• Energy Research

Abstract In this paper, a thermo-economic analysis concerning a methanol production plant is performed. In particular, this study was developed with the aim of evaluating the opportunity and viability of obtaining methanol from the chemical reaction between recycled CO2, emitted from a fossil-fuel power station, and hydrogen produced by water electrolysis. This solution can represent an interesting carbon dioxide reduction method and methanol as a product can be considered an energy storage means. As a first step, a thermodynamic analysis is performed in order to determine the mass and energy flows of the plant; then, a feasibility analysis concerning a large size methanol production plant is performed taking into account three different economic scenarios (Germany, Italy, and China). In order to evaluate the economic viability, the total investment cost and payback period are calculated in all the scenarios. Different methanol and electrical energy prices are considered, to take into proper account the influence of these parameters on mid-term future scenarios. Moreover, a sensitivity analysis, considering different oxygen selling prices and PEM electrolyzer capital costs, were performed.

This paper presents a techno-economic feasibility analysis related to a heat pump installation in a poly-generative energy district to convert the overproduction of electricity into thermal power, easy to be stored in thermal storage tanks. The heat pump technology is already used for thermal/cooling energy production in different areas although application in energy districts in a power-to-heat modality to improve management of electrical/thermal energy demands is still limited.In this research, the installation of a heat pump in the poly-generative smart grid located at the University of Genoa Campus is presented. A time dependent one-year techno-economic analysis of the energy district is performed, throughout a model built with a software developed by the authors. The integration of the heat pump in the energy district is analysed, comparing the energetic, environmental and economic performance to the present configuration of the poly-generative energy district. The results show that the heat pump introduction grants several advantages, such as a reduction in gas consumption (24 ton/year, −15%) and an increase in the annual energy efficiency of cogenerative prime movers which can work for a higher number of hours (+23%) close to the design point.

Abstract In this paper, the authors present an innovative approach to compare the most promising innovative technologies for energy production and storage for maritime applications. The developed algorithm, which include a large database built with market and literature data, compares several possible solutions, including innovative ones, from the environmental, economic and energetic standpoints. A detailed decription of the functions implemented in the database is reported, explaining also in detail the algorithm developed to evaluate and compare the technologies. Then, the methodology is applied to two case studies to demonstrate the algorithm’s potential, the reliability of the wide range of data included in the database and the impact of the scenario on the final results. The investigated case studies are: (i) a small size passenger ship operating in urban areas (ii) a large size cruise ship. Analyzing the first case study, a focus on the impact of generation unit and fuel storage systems is developed for the most promising solutions, represented by fuel cells in comparison to standard solutions. The second case study shows that, as could be expected, the most promising solutions in this range of application is the use of MDO or LNG in Internal Combustion Engines. In order to evaluate the future potential of the different alternative fuels, a sensitivity analysis is performed to evaluate the impact of the increasing emissions' importance: methanol, LNG, and ammonia are indicated as the most futurible fuels. It is worth noting that the presented approach has a general validity, thus it can be applied to other ships' typologies; the modular structure also allows for including further emerging technologies.

Abstract This paper proposes a time-dependent, thermo-economic hierarchical approach for the analysis of energy districts and smart poly-generation microgrids, in order to determine the optimal size of different prime movers, required to meet the energy demand of a generic user. This approach allows for determining the optimal size for each component of the energy district, as well as defining its most efficient operation management for the entire year, taking into proper account the time-dependent nature of the electrical, thermal and cooling demands, which are the main constraints of the optimisation problem. Additionally, the proposed method takes into consideration both energy performance and operation costs. A specific case study is developed around the smart poly-generation microgrid at the University of Genoa, Savona Campus (Italy), which has been operational since 2013. In the original design, the microgrid includes different co-generative prime movers, renewable generators and a thermal storage system. In a second design an absorption chiller is included to supply the campus' energy cooling demand. Obtained results allowed identifying the best operation configuration, from a thermo-economic standpoint, for the considered scenario. The proposed method can be easily replicated in different applications and configurations of different smart poly-generative grids.

Abstract In this paper, the impact of not controllable renewable energy generators (wind turbines and solar photovoltaic panels) on the thermo-economic optimum performance of poly-generation smart grids is investigated using an original time dependent hierarchical approach. The grid used for the analysis is the one installed at the University of Genoa for research activities. It is based on different prime movers: (i) 100 kWe micro gas turbine, (ii) 20 kWe internal combustion engine powered by gases to produce both electrical and thermal (hot water) energy and (iii) a 100 kWth adsorption chiller to produce cooling (cold water) energy. The grid includes thermal storage tanks to manage the thermal demand load during the year. The plant under analysis is also equipped with two renewable non-controllable generators: a small size wind turbine and photovoltaic solar panels. The size and the management of the system studied in this work have been optimized, in order to minimize both capital and variable costs. A time-dependent thermo-economic hierarchical approach developed by the authors has been used, considering the time-dependent electrical, thermal and cooling load demands during the year as problem constraints. The results are presented and discussed in depth and show the strong interaction between fossil and renewable resources, and the importance of an appropriate storage system to optimize the RES impact taking into account the multiproduct character of the grid under investigation.

Abstract This paper aims to present a feasibility study of the innovative plant for methanol synthesis from carbon dioxide-sequestered by fossil fuel power plant and hydrogen, which is produced by water electrolyzer employing the over-production on the electrical grid. The thermo-economic analysis is performed in the framework of the MefCO2 H2020 EU project and it is referred to the German economic scenario, properly taking into account the real market costs and cost functions for different components of the plant. Three different plant capacities for methanol production (4000 10,000 and 50,000 ton/year) have been investigated, assuming an average cost for electrical energy to feed electrolysers and analyzing the influence of the most significant parameters (oxygen selling option, methanol selling price and electrolysers’ capital cost) on the profitability of the plant. The analysis has been performed in W-ECoMP, software for the thermo-economic analysis and plant optimization developed by the University of Genoa.

Abstract This paper aims to present a thermo-economic approach for methanol production comparing different renewable energy sources. In this study, the methanol is produced from the CO2 hydrogenation in a pressurized reactor; two different plant configurations are analyzed: in the first carbon dioxide is obtained from biogas upgrade, while in the second one CO2 is acquired from external sources. Carbon dioxide is mixed with hydrogen and then the gas is sent into the reactor for methanol synthesis. Hydrogen is produced by an alkaline pressurized electrolyzer (1 MW, 30 bar) fed by time-dependent electrical energy produced by renewable plants (hydroelectric, wind or photovoltaic), when available; in the remaining periods, electricity is purchased by the national grid. Since the available electrical energy from the different renewable sources is not constant throughout the year, a time-dependent hierarchical thermo-economic analysis is performed in order to investigate the best plant configuration. The analyses are performed with the W-ECoMP simulation tool (developed by the authors' research group) considering different costs of electricity and different methanol selling prices taking into account the future market forecast. The results for the two plant lay-outs are compared from energetic, economic and environmental point of view for the different renewable energy sources to evaluate the best solution in the Italian scenario.

Abstract In this paper an approach for the determination of the optimal size and management of a plant for hydrogen production from renewable source (photovoltaic panels) is presented. Hydrogen is produced by a pressurized alkaline electrolyser (42 kW) installed at the University Campus of Savona (Italy) in 2014 and fed by electrical energy produced by photovoltaic panels. Experimental tests have been carried out in order to analyze the performance curve of the electrolyser in different operative conditions, investigating the influence of the different parameters on the efficiency. The results have been implemented in a software tool in order to describe the behavior of the systems in off-design conditions. Since the electrical energy produced by photovoltaic panels and used to feed the electrolyser is strongly variable because of the random nature of the solar irradiance, a time-dependent hierarchical thermo-economic analysis is carried out to evaluate both the optimal size and the management approach related to the system, considering a fixed size of 1 MW for the photovoltaic panels. The thermo-economic analysis is performed with the software tool W-ECoMP, developed by the authors’ research group: the Italian energy scenario is considered, investigating the impact of electricity cost on the results as well.