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Publications TME

An overview of the papers published in the TME division since 2014 is shown below. This overview is automatically generated based on the entries in the Lirias repository.

query=user:U0004531 OR U0009689 OR U0014331 OR U0011045 OR U0050011 year:[2014 TO 2019] &institution=lirias&from=1&step=20&sort=scdate
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  • thesis-dissertation
    Van Erdeweghe, S; 2019. Binary Geothermal Combined Heat-and-Power Plants — Optimal Design and Control of Low-Temperature ORC-based Systems.
    LIRIAS2821607
    description
    Deep-geothermal energy is readily available all over the world as long as one is willing to drill deep enough. However, in northwest European countries, the geothermal gradient is low (~30 °C/km) which leads to high drilling costs and low geothermal source temperatures (110-150 °C). As a result, the stand-alone electrical power generation from a low-temperature geothermal energy source is not economically viable without some kind of support scheme. The goal of this PhD research is to investigate whether the economics of a binary geothermal electrical power plant can be increased by providing heat in addition to electricity. Four promising alternative Combined Heat-and-Power (CHP) plant configurations are studied, referred to as the series, the parallel, the so-called preheat-parallel and the HB4 configurations, and the connection to third- (current technology) and fourth-generation (near-future technology) district heating systems is considered for the heat delivery. The developed computer tool can be applied to current and (near-)future deep-geothermal projects. The main outcome of this PhD research is a two-step thermoeconomic optimization framework which allows indicating the most suited CHP plant configuration or stand-alone electrical power plant for a certain application. In the first step of the optimization framework, the design of the heat exchangers and the air-cooled condenser is optimized towards maximum net present value. The net present value is considered since it takes into account the thermodynamic performance, the size and cost of the components and the time value of money (as reflected in the discount rate). In the second step, the operating conditions are optimized for the installed CHP plant design in order to maximize the net electricity generation depending on the fluctuating heat demand and environment conditions. It is found that for a certain CHP layout which has been installed, the off-design operational performance might be improved by changing the physical connection of the heat and electricity generation parts; e.g., to allow a CHP plant which was designed for the series layout to be configured in parallel to be able to provide high heat demands. Finally, the actual (or real) performance indicators can be calculated, taking into account the off-design operational performance. The thermoeconomic design optimization of binary geothermal CHP plants, taking into account the off-design operational behavior and allowing the configuration to change during operation, is novel compared to the existing literature. The results of a detailed sensitivity analysis have indicated that the (site-specific) geological conditions, the electricity selling contract, the type of investor and the experience of the well drilling company are the most important criteria with respect to the project feasibility. Of course, also economic support schemes might trigger the roll-out of deep-geothermal energy utilization. Furthermore, and based on the off-design optimization results, the parallel CHP plant configuration is indicated as the most flexible layout since the ORC operation does almost not depend on the temperature levels of the heat demand. The off-design optimization model is also capable of calculating the optimal amounts of electricity and heat to be produced for an installed CHP facility, depending on the electricity and gas price signals. However, due to the high level of technical detail, this approach is rather slow (~100 s/data point) and part-load maps for the heat versus electricity production are derived from the detailed off-design optimization model results. These part-load maps are implemented in a high-level control optimization model, which is very fast (~milliseconds) and which can calculate the optimal amounts of heat and electricity to be produced for real-time wholesale price signals and environment conditions. The thermoeconomic optimization framework is applied to a case study. An existing third-generation district heating system is considered and the geological, environment and economic conditions are based on the Belgian context. For this case study, the series CHP plant design is optimal and the parallel configuration is used for providing high heat demands during operation. The considered CHP plant is economically feasible without some kind of support scheme. Note, however, that this conclusion cannot be generalized due to the site-specific input parameters, especially for the district heating system operation. In conclusion, although the net electricity generation is lower, the economic viability of a binary geothermal CHP plant might be better than for a binary geothermal stand-alone electrical power plant. The largest improvements are possible for low geothermal source temperatures and low flow rates. Furthermore, also the geothermal energy source utilization is generally better in a CHP plant. From this finding, it is recommended to pay more attention to the use of deep-geothermal energy for heat purposes in northwest European countries.

    Accepted
  • Lasagna, Davide; Sharma, Ati; Meyers, Johan; 2019. Periodic shadowing sensitivity analysis of chaotic systems. Journal of Computational Physics; 2019; Vol. 391; pp. 119 - 141
    LIRIAS2797852
    description
    © 2019 Elsevier Inc. The sensitivity of long-time averages of a hyperbolic chaotic system to parameter perturbations can be determined using the shadowing direction, the uniformly-bounded-in-time solution of the sensitivity equations. Although its existence is formally guaranteed for certain systems, methods to determine it are hardly available. One practical approach is the Least-Squares Shadowing (LSS) algorithm (Wang (2014) [18]), whereby the shadowing direction is approximated by the solution of the sensitivity equations with the least square average norm. Here, we present an alternative, potentially simpler shadowing-based algorithm, termed periodic shadowing. The key idea is to obtain a bounded solution of the sensitivity equations by complementing it with periodic boundary conditions in time. We show that this is not only justifiable when the reference trajectory is itself periodic, but also possible and effective for chaotic trajectories. Our error analysis shows that periodic shadowing has the same convergence rates as LSS when the time span T is increased: the sensitivity error first decays as 1/T and then, asymptotically as 1/T. We demonstrate the approach on the Lorenz equations, and also show that, as T tends to infinity, periodic shadowing sensitivities converge to the same value obtained from long unstable periodic orbits (Lasagna (2018) [14]) for which there is no shadowing error. Finally, finite-difference approximations of the sensitivity are also examined, and we show that subtle non-hyperbolicity features of the Lorenz system introduce a small, yet systematic, bias.
    Publisher: Elsevier
    Published
  • van der Heijde, Bram; Vandermeulen, Annelies; Salenbien, Robbe; Helsen, Lieve; 2019. Representative days selection for district energy system optimisation: a solar district heating system with seasonal storage. Applied Energy; 2019; Vol. 248; pp. 79 - 94
    LIRIAS2788060
    description
    The design and operational optimisation of fourth generation district heating networks is a crucial step towards highly renewable energy systems of the future. In order to optimise such complex systems, a toolbox modesto (multi-objective district energy systems toolbox for optimisation) is being developed. Seasonal thermal energy storage is an essential technology to allow larger shares of renewable energy sources, yet large computational power is required for its representation in fullyear operational optimisations, as a step towards district energy system optimal design. To decrease computational complexity, a technique with representative days able to include seasonal thermal energy storage systems is developed and validated. This methodology combines different part-solutions from literature, but also adds a novel aspect to safeguard the chronology of the optimisation problem. To validate the approach, the design optimisation of a ctitious solar district heating system with seasonal thermal energy storage is compared to different representative day optimisations in two cases. The operational optimisation is a linear optimisation problem, implemented using modesto; the design optimisation is built as a genetic algorithm, optimising the size of the storage and solar systems in the network. The validation exercise is done for the operational and for the design optimisation separately. This comparative study shows that modelling with representative days adequately mimics the behaviour for the presented case. Furthermore, a solution speed-up in the order of 10-30 times is shown for the representative optimisations with respect to the full year optimisation, in line with the reduction of the number of variables.
    Publisher: Elsevier
    Published online
  • Uytterhoeven, Anke; Bruninx, Kenneth; Deconinck, Geert; Arteconi, Alessia; Helsen, Lieve; 2019. Leveraging residential thermal loads in local energy communities – the role of demand response aggregators.
    LIRIAS2370294
    description


    Accepted
  • Van Erdeweghe, Sarah; Van Bael, Johan; Laenen, Ben; D'haeseleer, William; 2019. Optimal configuration for a low-temperature geothermal CHP plant based on thermoeconomic optimization. Energy; 2019; Vol. 179; pp. 323 - 335
    LIRIAS2799498
    description
    In this paper, we propose a thermoeconomic optimization procedure for four configurations of low-temperature geothermal combined heat-and-power (CHP) plants. The series, parallel, preheat-parallel and HB4 configurations are investigated. Electricity is produced via an organic Rankine cycle (ORC) and two types of district heating (DH) systems are considered for the heat delivery: a 90/60 and a 65/40 DH system. The objective is to maximize the net present value (NPV) of the CHP plant for given DH system requirements. We conclude that, under the assumptions considered, the NPV can be increased from −2.81MEUR (unprofitable) for a stand-alone electrical power plant to 12.5, 28 and 58MEUR (economically feasible) for the optimal CHP, and for a heat demand of 5, 10 and 20 MW th, respectively. Also, the exergetic plant efficiency is higher for the CHP plants, which means that the geothermal energy source can be utilized in a better way. Furthermore, we have found that the series CHP is generally the optimal CHP configuration. Only for the 90/60 DH system and low heat demands, the HB4 is more suitable. Compared to the simple series and parallel CHPs, the HB4 configuration has a 16% and 5.5% higher NPV, for heat demands of 5 and 10 MW th, respectively.
    Publisher: Elsevier
    Published
  • van der Heijde, B; 2019. Optimal Integration of Thermal Energy Storage and Conversion in Fourth Generation Thermal Networks.
    LIRIAS2802200
    description
    This dissertation investigates the integration of thermal energy storage and conversion systems in fourth generation thermal networks, with a focus on district heating networks. Energy storage, more specifically in the form of heat or cold, will play a crucial role in future energy systems where large shares of renewable and residual energy sources are included. Due to the variability and seasonality of particular renewable sources, energy storage is needed to bridge the mismatch between moments where energy is needed by end-users and when it is available. Thermal networks are a second technology that may be crucial in the energy system of the future. Whereas energy storage systems solve mismatches in time, thermal networks are able to solve misalignments in space, between locations with large heat or cold surpluses on the one hand and large demands on the other. Moreover, collective systems may exploit the economy of scales, and the lower supply temperatures of the newest generation of district heating allow for more efficient heat production systems, both renewable (such as solar thermal collectors or low-temperature geothermal heating) and electricity based (such as heat pumps). This thesis investigates how thermal energy storage and conversion systems can be integrated in an optimal way in future thermal networks. Therefore, an optimisation algorithm is set up with the goal to find the optimal sizes of several network components. The first part of the thesis focuses on the thermal and hydraulic behaviour of thermal network pipes. Firstly, steady-state and dynamic simulation models are derived and validated to understand which effects are most important. Based on these detailed models, a model for optimisation is derived. In order to keep the solution of the mathematical model feasible within reasonable time, a number of assumptions need to be made. In the second part, additional models for thermal energy storage and conversion systems are described. The final part of the thesis integrates all previously derived models into a large optimisation problem. Given the complex interactions between different system components, the operational aspect of the network is essential. Whereas a number of previous studies employed simulation-based control evaluations, this thesis introduces modesto, a Python toolbox for the compilation of optimal control problems for district energy systems and district heating systems in particular. This toolbox is used as the lower layer of a two-layer optimisation structure. The upper layer comprises an evolutionary algorithm that explores the design space with respect to multiple objective functions. The objective function values result from the lower layer's evaluation of individual network designs. The lower, operational layer's calculation time is reduced by using an optimal representative days selection algorithm, compatible with seasonal thermal energy storage systems. As such, an integrated optimal control and design of district energy systems can be performed. The resulting design optimisation algorithm is shown to be very flexible in terms of which design variables are included. The design optimisation algorithm is applied to a fictitious case study, based on real geographical data and building geometries from the city of Genk. Although the results show that the algorithm is capable of proposing a set of optimal designs with respect to multiple objective functions, it is hard to derive general design rules or rules of thumb that can be easily applied in real designs. On the other hand, it is shown that seasonal thermal energy storage will be a crucial component of future renewable-based energy systems, since every proposed design includes substantial storage volumes that act on a seasonal time scale.

    Published
  • journal-article
    Jorissen, F; Boydens, W; Helsen, L; 2019. Model implementation and verification of the envelope, HVAC and controller of an office building in Modelica. Journal of Building Performance Simulation; 2019; Vol. 12; iss. 4; pp. 445 - 464
    LIRIAS2346352
    description
    © 2018, © 2018 International Building Performance Simulation Association (IBPSA). Modelica is a promising open-source modelling language for simulation and derivative-based optimization of multi-zone buildings, including detailed pressure-driven flow networks and building controllers. Such Modelica models have however not yet been demonstrated for buildings with many zones and complex HVAC systems. This paper presents and provides implementation details of the simulation model of a 32-zones building model in Modelica, with pressure-driven flow networks and a building controller, demonstrating the potential of Modelica. The modelling approach and computational aspects are presented. Furthermore, the model is calibrated and verified using on-site measurement data, which shows that, for the presented case study, HVAC can be modelled with errors up to only a few percent, while larger errors are observed for the building envelope model. A detailed building description is provided as supplementary material.
    Publisher: Taylor & Francis Ltd.
    Published
  • Poncelet, Kris; Delarue, Erik; 2019. Comments on: A comparative study of time aggregation techniques in relation to power capacity-expansion modeling. TOP: An Official Journal of the Spanish Society of Statistics and Operations Research; 2019
    LIRIAS2822665
    description

    Publisher: Springer Verlag
    Accepted
  • Wei, Tiwei; Oprins, Herman; Cherman, Vladimir; Qian, Jun; De Wolf, Ingrid; Beyne, Eric; Baelmans, Martine; 2019. High-Efficiency Polymer-Based Direct Multi-Jet Impingement Cooling Solution for High-Power Devices. IEEE Transactions on Power Electronics; 2019; Vol. 34; iss. 7; pp. 6601 - 6612
    LIRIAS2243007
    description
    © 1986-2012 IEEE. A high-efficiency three-dimensionally (3-D) shaped polymer multi-jet impingement cooler based on cost-efficient fabrication techniques is introduced for the cooling of high-power applications. State-of-the-art highly efficient multi-jet cooling solutions rely on expensive Si or ceramic fabrication techniques, while low-cost cooling solutions have been proposed for less performant single-jet impingement. In this paper, we present the concept, modeling, design, fabrication, experimental characterization, and benchmarking with literature data of a multi-jet impingement based liquid cooling solution, fabricated using low-cost polymer fabrication techniques, targeted to directly cool the backside of high-power devices. For the modeling study, unit cell model and full system level models are used to study the nozzle array scaling trends and thermal and fluidic jet-to-jet interactions. Furthermore, design guidelines for high-power electronics cooling are provided, including geometry selections, material selection, and fabrication techniques. Based on the design guidelines and cooling concept, this paper demonstrates a 3-D-shaped polymer impingement cooler with a 4 × 4 nozzle array, showing a very good thermal performance with low required pumping power. The multi-jet cooler can achieve heat transfer coefficients up to 6.25 × 10 4 W/m 2 ·K with a pump power as low as 0.3 W. The benchmarking study confirms furthermore that multi-jet cooling is more efficient than single-jet cooling and that direct cooling on the backside of the semiconductor device is more efficient than cooling the substrate or base plate.
    Publisher: Institute of Electrical and Electronics Engineers
    Published
  • presentation
    Bruninx, Kenneth; Belderbox, Andreas; Valkaert, Thomas; Delarue, Erik; D'haeseleer, William; 2019. Facilitating renewables and power-to-gas via integrated electrical power-gas system scheduling.
    LIRIAS2815255
    description


    Accepted
  • presentation
    Hermans, Mathias; Bruninx, kenneth; Delarue, Erik; 2019. On the Clearing Frequency of Joint Energy-Operating Reserve Markets and Generator Start-up Flexibility.
    LIRIAS2815408
    description


    Published
  • presentation
    Govaerts, Niels; Bruninx, Kenneth; Le Cadre, Hélène; Meeus, Leonardo; Delarue, Erik; 2019. On cost-reflectivity of distribution network tariffs: an equilibrium modeling approach.
    LIRIAS2818017
    description


    Accepted
  • Poncelet, Kris; Kaminski, Steffen; Delarue, Erik; 2019. Ability and limitations of optimization models for computing the equilibrium in competitive energy markets.
    LIRIAS2815291
    description


    Published
  • presentation
    Dolányi, Mihály; Bruninx, Kenneth; Deconinck, Geert; Delarue, Erik; 2019. Strategic operation of storage in energy markets: an EPEC approach.
    LIRIAS2823106
    description


    Published
  • Meus, Jelle; Van den Bergh, Kenneth; Delarue, Erik; Proost, Stef; 2019. On international renewable cooperation mechanisms: The impact of national RES-E support schemes. Energy Economics; 2019; Vol. 81; pp. 859 - 873
    LIRIAS2814403
    description
    The deployment of renewable cooperation mechanisms within the European Union (via statistical transfers,joint support schemes and joint projects) is expected to increase in the near future. Such cooperation mechanisms can significantly reduce the compliance cost for meeting renewable energy targets. Nevertheless,as it is known that ill-designed national support instruments distort renewable investment and production decisions, it can also be expected that these impact the performance of cooperation mechanisms. In this paper, we develop a bi-level two-country competitive equilibrium model that analyzes the impact of national RES-E support instruments on the performance of renewable cooperation mechanisms. Further-more, we assess the efficiency of two international cooperation mechanisms (statistical transfers and joint support schemes) and compare it to the situation without renewable cooperation. Based on an analytical derivation and a numerical example, we first confirm that fixed feed-in premiums are the globally most efficient instrument, given production-based quotas (in MWh). Other national instruments (feed-in tariffs and capacity-based subsidies) can distort renewable investment decisions, and are sub-optimal. Second, the employment of statistical transfers always outperforms the no-renewable cooperation case, independent of the national support instruments. Third, statistical transfers are preferred over joint support schemes when employing sub-optimal national policy instruments. In fact, it even is possible that sub-optimal joint sup-port schemes (i.e. not based on the fixed feed-in premium) perform worse than no renewable cooperation at all. Finally, we also consider the country-level distributional effects and conclude that country-level incentives for renewable cooperation may not align with the global optimum, i.e. national policy makers might be incentivized to constrain their cooperation levels.
    Publisher: Elsevier
    Published
  • Ghoos, K; 2019. Accuracy-based Simulation Strategies for Plasma Edge Simulations for Nuclear Fusion Devices.
    LIRIAS2368574
    description
    Nuclear fusion has the potential to provide the world's energy needs with safe, sustainable and virtually limitless energy. A key challenge in the realization of magnetically confined nuclear fusion is the power exhaust in the so-called divertor region near the reactor walls, which has to withstand enormous power loads. To predict and analyze divertor performance, accurate plasma edge simulations are indispensable. State-of-the-art plasma edge codes, such as B2-EIRENE, solve non-linear plasma and neutral transport equations iteratively. While plasma transport is modeled with fluid equations and implemented with a finite volume (FV) code, neutral transport requires a kinetic equation, implemented with a Monte Carlo (MC) code. In an MC code, particle trajectories are traced out to determine the average behavior of the particles. However, a statistical error remains on the result, which has a large impact on the convergence of the coupled FV-MC system. This complicates accuracy analysis and makes plasma edge simulations time-consuming. The goal of this PhD is to improve the speed and accuracy of B2-EIRENE simulations by optimizing the simulation strategy. Based on a detailed accuracy analysis, where all numerical error contributions are quantified, the coupling technique and the numerical parameters can be chosen more adequately. That way, a solution can be obtained in less computational time without losing accuracy. Or, similarly, a more accurate solution can be computed in the same computational time. First, we examine convergence and accuracy in a systematic way for several coupling techniques using a simplified 1D plasma edge model. Several error contributions are defined and methods to estimate these errors are proposed. We found the Random Noise coupling technique, where particle trajectories are uncorrelated between iterations, to be superior to Correlated Sampling, where trajectories are correlated, and Robbins Monro, where averaged values are used during the simulation. When the results of consecutive statistically stationary iterations are averaged in post-processing, an order of magnitude speed-up can be obtained without losing accuracy compared to the traditional simulation approach without averaging. Subsequently, we perform a first comprehensive accuracy analysis of B2-EIRENE simulation for a partially detached ITER divertor plasma. The speed-up obtained with averaging enabled simulations with on higher resolution discretization grids, which were previously unfeasible. A grid resolution study reveals that the discretization error in typical simulations is very large with some peak values increasing more than 40%. With a more suitable parameter choice, the total numerical error was limited to 15% within a feasible computational time. Finally, we extend the developed methodology for time-dependent FV-MC simulations and iterative MC codes using simplified 1D models. The extensions demonstrate the generality of the developed framework, which opens the way to accuracy analysis for many more applications within plasma edge simulations as well as in other fields where coupled stochastic-deterministic codes are emerging.

    Published
  • presentation
    Mertens, Tim; Poncelet, Kris; Duerinck, Jan; Delarue, Erik; 2019. Representing Cross-border Trade in Long-term Power system Planning Models with Limited Geographical Scope.
    LIRIAS2822710
    description


    Accepted
  • presentation
    Mertens, Tim; Poncelet, Kris; Duerinck, Jan; Delarue, Erik; 2019. Representing Cross-border Trade in Long-term Power system Planning Models with Limited Geographical Scope.
    LIRIAS2822709
    description


    Accepted
  • presentation
    Hermans, Mathias; Bruninx, Kenneth; Delarue, Erik; 2019. On the Clearing Frequency of Joint Energy-Operating Reserve Markets and Generator Start-up Flexibility.
    LIRIAS2809097
    description


    Published
  • De Vivero-Serrano, Gustavo; Bruninx, Kenneth; Delarue, Erik; 2019. Implications of Bid Structures on the Offering Strategies of Merchant Energy Storage Systems. Applied Energy; 2019
    LIRIAS2804516
    description

    Publisher: Elsevier
    Accepted