References of "Berger, Mathias"
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See detailJointly Learning Environments and Control Policies with Projected Stochastic Gradient Ascent
Bolland, Adrien ULiege; Boukas, Ioannis ULiege; Berger, Mathias ULiege et al

in Journal of Artificial Intelligence Research (2022), 73

We consider the joint design and control of discrete-time stochastic dynamical systems over a finite time horizon. We formulate the problem as a multi-step optimization problem under uncertainty seeking ... [more ▼]

We consider the joint design and control of discrete-time stochastic dynamical systems over a finite time horizon. We formulate the problem as a multi-step optimization problem under uncertainty seeking to identify a system design and a control policy that jointly maximize the expected sum of rewards collected over the time horizon considered. The transition function, the reward function and the policy are all parametrized, assumed known and differentiable with respect to their parameters. We then introduce a deep reinforcement learning algorithm combining policy gradient methods with model-based optimization techniques to solve this problem. In essence, our algorithm iteratively approximates the gradient of the expected return via Monte-Carlo sampling and automatic differentiation and takes projected gradient ascent steps in the space of environment and policy parameters. This algorithm is referred to as Direct Environment and Policy Search (DEPS). We assess the performance of our algorithm in three environments concerned with the design and control of a mass-spring-damper system, a small-scale off-grid power system and a drone, respectively. In addition, our algorithm is benchmarked against a state-of-the-art deep reinforcement learning algorithm used to tackle joint design and control problems. We show that DEPS performs at least as well or better in all three environments, consistently yielding solutions with higher returns in fewer iterations. Finally, solutions produced by our algorithm are also compared with solutions produced by an algorithm that does not jointly optimize environment and policy parameters, highlighting the fact that higher returns can be achieved when joint optimization is performed. [less ▲]

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See detailSiting Renewable Power Generation Assets with Combinatorial Optimisation
Berger, Mathias ULiege; Radu, David-Constantin ULiege; Dubois, Antoine ULiege et al

in Optimization Letters (2021)

This paper studies the problem of siting renewable power generation assets using large amounts of climatological data while accounting for their spatiotemporal complementarity. The problem is cast as a ... [more ▼]

This paper studies the problem of siting renewable power generation assets using large amounts of climatological data while accounting for their spatiotemporal complementarity. The problem is cast as a combinatorial optimisation problem selecting a pre-specified number of sites so as to minimise the number of simultaneous low electricity production events that they experience relative to a pre-specified reference production level. It is shown that the resulting model is closely related to submodular optimisation and can be interpreted as generalising the well-known maximum coverage problem. Both deterministic and randomised algorithms are discussed, including greedy, local search and relaxation-based heuristics as well as combinations of these algorithms. The usefulness of the model and methods is illustrated by a realistic case study inspired by the problem of siting onshore wind power plants in Europe, resulting in instances featuring over ten thousand candidate locations and ten years of hourly-sampled meteorological data. The proposed solution methods are benchmarked against a state-of-the-art mixed-integer programming solver and several algorithms are found to consistently produce better solutions at a fraction of the computational cost. The physical nature of solutions provided by the model is also investigated, and all deployment patterns are found to be unable to supply a constant share of the electricity demand at all times. Finally, a cross-validation analysis shows that, except for an edge case, the model can successfully and reliably identify deployment patterns that perform well on previously unseen climatological data from historical data spanning a small number of weather years. [less ▲]

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See detailRemote Renewable Hubs for Carbon-Neutral Synthetic Fuel Production
Berger, Mathias ULiege; Radu, David-Constantin ULiege; Detienne, Ghislain et al

in Frontiers in Energy Research (2021)

This paper studies the economics of carbon-neutral synthetic fuel production from renewable electricity in remote areas where high-quality renewable resources are abundant. To this end, a graph-based ... [more ▼]

This paper studies the economics of carbon-neutral synthetic fuel production from renewable electricity in remote areas where high-quality renewable resources are abundant. To this end, a graph-based optimisation modelling framework directly applicable to the strategic planning of remote renewable energy supply chains is proposed. More precisely, a hypergraph abstraction of planning problems is introduced, wherein nodes can be viewed as optimisation subproblems with their own parameters, variables, constraints and local objective. Nodes typically represent a subsystem such as a technology, a plant or a process. Hyperedges, on the other hand, express the connectivity between subsystems. The framework is leveraged to study the economics of carbon-neutral synthetic methane production from solar and wind energy in North Africa and its delivery to Northwestern European markets. The full supply chain is modelled in an integrated fashion, which makes it possible to accurately capture the interaction between various technologies on an hourly time scale. Results suggest that the cost of synthetic methane production and delivery would be slightly under 150 €/MWh (higher heating value) by 2030 for a system supplying 10 TWh annually and relying on a combination of solar photovoltaic and wind power plants, assuming a uniform weighted average cost of capital of 7%. A comprehensive sensitivity analysis is also carried out in order to assess the impact of various techno-economic parameters and assumptions on synthetic methane cost, including the availability of wind power plants, the investment costs of electrolysis, methanation and direct air capture plants, their operational flexibility, the energy consumption of direct air capture plants, and financing costs. The most expensive configuration (around 200 €/MWh) relies on solar photovoltaic power plants alone, while the cheapest configuration (around 88 €/MWh) makes use of a combination of solar PV and wind power plants and is obtained when financing costs are set to zero. [less ▲]

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See detailModel Reduction in Capacity Expansion Planning Problems via Renewable Generation Site Selection
Radu, David-Constantin ULiege; Dubois, Antoine ULiege; Berger, Mathias ULiege et al

in Proceedings of the 2021 IEEE Madrid PowerTech (2021, June)

The accurate representation of variable renewable generation (RES, e.g., wind, solar PV) assets in capacity expansion planning (CEP) studies is paramount to capture spatial and temporal correlations that ... [more ▼]

The accurate representation of variable renewable generation (RES, e.g., wind, solar PV) assets in capacity expansion planning (CEP) studies is paramount to capture spatial and temporal correlations that may exist between sites and impact both power system design and operation. However, it typically has a high computational cost. This paper proposes a method to reduce the spatial dimension of CEP problems while preserving an accurate representation of renewable energy sources. A two-stage approach is proposed to this end. In the first stage, relevant sites are identified via a screening routine that discards the locations with little impact on system design. In the second stage, the subset of relevant RES sites previously identified is used in a CEP problem to determine the optimal configuration of the power system. The proposed method is tested on a realistic EU case study and its performance is benchmarked against a CEP set-up in which the entire set of candidate RES sites is available. The method shows great promise, with the screening stage consistently identifying 90% of the optimal RES sites while discarding up to 54% of the total number of candidate locations. This leads to a peak memory reduction of up to 41% and solver runtime gains between 31% and 46%, depending on the weather year considered. [less ▲]

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See detailAssessing the Impact of Offshore Wind Siting Strategies on the Design of the European Power System
Radu, David-Constantin ULiege; Berger, Mathias ULiege; Dubois, Antoine ULiege et al

in Applied Energy (2021), 305

This paper provides a detailed account of the impact of different offshore wind siting strategies on the design of the European power system. To this end, a two-stage method is proposed. In the first ... [more ▼]

This paper provides a detailed account of the impact of different offshore wind siting strategies on the design of the European power system. To this end, a two-stage method is proposed. In the first stage, a highly-granular siting problem identifies a suitable set of sites where offshore wind plants could be deployed according to a pre-specified criterion. Two siting schemes are analysed and compared within a realistic case study. These schemes essentially select a pre-specified number of sites so as to maximize their aggregate power output and their spatiotemporal complementarity, respectively. In addition, two variants of these siting schemes are provided, wherein the number of sites to be selected is specified on a country-by-country basis rather than Europe-wide. In the second stage, the subset of previously-identified sites is passed to a capacity expansion planning framework that sizes the power generation, transmission and storage assets that should be deployed and operated in order to satisfy pre-specified electricity demand levels at minimum cost. Results show that the complementarity-based siting criterion leads to system designs which are up to 5% cheaper than the ones relying on the power output-based scheme when offshore wind plants are deployed with no consideration for country-based deployment targets. On the contrary, the power output-based scheme leads to system designs which are consistently 2% cheaper than the ones leveraging the complementarity-based siting strategy when such constraints are enforced. The robustness of the reported results is supported by a sensitivity analysis on offshore wind capital expenditure and inter-annual weather variability, respectively. [less ▲]

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See detailGraph-Based Optimization Modeling Language: A Tutorial
Berger, Mathias ULiege; Bolland, Adrien ULiege; Miftari, Bardhyl ULiege et al

E-print/Working paper (2021)

This paper introduces the graph-based optimization modeling language (GBOML), which enables the easy implementation of a broad class of structured mixed-integer linear programs typically found in ... [more ▼]

This paper introduces the graph-based optimization modeling language (GBOML), which enables the easy implementation of a broad class of structured mixed-integer linear programs typically found in applications ranging from energy system planning to supply chain management. More precisely, the language is particularly well-suited for representing problems involving the optimization of discrete-time dynamical systems over a finite time horizon and possessing a block decomposable structure that can be encoded by a sparse connected hypergraph. The language combines elements of both algebraic and object-oriented modeling languages in order to facilitate problem encoding and post-processing. This document discusses the abstract problem class that can be represented using the modeling language, details its grammar and provides two relevant examples of applications. The first example deals with the deployment of a microgrid system, while the second example focuses on the design and analysis of remote carbon-neutral fuel supply chains. [less ▲]

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See detailThe Role of Hydrogen in the Dutch Electricity System
Berger, Mathias ULiege; Radu, David-Constantin ULiege; Ryszka, Karolina et al

Report (2020)

This technical report investigates the role power-to-gas, hydrogen and battery storage technologies may play in the Dutch electricity system using a recently published optimization-based energy system ... [more ▼]

This technical report investigates the role power-to-gas, hydrogen and battery storage technologies may play in the Dutch electricity system using a recently published optimization-based energy system model. [less ▲]

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See detailThe Role of Power-to-Gas and Carbon Capture Technologies in Cross-Sector Decarbonisation Strategies
Berger, Mathias ULiege; Radu, David-Constantin ULiege; Fonteneau, Raphaël ULiege et al

in Electric Power Systems Research (2020), 180

This paper proposes an optimisation-based framework to tackle long-term centralised planning problems of multi-sector, integrated energy systems including electricity, hydrogen, natural gas, synthetic ... [more ▼]

This paper proposes an optimisation-based framework to tackle long-term centralised planning problems of multi-sector, integrated energy systems including electricity, hydrogen, natural gas, synthetic methane and carbon dioxide. The model selects and sizes the set of power generation, energy conversion and storage as well as carbon capture technologies minimising the cost of supplying energy demand in the form of electricity, hydrogen, natural gas or synthetic methane across the power, heating, transportation and industry sectors whilst accounting for policy drivers, such as energy independence, carbon dioxide emissions reduction targets, or support schemes. The usefulness of the model is illustrated by a case study evaluating the potential of sector coupling via power-to-gas and carbon capture technologies to achieve deep decarbonisation targets in the Belgian context. Results, on the one hand, indicate that power-to-gas can only play a minor supporting role in cross-sector decarbonisation strategies in Belgium, as electrolysis plants are deployed in moderate quantities whilst methanation plants do not appear in any studied scenario. On the other hand, given the limited renewable potential, post-combustion and direct air carbon capture technologies clearly play an enabling role in any decarbonisation strategy, but may also exacerbate the dependence on fossil fuels. [less ▲]

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See detailCritical Time Windows for Renewable Resource Complementarity Assessment
Berger, Mathias ULiege; Radu, David-Constantin ULiege; Fonteneau, Raphaël ULiege et al

in Energy (2020), 198

This paper proposes a framework to assess the complementarity between geographically dispersed variable renewable energy resources over arbitrary time scales. More precisely, the framework relies on the ... [more ▼]

This paper proposes a framework to assess the complementarity between geographically dispersed variable renewable energy resources over arbitrary time scales. More precisely, the framework relies on the concept of critical time windows, which offers an accurate, time-domain description of low-probability power production events impacting power system operation and planning. A scalar criticality indicator is also derived to quantify the spatiotemporal complementarity that renewable generation sites may exhibit, and it is leveraged to propose optimisation models seeking to identify deployment patterns with maximum complementarity. The usefulness of the framework is shown in a case study investigating the complementarity between wind regimes in continental western Europe and southern Greenland, using roughly 300 candidate locations and 10 years of reanalysis and simulated data with hourly resolution. Besides showing that the occurrence of low wind power production events can be reduced on a regional scale by exploiting diversity in local wind patterns, results highlight the fact that aggregating wind power production sites located on different continents may result in a lower occurrence of system-wide low wind power production events and point to potential bene ts of intercontinental electrical interconnections. [less ▲]

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See detailSector Coupling: Concepts, State-of-the-art and Perspectives
Munster, Marie; Moller Sneum, Daniel; Bramstoft, Rasmus et al

Report (2020)

Sector coupling has recently gained increased attention, bringing new complexity into infrastructure investment decisions but also new opportunities for its smart operation. In a multi-energy system the ... [more ▼]

Sector coupling has recently gained increased attention, bringing new complexity into infrastructure investment decisions but also new opportunities for its smart operation. In a multi-energy system the benefits of an investment in one system may spread over other connected sectors, calling for new metrics when evaluating the cost-benefit analysis (CBA) and for widening scenarios of investment decisions to alternative solutions in the cross-energy system which can be more economical. Sector coupling brings new challenges such as: amount and shape of electric demand growth with electrification of heating and transport; how much distribution-grid based system reinforcement is needed to accommodate the charging of Electric Vehicles (EV) or electricity needs of Heat Pumps (HP), and when in the coming decades or years these devices should be installed; whether the costs of electrolysers for power-to-gas decreases significantly , and how that affects the economics of electricity vs. gas transmission and distribution. There are great expectations about the role of sector coupling in the achievement of a swift, economical efficient green transition with a high security of supply, but it is unclear to which extent current technologies can provide on this agenda. This ETIP SNET White Paper aims to elaborate on those questions, starting with clarification of concepts and assessment of potential impacts. [less ▲]

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See detailGlobal electricity network - Feasibility study
Yu, J.; Bakic, K.; Kumar, A. et al

Report (2019)

With the strong development of renewable energy sources worldwide, the concept of a global electricity network has been imagined in order to take advantage of the diversity from different time zones ... [more ▼]

With the strong development of renewable energy sources worldwide, the concept of a global electricity network has been imagined in order to take advantage of the diversity from different time zones, seasons, load patterns and the intermittency of the generation, thus supporting a balanced coordination of power supply of all interconnected countries. The TB presents the results of the feasibility study performed by WG C1.35. It addresses the challenges, benefits and issues of uneven distribution of energy resources across the world. The time horizon selected is 2050. The study finds significant potential benefits of a global interconnection, identifies the most promising links, and includes sensitivity analyses to different factors, such as wind energy capacity factors or technology costs. [less ▲]

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See detailComplementarity Assessment of South Greenland Katabatic Flows and West Europe Wind Regimes
Radu, David-Constantin ULiege; Berger, Mathias ULiege; Fonteneau, Raphaël ULiege et al

in Energy (2019), 175

Current global environmental challenges require vigorous and diverse actions in the energy sector. One solution that has recently attracted interest consists in harnessing high-quality variable renewable ... [more ▼]

Current global environmental challenges require vigorous and diverse actions in the energy sector. One solution that has recently attracted interest consists in harnessing high-quality variable renewable energy resources in remote locations, while using transmission links to transport the power to end users. In this context, a comparison of western European and Greenland wind regimes is proposed. By leveraging a regional atmospheric model specifically designed to accurately capture polar phenomena, local climatic features of southern Greenland are identified to be particularly conducive to extensive renewable electricity generation from wind. A methodology to assess how connecting remote locations to major demand centres would benefit the latter from a resource availability standpoint is introduced and applied to the aforementioned Europe-Greenland case study, showing superior and complementary wind generation potential in the considered region of Greenland with respect to selected European sites. [less ▲]

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See detailCentralised Planning of National Integrated Energy System with Power-to-Gas and Gas Storages
Berger, Mathias ULiege; Radu, David-Constantin ULiege; Fonteneau, Raphaël ULiege et al

in Proceedings of the 11th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion (Medpower2018) (2018, November)

This paper proposes an optimisation-based framework to tackle long-term centralised planning problems of integrated energy systems with bi-directional electricity-gas carriers coupling under various ... [more ▼]

This paper proposes an optimisation-based framework to tackle long-term centralised planning problems of integrated energy systems with bi-directional electricity-gas carriers coupling under various policy constraints. The framework is leveraged to gain insight into possible configurations of the future Belgian energy system, and identify the cost-optimal energy mix as well as short and long-term storage requirements to satisfy CO2 emissions reductions and energy security targets. Results shed light on the economics of a transition to a low-carbon energy system and reveal the potential of power-to-gas and storage in gas form to help achieve ambitious emissions reduction goals. [less ▲]

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