy schemes available in Cyprus.

Solar energy potential for heating and cooling systems in big cities of Turkey : Şaylan, L. et al. Energy Conversion and Management, 2002, 43, (14), 1829–1837

The thermal utilization of solar energy is usually confined to domestic hot water systems and somewhat to space heating at temperatures up to 60 °C. Industrial process heat has a considerable potential for solar energy utilization. Cyprus has a small isolated energy system, almost totally dependent on imported fuels to meet its energy demand. The abundance of solar radiation together with a good technological base, created favorable conditions for the exploitation of solar energy in the island. The number of units in operation today corresponds to one heater for every 3.7 people in the island, which is a world record. Despite this impressive record no solar industrial process heat system is in operation today. The main problem for this is the big expenditure required for such a system and the uncertainty of the benefits. The objective of this work was to investigate the viability of using parabolic trough collectors for industrial heat generation in Cyprus. The system is analyzed both thermally and economically with TRNSYS and the TMY for Nicosia, Cyprus, in order to show the magnitude of the expected benefits. The load is hot water delivered at 85 °C at a flow rate of 2000 kg/h for the first three quarters of each hour from 8:00–16:00 h, 5 days a week. The system consists of an array of parabolic trough collectors, hot water storage tank, piping and controls. The optimum collector area for the present application is 300 m2, the optimum collector flow rate is 54 kg/m2 h and the optimum storage tank size is 25 m3. The system covers 50% of the annual load of the system and gives life cycle savings of about C£6200 (€10800). This amount represent the money saved from the use of the system against paying for fuel. The savings however refer to a non-subsidized fuel price, which will be in effect from 2003. The optimum system can deliver a total of 896 GJ per year and avoids 208 tons of CO2 emissions to the atmosphere. The effect of various design changes on the system performance was investigated. The E–W tracking system (collector axis aligned in N–S direction) was found to be superior to the N–S one. The required load temperature affects the performance of the system as for higher temperatures the auxiliary energy required is bigger. Also a number of variations in the load use pattern have been investigated and presented in this paper. It was found that the bigger the load (double shift, full hour use pattern) the bigger the collector area required, the greater the first year fuel savings and the greater the life cycle savings of the installation. This means that it is more viable to apply solar industrial process heat to higher energy consumption industries.

Parabolic trough collectors for industrial process heat in Cyprus

The thermal utilization of solar energy is usually confined to domestic hot water systems and somewhat to space heating at temperatures up to 60 °C. Industrial process heat has a considerable potential for solar energy utilization. Cyprus has a small isolated energy system, almost totally dependent on imported fuels to meet its energy demand. The abundance of solar radiation together with a good technological base, created favorable conditions for the exploitation of solar energy in the island. The number of units in operation today corresponds to one heater for every 3.7 people in the island, which is a world record. Despite this impressive record no solar industrial process heat system is in operation today. The main problem for this is the big expenditure required for such a system and the uncertainty of the benefits. The objective of this work was to investigate the viability of using parabolic trough collectors for industrial heat generation in Cyprus. The system is analyzed both thermally and economically with TRNSYS and the TMY for Nicosia, Cyprus, in order to show the magnitude of the expected benefits. The load is hot water delivered at 85 °C at a flow rate of 2000 kg/h for the first three quarters of each hour from 8:00–16:00 h, 5 days a week. The system consists of an array of parabolic trough collectors, hot water storage tank, piping and controls. The optimum collector area for the present application is 300 m 2, the optimum collector flow rate is 54 kg/m 2 h and the optimum storage tank size is 25 m 3. The system covers 50% of the annual load of the system and gives life cycle savings of about C£6200 (€10800). This amount represent the money saved from the use of the system against paying for fuel. The savings however refer to a non-subsidized fuel price, which will be in effect from 2003. The optimum system can deliver a total of 896 GJ per year and avoids 208 tons of CO 2 emissions to the atmosphere. The effect of various design changes on the system performance was investigated. The E–W tracking system (collector axis aligned in N–S direction) was found to be superior to the N–S one. The required load temperature affects the performance of the system as for higher temperatures the auxiliary energy required is bigger. Also a number of variations in the load use pattern have been investigated and presented in this paper. It was found that the bigger the load (double shift, full hour use pattern) the bigger the collector area required, the greater the first year fuel savings and the greater the life cycle savings of the installation. This means that it is more viable to apply solar industrial process heat to higher energy consumption industries.