Building automation systems: Concepts and technology review
Introduction
A building automation system (BAS) consists of a system installed in buildings that controls and monitors building services responsible for heating, cooling, ventilation, air conditioning, lighting, shading, life safety, alarm security systems, and many more. A BAS aims at automating tasks in technologically-enabled environments, coordinating a number of electrical and mechanical devices interconnected in a distributed manner by means of underlying control networks. These systems may be deployed in industrial infrastructures such as factories, in enterprise buildings and malls, or even in the domestic domain.
Building automation has been receiving greater attention due to its potential for reducing energy consumption and facilitating building operation, monitoring and maintenance, while improving occupants' satisfaction. These systems achieve such potential by employing a wide range of sensors (e.g., for sensing temperature, CO2 concentration, zone airflow, daylight levels, occupancy levels), which provide information that enables decision-making regarding how the building equipment will be controlled, aiming at reducing expenses while maintaining occupant comfort [1].
The engineering practice of BA has primarily emerged from manufacturer documentation, and was followed by technology standards such as BACnet [2], KNX [3], LonWorks [4], Modbus [5], ZigBee [6], [7] or EnOcean [8], [9], which are not in agreement with regards to concepts and terminology. One example of literature disagreement concerns the application of LonWorks and KNX at the management level of a BAS [10], [11]. Similarly, the definition of the concept of datapoint is also inconsistent across literature (compare [12, p. 54] with [13]). Moreover, with the evolution of BAS and technology in general, some related literature references became outdated, no longer offering coherent definitions in this topic. One example is the large number of literature references describing Supervisory Control and Data Acquisition (SCADA) systems that are unable to provide a sufficiently generic description of the SCADA systems' most common architectures [14], [15], [16], [17], [18], [19], [20]. Some of these references are outdated, thus their accuracy with respect to the current SCADA systems is questionable [13, Section 3.61 Note 7] [21]. Indeed, BA is a multidisplinary field where definition inconsistency and disagreement are recurring issues and for which almost no authoritative text exists.
The lack of commonly agreed field-knowledge and the existence of functionality gaps leads solution developers to repeatedly redefine basic concepts, creating their solutions bottom up instead of relying on the existing body of knowledge. Despite the fact that this problem has been identified and acknowledged in previous surveys and even considered by some authors as the “potential barrier for BA technologies around the turn of the millennium” [22], [23], [24], an inclination to create custom solutions persists, which greatly explains the heterogeneous nature of BA. Most solutions (i) are not able to inter-operate with other vendors' solutions without additional overheads, locking costumers to specific product lines—a major issue if such lines get discontinued—, (ii) have closed specifications, (iii) are too complex to be used by non-specialized personnel, whether they are end-users or system developers, (iv) only perform satisfactorily in the exact conditions they were tailored for, not performing so well if the working environment changes, thus lacking flexibility, and (v) do not cover all the desired functionalities expected in a BAS.
Over the years several interoperability solutions that target the problems of heterogeneity have emerged from BA technology standards with variable degrees of success. Despite a few scattered literature references, a principled discussion on how interoperability solutions cover the main features of BA has never been carried out.
This article starts by introducing and unifying the basic concepts of building automation systems with the goal of contributing with up-to-date definitions in this field. In addition, a set of features that, according to documented standards, should be implemented in building automation systems, is detailed and the extent to which most common BA technology specifications cover the expected functionalities of a BAS is evaluated. Finally, the main solutions for interoperability are analyzed with a special focus on the Service Frameworks that have been created within the BA field.
By analyzing information models of standard BA technologies we conclude that none is able to fully cover the breath of functionality expected from BAS, and that distinct technologies are required in order to create a fully functional system. However, the interoperability of these technologies is hampered by the fact that, as we observe, a number of concepts cannot be mapped between them. As a direct consequence of this circunstance, manufacturers have been led to create their own proprietary extensions thereby exacerbating the problem of heterogeneity.
Section snippets
Building automation concepts
As discussed earlier, current literature references leave readers with several unclear definitions and terminology that, in the long run, promotes heterogeneity among BA technologies.
This section draws on established literature references to systematize fundamental concepts of BAS prescribed by the ISO 16484-3 [25] and EN 15232 [26] standards and characterizes the scope of functionality expected from the typical BAS that will late be used to evaluate the coverage of each technology standard.
Building automation technologies
This section maps out the essential functionalities of a BAS to state-of-the-art BA standard technologies available in the market. This analysis is based on an extensive analysis of the information models of each technology specifications, studying how each information model of deals with the functionalities identified in the previous section. Information models represent, characterize and relate concepts of a given domain by abiding to a common domain model where applications can share
Management service frameworks
Service-Oriented Architectures (SOA) or Service Frameworks describe architectural principles and patterns aiming at reducing dependencies between systems to ensure interoperability, sustainability and autonomy, through the abstraction of service [59].
Services are an abstraction of functionality available as a remote procedure call and service provider applications provide services to consumer applications. One key aspect of most SOAs is that service providers and consumers are loosely coupled.
Discussion
The previous sections analyze the main BA technology standards aiming at understanding the extent to which their information models cover BAS concepts and functionality. Table 2, Table 3 summarize the analysis made concerning these technologies organized in terms of functionality coverage of the official standards specifications.
It becomes clear that no single BA solution specification provides all the functionality prescribed in the international reference standards ISO 16484-3 [25] and EN
Conclusions
This article systematizes fundamental aspects of BAS, contributing to a common understanding of fundamental building automation concepts aligned with the well known standards ISO 16484-3 and EN 15232. Using these standards as guidelines this work highlights the scope of the functionality that should be expected from the typical BAS.
Another contribution of this work is the assessment of the industry's standard building automation technologies in terms of functional requirements employing a
Acknowledgments
The work of INESC-ID authors was supported by national funds through FCT (Fundação para a Ciência e Tecnologia), with references UID/CEC/50021/2013 and EXCL/EEI-ESS/0257/2012 (DataStorm). Access to automation technologies was facilitated by IST in the scope of the SMARTCAMPUS EU project. The work of TU Vienna was partially carried out in the context of research regarding IEA-EBC Annex 58 (supported by Austrian Research Promotion Agency under the project number P- 843156).
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