BIM-based Collaboration Platform for the Holistic Integration of Energy Active Façade
Components
Christian Leifgen1, Tilmann E. Kuhn2, Uwe Rüppel3, and Jochen Teizer4
1)
2)
3)
4)
Research Assistant, Institute of Numerical Methods and Informatics in Civil Engineering, TU Darmstadt, Darmstadt,
Germany. Email: [email protected]
Head of Group Solar Façades, Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, Germany. Email:
[email protected]
Prof. Dr.-Ing., Chair of Informatics in Civil Engineering, TU Darmstadt, Darmstadt, Germany. Email: [email protected]
Ph. D., Team Leader, Zentrale Technik, Ed. Züblin AG, Stuttgart, Germany. Email: [email protected]
Abstract:
In the future renewable energy sources will inevitably be needed to satisfy the world-wide energy demand. One of
the most important sources of renewable energy is solar energy. Today, solar power parks are built and
photovoltaic elements are placed onto rooftops. However, in large urban regions there is little space for solar parks
and rooftops are already occupied with solar systems or have to serve other needs. In contrast to roof surface areas,
the building façades offer large spaces that are not utilised yet. Therefore, Energy Active Façade Components
(EAFC) might be used to increase the (electrical and/or thermal) solar yield noticeable.
The successful accomplishment of construction projects requires accurate planning in every aspect. A variety of
processes has to be managed involving stakeholders of many domains (e.g., architects, engineers, contractors,
subcontractors, suppliers, and vendors). The continuously increasing complexity of structures and buildings
necessitates a thereto adapted level of project management and construction techniques. A major evolution in the
construction sector was the introduction of computer-based systems in management, design, and engineering
domains. As these domains are depending from each other, a comprehensive management of all project relevant
aspects requires a software environment providing appropriate interfaces for information exchanges and a
collaborative working mentality of the project participants.
The origin of the in this paper introduced development of a BIM-based collaboration platform lies within the
complexity of EAFC. EAFC (e.g., building-integrated photovoltaic or building-integrated solar thermal
components) come with a wide range of properties, requirements, and constraints that have to be regarded during
all project phases. In particular, giving the opportunity of a holistic consideration of all these aspects and a
facilitation of the integration of EAFC in the building process as early as possible is a main goal of this research.
Therefore, a concept of a collaboration platform is introduced. A BIMserver implementation provides the core for
the coordination of the project participants and the exchange of building and product models. Model-based data is
exchanged in the Industry Foundation Classes (IFC) standard, as well as other information shall be distributed in
open file formats. A multi-agent system brings a decent level of automation and intelligence into this environment.
This is needed as the complexity of EAFC combined with the dependencies between the involved stakeholders
make their integration a tough challenge.
Keywords: Building Information Modelling, BIM, BIMserver, Construction Process Chain, Collaboration,
Energetically Active Façade, Multi-Agent System, MAS, Photovoltaics, Solar Power
1. INTRODUCTION
1.1 Motivation
In 2000, the German Bundestag passed the Renewable Energy Sources Act that aims at restructuring the energy
sector fundamentally. Its goal is to promote the use of renewable energy sources in the entire energy generation to
about 55 – 60 % in 2035 and to decrease the CO2-emissions by 85 – 90 % until 2050. Generation of renewable
energy encompass different technologies, e.g., biomass, hydropower, and geothermal energy. Though these are
providing an important contribution to power generation, solar power and wind energy are the most important
issue in the German energy transition (Henning & Palzer, 2015). Photovoltaic systems convert solar power into
electricity. A common practice is the installation of solar panels on rooftops. However, considering the entire
building envelope, building façades offer significant additional space which can be utilised for mounting active
solar elements. As photovoltaic or solar thermal façade elements are very complex components, they have to be
planned accurately. All related processes during design, construction, and operation phases have to be considered
early on in the lifecycle of buildings. Besides the complex decision-making processes themselves, the data
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exchange also has to be managed during all phases. A process that can facilitate these goals is Building Information
Modelling (BIM). BIM-based building models provide data along the whole process chain.
1.2 Building Information Modelling in Germany
Nowadays, in the construction industry nearly the entire workload apart from the actual (physical) construction
process is computer based. A variety of software applications is used by the companies depending on factors like
their specialisation, size or business philosophy. Besides company-internal choices, legal constraints regulate the
scope and degree of detailing these applications have to cover.
In Germany, the building industry is highly fragmented and consists mainly of smaller companies with less than
50 employees (Stiepelmann et al., 2015). Also, there are no valid regulations yet, that claim the usage of BIMbased working methods. Hence, only a small number of companies are willing to take the cost- and personnelintensive step of adapting their software environment and working methods. The majority of the companies would
only make use of the capabilities BIM software applications offer, if further incentives are provided or regulations
claim the usage of BIM. To face this state and promote the usage of BIM-based working methods the German
Federal Ministry of Transport and Digital Infrastructure has introduced a step-by-step plan for the “introduction
of modern IT based processes and technologies for planning, building and operation of buildings” (“Stufenplan
Digitales Planen und Bauen”) (BMVI, 2015). Therein is stated, that the introduction of BIM in Germany assumes
a high degree of coordination and cooperation that has to be covered by the project organisation. The foundation
of the collaboration is the compatibility of exchanged data, whereby the participants can “understand” each other.
For that, vendor neutral file formats have to be supported by all software applications. An example for such an
open standard are the Industry Foundation Classes (IFC).
The mentioned procedure for the introduction and establishment of BIM as a standard in a legal framework is a
generic proposal for the infrastructure sector until 2020. However, this step shall initiate the holistic introduction
of BIM in all building sectors in Germany.
This paper is introducing the basis of our approach in the research project Solar Construction Process (SolConPro,
2016). In the following chapter, basics as well as essential work, related to our research, is presented. Thereafter,
a new collaborative working method is described, which is needed for the holistic consideration of Energy Active
Façade Components (EAFC). Then, our concept of a collaboration platform and an implementation approach are
presented.
2 RELATED WORK
2.1 Energetically Active Façades
The presented work focuses on the use of EAFC like exemplary shown in Figure 1. For the classification of these
elements, this section gives a brief overview over the most important types and introduces terms used in this paper.
Figure 1. Integration of photovoltaic components at the Zueblin “Z3” Office Building
Façades are part of the building envelope. Thus, their appearance as well as their technical characteristics are
essential for the design of buildings. Nowadays, façades not only serve as weather protection, but rather can have
multiple features (multifunctional façades). For instance, they can cover aspects of Heating, Ventilation and Air
Conditioning (HVAC), since parts of the HVAC systems can be integrated in façade components. This work
focuses on the energetic aspects of façades. In particular, Active Solar Façades (ASF) are regarded. ASF
encompass Photovoltaic (PV) and Solar Thermal Façades or combined PV and Thermal Façades (PVT). Basically,
there are two possible ways to install active elements to façades: adding them on top of a non-active façade or
integrating them into the façade components. In the field of solar thermal elements, (Maurer et al., 2015) show
that the integration of active elements into the façade is of advantage. It, for example, causes less needed insulation
or an increased solar thermal yield. In our research we focus on these building-integrated solar active elements,
termed as Building-Integrated Solar Thermal (BIST) or Building-Integrated Photovoltaic (BIPV) components.
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There are further types of ASF elements, as their transparency can be an indicator for their classification, e.g.
Transparent Solar Thermal Collectors (TSTC), like mentioned in (Maurer, 2013).
2.2 Mefisto
Mefisto was a research project with the goal of developing “a Management Information System for partneringbased, process-driven and risk-controlled construction planning and management” (Schapke & Pflug, 2012). It
was embedded in the European research and innovation programme “Horizon 2020” in the project “IKT 2020 –
software systems and knowledge technologies” of the German Federal Ministry of Education and Research. The
perception of a cooperative work with one building-centric, comprehensive model covering all purposes was seen
as very unlikely. For that, the approach of Mefisto was to assume that models created by specialists of different
domains, such as design, costs or scheduling, need to be thought of as equivalent and are still created separately.
The introduced concept of Mefisto encompasses three main areas: multi-models, a platform, and information
logistics. Multi-models are represented by so-called multi-model containers containing various interlinked
application models. The platform offers web service interfaces for the connection of the stakeholders and thereby
allowing an exchange of the multi-model containers. The third areas’ task is the definition of a business logic for
the management of collaboration processes.
2.3 BIMserver
The BIMserver platform (Beetz et al., 2010) offers a Java-based, open source, and fully customisable, web-based,
server environment for the storage and exchange of building models and building related data. Although there is
no end-user support, it comes with a decent set of functionalities for developers. One of the most important
characteristics is its IFC core, which means that all IFC data is stored “as is”. This enables users to store and
exchange this data without loss of information. The BIMserver also offers compatibility to other open standards
like BCF, CityGML or COBie. Another useful feature is its modularity. Only the main features are implemented
directly within the core, all additional extensions are managed by plugins that can be adjusted easily to the projects’
specific needs.
3. EVOLUTION OF COOPERATION IN THE CONSTRUCTION SECTOR
Figures 2 (a) to (c) show the evolution of digital working methods and cooperation between the stakeholders of
the construction sector to date. At first, two-dimensional building models as well as other information were stored
and exchanged in files as “flat data”. The first step in the shown evolution of civil engineering informatics was the
transition to an object based way of working. Meanwhile, the adaption of the Standard for the Exchange of Product
Model Data (STEP) and later the development of the Industry Foundation Classes (buildingSMART, 2015)
occurred. The storage of these object based building models in central databases allowed simultaneous access of
multiple users and a significantly more efficient workflow.
Figure 2. Evolution of the cooperation in the building sector
The ongoing increase of the construction projects’ complexity necessitated the investigation of further approaches.
These approaches were facilitated by the evolution in the field of information technology. Nowadays, constraints
like low bandwidth or little storage space are no longer hindering the work with big data volumes. Information can
be distributed via networks, locally or globally. Thereby, the third level in the evolution of cooperation could be
reached - distributed objects (building and product model data). This approach is the basis of the above mentioned
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Mefisto project. Different objects, e.g. building or product models, can be exchanged via middleware. It allows a
collaborative work of different stakeholders based on predefined processes, which are performed resp. triggered
by humans. However, focusing on complex structures, like active façades, this approach is inefficient and
insufficient as the components integration is increasing the amount and complexity of processes in the workflow
tremendously. The reasons for this are manifold, as shown in the following sections.
3.1 Product Data
The information needed for the complete description of active façade products covers many spheres like geometry
(e.g. measures of all parts), thermal aspects (e.g. ambient or module temperature), environmental information
(position of the sun, sunrays, shadows etc.), or electrical information in case of BIPV. All these aspects have to be
gathered and processed as a decision base.
3.2 Functional Description and Simulation
The product data describes products and their properties. Still, functional descriptions are needed in addition to
describe the ASF’s mechanics. These functional descriptions have to be accessible for the execution of simulations
(e.g. building energy demand calculations). The simulation domain cannot be treated isolated from the residual
construction process, as the generated results influence the choice of products and thereby the entire design
process.
3.3 Vendors and Products
During the design and simulation processes planners compare multiple variants and different products from various
vendors regarding their design, function, costs, etc. Although these products’ properties have to suffice standards,
there are noticeable differences that have to be regarded. For a comprehensive consideration of all products
available, the properties must be accessible whilst the design process.
3.4 Dependencies
Building projects inherently have numerous dependencies between the different and highly specialised project
participants. Nevertheless, the integration of energy active façade elements creates additional complex relations.
For instance, simulations need input data such as the above mentioned product data, functional descriptions,
electrical or environmental information, and the building geometry. In Figure 3 these dependencies are illustrated.
3.5 Conclusion
The presented points illustrate that the complexity of ASF not only is a problem of describing data structures. It
rather is essential that all participants and the information flow have to be well coordinated to guarantee an efficient
and elaborated operation. This can only be reached by a precise determination of process models containing
detailed process chains, workflows, and their (partial) automation. For this purpose, the next step of the evolution
shown earlier has to be taken. The approach of the presented research is to investigate if a process-driven multiagent system, which automatically distributes objects and information, can offer an additional value in the process
chain. The aim is to reduce the participants’ effort for making the integration of ASF. Hereby, ASF shall be
considered more frequently and much earlier in construction projects.
Environment
Sun, Weather, Location
Simulation
Sun, Location
Design /
Architecture
Building Geometry
Product Data,
Functional Descriptions
Cables,
Electrical Devices
Geomtry,
Appearance
ASF Vendor
Electrical
Parameters
Electrical
Parameters
Electrical Engineering
Figure 3. Influences and dependencies concerning active solar façades
4. APPROACH
Although the building sector is very heterogeneous, the major processes appearing during construction projects
are almost identical for each project. In (5D Initiative, 2015) an exemplarily segmentation is made, as illustrated
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in Figure 4. Based on this assumption and innovative process-orientated and collaborative working methods in our
research, an approach detached from a country-specific process model or scale of fees, like the RIBA Plan of Work
or the German “Honorarordnung für Architekten und Ingenieure” (Official Scale of Fees for Services by Architects
and Engineers), is intended. Likewise, the challenges ASF entail, shall be investigated from a process-orientated
point of view.
5D Initiative Process Map
Project
Development
Technical Design
Work Preparation
Construction
Facility
Management
Figure 4. Project phases by 5D Initiative
For identifying relevant processes, in a first step a process chain of a building company was investigated and major
problems identified. The investigated process chain was settled in the façade and technical building equipment
planning process involving the following stakeholders / domains: architecture, façade planning, technical building
equipment, prime contractor. As the research is in an early stage, the focus lay on the first project phases (Project
Development and Technical Design). An important identified issue in the sphere of information exchange was the
deficient compatibility of software applications resp. their (proprietary) file formats and the lack of suitable
interfaces. Another appearing point was that even in larger companies the adoption of BIM-based working methods
has only just begun, disregarding BIM software is already applied. Finally, the mentality in the construction sector
was pointed out. It has to change fundamentally as the present way of cooperation is characterised by a
confrontational behaviour, which does not fit the idea of a collaborative workflow.
By the comprehension of these real processes and the occurring problems, ideal process chains, workflows, and
working methods for the holistic integration of active façade elements in the building process will be defined. In
the end, the final goal of our research project is to cover all issues concerning energetic aspects of multi-functional
façades, not only the energy ones.
5. BIM-BASED COLLABORATIVE WORKING METHOD
The approach we want to present in this paper shall on the one hand be abstractive and adaptable and on the other
hand particularly support the application of energy active façades. For that, all development must focus on free
accessibility and open standards. Our approach concerning responsibilities and the major structure is partly based
on the one made in the Mefisto research project. We want to handle specialised models separately and create a
platform that enables all project participants to work in a cooperative and coordinated way by storing data and
providing its exchange. In detail, the following aspects are considered in our research.
5.1 Central Collaboration Platform
As basis for a collaborative work, a central platform is needed, which enables all participants to exchange data in
a structured way. The platforms’ most important task is to coordinate the participants and their work results.
However, the creation and editing of contents stays at the participants’ domains. In addition, the platform has to
provide a framework for extensions by intelligent systems, like the hereafter mentioned multi-agent systems or
process modelling aspects. Other central requirements are the abilities to handle open standards, to react on specific
events, to link information with a building model, and to store and manage revisions of building and product
models. Besides these points, the project timeline has to be considered. All project phases as well as the operation
phase of the building shall be covered by the developed platform.
5.2 Processes
Processes need to be modelled to create a structured, efficient and flawless workflow. The topic of process
modelling has been investigated for a long time, wherefore several modelling approaches were developed, e.g. the
Unified Modelling Language (UML), Business Process Modelling Language (BPML), network plans, or Petri
Nets. In our research the process model is not only intended to graphically represent the process chains. Instead, a
basic requirement is the determination of a distinct state in the current workflow. For this purpose, Petri Nets fit
best. Besides the graphical representation all stated modelling approaches offer, Petri Nets possess a mathematical
representation. In (Peterson, 1981) Petri Nets are introduced and described in detail.
5.3 Automation of Processes and Workflows
The above mentioned complexity of the intended system requires the implementation of a certain level of
automation and intelligence. This can be reached by the application of a Multi-Agent System (MAS). (Shehory &
Sturm, 2014) define a core set of dimensions that a MAS and its agents have to offer: autonomy, intelligence,
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sociality and mobility. MAS can be classified within the sphere of Artificial Intelligence (AI). In general, a MAS
consists of an environment which hosts multiple interacting agents. Agents may be human beings, robots or – as
is the case in our research – realised as software agents.
In terms of our research a centrally managed agent platform has to be implemented on the cooperation platform.
Besides this central part, all connected participants need a local agent platform to allow communication and
migration of agents with the central platform. The platform’s structure is exemplary shown in Figure 5. Eventually,
we want to investigate, if a nexus between Petri Nets and MAS, like shown in (Cabac, 2010) or (Pujari &
Mukhopadhyay, 2012), can be of use for us and create an additional value.
5.4 Scalability
As each phase of a construction project has its distinct needs, a software environment that adapts to these needs
has to be created. A common concept is the description of different levels of development (LoD), like proposed
by (AIA, 2013). Definitions for LoDs can be found in (BIMForum, 2015). In our research we want to cover this
approach by the usage of the MAS, wherein agents deliver only information needed in the current stage and use
case. The central platform has to support this method by providing data in an appropriate way.
A general example for this approach can be found in the sphere of IFC. The exchange of IFC based data can be
controlled by the usage of Model View Definitions (MVD). MVDs allow an exact determination of necessary
information within an IFC file. By the usage of differently detailed MVDs, distinct LoDs can be realised. Another,
more specific example can be illustrated by the use case of ASF planning. In the early project development phase,
the architect defines that ASF should be used and places a wildcard object in the building model. Then, these ASF
are getting detailed by choosing a range of possible products, what allows exact simulations and a comparison
between the chosen products. Thereby, the decision for one specific product can be made. In our research we want
to cover this approach by the usage of the above mentioned MAS, wherein agents recognize the present LoD (e.g.
on the basis of the available data) and trigger appropriate processes.
Furthermore, this approach can be useful after the construction phase, as centrally deposited product information
can be accessed in the adequate LoD to facilitate the facility management.
5.5 Data Exchange and Standards
The “Stufenplan Digitales Planen und Bauen” as well as our recent analysis of real workflows show that
information gets lost or has to be created redundantly in the building process chain. This is mainly caused by
incompatible software interfaces and file formats. Thus, open standards that are vendor neutral need to be the basis
for all data exchanges between the participants. Nevertheless, the expert software applications can still have their
proprietary data formats for the internal editing as long as a complete export to an open standard is available. With
the IFC such a comprehensive open standard for the building sector is available. But as they are still under
development, several aspects cannot be described yet. For example, neither façades nor energetically active
elements are implemented explicitly.
Within our further research we are going to examine the possibility to develop standards for energetically active
façades. This includes on the one hand the digital description in form of creating or extending file formats and on
the other hand a normative manifestation in standards. (Franz et al., 2016) describe an approach for the extension
of the IFC concerning façades in general.
6. CONCEPT AND IMPLEMENTATION
Based on the introduced considerations concerning a BIM-based and cooperative working method we are
implementing a prototypical software environment which can provide the specified demands concerning ASF. It
consists of a collaboration platform and a MAS, which are briefly introduced below. Figure 5 gives an overview
of the environments’ architecture.
6.1 Central Collaboration Platform
The introduced collaboration platform consists of five components. It is intended to exist from the early beginning
of the project and as long as the building exists. The first component is the handling of building models and
building related information. This core feature is realised by a BIMserver implementation. To store and access
product data (e.g., EAF or HVAC components) virtual product catalogues are needed. These standardised
catalogues form the second component of the platform. They either can be provided externally by third parties via
a web interface or managed internally on the collaboration platform itself, as shown in Figure 5. The project
participants of all domains need to be coordinated on the basis of provided data, process models, and schedules.
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Hence, the third task of the collaboration platform is the centrally controlled process management, realised by a
workflow management system. Ontologies form the fourth component. They are integrated to formalise the
description of information and the expression of relations between different representations of data. Finally, the
hereafter described MAS has to be integrated into the central platform as well as into project participants’
environments to generate a certain amount of needed intelligence.
Construction Project Timeline
5D Initiative Process Map
Project
Phases
Project
Development
Work Preparation
Technical Design
Construction
Facility
Management
German HOAI (Phases 1 – 9)
RIBA Plan of Work (Stages 0 – 7)
External Product Catalogue
Local Product Catalogue
BIMserver
IFC based Building Models
Collaboration
Platform
Process Management
Ontologies
Major MAS Platform
Building Services Department
Client MAS Platform (BSD)
Façade Planner
Project
Participants
Client MAS Platform (FP)
Additional Project Participants
Client MAS Platforms
Information
Density
Level of Development
Figure 5. Architecture of the introduced software environment
6.2 Multi-Agent System
The intended implementation of the MAS includes multiple platforms. The main agent platform is settled within
the central collaboration platform. It is connected to the local MAS platforms placed on the project participants’
computer environments. This structure enables agents to communicate and migrate between all platforms and
exploit the complete set of MAS features. The local platforms have to be connected to the by the participants used
software applications itself or at least be able to access their file systems. However, the external product catalogues
can directly be connected and accessed via web-services controlled by software-agents.
In line with the aims of an open and standardised platform, an appropriate MAS implementation has to be chosen.
It should comply with the Foundation for Intelligent Physical Agents (FIPA, 2015) specifications. An important
FIPA specification is the Agent Communication Language (ACL). ACL gives the opportunity to communicate
with agents on other FIPA (or at least ACL) compliant platforms. A promising implementation we currently
investigate is the JAVA Agent DEvelopment (JADE) Framework (Bellifemine et al., 2007). JADE offers a
comprehensive set of functionalities and is well documented.
In (Franz et al., 2016) we introduce an example of how agents can be applied to solve complex problems in the
field of energy active façades. The example describes the agent types needed for a consideration of active façade
components in the early design phase. It is shown how these elements can be integrated in the design process and
how agents can facilitate this.
CONCLUSION AND OUTLOOK
In this paper, we introduce a concept and an implementation in favour of the holistic integration of energy active
façade elements into the building process chain. Our approach encompasses a central collaboration platform for
the coordination of the project participants and the management of occurring data. All building related information
is handled by a BIMserver environment. A multi-agent system helps to simplify and automate complex workflows
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in the process chains. Our concept is based on analysis of real process chains and problems occurring in practice,
as well as on new technology approaches.
A variety of stakeholders from different domains is connected to our platform during all project phases. For that,
our next major task is the definition of process models and a corresponding workflow management system, and
thereby the implementation of an encompassing multi-agent system. Besides that, an important step we want to
take is the definition of digital representations of product data models, as introduced in (Franz et al., 2016).
After the prototypical implementation a validation of the proposed system is planned. For that, real use cases as
well as a complex case study will be investigated.
ACKNOWLEDGMENTS
This work is part of the research project Holistic Integration of Energy Active Façade Components in Building
Processes (SolConPro, 2015) founded by the German Federal Ministry for Economic Affairs and Energy (BMWi).
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