## 1 Introduction
The plant energy and exergy efficiencies were determined to be 41.0% and 28.4%, respectively, while the hydrogen production rate was determined at 0.01 kg/s. Furthermore, [PERSON] et al. [24] proposed a multigeneration configuration that provided electricity, heating, cooling, drying, hydrogen, hot water, and freshwater. Consequently, the unit included a PTC field, a distillation plant, a PEM electrolyzer, a hydrogen compression system, a Kalina cycle, an ORC, an ejector cooling cycle, a domestic water heater, a dryer, as well as a hot and a cold storage tank. The overall energy efficiency, the exergy efficiency, and the hydrogen production rate were calculated to be equal to 59.34%, 56.51%, and 0.0043 kg/s, respectively. In parallel, the integration of hydrogen into the energy networks of islands and remote communities has also been investigated. More specifically, [PERSON] et al. [25] proposed the installation of a PHES system and a wind park, which would work together with the existing PV panels and wind turbines, on the Greek island of Sifinos. The fundamental purpose of the whole project was the coverage of the entire electricity demand by the previously mentioned modules, and the energy independence of the island. The surplus electricity was used to produce potable water and hydrogen. Then, the produced hydrogen would power the passenger ships connecting Sifinos with the nearby islands. According to the previous literature review, the majority of solar-based power plants and polygeneration systems, include storage tanks to store the excess thermal energy that comes from solar irradiation. This method can store energy only for a couple of hours. Hydrogen energy storage is a long-term method, as hydrogen can be stored and used as a fuel with numerous applications. The present study is an innovative one because two storage technologies are incorporated simultaneously, the solar TES tank and chemical energy storage in the form of compressed hydrogen. Moreover, there is a lack of studies that focus on the hydrogen storage capacity of an energy plant powered by solar energy. The surplus electricity produced by the solar ORC unit is fed to a water electrolyzer to produce hydrogen for later use after several days and even months. The examined configuration is planned to be installed on the Greek island of Kythnos, close to Athens. This island is not interconnected to the national grid; therefore, it is important to cover the electricity demand with its own sources and to store energy for later use. The proposed plant consists of a few PTC modules that absorb the solar beam irradiation to provide useful heat as an input to the ORC module. Furthermore, the installation contains a TES tank, a PEM water electrolyzer, a hydrogen compressor, and a hydrogen storage tank. A share of the ORC power generation feeds both the electrolyzer and the hydrogen compression system, while the remaining electricity can cover the island's electricity demand. The other useful output is compressed hydrogen fuel, which can be sold or used on-site to power fuel cell vehicles or vessels. Therefore, this small-scale solar-powered energy unit provides electricity and green hydrogen while the integration of two storage technologies increases the system's dispatchability. At first, a preliminary analysis is conducted, and then the system is analyzed and optimized under dynamic conditions. The whole configuration is evaluated by calculating the main energetic, exergetic, and economic indexes. Finally, the preliminary analysis is performed by an Engineering Equation Solver (EES) software code, while the dynamic simulation is carried out using Matlab.