Clustering a building stock towards representative buildings in the context of air-conditioning electricity demand flexibility

Energy modeling for the prediction of energy use in buildings, especially under novel energy management strategies, is of great importance. In buildings there are several flexible electrical loads which can be shifted in time such as thermostatically controllable loads. The main novelty of this paper is to apply an aggregation method to effectively characterize the electrical energy demand of air-conditioning (AC) systems in residential buildings under flexible operation during demand response and demand shaping programs. The method is based on clustering techniques to aggregate a large and diverse building stock of residential buildings to a smaller, representative ensemble of buildings. The methodology is tested against a detailed simulation model of building stocks in Houston, New York and Los Angeles. Results show good agreement between the energy demand predicted by the aggregated model and by the full model during normal operation (normalized mean absolute error, NMAE, below 10%), even with a small number of clusters (sample size of 1%). During flexible operation, the normalized mean absolute error rises (around 20%) and a higher number of representative buildings becomes necessary (sample size at least 10%). Multiple cases for the input data series were considered, namely by varying the time resolution of the input data and the type of input data. These characteristics of the input time series data are shown to play a crucial role in the aggregation performance. The aggregated model showed lower NMAE compared to the original model when clustering is based on a hybrid signal resolved at 60-minute time intervals, which is a combination of the electricity demand profile and AC modulation level.status: publishe

Using representative time slices for optimization of thermal energy storage systems in low-temperature district heating systems

4 th generation district heating and cooling networks (shortly THERNETs) are often coined as a crucial technology to enable the transition towards low-carbon smart energy systems. Most importantly, they open perspectives for integration of low-grade residual heat from industry, renewable energy sources (such as geothermal heat and cold and solar thermal collectors), more efficient energy conversion units (such as collective heat pumps), while thermal energy storage (TES) systems increase system flexibility. In order to optimize design and control of such complex systems, a toolbox modesto (Multi-objective district energy systems toolbox for optimization) is under development. However, the representation of seasonal heat and cold storage systems on an annual basis requires large computational power. In an attempt to decrease computational cost, a technique with representative time slices (inspired by and combining aspects from optimization studies of electrical energy systems, unit commitment problems, thermal systems with short term energy storage and smaller scale industrial thermal systems with longer term energy storage) is developed and tested. The aim of this study is to investigate the applicability of such representative time periods to optimize seasonal TES systems in THERNETs. To this end a full year optimization is compared to one with representative time periods for a realistic case study that uses demand profiles from the city of Genk (Belgium) and energy system parameters from Marstal (Denmark). This comparative study shows that modelling with representative periods is sufficient to mimic the behaviour of a full year optimization. However, when curtailment of solar heat injection occurs, not all representations yield the same results. It was found that for the studied case, a selection of 12 representative weeks performs best, while all reduced optimizations result in a substantial reduction (speed-up of on average x4.8 to x7.7) of the calculation time

Using representative time slices for optimization of thermal energy storage systems in low-temperature district heating systems

\u3cp\u3e 4 \u3csup\u3eth\u3c/sup\u3e generation district heating and cooling networks (shortly THERNETs) are often coined as a crucial technology to enable the transition towards low-carbon smart energy systems. Most importantly, they open perspectives for integration of low-grade residual heat from industry, renewable energy sources (such as geothermal heat and cold and solar thermal collectors), more efficient energy conversion units (such as collective heat pumps), while thermal energy storage (TES) systems increase system flexibility. In order to optimize design and control of such complex systems, a toolbox modesto (Multi-objective district energy systems toolbox for optimization) is under development. However, the representation of seasonal heat and cold storage systems on an annual basis requires large computational power. In an attempt to decrease computational cost, a technique with representative time slices (inspired by and combining aspects from optimization studies of electrical energy systems, unit commitment problems, thermal systems with short term energy storage and smaller scale industrial thermal systems with longer term energy storage) is developed and tested. The aim of this study is to investigate the applicability of such representative time periods to optimize seasonal TES systems in THERNETs. To this end a full year optimization is compared to one with representative time periods for a realistic case study that uses demand profiles from the city of Genk (Belgium) and energy system parameters from Marstal (Denmark). This comparative study shows that modelling with representative periods is sufficient to mimic the behaviour of a full year optimization. However, when curtailment of solar heat injection occurs, not all representations yield the same results. It was found that for the studied case, a selection of 12 representative weeks performs best, while all reduced optimizations result in a substantial reduction (speed-up of on average x4.8 to x7.7) of the calculation time. \u3c/p\u3

Energy Scenarios for the Future of Mankind

none14noneArteconi, Alessia; Caresana, Flavio; Cesini, Gianni; Comodi, Gabriele; Corvaro, Francesco; D’Alessandro, Valerio; Di Nicola, Giovanni; Latini, Giovanni; Pacetti, Marco; Paroncini, Massimo; Passerini, Giorgio; Pelagalli, Leonardo; Polonara, Fabio; Ricci, RenatoArteconi, Alessia; Caresana, Flavio; Cesini, Gianni; Comodi, Gabriele; Corvaro, Francesco; D’Alessandro, Valerio; Di Nicola, Giovanni; Latini, Giovanni; Pacetti, Marco; Paroncini, Massimo; Passerini, Giorgio; Pelagalli, Leonardo; Polonara, Fabio; Ricci, Renat

Trajectoires doctorales

Presque deux décennies après la première mise en place des diplômes d’études approfondies au sein de quelques écoles nationales supérieures d’architecture françaises, les rencontres doctorales organisées à Nantes en septembre 2010 ont mis en avant une jeune communauté de chercheurs structurée à l’échelle nationale. Premières d’une longue série, elles illustrent la capacité des disciplines de la transformation de l’espace à l’acclimatation au monde réel : d’une part, notamment dans le contexte des problématiques environnementales ; d’autre part, à l’égard des exigences relatives à l’évaluation scientifique. Il n’y a là rien d’étonnant, alors qu’à l’échelle internationale cette filière de recherche et d’enseignement a su trouver une place méritée au sein des universités. Peut-on par conséquent considérer les « objets de recherche comme attracteurs ? », s’interroge Laurent Devisme en introduction, évoquant la force de certaines thématiques en ce qu’elles peuvent transgresser les limites disciplinaires pour rejoindre des préoccupations dominantes de la société. Yannis Tsiomis dans son post-scriptum souligne à son tour que « toutes ces recherches nous parlent aussi, et pour certaines de manière critique, des visions du monde, des visions politiques, au sens générique du terme ». Phrase emblématique d’une trajectoire personnelle qui a su donner forme et contenu au « triangle vertueux » profession / enseignement / recherche. Trajectoires doctorales dessine dans ce numéro les contours d’un paysage de la recherche architecturale, urbaine et paysagère en pleine transformation, par des documents de docteurs et de doctorants explorant avec rigueur et inventivité de nouveaux horizons