The future electric grid will be characterized by the ever-increasing penetration of renewable energy technologies. The variability, discontinuity and unpredictability of renewable sources can be faced by introducing electric energy storage (EES) systems in the electric grid. Currently pumped hydropower, the only commercially available large-scale EES, is limited to mountainous regions. Reversible solid oxide cells (Re-SOCs) are electrochemical devices capable of providing highly efficient and cost-effective EES. Re-SOCs have been investigated for storing energy, in the form of fuel, during low electricity demand periods, and for producing electric energy during high electricity demand periods. The goal of this M.Sc. project is to develop EES systems based on pressurized Re-SOCs. A zero-dimensional modeling tool developed at the Technical University of Denmark (DTU) has been used for this scope: Dynamic Network Analysis (DNA). During this project the DNA-model of the Re-SOC has been optimized to have a more realistic behavior. The Re-SOC employed in this project operates at high pressure: this produces an advantage during electrolysis mode. Pressurized operation of the solid oxide electrolytic cell (SOEC) boosts the production of methane directly inside the cell, thus making the cell operate with an exothermic behavior also during charge (electrolysis) mode. First, the state-of-the-art EES system is reproduced, consisting of employing a Re-SOC running at 650 °C and 20 bar. DNA results are compared with literature information about efficiency and stream compositions. The obtained results in terms of efficiencies and compositions coincide with available data. A novel hybrid EES system is then introduced and investigated in this work. An innovative configuration improves the thermal management of the system, especially during electrolysis mode, resulting in higher performance for the entire EES system. The Re-SOC employed in this novel EES operates at 700 °C and 18.70 bar. The methane molar content in the stored fuel produced during low energy demand is significatly large and allows to inject the produced fuel directly into the natural gas grid. Furthermore this promising EES system allows many operating modes, combining fuel and exhausts storage with the use of syngas coming from a gasifier plant. The novel hybrid EES system has increased flexibility, as it can be operated considering both the electricity and the natural gas markets. In conclusion a study of the temperature and Nernst voltage inside the channels of the Re-SOC is performed for co-flow and counter-flow geometries, for both solid oxide electrolytic cell (SOEC) and solid oxide fuel cell (SOFC). The results are compared with the ones for the black box model.
In futuro le tecnologie rinnovabili assumeranno un ruolo sempre più importante nella rete elettrica. La variabilità, la discontinuità e l’imprevedibilità delle fonti rinnovabili possono essere bilanciate con l’uso di sistemi di accumulo di energia elettrica (EES). Al momento l’idroelettrico di pompaggio (PHS) costituisce l’unico sistema di accumulo commerciale su larga scala, ma rimane limitato a particolari regioni geografiche. Celle a ossidi solidi reversibili (Re-SOCs) sono componenti elettrochimici utilizzabili in sistemi di accumulo ad alta efficienza. Le Re-SOCs sono state studiate per accumulare energia su larga scala durante periodi di bassa richiesta di energia elettrica e per produrre energia elettrica quando la richiesta energetica è alta. L’obiettivo di questa tesi di laurea magistrale è lo sviluppo di sistemi di accumulo di energia elettrica basati sull'utilizzo di Re-SOCs ad alte pressioni. Il software utilizzato per la modellazione dei sistemi è Dynamic Network Analysis (DNA), sviluppato presso la Technical University of Denmark (DTU). L’utilizzo di Re-SOC ad alte pressioni promuove la formazione di metano all'interno della Re-SOC e porta ad un comportamento esotermico della stessa, anche quando al suo interno avvengono reazioni di elettrolisi. La prima parte del progetto prevede la riproduzione di un sistema EES allo stato dell’arte, dove vengono impiegate Re-SOCs che lavorano a 650 °C e 20 bar. I risultati di DNA riguardanti le performance e la composizione dei flussi corrispondono ai dati disponibili in letteratura. Un nuovo sistema EES ibrido è introdotto nella seconda parte del lavoro. La nuova configurazione permette una migliore gestione dei flussi termici, che si traduce in migliori performance dell’intero impianto. Le Re-SOCs impiegate in questo sistema EES operano a 700 °C e 18.70 bar. La frazione molare di metano prodotta durante i periodi di accumulo di energia è decisamente alta e permette di iniettare il combustibile prodotto direttamente nella rete del gas naturale. Inoltre questo sistema EES permette differenti modalità operative, combinando l'accumulo di combustibile ed esausti con syngas proveniente da un impianto di gassificazione. Questo sistema EES può operare considerando allo stesso tempo il mercato elettrico e il mercato del gas naturale. In conclusione è affrontato uno studio dei profili di temperatura e del potenziale di Nernst nei canali di una Re-SOC con flussi equicorrenti e contro-corrente. I risultati sono confrontati con il modello zero-dimensionale di DNA.
Modeling of large-scale electricity storage systems based on pressurized reversible solid oxide cells
BUTERA, GIACOMO
2015/2016
Abstract
The future electric grid will be characterized by the ever-increasing penetration of renewable energy technologies. The variability, discontinuity and unpredictability of renewable sources can be faced by introducing electric energy storage (EES) systems in the electric grid. Currently pumped hydropower, the only commercially available large-scale EES, is limited to mountainous regions. Reversible solid oxide cells (Re-SOCs) are electrochemical devices capable of providing highly efficient and cost-effective EES. Re-SOCs have been investigated for storing energy, in the form of fuel, during low electricity demand periods, and for producing electric energy during high electricity demand periods. The goal of this M.Sc. project is to develop EES systems based on pressurized Re-SOCs. A zero-dimensional modeling tool developed at the Technical University of Denmark (DTU) has been used for this scope: Dynamic Network Analysis (DNA). During this project the DNA-model of the Re-SOC has been optimized to have a more realistic behavior. The Re-SOC employed in this project operates at high pressure: this produces an advantage during electrolysis mode. Pressurized operation of the solid oxide electrolytic cell (SOEC) boosts the production of methane directly inside the cell, thus making the cell operate with an exothermic behavior also during charge (electrolysis) mode. First, the state-of-the-art EES system is reproduced, consisting of employing a Re-SOC running at 650 °C and 20 bar. DNA results are compared with literature information about efficiency and stream compositions. The obtained results in terms of efficiencies and compositions coincide with available data. A novel hybrid EES system is then introduced and investigated in this work. An innovative configuration improves the thermal management of the system, especially during electrolysis mode, resulting in higher performance for the entire EES system. The Re-SOC employed in this novel EES operates at 700 °C and 18.70 bar. The methane molar content in the stored fuel produced during low energy demand is significatly large and allows to inject the produced fuel directly into the natural gas grid. Furthermore this promising EES system allows many operating modes, combining fuel and exhausts storage with the use of syngas coming from a gasifier plant. The novel hybrid EES system has increased flexibility, as it can be operated considering both the electricity and the natural gas markets. In conclusion a study of the temperature and Nernst voltage inside the channels of the Re-SOC is performed for co-flow and counter-flow geometries, for both solid oxide electrolytic cell (SOEC) and solid oxide fuel cell (SOFC). The results are compared with the ones for the black box model.File | Dimensione | Formato | |
---|---|---|---|
Giacomo_Butera_Master_Thesis_2015_2016.pdf
non accessibile
Descrizione: Testo della tesi
Dimensione
2.74 MB
Formato
Adobe PDF
|
2.74 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/133998