One of the easier solutions for the smart grid is to put the connectivity into the hands of cellular technology, but the bleeding edge is not necessarily required. Kurt presents some considerations for choosing the right hardware to design a smart grid system with cellular technologies.
The U.S. Department of Energy defines the smart grid as the system that delivers electricity from suppliers to consumers using digital technology to save energy, reduce costs, and increase reliability and transparency.
To ensure the growth and viability of the smart grid, companies must successfully deploy embedded technologies with reliable and low-cost two-way communications. Cellular networks have become the common solution for an easily deployed, ubiquitous network. Effectively incorporating cellular technologies into embedded solutions is the foundation for connecting the smart grid.
Data leads to control
The smart grid comprises several end-to-end operational components connecting power-generation plants to consumers. The full value of the smart grid will eventually be realized by integrating the technology behind every component to merge data for a complete view of load management and control. Figure 1 shows a simplified illustration of the smart grid.
Electricity generation, transmission, and distribution are automated based on calculated demand derived from monitoring usage and adjusting the electric supply from generators. However, the smart grid of the future is self-sustaining and self-correcting as electricity travels between the supplier and the consumer, balancing flow in real time while offering consumers greater control of their energy use.
The drawbacks of simple reading
Automatic Meter Reading (AMR) systems automate the billing process and eliminate the need and expense of having meter counters walk from house to house. AMR systems are available based on various proprietary technologies, and each is a stand-alone system separate from operations. Built mostly to minimize cost, these meters provide very simplistic data sets. Figure 2 shows a cross-section of the technologies deployed prior to the smart grid concept.
Disadvantages of these systems include a lack of real-time connectivity, infrequent data collection (once a day or less), a proprietary communication network, and a closed architecture not built on open standards.
Getting real in real time
The top rationales for smart grid implementation are to establish connectivity, enable smart meters, simplify operations, and reduce costs for power companies and consumers. Due to the typical hub-and-spoke topology, the technology selected for use at a concentrator site that connects to a geographical area of smart meters is important. These networks consist of spread spectrum radio, private RF, power line carrier, mesh networking, and other technologies that allow for real-time connectivity and control. These technologies do not require monthly fees and are generally a fixed-cost solution, with ongoing maintenance requiring little construction and build-out.
The second area of focus is the communication that transpires during the handoff to the grid at the gateway, edge controller, or concentrator. The design is crucial to system performance, and costs must simultaneously be minimized to make the smart grid viable. These communications must be two-way, based on open standards, secure, low cost, easy to deploy, and ubiquitous.
If there is no communication backbone available from a local substation or a stub on a private network, other technologies meet the requirements, including DSL or cable modem, IP radio, and cellular.
DSL or cable modems work but pose some problems with uptime and reliability. Cost is also an issue, and both require copper or cable connectivity to run to the endpoint, which can entail costly trenching and right-of-way issues for installation. IP radio is another option, but installing towers is expensive and maintenance costs are high.
Cellular communication is the ideal choice for ubiquitous IP networking, with simple installation and low maintenance costs. Cellular coverage is excellent because it corresponds to population concentrations, meaning there is power where there are people. Advances in IP cellular technology and competitive pricing among carriers as an expanding revenue stream aside from voice communication create an ideal environment for the smart grid. The smart grid typically combines the last mile of connectivity to smart meters through a private radio network into the edge gateway, providing the entry point to the cellular networks, as depicted in Figure 3.
Using cellular communication offers many benefits, including:
- Installation: The plug-and-play or bolt-on-wall installation of cellular technology is simple and nonintrusive.
- Networking: Cellular provides private or public TCP/IP networks with connectivity either to the Internet or through private backhauls to the carrier. Routing, security, and virtual private network technologies such as IPsec and tunneling provide the open two-way communications standard required.
- Availability: More than 95 percent of consumers reside within cellular network coverage.
- Pricing: Leveraging the carriers and large quantities of devices based on the data requirements results in a price-competitive solution.
- Maintenance: Cellular communication is robust and has been tested over time to provide a solid networking solution that needs little maintenance.
Cellular implementation strategies
Several important factors must be considered when choosing the correct hardware path to design a smart grid system with cellular technologies. Whereas making the best selection of cellular technology leads to long product life cycles and shortened deployment time, making a mistake leads to potential redesigns and expensive cellular network certifications that delay system development.
Cellular networks consist of several technologies with their own limitations or features. GSM and CDMA are two current platforms to consider, each with multiple technology implementations based on their development over time increasing throughput. Table 1 shows variants of these two platforms.
Data throughput needs in the smart grid are relatively low, but designers must consider longevity, device management, and scaling the solution if data needs grow. From a cost standpoint, the greater the speed and latest technology, the higher the initial cost of the hardware. However, understanding the maintenance of cellular devices such as updating the preferred roaming list map and other features can require a physical presence for older platforms. These changes can be done over the air on newer modules, reducing ongoing system support.
Systems designers also need to consider the hardware interface or cellular module design. Using a standard interface such a Mini PCI Express, connected electrically through USB versus a proprietary module, is appealing. Although both will work fine, the ability to use another manufacturer has its advantages, and using custom headers can cause some sourcing issues. The certification process is also important to consider since carriers and standards require certification prior to deployment in the United States and other countries. The certification process can be expensive and delay deployment by six to nine months. Designers need to work with wireless carriers early in the development process to receive guidance and eliminate problems before they occur.
Creating the grid with cellular
Connecting the smart grid with cellular technologies assists in creating an advanced network of real-time electricity information. Digitally automating the entire power supply system makes the grid more reliable and efficient. Cellular technology will help grid operators better anticipate where problems might develop and enable them to precisely manage the grid with real-time information. IES
Eurotech 913-549-1004 kurt.hochanadel@eurotech.com www.eurotech.com
