1,720,981 research outputs found
Optimization of large scale bio-methane generation integrating “spilled” hydraulic energy and pressurized oxygen blown biomass gasification
No full textThermo-economic optimization of the impact of renewable generators on poly-generation smart-grids including hot thermal storage
No full textAbstract
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
Hydrogen and methane generation from large hydraulic plant: Thermo-economic multi-level time-dependent optimization
No full textThis paper investigates hydrogen and methane generation from large hydraulic plant, using an original multilevel thermo-economic optimization approach developed by the authors.Hydrogen is produced by water electrolysis employing time-dependent hydraulic energy related to the water which is not normally used by the plant, known as "spilled water electricity". Both the demand for spilled energy and the electrical grid load vary widely by time of year, therefore a time-dependent hour-by-hour one complete year analysis has been carried out, in order to define the optimal plant size. This time period analysis is necessary to take into account spilled energy and electrical load profiles variability during the year.The hydrogen generation plant is based on 1MWe water electrolysers fuelled with the "spilled water electricity", when available; in the remaining periods, in order to assure a regular H2 production, the energy is taken from the electrical grid, at higher cost. To perform the production plant size optimization, two hierarchical levels have been considered over a one year time period, in order to minimize capital and variable costs.After the optimization of the hydrogen production plant size, a further analysis is carried out, with a view to converting the produced H2 into methane in a chemical reactor, starting from H2 and CO2 which is obtained with CCS plants and/or carried by ships. For this plant, the optimal electrolysers and chemical reactors system size is defined.For both of the two solutions, thermo-economic optimization results are discussed and compared with particular emphasis to energy scenario, economic aspects, system size, capital costs and related investments. It is worth noting that the results reported here for this particular large H2 plant case represents a general methodology, since it can vary according to their different sizes, primary renewable energy, plant location, and different H2 utilization. © 2013 Elsevier Ltd
Hydrogen production system from photovoltaic panels: experimental characterization and size optimization
No full textIn 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 thermoeconomic 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
Thermo-economic comparison of hydrogen and hydro-methane produced from hydroelectric energy for land transportation
No full textThis paper aims to investigate a system for large size hydrogen production, storage and distribution to refueling stations for its employment in land transportation. Hydrogen is produced by pressurized alkaline electrolysers, employing time-dependent renewable electricity produced by a large size hydroelectric plant (100 MW); the hydrogen is stored into pressurized tanks and delivered by trucks to the refueling stations. Since the technologies related to hydrogen vehicles still present high costs, an alternative solution is investigated: the hydrogen produced by water electrolysis is converted into Hydro-methane (a blend of methane and hydrogen, where H2 maximum volume content is 30%), which is easier to be stored and transported to the refueling stations, considering its higher energy content in volume terms. Since electricity available from the hydroelectric plant varies widely throughout the year, a time-dependent hierarchical thermo-economic analysis is performed in order to investigate both the optimal size of the whole plant and the management of the alkaline electrolysers. The analysis is carried out for the H2 and Hydro-methane plant lay-outs, comparing the results from energetic, strategic and economic point of view in a typical European economic scenario (Italy). For the different plant lay-outs, two energy scenarios are considered: (i) to feed the electrolysers only with renewable hydroelectricity during the year, keeping them off when it is not available; (ii) to purchase electricity from the national grid in shortage periods, in order to increase the utilization factor of the electrolysers and the production of H2 and Hydro-methane for the refueling stations
Design optimisation of smart poly-generation energy districts through a model based approach
No full textThis 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
Hydro-methane and methanol combined production from hydroelectricity and biomass: Thermo-economic analysis in Paraguay,
No full text“Time-dependent optimization of a large size hydrogen generation plant using “spilled” water at Itaipu 14 GW hydraulic plant”
No full textIn this paper hydrogen generation and storage systems optimization, related to a very large
size hydraulic plant (Itaipu, 14 GW) in South America, is investigated using an original
multilevel thermo-economic optimization approach developed by the Authors. Hydrogen
is produced by water electrolysis employing time-dependent hydraulic energy related to
the water which is not normally used by the plant, named “spilled water”.
From a thermo-economic point of view, the two main aspects of the study are the
optimal definition of the plant size and the whole system management. Both of them are
strongly influenced by (i) spilled water energy variability related to its time-dependent
distribution during the whole year, (ii) time-dependent electricity demand of Paraguay and
Brazil (the owners of the Itaipu plant) electrical grids, and (iii) the hydrogen demand profile.
The system analyzed here consists of a very large size hydrogen generation plant
(hundreds of MW) based on pressurised water electrolysers fed with the so called “spilled
water electricity”, the related H2 storage, and the H2 demand profile for Paraguay transport
sector utilization.
Since H2 plant optimal size is strongly correlated to optimal management and viceversa,
in this paper two hierarchical levels have been considered hour by hour on
a complete year time period, in order to minimize capital and variable costs. This time
period analysis is necessary to properly take into account spilled energy variability to find
out H2 production system optimal size, optimal storage solution and best economical
results.
For the optimal storage size, two different solutions have been carefully investigated: (i)
classical long time H2 physical storage using pressurised tanks at 200 bar; (ii) hybrid one
using reduced size physical storage (one day time demand) where the energy to feed
electrolysers is taken from electrical grid when spilled water energy is not available
[Rivarolo M, Bogarin J, Magistri L, Massardo AF. Hydrogen generation with large size
renewable plants: the Itaipu 14 GW hydraulic plant case. In: 3rd international conference of
applied energy (ICAE), 16e18 May 2011, Perugia; 2011.]. For both the two solutions, timedependent
results are presented and discussed with particular emphasis to economic
aspects, system size, capital costs and related investments. It is worthy to note that the
results reported here for this particular H2 large size plant case represent a general methodology, since it is applicable to different size, primary renewable energy, plant
location, and different H2 utilization
Thermo-economic analysis of the energy storage role in a real polygenerative district
No full textThis paper presents a thermo-economic analysis based on data from a real Smart polygeneration microgrid (SPM), designed to satisfy energy demands of the university campus of Savona (Italy). The plant is made up of different cogenerative generators (micro gas turbines and an internal combustion engine), renewable generators and two auxiliary boilers (one of them is off during the most of the time): the generators are “distributed” around the campus and coupled to electrical and thermal storages. Since several cogenerative units are included in the grid, the integration of the different storage systems is relevant in order to determine the best management strategy, following both thermal and electrical requests and taking into proper account the strong difference between the two energy demand profiles.
The thermo-economic analysis is performed exploiting the software W-ECoMP, developed by the authors’ research group, in order to find the best operational strategy, considering the importance of an appropriate storage system to manage the polygenerative energy district; attention is paid to the integration and combination of three different kinds of storage (hot and cold water tanks and electrical battery). Different scenarios are presented, combining the storages and showing their impact in terms of money savings and reduction of electrical energy purchasing from the National grid. Both the grid connected mode and island mode of operation of the SPM are considered.
The analysis is performed considering the time dependent nature of the energy demands throughout the whole year and implementing the experimental off-design curves of the real devices installed in the grid
Feasibility study of methanol production from different renewable sources and thermo-economic analysis
No full textThis 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
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