Most of Sub-Saharan Africa countries rely on hydropower to satisfy energy demand, and, as a consequence, their energy security is highly dependent upon water availability and spatiotemporal variability. Conversely, water and food security might be negatively affected by the development of large hydropower schemes potentially altering existing flow patterns. Projected changes in the hydrological cycle, driven by climate change, and population growth are triggering investment for expanding water storages and power generation capacity on major African rivers (Nile, Congo, Zambezi). In this context, novel modeling tools are required to support robust and reliable planning of new infrastructure accounting for the tight interconnection between water and energy, and the uncertainty stemming from the future co-evolution of these two domains. At present, models usually adopt simplifying assumptions for these linkages that are partially removed in this work. Focusing on the Zambezi River, a soft model integration approach for water-energy systems is adopted. First, the original version of the energy system OSeMOSYS model is expanded to include the main components of the hydrological cycle and their dynamics. Then, the improved OSeMOSYS and a Water Resources Optimization Model (WROM) are coupled to evaluate what benefits can derive via soft integration for both the energy and hydrological point of view. For what concerns the energy model, a more adaptive reservoir management policy is implemented using a target storage trajectory, result of the WROM optimization, so as to account also for the multiple objectives defined in the WROM. This results in lower total discounted costs and price of energy (-1.25%) and increased hydropower production (+15.4%). Regarding the hydrology point of view, the effects of the energy grid on the WROM are assessed with respect to the objectives of the original WROM (-6.7% hydropower production when this is the only objective in the WROM). The work is of interest for joint water-energy systems optimization as it allows a thorough evaluation of the management policies within the nexus approach.
La maggior parte dei paesi dell'Africa subsahariana soddisfa la propria domanda di energia elettrica grazie agli impianti idroelettrici. Di conseguenza, la loro la sicurezza energetica dipende anche dalla disponibilità di acqua e dalla variabilità spaziotemporale di quest'ultima. I cambiamenti climatici e l'aumento della popolazione hanno dato il via a investimenti per l'espansione dei serbatoi e della potenza installata nelle centrali idroelettriche. Tali progetti possono influire negativamente sulla sicurezza idrica e sulla sicurezza alimentare. Quindi, nuovi approcci di modellazione che considerino le interazioni tra acqua ed energia sono necessari per pianificare in maniera robusta e affidabile le nuova infrastrutture e gestire i due sistemi. Concentrandosi sul bacino del fiume Zambesi, questo lavoro implementa un approccio di soft integration per il sistema acqua-energia. La versione originale del noto modello per sistemi energetici OSeMOSYS viene ampliata per descrivere le componenti principali del ciclo idrologico e le loro dinamiche. Successivamente, questo modello e un modello di ottimizzazione delle risorse idriche (WROM) vengono utilizzati per valutare i benefici derivanti dalla soft integration sia dal punto di vista energetico che idrologico. Per quanto riguarda il modello energetico, l'ipotesi di stazionarietà del sistema idrologico viene rimossa e vengono implementati i vincoli operativi per i serbatoi. Traiettorie di volume provenienti dall'ottimizzazione del WROM sono utilizzate come obiettivo per implementare una politica di gestione del serbatoio più flessibile, che tenga conto anche dei molti obiettivi definiti nel WROM. Ciò si traduce in minori costi totali attualizzati, minore prezzo dell'energia e aumento della produzione idroelettrica, anche in presenza di altri obiettivi. Per quanto riguarda l'idrologia, gli effetti della rete energetica su WROM sono valutati e rappresentati sulla frontiera di Pareto rispetto al valore degli obiettivi del problema originario del sistema idrico, consentendo una valutazione più esaustiva delle politiche di gestione.
Hydro-energy systems modeling in the Zambezi river basin : exploring benefits from soft model integration
CARLINO, ANGELO
2016/2017
Abstract
Most of Sub-Saharan Africa countries rely on hydropower to satisfy energy demand, and, as a consequence, their energy security is highly dependent upon water availability and spatiotemporal variability. Conversely, water and food security might be negatively affected by the development of large hydropower schemes potentially altering existing flow patterns. Projected changes in the hydrological cycle, driven by climate change, and population growth are triggering investment for expanding water storages and power generation capacity on major African rivers (Nile, Congo, Zambezi). In this context, novel modeling tools are required to support robust and reliable planning of new infrastructure accounting for the tight interconnection between water and energy, and the uncertainty stemming from the future co-evolution of these two domains. At present, models usually adopt simplifying assumptions for these linkages that are partially removed in this work. Focusing on the Zambezi River, a soft model integration approach for water-energy systems is adopted. First, the original version of the energy system OSeMOSYS model is expanded to include the main components of the hydrological cycle and their dynamics. Then, the improved OSeMOSYS and a Water Resources Optimization Model (WROM) are coupled to evaluate what benefits can derive via soft integration for both the energy and hydrological point of view. For what concerns the energy model, a more adaptive reservoir management policy is implemented using a target storage trajectory, result of the WROM optimization, so as to account also for the multiple objectives defined in the WROM. This results in lower total discounted costs and price of energy (-1.25%) and increased hydropower production (+15.4%). Regarding the hydrology point of view, the effects of the energy grid on the WROM are assessed with respect to the objectives of the original WROM (-6.7% hydropower production when this is the only objective in the WROM). The work is of interest for joint water-energy systems optimization as it allows a thorough evaluation of the management policies within the nexus approach.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/139861