Distributed Detection of Events for Evaluation of Energy Efficiency in Buildings Sergio A. de la Campa, Ana B. Rodr´ ıguez-Gonz´ alez, Javier Ramos, and Antonio J. Caama˜ no Abstract—Increasing awareness of energy production evolution and global warming issues have forced regulatory international organizations to supervise energy consumption in different areas. Specifically the energy efficient operation of buildings, consumers of almost a third of the energy produced globally, is to be evaluated by means of specific procedures. The usual methods involve the use of normalized software engines prior to the construction of the building. Two pending issues hamper the accuracy of the evaluations: (1) in such procedures actual usage patterns of the building are taken into account by means of highly simplifying assumptions and (2) no procedure is envisaged to evaluate pre-existing buildings. Wireless Sensor Networks (WSN) are proposed to be employed in order to measure the actual energy consumption behaviour of buildings. A general structure of a scalable WSN and basic algorithms both to continuously monitor energy-consumption patterns and to detect whether energy usage in buildings is inefficient, are presented. A hierarchical topology with fusion centers (FCs), wireless sensor nodes organized in clusters and in-network distributed detection is presented. This work aims at the scalability and reliability of communications of the nodes with the FCs, in order to establish a reference design. Finally, simulations results are presented in order to show the need of accurate measurements of the usage patterns of a building in order to precisely evaluate its energy efficiency. Index Terms—Distributed detection, Wireless Sensor Networks, Energy Efficiency in Buildings I. I NTRODUCTION Over the last decades the economic growth has steadily in- creased the demand for energy, but “without a change in policy, the world is on a path for a rise in global temperature of up to 6 o C, with catastrophic consequences for our climate” [1]. This is an important issue presented in the World Energy Outlook 2009 of the International Energy Agency (IEA) in which are treated a lot of reasons leading global energy development is unsustainable. This mentioned change in policy implies a world wide common position and a very high economic cost which will be offset by health and energy-security benefits, so worth the economic cost. For that reason in this regard have been made some efforts. Some of these efforts are focus on the energy efficiency, a concept with increasing significance and that is playing an im- portant role in current energy-saving scenario since encompass Authors are with the Department of Signal Theory and Communications, University Rey Juan Carlos, Camino del Molino, s/n, 28943, Fuenlabrada (Madrid, Spain). Email (Corresponding Author): antonio.caamano@urjc.es This work was partially supported by the Spain Department of Science and Innovation through the project TEC2009–12098. This paper has been accepted for publication in the proceedings of WSN Workshop that had been held in conjunction with NTMS 2011. energy saving but keeping (or rising) levels of service, produc- tivity, comfort, etc (depending on scope). Some definitions of energy efficiency of buildings can be found in [2], [3], [4] and [5], but all these can be summarized in: consuming less energy while providing equal or improved building services. In this sense and complying with European Energy Per- formance of Buildings Directive (EPBD) of 2002 [2], Spain adopted its own strategy by mean of a Royal Decree [4] which has a lot of similitudes with the common framework of certification scheme presented in [5], and is based in the use of a software named Calener [6] that employs references in order to put new buildings or buildings with major reformations into one of seven categories of energy efficiency. The Spanish certification scheme (as well as EPBD) regards architectonic, geographical, climatic and other aspects that are related with buildings’ constructive characteristics and the installations on them, but always are assumed standard pattern of usage, so lacks of real and detailed analysis of human behavior. The certification process begins before the construction of the building, based on blueprints and estimations, so it is valid for new buildings for a limited period of time and for average intended patterns of use. This technique is, however, not valid for existing buildings where intended uses or patterns of use have changed. Considering the importance of continuous monitoring of power energy parameters of buildings, WSNs arise as a feasible solution to reach this continuous monitoring in order to evaluate inefficient energy consumption. However, the nature of the events that lead to energy inefficiency results, impacts on the scalability and performance of operation of WSNs. Taking this limitations into account, it is needed a proposal of a framework for the design and operation of a dense Wireless Sensor Network to detect the inefficient energy consumption in buildings and to gather enough data to improve current procedures to evaluate energy efficiency of buildings. This proposal can be more or less detailed depending on the accuracy level but it has to take into account aspects as important as topology, reliable communication, processing and algorithms of decision. In [7] and [8] WSNs are used in order to analyze en- ergy consumption in buildings. This is another approach very different from energy certification software engines. In both works authors center attention on how to measure AC power consumption using a WSN and how to analyze all gathered measurements. In [8] is described the design, deployment, and experience with a wireless sensor network for high-fidelity 978-1-4244-8704-2/11/$26.00 ©2011 IEEE