ABSTRACT

Energy management in the home is rapidly emerging as a major opportunity in programs geared towards energy efficiency. As such the home energy consumption is increasingly becoming a major focus area due to the increasing awareness of the ever rising prices of energy and the environmental impact of greenhouse gas emissions which are the largest contributors to climatic changes.

 ABSTRACT

Energy management in the home is rapidly emerging as a major opportunity in programs geared towards energy efficiency. As such the home energy consumption is increasingly becoming a major focus area due to the increasing awareness of the ever rising prices of energy and the environmental impact of greenhouse gas emissions which are the largest contributors to climatic changes.

Apart from the apparent high concentration of energy consuming devices in the home, it is projected that the home could also be an environment of interest for utilities for peak shaving or shifting demand from peak demand duration as the homes become centres of distributed generation.In order to effectively coordinate energy consumption in the home as well as manage power exchange activities between the home and the smart grid, there has emerged the need for energy management systems in the home that coordinate the energy utilization of appliances in the home, schedule optimal energy consumption in the home as well as dispatch excess energy from the home into the grid.The domestic energy management system would interact with the energy consuming devices in the home as well as the utility grid via the smart meter. This paper reviews the current domestic energy management technologies and the emerging trends in home automation.

I.    INTRODUCTION
Energy efficiency of electricity supply is a direct result of the increasing awareness of the ever rising prices of energy and the environmental impact of greenhouse gas emissions which are noted to be the largest contributors to climatic changes [1].In the context of energy efficiency, energy management is considered as a collective term for all the systematic practices to minimize and control both the quantity and cost of energy used in providing a service[2].Domestic energy management refers to the process of monitoring and controlling energy usage in residential houses with the major objective of energy conservation albeit with other ancillary benefits such as bill reduction. The tools used in domestic energy management provide users with feedback which help to influence the behaviour change in regards to energy consumption and conservation[3].Domestic Energy management technologies have been developed over time to improve energy efficiency of electricity supply [4] at the home level.Studies have shown that the electrical energy dedicated to the operation of refrigerators, freezers, (water) heaters, washing machines or dryersand similar appliances constitutes approximately half of all the usage in a private household’s consumption [5].

Domestic energy management can therefore not only result in great reduction in the power bill but also greatly reduce greenhouse gas emissions as well as contribute greatly to peak shaving and shifting of the demand from peak time. As such Domestic energy management is increasingly becoming a tool of major interest for electrical utilities due to its large contribution to demand side management and energy efficiency programs.

Although new electrical products are low consumers of electricity and more efficient, modern living is highly electricity dependent and as such the use of electricity is projected to continually increase. This implies increased demand which results in generation of greenhouse gas (GHG)emissions hence affecting the environment. It is therefore inevitable that measures must be put in place to mitigate against this eventuality. To achieve this, without adversely affecting the development and comfort of consumers, domestic energy management technologies are explored as the ultimate premise for energy efficiency. Although the domestic energy management systems provide the consumer with greater control over their use of energy in the home, the success of these systems are largely dependent on advancement in smart appliances as well as the consumers continued interest in smart homes.

This paper seeks to review the development of energy management technologies as applied in the home up to the utility meter to manage the energy efficiency within the home. This shall cover all devices connected to the Home Area Network (HAN) and how they interact with the utility smart meter to give feedback to the utility smart grid and trigger subsequent events relating to electricity supply.

The main purpose of this paper is to present the current technologies for energy management in the home, their benefits and shortcomings as well asan analysis of the emerging technologies and how they will transform the energy management in future homes.The remaining parts of this paper are structured as follows;first we present the background to the need for energy efficiency in the home, so as to help the reader understand the need for domestic energy management systems. The next section then presents an overview of development of domestic energy management systems to current technologies with an analysis based on how they achieve their functionalities. Finally we delve into the latest domestic energy management technologies and conclude our discussion with the trend in the development of domestic energy management systems for future systems.

II.    BACKGROUND TO ENERGY EFFICIENCY

The first collective effort by world environment bodies to put into perspective the concerns of the impact of climate change was in 1988. During this time, the United Nations Environment programme (UNEP) and the World Meteorological Organisation (WMO) created the Intergovernmental Panel on Climate Change (IPCC) to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts [6].Global trends over the years indicate increased effects of climate change manifesting itself in various forms associated with global warming [7].
 
According to IPCC, the largest contributor of climatic changes is Green House Gas (GHG) emissions [1]. In the United States for example, 32% of the total GHG emissions produced are due to activities related to electricity generation, 28% is from transportation, 20% is produced due to industrial activities, 10% in residential & commercial areas while 10% is attributed to agricultural activities [8]. Similar to the global trend, the general trend of GHG emissions in US is on a rise. Since 1990, there has been a constant rise of greenhouse emissions from year to year depending upon factors like economy, fuel charge and other factors[8]. From these aspects, it is evident that 62% of the total greenhouse contributions in US are from the electrical utility industry consisting of power generation, transmission, distribution and consumption of energy for industrial, commercial and domestic use.

In the year 2012, the European Union contributed 10% of the total greenhouse gas emitted worldwide [9]. Table 1 below gives the top nine energy consuming nations in the world as at June 2013. They account for 74.2% of total world energy consumption. It is evident that oil and coal form 65% of total energy consumed by these nations as illustrated in Figure 1.This demonstrates the relative GHG emissions contributed by these nations.

 Table 1 World Primary energy consumption of selected countries in 2013
S/No    Country    Oil    Natural gas    Coal    Nuclear energy    Hydro–electricity    Renewables    Total    % of world total consumption
1    China    507.4    145.5    1925.3    25    206.3    42.9    2852.4    22.4
2    USA    831    671    455.7    187.9    61.5    58.6    2265.8    17.8
3    EU    605.2    394.3    285.4    198.5    81.9    110.6    1675.9    13.2
4    Russia    153.1    372.1    93.5    39.1    41    0.1    699    5.5
5    India    175.2    46.3    324.3    7.5    29.8    11.7    595    4.7
6    Japan    208.9    105.2    128.6    3.3    18.6    9.4    474    3.7
7    Canada    103.5    93.1    20.3    23.1    88.6    4.3    332.9    2.6
8    Brazil    132.7    33.9    13.7    3.3    87.2    13.2    284    2.2
9    South Korea    108.4    47.3    81.9    31.4    1.3    1.0    271.3    2.1
TOTAL    2825.4    1908.7    3328.7    519.1    616.2    251.8    9450.3     
Source: BP Statistical Review of World Energy June 2014 [10]

Source: BP Statistical Review of World Energy June 2014 [10]
Figure 1 Total primary energy consumed by top nine nations as at 2013

 
Generally, in the developed countries, energy related fuel combustion constitutes the major contributors to GHG emissions accounting for as much as 65% to 85% of the nation’s total [11]. It is therefore imperative to put measures to mitigate against the increase in greenhouse gas emissions from these sources. Energy efficiency programs and low carbon energy sources provide the best options as major mitigation measures [11]. In the domestic and commercial areas, electricity is mainly utilised for heating, cooling and lighting and therefore managing such usages will go a long way in increasing energy efficiency as well as reducing energy demand hence GHG emissions and the home provides one of the fronts for management of energy consumption.

III.    DEVELOPMENT OF DEMS TO CURRENT TECHNOLOGIES

a.    Era of Programmable Controllable Thermostats
The earliest form of Domestic Energy Management (DEM) system included systems such as programmable controllable thermostats(PCT’s) [12]. These were the simplest forms of in-Home Energy Management systems capable of making intelligent decisions based on the information from the smart grid such as least cost pricing, peak load curtailment, demand response and distributed generation[12]. In installing the PCT’s, the consumers primary objective was to save energy by utilising the basic functionality of the residential thermostat which is to set a target temperature, see the current temperature, and control theequipment accordingly[13]. The introduction of new features and expansion of functions of the residential thermostat over a twenty year period has enabled it to embrace the role of energy saving in the home though with limited effectiveness. Furthermore, the inconvenience of controls for each individual appliance in the home by the consumer drove the need for a more centralised system for managing devices in the home and this gave rise to a smart thermostat [14].

Whereas the consumers were able to make an attempt to control their energy use with the application of residential thermostat, a lot of vital links to the total energy management cycle was still missing. The consumers were not able to access their energy consumption data when they needed the information to make the vital decisions. Similarly, the utilities could not provide this information in period’s shorter than the billing cycle. An attempt at solving this saw the introduction of the Automatic Meter Reading (AMR). Initially available as walk by or drive by Automatic Meter Reading systems (AMR) the primary objective was to provide monthly consumption data and status information for billing.

b.    The Automatic Meter Reading Era

The year 1985 marked the onset of the major developments of Automatic Meter Reading (AMR) Systems. The basic architecture consisted of meter interface module, the communications system and the central office module. Beginning from the meter, it incorporated some means of taking readings form the rotating meter dials and converting them to digital formats that can then be sent from the customer site to a central point as the meter reader either walked by or drove by the customer premises [15]. At this stage, the main objective of the utilities was to minimize fraud in the electricity distribution system as well as maximise revenues by modernizing the metering, billing and the collection process [16]. This therefore did not fill the gap of providing the consumer with the vital information needed for energy management in the home.

The introduction of Advanced Metering Infrastructure (AMI) commenced the match towards the development of smart grids which would eventually lead to the advancement of the rudimentary energy management technologies in the home[17].

c.    Advanced Metering Infrastructure

In its basic form, the AMI provided consumers with the vital data to help them make informed decisions thus enabling the execution of the decisions so as to exploit the benefits previously not available to them. AMI achieved this through the integration of technologies of HAN, integrated communications, data management applications, standardised software and smart metering [17]. In essence, AMI provided the essential link between the consumers, their energy consumption data and the grid, a fundamental architecture for the smart grids even though in its basic form.

The advancement of the AMI led to the introduction and development of Machine to Machine (M2M) communication whose evolution has set the framework for the development of the smart grid commonly referred to as SG [18].The smart grid is essentially an electric grid having smart capability that allows the power providers, distributors, and consumers to maintain near-real-time awareness of one another’s operating requirements and capabilities[18].

d.    Machine to Machine Communication

A prediction had been made in 2011 that by 2014 there would be 1.5 billion smart devices that wouldn’t need human intervention to operate would be connected to the home automation network using wireless and wired technologyand these would be excluding mobile phones [18].More recent estimates put the projection of machine to machine enabled devices to reach between 20 to 50 billion by the year 2020 [19].The main concern with this projected load on the communication network are that it requires a really high bandwidth for its operation whereasthe current network infrastructure is mostly based on synchronous optical network (SONET) and synchronous digital hierarchy (SDH) technologies. Such networks cannot physically or economically support the ever changing demands caused by the over-whelming increase in bandwidth, transport of IP traffic, and the need for more flexible connectivity, higher resiliency, and network automation as envisaged in the home automation[18].

Due to these limitations, advances M2M was introduced. M2M technology acts to establish the conditions allowing a device to have a two way exchange of information with a business application through a communication network in such a way that the device and/or application can act as the basis of the information exchange [20]. This framework is what facilitates the exchange of vital information between appliances in the home.

e.    Advanced Machine to Machine Communication

M2M communication architecture are then divided into three major hierarchical networks namely Home area network (HAN), Building area network (BAN) and Neighbourhood area network (NAN). Each of these networks is interconnected using smart meters which act as gateway between the networks. In this particular configuration, IP based communications networking is preferred as it permits virtually effortless interconnections with HANs, BANs, and NANs[18]. The major shortcoming of these networks is the latency which could cause serious transmission delays that can have serious ramifications.
 
Source: Toward intelligent machine-to-machine communications in smart grid, 2011 [18].

Figure 2 Smart Grid communication architecture showing HAN, BAN & NAN

HAN, BAN and NAN architectures employ Wi-Fi, Zigbee and Bluetooth communication protocols to communicate between the machines[18, 21].Wi-Fi is most suitable for wireless in-home communication especially in large areas while Bluetooth is most suited for short range applications. These network standards form the basic building blocks for the design for the next generation Home Energy Management (HEM) Systems discussed below.

The next technology that leverages on the development of various networks around the home, building or neighbourhood is the Appliance Coordination (ACORD) scheme that uses the in-home Wireless Sensor Network (WSN) to reduce the cost of energy consumption[22]. The architecture for ACORD consists of four components, namely the Energy Management Unit (EMU), the appliances, the control unit and the WSN. Its major objective is to shift consumer demands to off peak hours by coordinatingappliance start time requests made by consumers through the EMU thereby saving the consumer from paying the high energy prices during peak periods [22].WSN is basically referred to small low cost devices, which sense and performs small data processing and transmission of that data to the main server, utilising the wireless technology as a way of communication between their peer systems[23].

A variant of the ACORD scheme is the Appliance coordination with Feed In (ACORD-FI) scheme [24]. This scheme embraces the concept of distributed generation where consumers generate different versions of environmentally friendly energy, use it and then sell the excess to the grid, thereby reducing their peak consumption and overloading the grids[24].In essence Appliance coordination with feed in (ACORD_FI) scheme is a protocol to manage consumer demands and locally generated energy. The difference is that the requests from the consumers are considered only after looking at variety of terms such as local production, peak hours and demand from additional sources to provide a controlled energy bill. The communication network used to reach the energy management unit will be different in different methods and one of those methods is Wireless sensor network (WSN).

Another scheme similar to ACORD is the Optimization-based residential energy management (OREM) scheme whose objective is to minimize the energy expenses of the consumers[25]. It implements electricity monitoring atboth household and appliance level as well asmonitoring of gas consumption.Based on an assumption that the daily consumption of electricity by appliances is divided into different time slots according to varying price in time of use tariffs (TOU), the appliances will get turned on only according to the convenient time slot .it uses the WSN protocol for communication between system but the limitation of this technology is that the consumer requests should be given in advance which might not happen in real time.
The utilization of the WSN technology for the energy management of domestic residential household has also been referred to as Home Energy Management System (HEMS)[26]. As mentioned earlier, a HEM utilising WSN would essentiallyconsist of a central Energy Management Unit (EMU), a smart meter and electric appliances in a household, which are able to communicate with the EMU, using Zigbee protocol enabling the data packets to be transmitted over WSN[23].

This technology is a replica of the functionality of the appliances coordination (ACORD) scheme[27] since the EMU continuously communicates with the smart meter regularly, to receive the price tariffs from the grid operator. Using this data it determines the time of utilizing the share of consumption of energy produced in the household and thus it reduce the energy bill share of the appliances to an extent[23].

On the other hand In-home energy management (iHEM) application[25]uses EMU to check whether the energy produced domestically is enough for accommodating the demand in the household itself , when it is not enough EMU will check with the peak hour demand and determines whether to get power from supply grids which means demand response (DR) of the system is possible[28] . DR deals with the unexpected supply limit events from the grid by restraining specific appliances drawing power and thus regains the balance between demand and supply, example of such system is a washing machine which draws high power from grid which will be cut off in the peak hours and its request to get turned on will only be accepted in the off pea hours when the tariffs are less.

iHEM reduces the energy bill to an extent and introduced the perspective of reducing the peak load through which the carbon footprint will also be minimised. iHEM reduces energy using different scenarios using local power production ,prioritised appliances and real time pricing.

The advantages of HEM is that it reduces the greenhouse emissions by introducing the power production at home using renewable resources so that peak load is reduced resulting in low load on power production facilities. The real time management of the household system according to the consumer is also possible which does not happen in optimization-based residential energy management OREM[29].

From the Domestic Energy Management technologies discussed so far, it is observed that advances in information and communication technology underpin their development. Based on this observation, the next DEM to be developed is the WSN-based Residential Energy Management (WREM) scheme [30]. It uses two-way communication between appliances and employs sensors to monitor the large energy consuming devices, this coupled with the TOU tariff awareness ability, it implements the consumers command inputs (requests) and responds with the economically optimum suggestion to shift non-urgent appliances to the Off-Peak hours. By shifting the non-urgentappliances, such as washing machine, pool pumps, water heaters to off peak hours it helps reduce electricity expenses which could not be possible with technologies such as OREM[30].

The previously discussed domestic energy management systems have largely dwelt on electrical energy as the basic energy consumed in the home. However, there are instances where gas forms a great proportion of energy consumed in the home. The Digital Environment Home Energy Monitoring System(DEHEMS)is a large scale domestic energy monitoring and managing system funded by the European Community’s Seventh Framework Programme[3]. It differs from other DEMs largely because of its large scale deployment and integration of gas monitoring module into the system. Its development originated from user driven innovations which underscore the role of consumers in shaping the DEMS of the future.

IV.    LATEST/EMERGING TECHNOLOGIES

The domestic energy management systems discussed have consolidated in their design and development the comfort of the consumer, the need to save on power bills through peak demand shifting, distributed generation as well as integration of the various forms of utility supplied energy used in the home. The introduction of the electric vehicle then is expected to instigate the next realignment in the design of domestic energy management systems. This is because the introduction of electrical cars will definitely influence the fluctuating electricity demand. Uncontrolled charging of electrical cars in the home environment can result in high peak demands of electricity as the users attempt to ensure enough capacity for the upcoming trip. The challenge for the utilities will thus be in Lowering the peaks in demand to prolong the usage of the available grid capacity [31].

There are three main types of EV’s currently in the markets namely the fully EV type, Fuel cell EV’s and hybrid EV’s [32]. The first two types are driven solely by electric power and their large scale deployment and use could cause unprecedented effects on the electrical network.Random and uncoordinated multiple domestic Plug in Electric Vehicles (PEV’s) charging activities are projected to cause stress and undue loading on the electrical distribution systems [33]. To minimise the consequences of such an eventuality, it is foreseen that utilities may want to play a bigger role in the operation of PEV’s by remotely coordinating the battery chargers and harnessing for storing surplus energy for use in peak shaving [33]. Vehicle to Grid technology can be used to briefly discharge EV batteries at times of system peak demand [34].

By integrating EV’s into the in-Home energy Management Systems, it largely allows customers to be net buyers or sellers of electricity at different times and with different tariffs. For example the charging of plug-in hybrid electric vehicles (PHEVs) to be achieved under differentiated prices during off-peak hours thus shifting the peak demand curve[12]. The use of electric cars is on a rapid increase and it is envisaged that with the rapid advances in battery and converter technology higher deployments of plug in vehicles will find wide application in future means of transport [35].Using inbuilt bidirectional energy transfer capabilities, electric vehicles can be utilized in Vehicle-to-Grid (V2G) scheme to temporarily inject energy back into the power grid thereby functioning as mobile energy storage systems [35]. With the increase in the use of the electric cars therefore, there is bound to be need for individual charging devices at residential units (homes) and these are likely to form part of the home energy network[36].

Five key areas will determine the trends in development of domestic energy management systems;
1.    Continued advances in the field of information communication and technology that could help overcome the current key challenges of lack of standards for interoperability, cognitive access to unlicensed radio spectrum and cyber security [37]
2.    Upscaling of installation of smart meters and advancement of the smart grid
3.    Simplicity on usability of smart appliances and functionality of DEMS to make it less burdensome for the consumers to operate.
4.    Availability of smart appliances and matching of their technology to that of the other components within the DEM framework
5.    Continued acceptance of the electric vehicle by more users.
Of these five, the nontechnical aspect which involves the consumers participation and involvement in the operation of smart appliances and/or configuration of the home energy network could prove to be the key for wide acceptances of the new technologies for domestic energy management systems. This is largely due to the potential complexity that
they bring as well as the level of skill that may be required of the consumer to operate them.

V.    CONCLUSION

Current Domestic Energy Management technologies have been presented and analysed. The main function of Domestic Energy Management System is to analyse and coordinate the electrical consumption of appliances in the home. This enables the system to predict and schedule electricity demand and supply based on the state of the smart grid depending on the available least cost generation capacity. The effectiveness of the system leverages on strong relationship between the appliances, the home networks and communication between the energy management unit and the smart grid.

Development of next generation domestic energy management systems is largely dependent on the availability of smart appliances with expansive functionalities. Besides, the home will also require great capabilities for networking resources to accomplish the intricate data transfers and other communications necessary for the functionality of the next generation domestic energy management system.As homes evolve into distributed generation making consumers become net sellers of electricity, the home energy management systems are projected to play a significant role as an extension of the smart grid. Utilities will continue to leverage on the domestic energy management systems to optimise on secure, efficient and reliable means of energy generation, transmission and distribution.The anticipated wide deployment of electric vehicles in the future is bound to revolutionise the domestic energy management systems however information and communication technology will remain the greatest single determinant of the general advancement of DEMS.

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