Wsn (wireless sensor network)

WSN (Wireless Sensor Network) Based Smart Sensors and Actuator for Energy Management in Intelligent Buildings

ByDebopam Bandyopadhyay

Department of Electrical and Computer EngineeringColorado State UniversityFort Collins, CO, U.S.A

INTELLIGENT BUILDINGS

• Definition: One that provides a productive and cost-effective environment through optimization of its four basic elements – structure, systems, services and management – and the interrelationships between them.

• Help building owners, property managers and occupants realize their goals in the area of cost, energy management, comfort, convenience, safety, long term flexibility and marketability.

o Automatically sense, infer and act in order to balance user comfort and energy efficiency occupancy, time of day and various other inputs, resulting in significant reductions in building energy usage.

o Characterized by three features:-

a) Automated control.

b) The incorporation of occupant preferences and feedback.

c) Learning ability (performance adjustment based on environmental and occupant changes).

WHY WSNs FOR ENERGY MANAGEMENT

What is WSN

• Group of specialized transducers with a communications infrastructure for monitoring and recording conditions at diverse locations.

• The transducer generates electrical signals based on sensed physical effects and phenomena. The microcomputer processes and stores the sensor output.

• The transceiver receives commands from a central computer and transmits data to that computer.

o Provide advantages with their low-cost nature and collaborative sensing/intelligence capabilities.

o Key solution for facilities that frequently reconfigure spaces and places where a wire communication is difficult to apply.

o Utilized as a promising and efficient solution for various application domains, ranging from environmental monitoring to healthcare.

EMERGENCE OF ZIGBEE PROTOCOL

• A revolutionary development to WSNs was the announcement of IEEE 802.15.4 standard in the year 2003 and it was the first major worldwide standard for WSNs.

• Limitations: Only specified and defined the RF communication with respect to the lower layers PHY(Physical) and MAC(Media Access Control). It provided proposals and did not define the networking techniques for the upper layers.

• In light of this, ZigBee Alliance and its Mesh network along with IPv6 (in recent years) standardized the protocol known as ZigBee communication protocol (IEEE 802.15 ZigBee protocol).

• These upper layer improvements offered authentication of network nodes, encryption, and an efficient and modern routing that lead to mesh networking topology.

• Although mesh topology is quite complex, ZigBee is mostly preferred by WSNs designers with Mesh topology only.

• IEEE 802.15.4 ZigBee offers tremendous specifications to short range and urban environment wireless sensors networks.

• The ZigBee Alliance published the smart energy profile for interoperable products that monitor, control and automate the delivery and use of energy. The profile includes several specifications related to the advanced metering, the demand response and load control, pricing, and text message.

ENERGY MANAGEMENT IN INTELLIGENT BUILDINGS

The three primary purposes of building energy management are:-

a) The reduction/management of building energy use.

b) The reduction of electricity bills while increasing occupant comfort and productivity.

c) The improvement of environmental stewardship without adversely affecting standards of living.

Focus is on effective management of two of the largest electricity consumers in buildings – Appliances and Lighting. Appliance Management Energy-efficient appliance management requires energy sensing/measurement, appliance control, and data

analysis. Visibility or feedback into energy use is the first step for energy management. Energy usage measurement schemes fall into two classes:-

Distributed or direct sensing

• Most accurate scheme for obtaining disaggregated appliance energy use data.

• Each of the sensed devices is connected to the mains through a smart plug or sensor which measures appliance energy usage.

• The smart plug either displays device energy usage directly or it transmits readings to a central controller.

o Feature: Ability to control attached appliances and switch them on or off.


Single point sensing

• Single point sensing addresses the cost and convenience issues associated with distributed sensing schemes.

• Disaggregated energy use data is obtained from a single point in the household or building.

o Feature: Cost-effective and easily deployed solution with fewer points of failure than a distributed solution.

Intelligent Lighting Sensors: The most commonly utilized sensors are occupancy and photo sensors.

• Occupancy sensors are used in detecting room occupancy and are utilized in locations such as conference rooms, toilets, hallways or storage areas. The primary technologies used in occupancy sensors are ultrasonic and Passive Infra-red (PIR) sensors.

• Photo sensors detect the amount of ambient light, use this information to determine the amount of artificial lighting required to maintain total ambient lighting at a defined value and are therefore an integral component of daylight harvesting systems.


Intelligent Lightning control schemes Prioritization Influence Diagrams Linear Programming Multi-agent

Systems

Overview

Conflicts resolved by deferring to the

highest priority user present

Complex interrelationships

formulated using simple graphs. Non-

deterministic decision-making

Effective optimization scheme for modeling

and satisfying competing objectives

Ideal for environments where

learning and prediction are

essential while interrelationships between system

parameters are either unknown or not well-

defined

Approach

Node prioritization

Bayesian probabilities Linear optimization,

scalarizationArtificial Intelligence -

Neural networks, expert systems

Response time Fastest Rapid response Rapid response Medium

Scalability

Centralized architecture which limits scalability and produces single-point failures

Highly scalable due to distributed architecture

Weaknesses Can only guarantee comfort for a single

occupant

Probabilities must be

determined via experimentation

Optimization problem formulation is a non-

trivial taskNo wireless scheme currently deployed

due to complexity of the problem


Architecture

• Three-level architecture has been designed for detecting the presence of the building inhabitants’ user and understanding their preferences with respect to the environmental conditions.

The lowest level, the physical layer, consists of sensor and actuator devices.

the middleware layer defines a set of AmI components that can be composed to implement intelligent AmI functionalities. The high-level AmI functionalities are provided by a centralized entity, called AmiBox, responsible for coordinating the Building Agent networks, for performing intelligent reasoning and for choosing the adopted energy saving strategy.

The application layer allows for applying the monitoring and controlling rules with respect of energy constraints.


System Architecture of iPower• An intelligent and personalized energy-conservation system by wireless sensor networks

(iPower) to reduce energy consumption of HVAC systems by exploiting the context-aware capability of sensors.

Sensor nodes: These nodes form multi-hop WSNs to collect information in the rooms.

WSN gateways: For each WSN, there is a WSN gateway. A WSN gateway has a wireless interface to communicate with sensor nodes and a wire-line interface to communicate with the intelligent control server.

Intelligent control server: The intelligent control server is used to collect the system’s status (e.g., rooms’ conditions and sensors’ states) and to perform power-saving decisions.

Power-line control devices: The power-line control devices allow the system to turn on/off or adjust the electric currents of appliances.X10 devices produced by SmartHome is adopted. Such devices contain one X10 transmitter and several X10 receivers. The X10 transmitter can talk to X10 receivers via power lines.

User identification devices: The user identification devices are portable devices that can be carried by users so that the system can determine users’ IDs and retrieve their profiles. Here the authors use the processor board of their sensor platform (without sensors) for user identification.

ROUTING PROTOCOL

Methods of data routing and transferring to the base station are very important because the sensor nodes run on battery power and the energy available for sensors is limited.

• Fair Efficient Location-based Gossiping (FELGossiping)

o Improvement from the problems of Gossiping and its extensions.

o What is Gossiping? Data-relay protocol, based on a Flooding protocol. Does not need routing tables or topology maintenance.

o Disadvantages of Gossiping The next hop neighbor is randomly chosen, this means it may include the source itself . The packet will

travel through these selected neighbors until it reaches the sink or exceeds the number of hops. It suffers from packet loss.

o Most significant disadvantage of Gossiping is that it suffers from latency caused by data propagation.

ROUTING PROTOCOL

Fair Efficient Location-based Gossiping (FELGossiping)

• The protocol consists of three phases: Network Initialization Phase, Information Gathering Phase and Routing Phase.

Network Initialization Phase Each node generates the gradient to the sink. Information Gathering Phase the FEL Gossiping sends a request message to the other nodes to receive the information of other

members or neighboring nodes. Routing Phase Once the hop count and the remainder energy of the member nodes are known, FELGossiping chooses

two nodes in the third phase. The nodes are chosen near to the base station, according to the hop count of the selected nodes with the

sink node, in order to deliver packet to the sink. After selecting two nodes, the protocol only chooses one of the two nodes to send the packet. The node

with more residual energy is selected, and the message is sent to the selected node to broadcast the packet to the base station.

ROUTING PROTOCOLFlowchart of Network Initialization

PhaseFlowchart of Information Gathering

Phase and Routing Phase

BUILDING MANAGEMENT ARCHITECTURE•

• An agent-oriented decentralized and embedded architecture.

• Main objective: Support distributed and coordinated sensing and actuation operations.

• Implemented at the WSAN side through MAPS (Mobile Agent Platform for Sun SPOTs), an agent-based framework for programming WSN applications based on the Sun SPOT sensor platform, and at the base station side through an OSGi(Open System Gateway Initiative)based application.

Mobile Agent (MA): Basic high-level component defined by user for constituting the agent-based applications.

Mobile Agent Execution Engine (MAEE): Manages the execution of MAs by means of an event-based scheduler enabling lightweight concurrency.

Mobile Agent Migration Manager (MAMM): Supports agents migration through the Isolate (de)hibernation feature provided by the Sun SPOT environment.

Mobile Agent Communication Channel (MACC): Enables inter-agent communications based on asynchronous messages (unicast or broadcast) supported by the Radiogram protocol.

Mobile Agent Naming (MAN): Provides agent naming based on proxies for supporting MAMM and MACC in their operations.

Timer Manager (TM): It manages the timer service for supporting timing of MA operations.

Resource Manager (RM): RM allows access to the resources of the Sun SPOT node.

BUILDING CONTROL PROTOTYPE AND ARCHITECTURE

Prototype

• Multi-layer architecture of the wireless sensor-actuator networks.

• Multimedia information collected is transferred from sensor nodes to the sink node by multi-hops method and the control demands are transferred from sink node to the actuator nodes hop by hop.

• The bottom layer is made up of several aggregation areas and each area contains several wireless multimedia sensor nodes and actuator nodes.

• In the path from sensor nodes to the sink node, the routing node, named as aggregator, is responsible for fusing the multi- source data and transferring the aggregated results to their aggregator in the higher level.

• The control commands from the sink node to actuator nodes are very important, assigned with high priority.

• When the command is finished, actuator returns a confirmation signal to the sink node.

BUILDING CONTROL PROTOTYPE AND ARCHITECTURE

Architecture

• Web services-based approach to integrate resource constrained sensor and actuator nodes into IP-based networks.

Key Feature: Automatic service discovery.

• API(Application Programming Interface) to access services on sensor nodes following the architectural style of representational state transfer (REST) is implemented.

• RESTful Application Programming Interface (API) on sensor nodes provide access to sensors and actuators through the Web.

• The IEEE 802.15.4 physical layer standard is optimized for energy efficient communication with low data rates.

• The 6LoWPAN header compression scheme allows to efficiently send IPv6 packets over IEEE 802.15.4-based networks.

CURRENT TRENDS

• Rangarao Venkatesha Prasad, et al. propose an ICT (Information & Communication Technology) architecture for realizing zero-energy homes using Wireless Sensor Networks.

• Kwang-Soo Kim, et al. propose a smart grid testbed which is implemented using a wireless sensor network within a small building.

To monitor and control the usage and the generation of the electricity in the building, two monitoring servers and several electric devices including five smart meters, two wind power generators, a photovoltaic power generator, a battery, two electric vehicle chargers, two light controllers, and a smart outlet are installed.

The light controllers exchange their data and control messages through PLC and the other devices exchange those through a wireless sensor network.

• S. Zahurul, et al. has developed a testbed using Wireless Sensor Network (WSN) based on IEEE 802.15.4 standard for remote real time monitoring of current production in a distributed Photovoltaic (PV) plant.

CURRENT TRENDS

• Subhas Mukhopadhyay, et al. has designed and develop reliable, real-time and realistic wellness sensor networks for smart home systems. In this research, the authors have designed an XBee series-2 based intelligent monitoring system that operates on the ZigBee protocol and uses the features of IOTs.

• Andreas Kamilaris, et al. discusses the principles of the Web of Things which are employed for the development of a comprehensive system for home automation.

By combining sensor devices with residential smart power outlets, the foundational pillars are built towards energy-aware smart homes that operate with Web technologies.

By designing an application framework for smart homes using request queues for communicating with home devices, reliability and time efficiency are ensured while prioritized requests can be easily included to the system and multiple simultaneous family members may be supported.

It is demonstrated through various case studies that Web-based, energy-aware smart homes have the potential to provide flexible solutions to challenges such as energy awareness, energy conservation and the integration of future smart homes to the smart grid of electricity.

FUTURE TRENDS

• Ali Norouzi, et al. propose the Green Network Project as a future project. In response to Green Network, Rangarao Venkatesha Prasad, et al. are investigating the use

of energy harvesting sensors that could provide the context as well as sensing to help in reducing the total energy consumption in indoor environment under Dutch national project IOPGencom-GoGreen.

• Lun-Wu Yeh, et al. propose to use INSTEON as device control protocol which could be more reliable and could transmit at a higher speed.

• Alessandra De Paola, et al. are finalizing a real prototype of the monitoring and controlling system for energy efficiency in the university buildings at the University of Palermo, Italy.

Challenges

• While implementing WSNs :- ISM band interference and attenuation issues should be considered. Wireless Sensor Networks are powered by the limited capacity of batteries. Due to the

power management activities of these sensor nodes, the network topology changes dynamically which pose additional challenges to communication protocols.

• Web-based schemes need to be developed that guarantee authentication, data integrity and confidentiality, from the home devices to the Web and vice-versa.

• The privacy of the residents should be taken into account. The sensors deployed in Ambient Assisted Living (AAL) must provide limited and sufficient information related to activities of daily living like sleeping, cooking, eating and going out. Any information that could be utilized beyond this purpose should be avoided.

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