Automated Generation of an Energy Simulation Model for an Existing Building from UAV Imagery

An approach to automatically generate a dynamic energy simulation model in Modelica for a single existing building is presented. It aims at collecting data about the status quo in the preparation of energy retrofits with low effort and costs. The proposed method starts from a polygon model of the outer building envelope obtained from photogrammetrically generated point clouds. The open-source tools TEASER and AixLib are used for data enrichment and model generation. A case study was conducted on a single-family house. The resulting model can accurately reproduce the internal air temperatures during synthetical heating up and cooling down. Modelled and measured whole building heat transfer coefficients (HTC) agree within a 12% range. A sensitivity analysis emphasises the importance of accurate window characterisations and justifies the use of a very simplified interior geometry. Uncertainties arising from the use of archetype U-values are estimated by comparing different typologies, with best- and worst-case estimates showing differences in pre-retrofit heat demand of about ±20% to the average; however, as the assumptions made are permitted by some national standards, the method is already close to practical applicability and opens up a path to quickly estimate possible financial and energy savings after refurbishment

Material investigations to facilitate the applicability of microwave radar to energy-related wall structure analysis

Existing buildings often have low energy efficiency standards. For the preparation of retrofits, reliable high-quality data about built-in materials is required. Contactless measuring technologies, especially microwave radar, have the potential to enable an easy-to-apply and automatable way to analyse the structures and thermal properties of existing building walls, but the relationship between materials, their thermal properties, and their electromagnetic properties, such as the permittivity, is needed for its application. This article presents an analysis of the relationship between electromagnetic and thermal properties for a variety of building materials. Systematic measurements were performed for samples (burnt clay bricks, calcium silicate bricks, autoclaved aerated concrete and lightweight concrete) mainly originating from demolished buildings. The thermal conductivity, thermal capacitance, and dielectric permittivity were measured and the hypothesis of a correlation between permittivity and thermal parameters was partly confirmed. This information is a prerequisite for using microwave radar sensing technology to determine heat transfer coefficients of existing building walls. The next research step is the development of a corresponding measurement and evaluation method

Building Tomograph – From Remote Sensing Data of Existing Buildings to Building Energy Simulation Input

Existing buildings often have low energy efficiency standards. For the preparation of retrofits, reliable high-quality data about the status quo is required. However, state-of-the-art analysis methods mainly rely on on-site inspections by experts and hence tend to be cost-intensive. In addition, some of the necessary devices need to be installed inside the buildings. As a consequence, owners hesitate to obtain sufficient information about potential refurbishment measures for their houses and underestimate possible savings. Remote sensing measurement technologies have the potential to provide an easy-to-use and automatable way to energetically analyze existing buildings objectively. To prepare an energetic simulation of the status quo and of possible retrofit scenarios, remote sensing data from different data sources have to be merged and combined with additional knowledge about the building. This contribution presents the current state of a project on the development of new and the optimization of conventional data acquisition methods for the energetic analysis of existing buildings solely based on contactless measurements, general information about the building, and data that residents can obtain with little effort. For the example of a single-family house in Morschenich, Germany, geometrical, semantical, and physical information are derived from photogrammetry and quantitative infrared measurements. Both are performed with the help of unmanned aerial vehicles (UAVs) and are compared to conventional methods for energy efficiency analysis regarding accuracy of and necessary effort for input data for building energy simulation. The concept of an object-oriented building model for measurement data processing is presented. Furthermore, an outlook is given on the project involving advanced remote sensing techniques such as ultrasound and microwave radar application for the measurement of additional energetic building parameters

Messung der Reflexionseigenschaften von Absorbern für die Strahlungsflussdichtemessung an Solarturmreceivern

Um die Flussdichtemessung an Solarturmreceivern zu verbessern, ist die Nutzung der am Absorber reflektierten Strahlung vielversprechend [1]. Zu diesem Zweck wurde im Rahmen dieser Arbeit ein Messverfahren weiterentwickelt, erprobt und bewertet, mit dem die orts- und richtungsabhängigen Reflexionseigenschaften von Solarturmabsorbern ermittelt werden können. Dabei wird der Absorber durch Überstreichen mit den Brennflecken einzelner Heliostaten „gescannt“. Am Solarturm Jülich wurde das Verfahren erstmalig vollständig angewendet und die BRDF aller Absorberteilbereiche für alle relevanten Einstrahlungsrichtungen ermittelt. Das Phänomen der Retroreflexion sowie Unterschiede in der Richtungsabhängigkeit der BRDF verschiedener Absorbercups wurden als relevant erkannt. Bei Testmessungen der Flussdichteverteilung zeigten sich deutliche Verbesserungen der Gleichmäßigkeit gegenüber einem bestehenden Verfahren, was zu einer positiven Beurteilung des Scan-Verfahrens führt

Using UAV-based RGB and thermography Images to generate Simulation Input about envelope geometry and U-values

Performance simulations can deliver valuable insights about the Status quo of buildings

Flux density measurement for industrial-scale solar power towers using the reflection off the absorber

Flux density measurement is precious for operation as well as for performance testing of solar power towers. The radiation reflected off the absorber can be used for this task. The disturbance of the plant operation is close to zero. Besides a digital camera, a computer and optionally a radiometer, almost no further hardware is required. That’s why it is suitable for industrial-scale receivers. This paper presents several enhancements for this measuring process. Especially the so-called “scan method” appears promising, because it leads to significantly smoother flux density results compared to formerly presented methods. The article also deals with the determination of the irradiation’s directional composition as well as with calibration routines. The proposed innovations were demonstrated at the Juelich Solar Tower with its open volumetric receiver and are likely to be suitable for external tube receivers, too. A plausibility check using CFD simulations was carried out. In summary, the discussed techniques show promise for future application at large-scale solar towers

Collecting Data for Urban Building Energy Modelling by Remote Sensing and Machine Learning

High-quality data on the investigated area is crucial for modelling urban building energy demands, but its availability is often insufficient. We present an approach to acquire (i) building geometries, (ii) their ages, and (iii) their retrofit states. It consists of creating a 3D model from aerial imagery, determining building ages through machine learning, generating a simulation model based on open-source tools, and assessing retrofit states by comparing simulated temperatures with infrared thermography (IRT) measurements. The demonstration on a case study quarter in Berlin shows that heat demand results are comparable to other tools. Using machine learning is already wellsuited to close knowledge gaps regarding building ages. However, retrofit state assessment using IRT was unsatisfactory due to insufficient measurement accuracy and is envisaged for improvement in future research, along with a validation of the approach