Service-oriented paradigm is the relatively new technique of providing the services. It is a service-based architecture that has objective to provide efficient heterogeneous services to the end users. It is capable of integrating the legacy and new applications and services those may be accessed over the internet in the form of web services. These are used to design and develop the large-scale dynamic systems (Pagani et al., 2007). In smart grid, services and resources are distributed over a network and are very dynamic in nature. These services and resources appear on the network, utilized, shifted and vanished after some time, the reliability and availability of these services are very important (Gadgil et al., 2007). The integrity, reliability, and availability of these services could be assured by using the service-oriented architecture (SOA) in the smart grid. Because, the SOA is specially designed for connecting the advance enterprises and providing the links between data sources, business process, platforms, and applications. The SOA is a good candidate for integrating the heterogeneous services provided by the smart grid to its users.
In a grid binding and discovery of services are handled by SOA. When a user access the grid for a particular service then grid by using the SOA tries to find out the relevant service providers. In case, the demanded service is not provided by any service provider then SOA tries to provide this service by integrating the available services (Bruning et al., 2007).In smart gird, the SOA focuses on the stacks of protocol and schemes for scheduling the services efficiently for fulfilling the requests of various users (Zhou and Rodrigues, 2013). Moreover, this architecture in smart grid integrates the data acquired from end users and other connected devices to provide fully satisfied services. Further, this architecture can integrate the heterogeneous devices such as camera, headphone, microphone and etc. This is made possible by incorporating the multiple open interfaces in the SOA for the interconnection of the heterogeneous networks and devices. The process of integrating and providing the heterogeneous services presented by Zhou and Rodrigues (2013) is shown in figure 2. In the smart grid, the SOA is used to integrate the different parts of smart grid such as presentation part also known as user part because user interacts with grid through this part of middleware to get required service, control part that performs the function of making interaction between transmission and presentation parts, and transmission part that is composed of processes of communication with user as well as generation and distribution of energy (Zhou and Rodrigues, 2013).
Figure 1: Heterogeneous Services Provided using the SOA in Smart Grid
In figure 2, the SOA is used as middleware to integrate the services of the smart grid such as security services, information exchange services, power distribution services and grid management services. This middleware SOA focuses on the users and collaborates with other functions of the smart grid. To handle the massive data exchange and its processing as well storing, the advanced form of SOA known “service-oriented cloud architecture” is used (Rajeev and Ashok, 2013). This architecture has a reliable and secure mechanism for integrating and sharing the information among users of the grid. Because this architecture uses the secure methods of communication such as the coding and encrypting the information to share over the network. The messages passed in the form of XML to interacting services and applications are properly encrypted.
There are certain benefits of using the SOA such as it is capable of integrating the programs and applications developed in different languages. Moreover, there is big of the benefit of using the services of existing systems and the services of new systems may be integrated into existing one (Bokhari et al., 2015). However, there are certain shortcomings of this architecture in using it in the smart grid. The first limitation of this architecture is that it is not useful for a standalone application that has no components to be integrated with other components (Bokhari et al., 2015). Further, if any service is included in the grid that does not support the message passing mechanism then the SOA will be useless for such services. Moreover, this architecture is also not suitable for the services included in the grid those have a very short time duration of their execution. In addition, this architecture will not support the services included in the grid those are highly coupled as this architecture is based on loose coupling (Bokhari et al, 2015). Further, the SOA is not suitable for integrating the services included in the gird those are developed in the homogeneous integrated development environment. Because, services developed in the homogeneous environment are developed using the same language, tools, and techniques; therefore such services can interact easily with each other and there is no need of paying for the overheads of the SOA. In addition, this architecture is not recommended for services those processes the massive data. If the SOA architecture used then there will be exponential connections to the server that will overload it. Moreover, in this architecture, the messages are transmitted and received in the XML format that enlarges the size of the message, as a result, more bandwidth is consumed and extra resources are utilized. In case, there are many failure points in the grid at the same time then it will hard to find out the reliability of the individual point using the SOA (Bokhari et al., 2015). Due to some basic limitations of system integrations, the trend is shifting to the interoperability. This is due to the fact that for integration of heterogeneous applications there is always the need for some extra resources such as adapters and interfaces those are used to make heterogeneous things compatible with each other. Moreover, in system integration, there may be many complications if it not done properly or anything is missing in the integration. Moreover, the development of the integrated systems is very difficult. Because the components of integrated systems are developed using the heterogeneous technologies and devices those require significant work for their collective operation and proper synchronization.
It is expected that SOA will be a key element of the future smart grids as it seems that this architecture will have the capability to interconnect the various components of the smart grid as the target of this architecture is the enterprise platforms. However, to get maximum advantages of the smart grid there is need to solve certain issues present in the current smart grids(Pagani and Aiello, 2012). These challenges are the interoperability of the software components, the scalability of the grid due to increase in the number of its users, discovery of the service providers and consumers, interaction of mobile consumers with the grid, integration of services as well as close interaction of the physical, data and business layers, the topology of energy distribution, design and development of smart meters those will perform the function of energy consumption measurement as well as the interaction with grid. Moreover, there is lack of standardization of mechanisms for sharing the information in the smart grids that need to be improved. To achieve the objective of two ways flow of information and electricity in an efficient way there is need to devise new devices and technologies those are easy to use and have good mobility. Moreover, extreme care should be exercised while adding new component or application to a grid. Because new addition in the grid may introduce serious security and safety issues. Moreover, the trend of adding the innovative applications in the smart grid is increasing as shown in figure 2.
Figure 2: Types of the New Application becoming part of the Smart Grid
In spite of presenting some challenges and issues in the smart grid and using the SOA in it, experts are expecting that smart grid will lead to the better services of the power supply, sound future environment and consequently the life of human will be revolutionized. Moreover, the use of SOA architecture in the smart grid will enhance the lifecycle of processes and management of its resources. The SOA is making the great contribution to almost every software project by integrating the traditional systems. It is considered as the standard architecture for designing and developing the business applications those incorporate the business data and processes. Due to these reasons, it used in organizations for the purpose of managing, securing and accessing the organizational data and speeding up the business processes. In short, the SOA has a tendency to provide the interacting the critical data, people, processes and technologies in most effective, scalable and consistent way.
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