
as element of the road map for the reduction of
primary energy consumption. All relevant data that is
used to describe the thermal and energetic behavior
of the campus areas was collected at the beginning of
the project. This includes but is not limited to
geographical data, geometrical and topological data,
building physics data and occupancy. Furthermore,
the energy performance of buildings and thermal
networks are closely monitored. All collected data is
stored in a common database.
For effectively organizing the data and as basis for
the transition to simulation, an appropriate and
comprehensive database structure is necessary such
as the GML-profile “CityGML” [Häfele 2013] and its
Application Domain Extensions “CityGML
EnergyADE” [Special Interest Group 3D 2015].
Based on the collected data and a structured database,
it is possible to visualize the current state of all
RWTH campus areas in a geographic information
system (GIS). In the settings of this project, the
specific software QGIS Vienna is used [QGIS 2015].
To build up the current state of the energy supply
system, several thermal dynamic simulation models
are created based on the collected dataset. The
simulation models include the buildings with their
building services systems, the distribution and
generation systems. All of those previously
mentioned systems have to be described by simplified
models in order to capture the scale of the whole
campus within a single simulation scenario. These
buildings and system models are then coupled with
thermal network models. Thus, the entire energy
system can be detected and simulated with its
dependent interactions. Consecutively, these coupled
models will help to find an optimized solution for
efficient measures and refurbishment options.
To ensure that the simulation results obtained by the
simplified models correlate with the current energy
consumption, important parameters, such as the
consumption data of the buildings are recorded
properly. Further monitored parameters represent
produced and transmitted energy flows or energy
quantities in the thermal network, for example. These
are used for indicating irregularities in daily
operation modes of energy systems and represent a
potential for improvement.
Based on the analysis of monitoring data and
simulation results, individual improvement measures
are derived and verified iteratively, through which the
primary energy demand and greenhouse gas
emissions can be reduced. The measures consist of
retrofitting the building stock, energy- and conversion
system technology, the thermal network typology, or
a combination of those. As well, savings resulting
from conversion of existing buildings or strategic
demolition and new construction of buildings can be
considered in the model. For all these optimization
approaches, a cost estimate is performed using the
present value method, assessing their impact,
feasibility and cost effectiveness, respectively. After
the evaluation of individual measures conclusive
refurbishment variants are developed. Various
measures and packages of measures are combined,
simulated and evaluated in the light of their
respective interactions. By simulating several
scenarios, refurbishment options can be tested under
different conditions and checked according to their
practical feasibility. This ensures that undesirable
consequences are excluded and detrimental effects
can be minimized. Hence, the simulated dynamic
energy flows are represented by a three-dimensional
GIS-based graphic model of the Aachen campus. In
the following, the mentioned tools like QGIS,
TEASER, and the developed PostgreSQL database
structure are described in detail.
METHODOLOGY
In order to use the entire mentioned tools in an
automated manner, the development of a central
database is essential. Through this, relevant data is
retrieved, which describes the current thermal
energetic state of the campus buildings. As it is the
aim of the project to develop a roadmap of measures
towards reducing heating and cooling energy
consumption, the data base necessarily needs to
reflect the building geometry, thermal building
properties (i.e., the building physics), usage, etc. in
the database. A viable and existing database scheme
is the "3D City Database for CityGML" [Kolbe et.al
2015]. It enables to store three-dimensional
geometries with respect of predefined levels of
geometric detailing (LOD) of a city in the database.
Building up on this database, in the EnEff:Campus
project the data base is extended by thermal and
energy-related characteristics of the buildings. These
characteristics become availabe in the CityGML
Energy Application Domain Extensions (ADE). It is
an extension of the CityGML standard and has the
intention “to define a standard for exchanging
information for energy simulation on urban level”
[Energ ADE 2016]. This extension is currently under
development; the currently available state is
integrated within the 3D city database. With this
extended database, an automated tool chain is created
for district simulation. In the following, the tools are
presented which are used for building performance
simulation in the EnEff:Campus project.
3D City database and 3D City Database Importer-
Exporter
The 3DCityDB is a PostgreSQL database based on
the CityGML schema [Kolbe et.al 2015]. It allows for
depicting roads, bridges or areas. Buildings can be
mapped up to LOD4. In addition to the database, the
”3D City Database Importer / Exporter v1.6 -
postgis“ tool [Kolbe et.al 2015] can be used to import
CityGML data. Thus, for example, the campus
C-03-2 Database development with “3D-CityGML”- and
“EnergyADE”- schema for city-district-simulation modelling
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