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See detailRule-based control and optimization of a hybrid solar microgrid for rural electrification and heat supply in sub-Saharan Africa
Altés Buch, Queralt ULiege; Orosz, Matthew; Quoilin, Sylvain ULiege et al

in Proceedings of the 30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS) (2017)

This work aims at developing, optimizing and controlling a hybrid solar microgrid for rural electrification and heat supply in sub-Saharan Africa. The considered system includes PV panels, Parabolic ... [more ▼]

This work aims at developing, optimizing and controlling a hybrid solar microgrid for rural electrification and heat supply in sub-Saharan Africa. The considered system includes PV panels, Parabolic Trough Collectors, ORC and LPG generator, as well as battery and thermal energy storage. A special focus is paid to the co-optimization of the thermal and electrical load satisfaction since it can improve the overall energy efficiency of the system. To that end, different sub-component models are developed: - A building model to predict thermal loads of a health clinic in rural communities of Lesotho. - A microgrid model built by interconnecting the subcomponent models. - A rule-based control strategy, dispatching heat and electrical powers of each component to cover the demand while minimizing the fuel consumption. - A particle-swarm optimization of the microgrid under different cost assumptions. For the studied community of Ha Nkau in Lesotho, the determined optimal system infrastructure is composed of PV (66 kW) and batteries (262 kWh), and the optimum control strategy achieves a levelized cost of electricity of 0.203 USD/kWh. Fuel consumption is mainly due to the burner, which supplies most of the thermal load together with CSP (66 m2) and TES (86 kWh). [less ▲]

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See detailMechanical design, control and optimization of a hybrid solar microgrid for rural electrification and heat supply in sub-Saharan Africa
Altés Buch, Queralt ULiege

Master's dissertation (2016)

This thesis aims at developing, optimizing and controling a hybrid solar microgrid for rural electrification and heat supply in sub-Saharan Africa. The considered system includes PV, Parabolic Trough ... [more ▼]

This thesis aims at developing, optimizing and controling a hybrid solar microgrid for rural electrification and heat supply in sub-Saharan Africa. The considered system includes PV, Parabolic Trough Collectors, Organic Rankine Cycle and LPG generator, as well as chemical battery storage and thermal energy storage. The work focuses on multiple aspects of the ongoing development of solar hybrid microgrids for the rural electrification of remote areas in Lesotho. These aspects range from very specific improvements (the mechanical design of a high expansion ratio expander) to the more global evaluation of their impact once included into a complex micro-grid system. Special attention has also been paid to the links between thermal and electrical demands. The main contributions of this thesis are: – The mechanical design of a high expansion ratio scroll expander, involving drawing, machining and assembly of the parts. – The detailed model of an organic Rankine cycle with the purpose of evaluating the improvement brought by the high expansion ratio scroll expander and mapping the ORC performance. – A building model developed to predict the thermal loads of a health clinic in rural communities of Lesotho. The developed lumped-parameter model can be used for various building typologies and communities. The model is designed to be as generic and simple as possible, and contrasts with the data-intensive models generally proposed in the literature. – The gathering of monitoring and weather data relative to a health clinic in Lesotho, and their use for the calibration of the building model. – A microgrid model built by interconnecting all of its subcomponent models. A rule- based control strategy is developed, accounting for interactions between thermal and electrical loads, and dispatching heat and power flows of each component in order to cover the demand while minimizing the fuel consumption. – A particle-swarm optimization model used to optimize the microgrid under different cost assumptions and control strategies. The above models prove that the system performs better with the developed high expansion ratio expander. The maximum output power of the ORC is increased by 33%, and the fuel consumption of the microgrid is reduced by 25%. For the studied community of Ha Nkau in Lesotho, the determined optimal system infrastructure is composed of PV (65 kW) and batteries (259 kWh) only, and the optimum control strategy achieves a levelized cost of electricity of 0.202 USD/kWh. Fuel consumption is mainly due to the burner, which supplies all the thermal load because no other heating system is selected by the optimization. [less ▲]

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See detailDynamic modeling of thermal systems using a semi-empirical approach and the ThermoCycle Modelica Library
Altés Buch, Queralt ULiege; Dickes, Rémi ULiege; Desideri, Adriano ULiege et al

in Proceedings of the 28th International Conference on Efficiency, Costs, Optimization and Simulation of Energy Systems (2015, June)

This paper proposes an innovative approach for the dynamic modeling of heat exchangers without phase transitions. The proposed thermo-flow model is an alternative to the traditional 1D finite-volumes ... [more ▼]

This paper proposes an innovative approach for the dynamic modeling of heat exchangers without phase transitions. The proposed thermo-flow model is an alternative to the traditional 1D finite-volumes approach and relies on a lumped thermal mass approach to model transient responses. The heat transfer is modeled by the well-known Logarithmic Mean Temperature Difference approach, which is modified to ensure robustness during all possible transient conditions. The lumped parameter models are validated with references models and tested within a Concentrating Solar Power plant model. Results indicate that the developed lumped models are robust and computationally efficient, ensuring the convergence of the Newton Solver. They are significantly faster (~10-fold) than the traditional finite volume models, although a more extensive comparisons would be needed to confirm this figure. They are well suited to be integrated in larger system models, but are not appropriate for the simulation of detailed thermo-flow phenomena. [less ▲]

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See detailDynamic modeling of a steam Rankine Cycle for Concentrated Solar Power applications
Altés Buch, Queralt ULiege

Master's dissertation (2014)

Concentrated solar power (CSP) is expected to play a key role in the necessary energy transition towards more sustainability. However, this type of system is inherently subject to transient boundary ... [more ▼]

Concentrated solar power (CSP) is expected to play a key role in the necessary energy transition towards more sustainability. However, this type of system is inherently subject to transient boundary conditions such as varying solar irradiation. Therefore, advanced control strategies are required to maintain safe operating conditions and to maximize power generation. In order to define, implement and test these control strategies, dynamic models of the system must be developed. This thesis aims at developing a model of a steam Rankine Cycle coupled to a field of parabolic troughs. The modeled system does not correspond to an existing plant, but its characteristics are defined as realistically as possible with information coming from different sources. Simplified but also physical, lumped dynamic models of each component (boiler, turbines, condenser, solar collectors) have been developed and parametrized using the ThermoCycle library, written in the Modelica language. These models have been further interconnected to build the CSP plant model, whose response has been tested to fluctuating atmospheric conditions. The proposed library of models is based on an innovative lumped-parameter approach aiming at developing physical models that are significantly more robust and computationally efficient than the traditional libraries of models already available. The final purpose of these models is high level simulations (e.g. for control purposes), but not the modeling of detailed physical phenomena. The different models have been successfully tested with the example of the CSP plant, but can also be applied in other fields of thermal engineering. They proved to be more robust and much faster than the traditional models, which was the objective. However, in the scope of this work, it has not been possible to validate them with experimental data or with more detailed models. This should be the priority for future works. [less ▲]

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