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This report describes the results of applying an open-source modelling framework to three African power pools : the Central African Power Pool, the Eastern Africa Power Pool and the North African Power Pool. The modelling framework is used to analyse results at country level - where insights regarding the power generation, system adequacy, total operational costs, freshwater consumption and withdrawals, water values (hydro storage shadow price), and CO2 emissions linked to the power sector are assessed. The model source code and the input data are provided together with the report for transparency purposes to facilitate further exploitation and analysis of the results. Water-energy nexus indicators such as the water exploitation index, or water withdrawal and consumption related to power generation, are computed for the three power pools and for major individual power plants. The indicators show that these three African Power Pools are strongly dependent on the availability of freshwater resources. The variation between wet and dry years significantly impacts the final energy mix, the total operational costs, the total carbon emissions and the water stress index of the system. The relative impact of water consumption over water withdrawals is low because of the predominance of once-through cooling systems in the most vulnerable countries. Furthermore, several isolated countries within each power pool exhibit a power system which is not adequate, leading to significant amounts of load not served. The importance of increasing the reliability as well as the capacity of interconnection lines is thereby highlighted. A well interconnected grid reduces the need for variable renewable energy (VRES) curtailment and water spillage in hydropower units, allows higher integration of renewable sources, and reduces the need for load shedding , especially in extremely dry years. A higher degree of interconnection also has a positive impact on water stress indicators since water consumption and water withdrawal can be significantly reduced. Africa presents an important potential of variable renewable energy sources (mainly wind and solar) which is still largely untapped. The addition of new VRES capacity can reduce the potential carbon emissions by more than 32% by 2045 compared to a business-as-usual scenario. However, this is only possible by reducing the congestion when energy flows from southern countries (hydro-rich), and energy flows from the northern countries (VRES-abundant) are enabled. This is particularly the case in future low carbon scenarios, in which power generation from thermal units is lower, resulting in a lack of flexibility and therefore in higher curtailment and load shedding., JRC.C.7-Knowledge for the Energy Union

Bolivia plans significant investments in conventional and renewable energy projects before 2025. Deployment of large hydro-power, wind and solar projects are foreseen in the investment agenda. However and despite the large renewable potential in the country non-conventional renewable technologies are not yet considered to be a main source in the supply chain. The aim of this article is to evaluate the flexibility of the Bolivian power generation system in terms of energy balancing, electricity generation costs and power plants scheduling in a scenario that considers large solar and wind energy technology deployment. This is done using an open source unit commitment and optimal dispatch model (Dispa-SET) developed by the Joint Research Center of the European Commission. National data for existing infrastructure, committed and planned energy projects are used to assess the case of Bolivia. The base scenario consider all techno-economic data of the Bolivian power system up to 2016. A harmonized dataset is gathered and released as open data to allow other researchers to run and re-use the model. This model is then used to simulate scenarios with different levels of solar and wind energy deployment. Results from the analysis show that an energy mix with participation of solar and wind technology with values lower than 30% is technically feasible and indicates that further grid reinforcements are required., International Journal of Sustainable Energy Planning and Management, Vol 22 (2019)

This paper presents an experimental investigation of the working fluid charge repartition in a 2kWe ORC (organic Rankine cycle) test bench. To this end, an online measurement apparatus is built and fully calibrated to evaluate the charge enclosed in the three heat exchangers and the liquid receiver of the ORC unit. By changing all the system boundary conditions (including the charge enclosed in the test rig), an experimental database of 304 steady-state points is gathered and post-treated. The charge inventories obtained by online measurements demonstrate promising results on average but experience high uncertainties when considering each point individually (i.e. the uncertainty on the global inventory is around ± 2.5 kg for a total charge of 31.2 kg). Deviations of the evaporator mass measurements are identified at high temperature of the heat source and discussed in details. A reconciliation method is applied to the raw measurements in order to retrieve consistent charge inventories while accounting for the different sources of uncertainty. Ultimately, the paper analyses the impact of increasing the charge in the ORC and how this parameter influences the thermodynamic state of the system.

status: Unpublished

Because of the depletion of fossil fuels and global warming issues, the world energy sector is undergoing various changes toward increased sustainability. Among the different technologies being developed, solar energy, and more specifically CSP (Concentrated Solar Power) systems are expected to play a key role to supply centralized loads and off-grid areas in the medium-term. Major performance improvements can be achieved by implementing advanced control strategies accounting for the transient and random nature of the solar heat source. In this context, a lab-scale solar power plant has been designed and is under construction for experimental purposes and dynamic analyzes. The test rig includes an ORC unit, a field of parabolic trough collectors and a thermal energy storage. This paper presents the results of an experimental campaign conducted on the ORC module alone. This power unit, designed for a 2.8 kW net electrical output, consists of two scroll expanders in series, an air-cooled condenser, a recuperator, a volumetric pump and an oil-heated evaporator. The ORC engine is constructed using standard mass manufactured components from the HVAC industry, this practice reducing considerably the system cost. The overall unit performance and components effectiveness are presented in different operating conditions and relevant empirical correlations are derived to be implemented in a steady state model of the ORC unit.

This paper describes an experimental study carried out on a refrigeration scroll compressor with and without vapour injection. The test rig designed for that purposed allows evaluating the performance over a wide range of operating conditions, by varying the supply pressure, the injection pressure, the exhaust pressure, the supply superheating and the injection superheating. 97 Steady-state points are measured, with a maximum isentropic efficiency of 64.1% and a maximum consumed electrical power of 13.1 kW. A critical analysis of the experimental results is then carried out to evaluate the quality of the data using a machine learning method. This method based on Gaussian Processes regression, is used to build a statistical operating map of the compressor as a function of the different inputs. This statistical operating map can then be compared to the experimental data points to evaluate their accuracy.

This paper presents an innovative system comprising a heat pump connected to a solar roof and a geothermal heat exchanger. This heat pump is able to invert its cycle and operate as an ORC. By using the whole rooftop (hereunder called “absorber”) as a heat source, a large amount of heat is generated throughout the year. This heat is used in priority to cover the building annual heating needs, while the surplus heat (mainly during summer months) is utilized to generate electricity in the so-called HP/ORC module. The same module can be used in winter time as an efficient heat pump which radically simplifies the complexity of the total system compared to competitive products. The main advantage of the proposed technology is related to the reversibility of scroll machines, which have proven to operate efficiently both as a compressor and as an expander. This paper focuses on three aspects: design of the prototype, results from experiments and validation of models based on the experimental data. To size the unit, the expander and the different exchangers are modeled thanks to semi-empirical correlations calibrated on experimental data. The sizing of the prototype is based on yearly simulations with a simulation step of one hour. The algorithm optimizes the operating mode based on the domestic heat demand, the meteorological conditions and the available heat in the storage. This paper demonstrates the feasibility of such a prototype with promizing experimentally-achieved performance (4.1% overall efficiency in ORC mode and a COP of 4.2 in HP mode)

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. Outgoing