What the Internet of Things Will Mean for the Smart Grid
- Written by Dominique Guinard
Inter-communicating devices and integrated Web-based services will open exciting opportunities. Smart appliances in smarter buildings will be linked in grids that can be more tightly monitored and regulated in real time. New communications protocols and software applications of fundamental importance are showing the way.
Over the last several years, we have witnessed two major trends in the world of embedded devices. First, hardware is becoming smaller, cheaper and more powerful, so that many devices will soon have communication and computation capabilities. Objects will be able to connect, interact and cooperate with other objects in their surrounding environment and with control centers—a vision generally dubbed the Internet of Things (IoT).
Second, the software industry is moving towards service-oriented integration technologies; especially in the business software domain, complex applications based on combined and collaborative services have been appearing. The Internet of Services (IoS) vision projects such integration on a large scale: services will reside in different layers of an enterprise; for example, in different operational units, IT networks or even run directly on devices and machines within a company.
As both of these trends are not domain-specific but common to multiple industries, we are facing a trend where the service-based information systems blur the border between the physical and virtual worlds, providing a fertile ground for a new breed of real-world aware applications.
What does this have to do with the smart grid? Thanks to real-world services, home appliances increasingly have ways to make their energy consumption known to their users, raising consumers’ energy awareness. Furthermore, appliances can increasingly communicate with each other to make whole buildings smarter by optimizing heating, ventilating and air conditioning systems (HVAC), among other things.
Even more importantly, through composite applications using real-world services, industrial machinery and city-wide infrastructures will be manageable remotely to negotiate energy consumption and shave consumption peaks.
To facilitate these connections, research and industry have come up with a number of low-power network protocols such as Zigbee and Bluetooth and, more recently, IPv6, in a version optimized for resource-constrained devices called 6lowpan.
Although they are increasingly part of our world, embedded devices still form multiple, small and incompatible islands at the application layer; developing applications to take advantage of them remains a very challenging task that requires expert knowledge of each platform. To ease the task, recent research initiatives have tried to provide uniform interfaces that create a loosely coupled ecosystem of services for smart things. The goal is to create a real-world grid in which smart things provide services that can be easily combined to create new applications, an eco-system increasingly more ready to implement some of the big visions of smart grids.
Two types of service-oriented architectures stand out as potential candidates to enable uniform interfaces to smart objects: the Representational State Transfer (REST) and WS-* Web services.
WS-* services declare their functionality and interfaces in a Web Services Description Language (WSDL) file. Client request and service response objects are encapsulated using the Simple Object Access Protocol (SOAP) and transmitted over the network, usually using the HTTP protocol. Further WS-* standards define concepts such as addressing, security and discovery. Although WS-* was initially created to achieve interoperability of enterprise applications, work has been done to adapt it to the needs of resource-constrained devices. Lighter forms of WS-* services, such as the Devices Profile for Web Services (DPWS), are targeted towards IoT applications.
At the core of a RESTful architecture lie resources that are uniquely identified through Uniform Resource Identifiers (URIs). The Web is an implementation of RESTful principles; it uses URLs to identify resources and HTTP as their service interface. Resources can have several representation formats (HTML, JSON, and so on) negotiated at run-time using HTTP content negotiation. In a typical REST request, the client discovers the URL of a service it wants to call by browsing or parsing and following links in its HTML representation. The client then sends an HTTP call to this URL with a given command (such as GET, POST or PUT), a number of options (i.e. “accepted format”) and a payload in the negotiated format (such as XML or JSON). Several recent research projects implement RESTful Web services for smart things, also known as "Web of Things" projects.
Both approaches have advantages and disadvantages. Generally, WS-* services are preferred when advanced security features are desirable, whereas RESTful services—thanks to their ease of use and light weight (studied in the IoT context by Yazar and Dunkels)—better fit resource-constrained devices and foster public innovation.
As the vision of an IoT is slowly materializing thanks to SOAs, researchers are busy solving some of the challenges that have been surfacing: How can the Internet and Web protocols be optimized to fit the needs of resource-constrained devices? When considering billions of things connected to the Web or the Internet, how do you identify the services that let you, for instance, negotiate the energy consumption of a smart thing? Furthermore, if billions of smart things are on the Web, how do you manage and control access to their services?
These are but a few of the questions on which researchers will have to focus to implement a global and interoperable network of everyday devices that will support some of the most challenging use-cases of smart grids.