Analysis Of Load Match and Grid Interaction Indicators in NZEB with High-Resolution Data

Abstract

A Net Zero Energy Building (Net ZEB) is succinctly described as a grid-connected building that generates as much energy as it uses over a year. The "Net Zero" balance is attained by applying energy conservation and efficiency measures and by incorporating renewable energy systems. The main objective of this report is to analyze the usefulness and relevance of proposed Load Match and Grid Interaction (LMGI) for Net Zero Energy Buildings. The methodology is based in the analysis of available high-resolution data (mainly hourly) both from simulated and monitored Net ZEBs (Net Zero Energy Buildings) or nZEB (nearly Zero Energy Buildings). The central question is to find a limited set of indicators which provide relevant information to building owners, local grid Distribution System Operators (DSO) when information from building simulations are available at design stage.The first two sections of the report introduces why load matching and grid interaction are key aspects to be analysed in Net ZEBs together with the fulfilment of the yearly energy balance between on-site generation and buildings load. Buildings will play a significant role as part of an energy system based on DER -Distributed Energy Resources. Section two analyses the subject from several perspectives from the operators of national energy grids to the building owners and users. More details and references to previous studies are given when the conditions for the distribution grids are discussed, as the buildings are mostly connected to the medium and low-voltage grid. Analysis concludes that an accurate analysis will need detailed information of the grid topologies, which in most of the cases is not the case when Net ZEBs are being planned. Also, it is highlighted that grid interaction is an aspect that should be analysed in the framework of urban planning (at the cluster of buildings level) more than at individual building level. IEA Joint Project SHC Task 40 / ECBCS Annex 52 Load Match and Grid Interaction in NZEBPage 6 of 102The third chapter of the report defines the load match and grid interaction indicators that should be computed with the case studies, together with describing the terminology. This is defined in coherence with the framework for Net ZEBs definition established in this current IEA Task IEA Joint Project SHC Task 40 / ECBCS Annex 52 Load Match and Grid Interaction in NZEBPage 7 of 102 A novel form of graphical representation using normalized load duration curve for net exported energy is proposed in this report. This graphical representation (see figure below) allows identifying the peak values of the net exported energy in a Net ZEB together with the profile of the grid interaction during the whole year knowing the percentage of time when the building is exporting energy. In the same graph, also the relation with the peak load, peak on-site generation and connection capacity are shown.The report concludes that load and supply cover factor, together with the loss of load probability are enough indexes to describe the relationship...

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