monitoring and improve control quality in BASs. In this context ... produced only by the company that manufactured the system, while non-proprietary BASs can ...
Control Application for Internet of Things Energy Meter – a Key Part of Integrated Building Energy Management System Andrzej Ożadowicz, Jakub Grela Faculty of Electrical Engineering, Automatics, Computer Science and Biomedical Engineering AGH University of Science and Technology Krakow, Poland e-mail: {ozadow, jgrela}@agh.edu.pl
Abstract — Nowadays, smart metering and energy management installations are becoming essential part of building automation systems (BASs). Field level integration in these kind of installations could provide new features in buildings energy monitoring and improve control quality in BASs. In this context an interoperability of BAS devices is very important. It could be achieved with standardized functional profiles and functional blocks. An Internet of Things (IoT) technology provides solutions to this integration and possibilities to transform these installations into building energy management systems (BEMSs). In this paper a control application of developed IoT energy meter is introduced. This application implements functions that should be provided by these kind of automation nodes – vital elements for integrated BEMSs. It is ready for integration within the BASs. Keywords— Internet of Things; Building Energy Management System; Building Automation Systems
I. INTRODUCTION In modern buildings, the building automation systems (BASs) are more and more implemented. They are generally classified as either proprietary (closed) or non-proprietary (open). Proprietary systems integrate equipment and software produced only by the company that manufactured the system, while non-proprietary BASs can integrate equipment from different manufacturers and software platforms. They integrate on a field level various sensors and actuators from the buildings infrastructure: lighting, heating, ventilation and air condition (HVAC), security, etc. The BASs are used to organize more advanced building management systems (BMSs), providing users and infrastructure of the buildings with comfort and security. In recent years an energy management as well as energy efficiency improvement questions are more often considered. In order to manage energy in buildings, building energy management systems (BEMSs) are implemented there. Buildings, one of the biggest energy consumer, also become elements of an active power demand management for electricity, as part of emerging Smart Grid systems. An increasing number of devices installed in the buildings is equipped with control and monitoring modules (network nodes), connected to the BMS. 978-1-4673-7929-8/15/$31.00 ©2015 IEEE
It enables to organize their work primarily according to schedules, but also depending on signals transmitted by distributed sensors, controllers or configuration parameters provided by users and data exchanged with other devices. It is very important to unify the communication standard on the field level in BASs to easy communicate all these nodes. Very popular the IP protocol, applied in IT networks, has been proposed and considered. Its new version - IPv6, is a basic component of the Internet of Things (IoT) [1]. This technology could be implemented on different levels of the control and monitoring networks and allows to integrate different kind of subsystems and devices. Bearing in mind all the mentioned aspects, this paper introduces a new control application for energy meter, dedicated for use in fully integrated BEMSs with the IoT technology. Proposed functional blocks, with their network variables and configuration properties, have been verified with an Industrial Internet of Things (IzoT) platform, introduced in 2014 by Echelon Corp. The paper is organized as follows. In Section II short information about the IoT and its applications in buildings is provided. In Section III our concept of energy meter control application in Building Internet od Things (BIoT), has been presented. First implementation and results of experiments are described as well. In Section IV there are conclusions and proposed future works. II. INTEGRATION IN THE BAS AND IOT Crucial features of the modern BASs are integration and flexibility. There are different kinds of systems dedicated for BASs on the market. Some of them based on main controllers (named “smart servers”), equipped with I/O modules. There are also popular so-called hybrid solutions, with partly implemented open standards (Modbus, CANopen). These automation systems are often offered as proprietary control systems. Another group of the BASs base on open, international standards, like the KNX and LonWorks. Both these standards provide standardised functional profiles, data point objects and network variables as elements of standard logical interface for automation network devices [2], [3]. The KNX and LonWorks are dedicated to fieldlevel communication networks, but also specify IP protocol to use in backbone lines [2].
A. Internet of Things – new paradigm in BASs Some solutions based on the Internet techniques have been already used in BASs. For example: oBIX, OPC UA or BACnet/WS (WS-Web Service) and most often implemented RESTful Web Services interface with HTTP protocol. However, those technologies are characterized by relatively high hardware requirements: processing power, memory and network bandwidth. The solution is for example Constrained Application Protocol (CoAP), a software protocol intended to be used in very simple electronics devices (sensors, switches) [2], [4], [5]. The IoT technology with its IPv6 and CoAP protocols, makes it possible to integrate all kinds of the BMS’s devices using IP protocol directly on the field level as well. New devices, with implemented IoT tools are appearing on the market. Some new complete IoT platforms have been introduced as well, replacing classic BASs. Although, the BASs and BMSs are still very popular and offer additional tools and functions to reduce energy consumption in buildings. They could operate effectively only in fully integrated networks. Coherence of these two technologies, the IoT and the BASs, provides new value and possibilities in automation [6], [7]. Therefore, the traditional concept of the Internet’s structure has been changing. The Internet is evaluating into distributed network of smart objects, exchanging data between each other periodically or on demand. This concept introduces an innovation into the Internet, providing considerable autonomy of the network nodes. They could operate and exchange the data directly on the field level. This mechanism is well-known in the industrial automation as machine-to-machine M2M and base on three basic assumptions: (1) automatic nodes identification, (2) peer-to-peer communication and (3) interoperability [7]. B. State of art In [3] prof. Kastner et al. present the BAS and BMS integration approach based on the IoTv6. The IP protocol has been already implemented in BASs, but only on automation and management levels, most often for remote access to the selected network segments and automation servers [8]. Novelty of the IoT technology implementation in the BAS and BMS is a possibility of a direct data exchange between all network nodes bound functionally, regardless of they are physically connected to the fieldbus or IP channels [9][10]. The proposed architectures of the IoT technology applying into the BAS have been presented in [11][12] and named BIoT. Nowadays, with the growing use of the BASs in buildings, many different devices nodes of the BASs have to be handled in the network [13]. This increases the design complexity for each device and the number of device variants, implemented in various control functions. To organize control functions, the functional profiles are used in design and integration processes of the BASs. The profiles are function-block-oriented application programs, with input and output data points, to connect with other profiles and form logical networks [14]. This approach is implemented in the BIoT as well. The integrated BIoT networks are ready for implementation in a self-organizing, co-operative BASs, using functional profiles. The BIoT opens the way to implement new functionalities in the BMSs. Integration within the IoT platform provides new possibilities to organize more advanced control functions in the BMSs and BEMSs, improving energy management and a power demand control in the buildings [15].
III. FUNCTIONAL INTEGRATION WITHIN THE BIOT To implement the IoT technology in the BASs, the IzoT platform, introduced by Echelon Corp., has been selected. It is offered as next generation of the LonWorks standard technology, with capability to use IP-all-the-way to the end device. The IzoT is full development environment with chips, stacks, communication, application interfaces (API) and management software. Interoperability between IzoT network devices is provided by functional profiles, in accordance with the LonWorks standard. A. An IoT energy meter functional profile concept Based on this platform, we have proposed a universal energy meter as a IoT platform module with logical device interface. Functionality of the energy meter has been implemented by developed a universal Energy Meter functional profile. It supports two main functions: energy meter and data logger. In the functional profile there are defined network variables (NVs) and configuration properties (CPs), together with their types and processing algorithms. The proposed Energy Meter functional profile is described by two blocks: (1) an Energy Meter and (2) an Energy Logger, presented in Fig. 1 and Fig. 2.
Fig. 1. A developed universal energy meter functional block.
Both functional blocks are presented in accordance with the Semantic Device Descriptions model introduced in [16]. They are open as well to use in Component-based Automation Systems (CBAS) model presented in [14]. Network variables and algorithms defined in our concept are universal and could be implemented easily in other BASs networks, based on open, international standards. These functional blocks are used to acquisition and register data from utility meters with remote reading of measured parameters. A very important objective of the Energy Meter profile is to provide interoperability. This developed profile supports the present meter value and a set of
the node. In this case, the desired output value is selected by the input NV nviTimeSelection, responsible for control which history value is shown. Another important group of NVs is dedicated to power demand handling. For example, the nvoDemand contains the registered value of the demand measurements. A demand is defined as the average power over a specified time interval. The logger also supports a rolling demand (also called “sliding window”), in which the demand intervals are evenly divided into a fixed number of subintervals. At the end of each subinterval, the average power over the demand interval is computed and sent. Moreover, the measured largest positive demand value, with its date and timestamp, is described by nvoDemandPeak and nvoDemandPeakTime respectively. In both cases there are the NVs and CPs useful for device/loads management in buildings. For example, some of the NVs are used to set current date and time (necessary to measurements synchronization), indicate the number of operating hours, set to zero meters’ readings or define the data points propagate factors of the appropriate register value. Fig. 2. A developed data logger functional block.
historical meter values; by default, the last-month meter value. The time between registration of meter values in the historical register can be configured (for example, at one hour or one month). The Energy Meter functional block is mainly used in utility applications, to register the cumulated value of measured parameters; hourly, daily or monthly. All stored, historical values are cumulative with a time stamp and status indication logging. B. The Energy Meter and Energy Logger functional blocks The developed Energy Meter functional profile describe the application layer interface (NVs, CPs) and define standard of the functional blocks for this application. The NVs are objects of node’s network interface that can be connected to one or more network variables of one or more other nodes. They define its functional inputs and outputs and allow sharing of data in a distributed network. The NVs greatly simplify the process of developing and installing distributed systems, since nodes can be defined individually, then connected and reconnected easily into new applications. They also promote interoperability between nodes, by providing a well-defined logical interface to communicate the nodes. The Energy Meter functional block contains NVs and CPs, describing its functions. The most important NVs in this functional block are those directly related to meter values, such as nvoEnergy, nvoPower, nvoVoltage, nvoCurrent, nvoFreq. Mentioned NVs contain the present value of the measured parameters, i.e., the actual running value with a timestamp. The output variable is transmitted when polled, or when the Send On Delta condition occurs. Some of the NVs are used to control the load connected to the node as well, by providing the state of the relay actuator. The most important NVs in another Energy Logger functional block are those designed to provide information about energy. The nvoEnergy contains by default, a copy of the valid meter value at the turn of the last month. This output NV is also able to display other historical data stored by
C. Implementation Those both universal functional blocks have been implemented in autonomic IzoT automation network node, with implemented IzoT device stack, based on Raspberry Pi microcontroller with integrated power measurement circuit. We have developed a measurement system based on integrated circuit (IC) with two Analog-to-digital Converters (ADC) CS5460 manufactured by CIRRUS LOGIC [17]. It is designed to accurately measure and calculate: Real (True) Energy, Instantaneous Power, current (IRMS), and voltage (VRMS) for single phase 2- or 3-wire power metering applications. In our application it has been connected with Raspberry Pi microcontroller by it’s a GPIO (general purpose input/output) pins [18][19] with SDI, SDO, CLK, GND, CS signals. A schematic diagram of the connections in the mentioned system is presented in Fig. 3.
Fig. 3. A schematic diagram of the measurement system with CS5460 IC and Raspberry Pi microcontroller with IzoT device stack.
In the next stage of implementation, a universal software application has been developed for proposed measurement system, implemented in device node with the IzoT platform stack. The software application provides and supports:
(1) communication between the CS5460 IC and Raspberry Pi by SPI interface and (2) reading of specific data from the CS5460, using the appropriate commands specified in datasheet. An application code has been written in C programming language to verify the IzoT platform versatility in programming aspect. Additionally, calibration of the CS5460 IC has been realized, together with implementation of a correction factor of measured values to real values. The developed universal Energy Meter and Energy Logger functional blocks have been implemented in this network node. In the last stage of the IoT energy metering system implementation, we have developed server application for another node with the Raspberry Pi microcontroller and IzoT server stack [20]. The IzoT server node communicates with the presented IzoT energy meter node. To implement this communication, a “device class” file, defined for the Raspberry Pi module, has been modified. During the tests, developed server node has been used to communicate with device node (energy meter and logger), to verify its functionalities. Some of the output NVs from device node have been handled by server, to provide remote access and simple visualisation. As a result of these works a complete prototype of the IoT measurement system has been developed and implemented. The energy meter and logger have been tested and met the requirements. The energy meter successfully interoperates with the IoT server device. Implementation of the Energy Meter and Energy Logger functional blocks with their NVs and CPs, allows to measure essential parameters and energy consumption of devices and loads distributed in buildings. It is possible to analyse the power demand for individual devices and subsystems of building’s infrastructure as well. With provided NVs to control devices/loads, the management of their work and active power demand could be performed. Further research works are conducted to develop advanced algorithms for more precise loads control, based on measured and registered data. IV. CONCLUSIONS All NVs and CPs have been tested by setting and monitoring tools, dedicated for the IzoT platform. They could be used in integrated BEMSs to monitor and control building infrastructure devices and eventually to improve energy efficiency in buildings. Tests conducted in experimental building automation network, verified energy meter automation node functionality and showed full capability for integration on the field level with other BAS devices. In future works new energy management functions will be implemented and integrated in the filed level with other BAS and IoT devices, to organize more efficient and fully active BEMSs in buildings. REFERENCES (TE REFERNCJE SĄ ROZRZUCONE LINIJKAMI) [1]
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