A Detailed Parametric Analysis of a Solar-Powered Cogeneration System for Electricity and Hydrogen Production  
[PERSON]  
1 The Thermal Department, School of Mechanical Engineering, National Technical University of Athens,  
Heroon Polytechniou 9, 15780 Athens, Greece  
1 The Department, School of Mechanical Engineering, National Technical University of Athens,  
Heroon Polytechniou 9, 15780 Athens, Greece
are utilized to drive power cycles such as the Organic Rankine Cycle (ORC) [7]. In the ORC, an organic substance with a lower boiling point is utilized, while a low-temperature heat source is exploited, which comes from solar energy, geothermal energy, biomass, or waste heat [8]. A solar-fueled ORC configuration coupled to a PTC solar field with both warm and cold thermal energy storage tanks was examined in the literature by [PERSON] et al. [9]. The recuperative ORC with toluene, which performed better than the other working media, achieved an overall efficiency, that increased by 24.8% compared to another published study. For the case of the supercritical ORC, both thermal and overall system efficiency were enhanced by 11.3% and 10.8%, respectively, compared to the corresponding sub-critical ORC. Moreover, another study [10] investigated a geothermal-based ORC energy system. The total energetic and exergetic efficiency was determined at 11.24% and 39.03%, respectively. Additionally, the incorporation of the recuperator improved both the energy and exergy efficiency by 15%. Furthermore, [PERSON] and [PERSON] [11] analyzed an ORC plant powered by low-temperature waste heat and solar energy which was absorbed by PTCs. When toluene was utilized as the working medium, the overall energy efficiency reached the value of 19.7%. On the other hand, according to the literature, researchers have investigated energy plants based on ORC that produce more than one useful output, apart from electricity. [PERSON] et al. [12] studied a micro-cogeneration installation, which produced electricity and domestic hot water. The plant, which could be incorporated into microgrids, contained a biomass boiler and an ORC unit. Therminol SP was used in the heating circuit. So, the maximum value of the ORC electrical efficiency was found at 7.3%, while the maximum cogeneration energy efficiencies of the whole system and the ORC unit were found at 62% and 93%, respectively. Furthermore, when the oil temperature was about 150 \({}^{\circ}\)C, the power production rate was calculated at 2.53 kW. In addition, [PERSON] and [PERSON] [13] analyzed a solar-powered trigeneration installation that produced electricity, heating, and cooling. It consisted of a PTC field, a thermal storage tank, an ORC unit, and a LiBr-H\({}_{2}\)O absorption machine, which was fed by the ORC-rejected heat. The maximum achieved exergy efficiency was equal to 29.42%. Finally, the electricity, heating, and cooling loads were calculated at 177.6 kW, 972 kW, and 398.8 kW, respectively, for the optimum scenario. In parallel, hydrogen has gained further attention and has been integrated into multi-generation configurations, recently. At first, hydrogen is a promising energy carrier that is not available in its molecular formula. It can be obtained from fossil fuels via hydrocarbon reforming or pyrolysis, as well as renewable sources, such as water or biomass. In addition, it can be combusted in an internal combustion engine or used in a fuel cell, while water is the only by-product of the reaction [14]. Apart from the traditional utilization in ammonia synthesis, the production of methanol, and petroleum refining, hydrogen can also be used in powering vehicles or electricity production [15]. Furthermore, hydrogen has been suggested as a solution to the energy storage problem because of the production fluctuations of renewable energy sources. Although this element has a high gravimetric energy density, it has a low volumetric one, so it must be compressed at high-pressure levels or liquefied [16].