A new power ma nagement algorithm for a stand-alone hybrid system supplying a desalination unit

Faced with increasing trend of water demand and decreasing resources of fossil fuels and their high costs, desalination units based on renewable energies have become the best solution to face this challenge. This paper aims to investigate the design and the operation strategy of stand-alone hybrid renewable power generation system supplying a desalination unit which feeds the Kerkennah islands (Tunisia) with fresh water. The sizing of all the main hybrid system components such as photovoltaic generator, wind turbine, a fuel cell, and an electrolyzer is investigated in order to obtain some technical and economic profitability. In order to ensure the optimal use of the produced energy and satisfy the fresh water needs, a novel power management algorithm that allows controlling the energy flows within the system components is developed. Simulation results were carried out over the two months of January and July, and its results are shown in our paper. These results demonstrate the feasibility and the efficiency of the used control strategy and the performance of the hybrid system.

Control, energy management and performance evaluation of desalination unit based renewable energies using a graphical user interface

Economic and environmental concerns over fossil fuels encourage the development of renewable energy. But to allow the penetration of intermittent energy sources, optimal sizing of hybrid renewable energy systems is quite necessary. This paper presents an optimal sizing algorithm which estimates the sizes of different components of hybrid photovoltaic/wind power generation system supplying a desalination unit. The optimal combination of the hybrid system is selected according to its technical and economic profitability. A case study is conducted to analyze a hybrid project, which is designed to supply a desalination unit feeding the Kerkennah islands (Tunisia) with fresh water.

Performance assessment of a renewable micro-scale trigeneration system based on biomass steam cycle, wind turbine, photovoltaic field

Introducing a new method for optimal sizing of a hybrid (wind/PV/battery) system considering instantaneous wind speed variations

This paper investigates a variable speed wind turbine based on permanent magnet synchronous generator and a full-scale power converter in a stand-alone system. An energy storage system(ESS) including battery and fuel cell-electrolyzer combination is connected to the DC link of the full-scale power converter through the power electronics interface. Wind is the primary power source of the system, the battery and FC-electrolyzer combination is used as a backup and a long-term storage system to provide or absorb power in the stand-alone system, respectively. In this paper, a control strategy is proposed for the operation of this variable speed wind turbine in a stand-alone system, where the generator-side converter and the ESS operate together to meet the demand of the loads. This control strategy is competent for supporting the variation of the loads or wind speed and limiting the DC-link voltage of the full-scale power converter in a small range. A simulation model of a variable speed wind turbine in a stand-alone system is developed using the simulation tool of PSCAD/EMTDC. The dynamic performance of the stand-alone wind turbine system and the proposed control strategy is assessed and emphasized with the simulation results.

Exergy and economic comparison between kW-scale hybrid and stand-alone solid oxide fuel cell systems

Hybrid membrane system for desalination and wastewater treatment : Integrating forward osmosis and low pressure reverse osmosis

In this paper, analysis, sizing and design of hybrid wind-photovoltaic system are presented for two different sites in Morocco: Dakhla and Laayoune regions. This system will be used to produce the required electrical energy to drive a medium scale desalination unit using mechanical vapor compression process with a production capacity of 17m3/h of distilled water. The design and optimization of the hybrid system is based on PV panels and wind turbines characteristics, meteorological data of each site, economic evaluation and the amount of CO 2 saving. The final objective is providing a renewable energy hybrid system with low energy production cost, and reducing the rate pollution generated by this kind of desalination process. Two scenarios are taken into consideration, the first one when the desalination unit operates only during sunshine time and the second one for full day operation. Results show that using PV system only is the most suitable configuration in the case of the first scenario, however using 40% and 35% as PV contribution in the renewable hybrid system is the best combination for Dakhla and Laayoune regions respectively, these systems allow a CO 2 -savings equals to 3,469 Tons/year.

3 - Off-grid full renewable hybrid systems: Control strategies, optimization, and modeling

Techno-economical analysis of stand-alone hybrid renewable power system for Ras Musherib in United Arab Emirates

The interplay between imbalance pricing mechanisms and network congestions – Analysis of the German electricity market

This paper presents a methodology for the prediction of power system balancing requirement and the probability of tail event (large imbalance between generation and load). Maintaining sufficient balancing reserves to match the difference between hourly generation schedule and real-time variable load and intermittent resources becomes more and more challenging with the increasing penetration of intermittent energy sources. The presented methodology uses yearly distributions and hourly distributions of balancing requirement and tail events to provide a high level look at the issue and warn system operators of those hours when problems are most likely to occur. For real-time prediction, a Bayes net model is constructed to model the statistical relationships between system imbalance and forecast errors, generation schedule control errors and other influential factors. The methodology will be able to provide reference information to system operators in determining the sufficiency of system balancing reserve and taking appropriate control actions.

The integration of large amounts of renewable energy is an important challenge for the future management of electric systems, since it affects the operation of the electric power system and the design of the transmission and distribution network infrastructure. This is specially due to the connection requirements of the renewable energy technologies, to the extension and adjustment of the grid infrastructure and to the identification of new solutions for operational reserve, in order to maintain the overall system flexibility and security.In this paper, the impact of high penetration of intermittent energy sources, expected in long term in the Portuguese Power System, is analysed and the operational reserve requirements to accomplish a reliable and reasonable electrical energy supply are identified. It was concluded that pumped storage power plants, special power plants with regulating capabilities, will have an important task to provide the operational reserve requirements of the Portuguese Power System. This technology assumes a fundamental role not only to ensure the adequate levels of security of supply but also to allow the maximum exploitation of the installed capacity in renewable energy sources.

The increasing penetration of intermittent energy sources along with the introduction of shiftable load elements renders transmission network expansion planning (TNEP) a challenging task. In particular, the ever-expanding spectrum of possible operating points necessitates the consideration of a very large number of scenarios within a cost-benefit framework, leading to computational issues. On the other hand, failure to adequately capture the behavior of stochastic parameters can lead to inefficient expansion plans. This paper proposes a novel TNEP framework that accommodates multiple sources of operational stochasticity. Inter-spatial dependencies between loads in various locations and intermittent generation units' output are captured by using a multivariate Gaussian copula. This statistical model forms the basis of a Monte Carlo analysis framework for exploring the uncertainty state-space. Benders decomposition is applied to efficiently split the investment and operation problems. The advantages of the proposed model are demonstrated through a case study on the IEEE 118-bus system. By evaluating the confidence interval of the optimality gap, the advantages of the proposed approach over conventional techniques are clearly demonstrated.