Abstract
Stand-alone systems in remote regions require the utilization of renewable resources; however, their natural intermittence requires the implementation of energy-storage systems that allow a continuous power supply. More than one renewable source is usually available at the same site. Thus, the choice of a hybrid system seems viable. It is relevant to study hybrid systems as they could reduce energy storage; however, sizing the hybrid system might have several implications, not only for the available daily energy, but also for the required daily energy storage and surplus seasonal energy. In this work, we present a case study of a stand-alone, conventional household powered by photovoltaic and marine-current-energy systems in Cozumel, Mexico. The analysis of different hybridization degrees serves as a guidance tool to decide whether hybrid systems are required for a specific situation; in contrast to previous approaches, where ideal consumption and generation profiles have been utilized, yearlong profiles were utilized here. The renewable potential data were obtained on site at an hourly resolution; requirements such as size of and cycles in the daily and seasonal energy storage were analyzed according to the degree of participation or hybridization of the proposed renewable systems through an algorithm that evaluates power generation and daily consumption throughout the year. A further analysis indicated that marine-current-energy implementation reduces the size of the daily energy-storage system by 79% in comparison to the use of only a photovoltaic system due to the similarity between the energy-demand profile and the marine-current-energy production profile. The results indicate that a greater participation of marine currents can help decrease daily storage while increasing seasonal storage by 16% compared to using only solar energy. On the other hand, hybridization enabled a reduction in the number of daily charge and discharge cycles at 0.2 hybridization degrees. It also allowed us to reduce the seasonal energy storage by 38% at 0.6 hybridization degrees with respect to only using energy from marine currents. Afterwards, energy-storage technologies were evaluated using the TOPSIS Multi-Criteria Decision Analysis to validate the best-suited technology for the energy-storage system. The evaluation considered the characteristics of the technology and the periods of energy storage. In this work, hybrid storage systems were mandatory since, for daily storage, lithium-ion batteries are better suited, while for seasonal storage, hydrogen-producing systems are more suitable to manage the amount of energy and the storage duration due to the high seasonal renewable-energy variations.
Highlights
Sun, wind, and marine energies are defined as Variable Renewable Energies (VREs) due to their inherent intermittence, irregularity, and dispatchability, VREs might have several small- to large-scale applications in stand-alone power systems where energy storage is essential
Applying the algorithm developed in the Matlab® program, the curves of the hybridization process were obtained at different hybridization degree (HD) for the 365 days of the year; daily variations during the year are shown in Appendix A in Figure A1 and includes daily variations in energy consumption and supply in the 12 months
For hybrid photovoltaics–marine-current system (MCS), this study indicates that for a greater participation of the MCS, the amount of required daily energy storage is lower (79%)
Summary
Wind, and marine energies are defined as Variable Renewable Energies (VREs) due to their inherent intermittence, irregularity, and dispatchability, VREs might have several small- to large-scale applications in stand-alone power systems where energy storage is essential. Marine Renewable Energy (MRE) is broadly available in different regions. Estimations indicate that ocean energy could contribute from 500 to 1000 MW of the installed capacity by 2030 [1,2]. Ocean currents or marine currents can produce energy from tidal movements and/or ocean circulation due to thermal and salinity gradients [3]. In Mexico, this type of energy is attractive due to its natural occurrence in certain regions such as the Gulf of California and the Cozumel Current in the Yucatan Peninsula where the potential for producing energy is as high as 100 W/m2 [4]. Even with the technology to harvest ocean energy, significant challenges for renewable energy include bringing the energy into the coast, storing it, and using it in a cost-effective manner
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