Most of our energy supply nowadays relies on converting thermal energy to mechanical energy; mechanical energy is then either used directly to drive vehicles or electric generators that supply the global needs of electricity. The main source of energy is combustion of fossil fuels, which are limited, and have many detrimental effects on polluting the environment and adding to the greengouse effect. Fuel cells offer the bst alternative to replace existing energy conversion processes, as they convert the chemical energy of hydrogen fuel directly into electricity, bypassing fuel combustion. In addition, the only by-product in fuel cells are water and low temperature heat, and both are benign to the environment. Being a single step energy converting devices, fuel cells have high efficiencies. However, fuel cells output power is given by unregulated voltage and current, that depends on the operating conditions of the fuel cell and the load connected across its terminals. Two dynamic fuel cell and battery models were developed in Simulink and integrated with the load in different ways and in what is believed to be a new approach to reproduce and analyse the actual fuel cell-load interactions. Upon this, two control strategies were developed to match the power demand and regulate the output voltage for varying power demand. The first strategy implement fuel cell stack dynamic load simulation using designed systems impedance to simulate the load power demand, the second strategy is based instead on using a DC/DC current control converter to regulate the fuel cell operating conditions. In Both strategy the reactants gases are regulated, the response delay of the air compressor is simulated. The overall fuel cell power generation system was simulated under varying load conditions given by WLTC standard driving cycle and by considering the ligh duty truck Chevrolet Silverado 1500 as the referene application vehicle. The two modeling methodologies were compared and evaluated to select the most appropriate design powertrain system for the application. Results showed promising performance of power regulation that meets the requirements of modern electrical voltage standards. The minimum battery capacity used in parallel with the fuel cell was computed foe each powertrain.
La maggior parte dell'energia al giorno dioggi viene prodotta attraverso conversioni da energia termica che poi viene a sua volta convertita in energia meccanica. L'energia meccanica viene poi utilizzata per il funzionamento dei veicoli o di altri generatori elettrici per soddisfare il fabbisogno elettrico globale. La principale fone di energia termica deriva dalla combustione di combustibili fossili, che sono limitati, e hanno determinanti effetti dannosi sull'ambiente e la salute dell epersone e contribuiscono ad aumentare l'effetto serra. Le celle al combustile rappresentano la miglior alternativa per sostituire gli esistenti processi di conversione energetica, in quanto convertono l'energia chimica direttamente in energia elettrica e non implicano alcun tipo di processo di combustione; gli unici prodotti di scarto che ne derivano sono l'scqua e calore a temperature basse, che non danneggiano l'ambiente. Le celle al caombustile, essendo caratterizate da un unico step di conversione dell'energia, hanno elevati potenziali in termini di efficienza- Tuttavia, questa tecnologia energetica è in grado di generare solamente un tensione non stabile e incontrollata che dipende non solo dalle condizioni operative della cella al combustibile, ma anche dai carichi di potenza connessi attraverso i suoi terminali. In questa tesi un modello elettrico-dinamico della cella al combustile e della batteria, che lavora in parallelo a quest'ultima, sono stati progettati e sviluppati per generare simulazioni dinamiche, al fine di simulare ed analizzare la reale interazione dinamica tra sistema fuel cell e sistema di carico di potenza, in un camion elettrico. Una strategia di controllo dell'energia è stata definita in base alla potenza richiesta dal veicolo durante uno ciclo di guida standardizzato. Sono state utilizzate due metodologie per lo sviluppo del modello di powertrain con cella al combustile, la prima in cui il carico viene simulato usando solo un sistema di impedenze connesse a valle della cella al combustil; mentre nella seconda il controllo dei punti operativi viene realizzato utilizzando un covertitore elettrico
Design and modelling of fuel cell electric truck powertrains
VACCA, ELEONORA
2016/2017
Abstract
Most of our energy supply nowadays relies on converting thermal energy to mechanical energy; mechanical energy is then either used directly to drive vehicles or electric generators that supply the global needs of electricity. The main source of energy is combustion of fossil fuels, which are limited, and have many detrimental effects on polluting the environment and adding to the greengouse effect. Fuel cells offer the bst alternative to replace existing energy conversion processes, as they convert the chemical energy of hydrogen fuel directly into electricity, bypassing fuel combustion. In addition, the only by-product in fuel cells are water and low temperature heat, and both are benign to the environment. Being a single step energy converting devices, fuel cells have high efficiencies. However, fuel cells output power is given by unregulated voltage and current, that depends on the operating conditions of the fuel cell and the load connected across its terminals. Two dynamic fuel cell and battery models were developed in Simulink and integrated with the load in different ways and in what is believed to be a new approach to reproduce and analyse the actual fuel cell-load interactions. Upon this, two control strategies were developed to match the power demand and regulate the output voltage for varying power demand. The first strategy implement fuel cell stack dynamic load simulation using designed systems impedance to simulate the load power demand, the second strategy is based instead on using a DC/DC current control converter to regulate the fuel cell operating conditions. In Both strategy the reactants gases are regulated, the response delay of the air compressor is simulated. The overall fuel cell power generation system was simulated under varying load conditions given by WLTC standard driving cycle and by considering the ligh duty truck Chevrolet Silverado 1500 as the referene application vehicle. The two modeling methodologies were compared and evaluated to select the most appropriate design powertrain system for the application. Results showed promising performance of power regulation that meets the requirements of modern electrical voltage standards. The minimum battery capacity used in parallel with the fuel cell was computed foe each powertrain.| File | Dimensione | Formato | |
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Eleonora_Vacca _Master _Thesis _837935.pdf
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https://hdl.handle.net/10589/139649