06-02-2013, 03:32 PM
An Intelligent System for Electrical Energy Management in Buildings
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Abstract
Recent studies have highlighted that a significant
part of the electrical energy consumption in residential and
business buildings is due to an improper use of the electrical
appliances. In this context, an automated power management
system - capable of reducing energy wastes while preserving
the perceived comfort level - would be extremely appealing. To
this aim, we propose GreenBuilding, a sensor-based intelligent
system that monitors the energy consumption and
automatically controls the behavior of appliances used in a
building. GreenBuilding has been implemented as a prototype
and has been experimented in a real household scenario. The
analysis of the experimental results highlights that
GreenBuilding is able to provide significant energy savings.
INTRODUCTION
Residential and business buildings account for
approximately 20% of the overall world-wide energy
consumption [1], with an increasing trend over time. The
major causes of energy consumption in buildings are space
heating and conditioning, water heating, lighting, and the
use of computers and other electronic devices [2].
A significant part of this energy consumption is due to
an improper use of such appliances and devices. Just
eliminating energy wastes, without lowering the level of
perceived comfort, would reduce the overall energy
consumption in buildings by approximately 30% [3]. One of
the main sources of energy waste is represented by electrical
appliances in standby mode which accounts for
approximately 10% of the overall energy consumption in
buildings [2].
RELATED WORK
Wireless sensor networks (WSNs) have been widely used
in the past for environmental monitoring applications.
Recently, they have also been considered for real-time and
fine-grained monitoring of electricity consumption in
buildings. In [7] the author describes the design and
implementation of ACme, a distributed monitoring system -
based on a network of AC power meters - that allows users
to view their individual energy consumptions through a web
interface. The same AC power meters are also used in [6]
where a detailed experimental study on energy
consumptions in computer science department is described.
The objective of the study in [6] is to achieve full and
detailed visibility of energy consumption, i.e., to understand
how, where, and for whom electricity is used. Since using a
dedicated power meter per electrical appliance is unpractical
and expensive, the authors consider several approaches to
infer the energy consumption of single appliances from
aggregated measurements. The same objective is also
targeted in [8] and [9]. Specifically, [8] proposes two
algorithms for disaggregating the circuit-level data into
device-level estimates, while [9] presents a system that is
able to provide a fine-grained recognition of single
appliances in real time through a single electricity sensor
attached to the main electrical unit.
SYSTEM ARCHITECTURE AND DESIGN
The overall system architecture is composed of two
subsystems, namely the monitoring and the control
subsystems. The former acquires at prefixed time intervals
measures of the energy consumption of the analyzed
electrical appliances and some environmental and context
information (e.g., temperature, light intensity, presence of
persons). The latter exploits the data collected by the
monitoring system and some energy conservation strategy
to control the behavior of each single appliance. In the
following, we will analyze the two subsystems in detail.
Monitoring Subsystem
The monitoring subsystem employs a number of
electricity and environmental sensors for, respectively,
measuring the power consumption of each single electrical
appliance in the building, and monitoring parameters such
as temperature, light intensity and human presence. Data
collected by both types of sensors are wirelessly
communicated to a base station located in the same floor
(there is at least one base station per floor) and, then,
conveyed to a central server. The communication between
base stations and the server typically occurs through a wired
LAN. The server processes the data and provides users with
real-time and/or periodic reports on energy consumption and
costs. It also sends alert messages to notify specific events
(e.g. a device active when it is supposed to be inactive)
suggesting possible actions to save energy.
PROTOTYPE IMPLEMENTATION
We implemented a prototype of the previously described
architecture. We used two different infrastructures for
monitoring and control. The monitoring subsystem employs
WiSensys [15] sensors and base stations. WiSensys sensors
plug into a standard electrical outlet and provide a standard
outlet at their turn. They send to the base station
measurements of the power absorbed by the appliance,
using a proprietary wireless communication protocol. Since
there is only one base station in our testbed, it is connected
to the central server through a direct RS232 link. In a real
system the connection could be through an Ethernet link.
The environmental sensor network consists of a number of
light intensity sensors. We built light sensors by ourselves
using the Arduino platform, which is a very popular opensource
prototyping platform based on flexible, easy-to-use
hardware and software [16]. Finally, the control
infrastructure is made up by a number of X10 receivers and
one X10 controller manufactured by Marmitek [17].
EXPERIMENTAL MEASUREMENTS
To test and evaluate GreenBuilding w
e deployed anumber of electricity and environmental sensors and X10
actuators in a real environment (i.e., a household scenario)
and measured the power consumption of a set of appliances
for a relatively long time interval (15 days). The objective of
this experimental study is to investigate possible energy
wastes and user’s bad habits in using electrical appliances.
We also applied some energy conservation strategies to
some appliances and measured the corresponding energy
savings.
CONCLUSIONS
In this paper we have presented GreenBuilding, a system
for efficient electrical-energy management in residential and
business buildings. The goal of GreenBuilding is twofold.
From one hand, it allows the user to better understand the
energy consumption of each single appliance, thus bringing
him/her to make more intelligent choices in terms of energy
consumptions. On the other hand, it allows an improved
energy efficiency by means of an appropriate management
of each single appliance, depending on rules specified by
the user. We have implemented GreenBuilding as a
prototype system and deployed it in a real household
scenario.