World energy resources | EPFL Graph Search

World energy resources are the estimated maximum capacity for energy production given all available resources on Earth. They can be divided by type into fossil fuel, nuclear fuel and renewable resources. Fossil fuel Fossil fuel Remaining reserves of fossil fuel are estimated as: These are the proven energy reserves; real reserves may be four or more times larger. These numbers are very uncertain. Estimating the remaining fossil fuels on the planet depends on a detailed understanding of Earth's crust. With modern drilling technology, we can drill wells in up to 3 km of water to verify the exact composition of the geology; but half of the ocean is deeper than 3 km, leaving about a third of the planet beyond the reach of detailed analysis. There is uncertainty in the total amount of reserves, but also in how much of these can be recovered gainfully, for technological, economic and political reasons, such as the accessibility of fossil deposits, the levels of sul

Advanced Frameworks to Aggregate and Unlock the Power Flexibility of Distributed Energy Resources Located in Active Distribution Networks

Mohsen Kalantar Neyestanaki

Environmental concerns are leading to a fast transition in electric power systems towards replacing fossil fuel and nuclear generation with renewable generation. This transition has two significant implications for electric power systems:1-The capacity of conventional dispatchable electric power plants, which are the main providers of power flexibility , is sharply falling. It is notable that the security of electric power systems can be preserved if and only if there is an adequate amount of power flexibility to guarantee the frequency stability, voltage regulation, power quality, and congestion management.2-The share of renewable energy sources (RESs) in the electric power generation portfolio is steeply soaring. It raises a significant stress on electric power systems due to the fact that the generated electricity from RESs is intrinsically intermittent and accompanied with uncertainties.The simultaneous realization of these two issues puts electric power systems in a turning point. This thesis devotes a deep attention to the power flexibility provision issue with the purpose of empowering transmission system operators (TSOs) and distribution system operators (DSOs) to steer electric power systems securely in this emerging architecture. To this end, it sets out to unlock the potential power flexibility of distributed energy resources (DERs) located in distribution networks. The first part of the thesis deals with the problem from TSO's perspective. It develops two decision making tools for TSOs to help them optimally quantify their required power flexibility from flexibility providers (including flexible distribution networks) in a decentralized energy and flexibility market structure. The first tool concentrates solely on active power flexibility and accordingly offers a framework to model aggregated active power flexibility of distribution networks from TSO's point of view. In contrast, the second tool introduces a holistic TSO-DSO coordination framework to enable TSO and DSO to exchange both active/reactive power flexibility. Both developed tools employ mathematical techniques to cast the TSO's decision making process as a two-stage linear stochastic optimization problem while accounting for risk associated to the uncertainties. The frameworks lay a ground for TSO and DSOs to exchange power flexibility without having to reveal their confidential grids data.The second part of the thesis deals with the problem from DSO's perspective. It first concentrates on an active distribution network (ADN) and constructs a set of linear scenario-based robust optimization problems to characterize the maximum active/reactive powers flexibility that the ADN can provide upon request at its point of common coupling (PCC) to the upper-layer grid. Second, it constructs a linear grid&uncertainties-cognizant ADN management method to determine the amount of active/reactive powers flexibility that should be provided by each DER during the real-time operation in such a way that the ADN can provide, with minimum deviation, the active/reactive powers flexibility requested by the upper-layer grid at the PCC.In addition to dealing with the problem from both TSO's and DSO's perspectives, a privileged feature of the thesis is that it offers linear tractable algorithms to deal with all above-mentioned tasks while considering grid's constraints and uncertainties stemming from the forecast errors of demand and renewable generation.

EPFL2022

Coordinating Distributed Energy Resources and Utility-Scale Battery Energy Storage System for Power Flexibility Provision Under Uncertainty

Mohsen Kalantar Neyestanaki

Relying on the power flexibility of distributed energy resources (DERs) located in an active distribution network (ADN), this ADN will be able to provide power flexibility to the upper-layer grid at their point of common coupling (PCC). The power flexibility is defined as additional bi-directional active/reactive powers a resource can provide to the grid by adjusting its operating point. In this context, this paper presents a two-stage ADN management method to deliver, at the PCC, the power flexibility that the upper-layer grid operator would request minutes-ahead real-time operation. The first stage updates the power set-points of DERs considering their offer curves as well as the uncertainties stem from the short-term forecast errors of demand and renewable generation profiles. The inter-temporal constraints and losses of the grid are accounted for by exploiting a linearized dynamic optimal power flow model, whereby the first stage is implemented as a linear scenario-based optimization problem. Then, in real-time operation, relying on a linear optimization problem, the second stage adjusts the power flexibility injection of a utility-scale battery energy storage system (ESS) to mitigate the imbalance at the PCC inherent in the above-mentioned uncertainties. The performance of the method is tested on a real ADN.

2021

Micro-tubular Solid Oxide Fuel Cells with Nickelate Cathode-support

Henning Lübbe

The shortage of natural resources, rising energy demands and global warming have created an urgent need for more efficient energy conversion devices and different energy resources to achieve a more sustainable and efficient economy. Solid Oxide Fuel Cells (SOFC) are one of the most promising devices for the direct conversion from chemical to electrical energy in conjunction with high system efficiencies. Micro-tubular SOFC have been investigated since roughly 15 years. In contrast to planar systems, which produce electricity in the kW to MW range and target utilisation in stationary applications such as CHP plants, micro-tubular SOFC systems can be envisaged for mobile application due to quick start-up/shutdown operation. While most micro-tubular cells are mechanically supported by the electrolyte or anode, only few researches have investigated cathode-supported cells due to challenging fabrication. In this work, the new cathode material neodymium nickelate (NNO), Nd1.95NiO4+δ, was used as mechanical support, which is a novelty of this work, for micro-tubular SOFC. Different fabrication routes were used to create small tubes of 2-6 mm diameter. These tubes were evaluated with respect to their gas-diffusion properties by a new, self-manufactured diffusion setup and a complementary permeation setup. In order to achieve an economical fabrication process, the low-cost dip-coating method was investigated for the deposition of thin films from wet-chemical suspensions to create entire SOFC single cells. As SOFCs require gas-tight electrolyte layers, cofiring of tubular substrates and thin films must be executed to allow sufficient shrinkage of the deposited electrolyte thin layers to full density. Various electrolyte and electrode powders were characterised in different solvents, dispersants and binders with respect to low-temperature sintering feasibility. The shrinkage of scandia-stabilised zirconia (ScSZ) powder was decreased to 18% to still deliver sufficient sintered density by optimisation of the green density (usually zirconia requires shrinkage of 25% and more for densification). The cofiring temperature depends on the densification behaviour of powders but also on reactivity between adjacent layers. The reactivity between gadolinia-doped ceria (GDC)-interlayers and different zirconia materials was tested and showed lower compatibility of yttria-stabilised zirconia (YSZ) with GDC than for ScSZ/GDC reaction couples, which has not been reported so far. The interface of NNO cathodes and GDC interlayers was analysed by reactivity mapping and quantitative phase analysis. The performance optimisation of NNO/GDC interfaces by exchange current density measurement of NNO-cathodes sintered at different temperatures on GDC pellets is a further contribution of this work. The reactivity and performance investigations provide clear guidelines for maximum allowable cosintering temperature. Some electrochemical single cell tests showed competitive area-specific resistances (ASR) of ca. 1 Ωcm2 but were limited unfortunately by the counterelectrode microstructure and current collection methods, which were not the focus of this work. Open-circuit voltages (OCV) were 0.6-1.1 V at 700 °C in dry hydrogen atmosphere for tubes prepared by extrusion but only 0.3 V for tubes prepared by slip-casting. The electrochemical performances were modest with only 0.035 W/cm2 power density at 700 °C for tubes prepared by extrusion due to the elevated resistances of the counterelectrode and current collection.

EPFL2012