Nico Keyaerts

Bio: Nico Keyaerts is an academic researcher. The author has contributed to research in topics: Flexibility (engineering). The author has an hindex of 1, co-authored 1 publications receiving 23 citations.

Gas Balancing and Line-pack Flexibility. Concepts and Methodologies for Organizing and Regulating Gas Balancing in Liberalized and Integrated EU Gas Markets. (Gasbalancering en netwerkflexibiliteit. Concepten en methodologieën voor de organisatie en regulering van gasbalancering in vrijgemaakte en geïntegreerde EU gasmarkten.)

Abstract: The liberalization and unbundling of the gas industry in Europe creates new challenges for the operation of the gas system. In particular the short-term coordination of shippers and the gas-transmission-system operator becomes difficult as information and responsibilities are distributed between them. The balancing mechanism establishes the main interface between these two gas-market actors and thus its design is important. The industry has been reflecting on the proper organization of gas balancing, but no consensus design could be agreed on yet. At the same time, the interest in this topic by academia has been limited, even though independent research into the gas-balancing problem can further advance the debate. In this thesis, therefore, the organization of balancing is properly discussed by taking both the shipper’s viewpoint and that of the TSO into account in a number of essays focusing on specific balancing problems and challenges. Moreover, this work presents quantitative methodologies on a conceptual level that can be applied to other, practical problems by other researchers and the industry. The first part of this work provides a thorough, but concise overview of what balancing is and how it is organized and how it can be organized drawing lessons from other sectors like the US gas market and the EU electricity sector. The second part presents essays on the challenges of balancing in a national context without cross-border interactions. First, current regulation of line-pack flexibility is found to be inefficient and actually gas-market distorting. Second, rising unpredictability of the gas demand, transferred from RES intermittency, creates challenges for gas-system balancing with respect to the balancing design. Both market-based and non-market-based designs are imperfect and policy makers have to be made aware of that problem. In a third part of this work, methodologies are developed to study the effects of cross-border balancing in a multi-region gas market. Efficiency gains are shown to be possible for hypothetical gas systems if the settlement designs provide correct incentives. If wrong incentives are provided, on the other hand, the overall efficiency can reduce because imbalances are moved to regions that are less efficient in balancing. In a market-based balancing mechanism, TSOs can also cooperate with regard to the procurement of flexible gas or the exchange of line-pack flexibility. This kind of cooperation is shown to improve efficiency for hypothetical cases, but researchers who have access to real data can apply the conceptual methodology to calculate the efficiency gains of cooperating across a particular border.

Integrated Power and Natural Gas Model for Energy Adequacy in Short-Term Operation

Abstract: The significant growth in gas-fired units worldwide has increased the grade of interdependency between power and natural gas networks. Since these units are usually required to ramp up during the peak and backup intermittent renewable generation and contingencies, the power system tends to demand more flexibility and reliability from the gas system. This paper contributes with a novel mixed-integer linear programing (MILP) formulation that couples power and gas networks taking into account the gas traveling velocity and compressibility. As a result, the model accounts for the gas adequacy needed to assure the power system reliability in the short term. The robustness of the MILP formulation allows guaranteeing global optimality within predefined tolerances. Case studies integrate the IEEE 24-bus system and Belgian high-calorific gas network for validating the formulation.

The gas transmission problem solved by an extension of the simplex algorithm

Abstract: The problem of distributing gas through a network of pipelines is formulated as a cost minimization subject to nonlinear flow-pressure relations, material balances, and pressure bounds. The solution method is based on piecewise linear approximations of the nonlinear flow-pressure relations. The approximated problem is solved by an extension of the Simplex method. The solution method is tested on real-world data and compared with alternative solution methods.

Convex Optimization Based Distributed Optimal Gas-Power Flow Calculation

Abstract: This paper proposes a convex optimization based distributed algorithm to solve the multi-period optimal gas-power flow (OGPF) problem in coupled energy distribution systems. At the gas distribution system side, the nonconvex Weymouth gas flow equations are convexified as quadratic constraints. Then, the optimal gas flow (OGF) subproblem is solved by an iterative second-order cone programming (SOCP) procedure, whose efficiency is two orders of magnitudes higher than traditional nonlinear methods. A convex quadratic program based initiation scheme is suggested, which helps to find a high-quality starting point. At the power distribution system side, convex relaxation is performed on the nonconvex branch flow equations, and the optimal power flow (OPF) subproblem gives rise to an SOCP. Tightness is guaranteed by the radial topology. In the proposed distributed algorithm, the OGF problem and the OPF problem are solved independently, and coordinated by the alternating direction multiplier method. Numerical results corroborate significant enhancements on computational robustness and efficiency compared with existing OGPF calculation methods.

A Linear Programming Approach to Expansion Co-Planning in Gas and Electricity Markets

Abstract: In a carbon-constrained world, the continuing and rapid growth of gas-fired power generation (GPG) will lead to the increasing demand for natural gas. The reliable and affordable gas supply hence becomes an important factor to consider in power system planning. Meanwhile, the installation of GPG units should take into account not only the fuel supply constraints but also the capability of sending out the generated power. In this paper, a novel expansion co-planning (ECP) model is proposed, aiming to minimize the overall capital and operational costs for the coupled gas and power systems. Moreover, linear formulations are introduced to deal with the nonlinear nature of the objective functions and constraints. Furthermore, the physical and economic interactions between the two systems are simulated by an iterative process. The proposed linear co-planning approach is tested on a simple six-bus power system with a seven-node gas system and a modified IEEE 118-bus system with a 14-node gas system. Numerical results have demonstrated that our co-planning approach can allow systematic investigations on supporting cost-effective operating and planning decisions for power systems.