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7.1 BENEFITS OF SMART METERS
Since the beginning of the global movement towards electricity deregulation and market-driven pricing, utilities have been looking for a way to balance consumption and generation. Traditional meters only provide information for total consumption between meter reads. They provide no information as to when the energy was consumed at each metered site. Smart meters provide a way of measuring this site-specific information, allowing utility companies to charge customers different prices for consumption based on the time of day and the season.
Smart metering offers many potential benefits from the consumer’s perspective, including:
- An end to estimated bills, which can be a major source of complaints for many customers
- A tool to help customers better manage their energy consumption – smart meters provide up-to-date information on gas and electricity consumption to help people manage their usage and reduce their energy bills
Electricity pricing usually peaks at certain predictable times of the day and the season. In particular, if generation is constrained, prices can rise if power from other jurisdictions or from more costly generation methods is brought online. Proponents of variable pricing state that billing customers at a higher rate for using energy during peak times will encourage customers to adjust their consumption habits to be more responsive to market prices. Furthermore, they suggest that regulatory and market design agencies hope these price signals could delay the construction of additional generation, or at least the purchase of energy from higher priced sources, thus controlling the increase of electricity prices. Whether or not low income and vulnerable consumers will benefit from time-of-use tariffs is a concern, however.
Another benefit of smart meters is the ability to connect and disconnect service and read meter consumption remotely. Not only does this save costs for utilities, the lack of manual meter readings also means the end of estimated bills. Smart meters offer additional possibilities for the future – such as improved time-of-day tariffs, offering cheaper rates at off-peak times to smooth out national energy usage throughout the day.
7.1.1 IN-HOME DISPLAY OF SMART METERS
In-home display (IHD) units provide energy customers with real-time energy consumption feedback. IHD units can acquire consumption information through a sensor with built-in RF and/or PLC. However, a more effective solution transmits information from a smart meter via a home area network.
Types of IHD units can vary from simple wall-mounted segment LCD displays to battery-operated products with color TFT displays and touchscreens. Advanced IHDs can display energy consumption advice from energy providers in addition to raw energy consumption information.
Features and Benefits of In-Home Displays:
- Range of microcontrollers, from entry-level 8-bit to sophisticated ARM9 with embedded LCD graphics display controllers, provide flexibility to support any application.
- Flexible touch solutions, from buttons and wheels to sophisticated touchscreens, provide support for a wide range of user interface features and capabilities.
- Power line communications (PLC) system-on-a-chip (SoC) solutions with full digital implementation deliver best-in-class sensitivity, high performance, and high temperature stability.
- Power-efficient solutions support battery-operated products.
- Low-power RF transceivers for connectivity.
In-house displays can range from a basic segment LCD to a more sophisticated color TFT. The display choice drives the processing power required, and the main microcontroller can be either an entry-level 8- or 32-bit microcontroller, to a more powerful embedded MPU with on-chip TFT LCD controller. As products become more sophisticated, the user interface will as well.
The communications within the IHD depend on the implemented architecture of the HAN (typically RF or PLC). Wireless connectivity can also be supported via secure digital input/output (SDIO) cards.
7.1.2 EQUIPMENT USED BY THE UTILITY
Utilities can send commands to a smart meter by both radio and carrier current communications, depending on the type of meter being used. For example, in California, the utilities presently deploying smart meters control the meters using a 902-928 MHz FHSS radio. The intended range and frequencies used for sending commands to a smart meter can also vary from utility to utility.
Each smart meter electric meter is equipped with a network radio. The radio periodically transmits your hourly meter readings to an electric network access point. Then, his data is transmitted to the utility through a dedicated radio frequency network. Radio frequency technology allows meters and other sensing devices to communicate and route data securely. The electric access points and meters create a mesh of network coverage.
Data collected at the access points from nearby electric meters is transferred to the utility industry through a secure cellular network. Radio frequency (RF) mesh-enabled devices, such as meters and relays connect to other mesh-enabled devices. The devices function as signal repeaters, relaying data to access points. The access point devices gather the information, encrypt it, and send it securely to the utility industry using a third-party network. The RF mesh network sends data over long distances and various terrain. The mesh always seeks the best route to transmit data. This helps ensure that the info travels from its source to its destination quickly and efficiently.
Home Network and Smart Meter
Home network and smart meter access points are tightly coupled. The term “home network” is not confined within a home. It applies to a closely located territory. The home network is controlled by the home area network (HAN) that connects smart appliances, electric vehicles, storage, and on premise electricity generators to an access point – the smart meter. A smart meter is able to interface digitally. The devices working in concert allow load management at peak hours and overall energy control. Peak load management is a critical consideration in the electricity market due to high associated costs. Other forms of energy control, though nice to achieve in theory, cannot currently incur the same level of reliability that is required. The amount of data transfer at a given point will likely consist only of a number representing the instantaneous electricity use of each device, expressed in watts. Hence the bandwidth requirement usually falls between 10kbps – 100 kbps per device. The required bandwidth could grow exponentially for large office buildings, so the chosen networking technology must scale.
Low-power, short-distance, and cost-effective technologies are well suited for on-site communications. Several choices are available: 2.4 GHz Wi-Fi, 802.11 wireless networking protocol, ZigBee (based on wireless IEEE 802.15.4 standard), IEEE 802.15.4g wireless smart utility networks (SUN) and HomePlug (a form of power line networking that carries data over the existing electrical wiring). Internet protocol (IP) based on uniform standardization is widely used for communications on the premise.
It should be noted that in-home applications can leverage the smart grid. They can also exist independently without being part of a smart grid. For instance, any meter – smart or traditional – can be connected to a HAN. For example, a wi-fi enabled sensor can read a traditional meter and send data to a webserver to build many kinds of energy-related consumer applications. These kinds of applications, whether they use traditional meters or smart meters, allow consumer-facing functions without the need for any communications technologies beyond those already installed in a usual internet-connected household.
The collected information from a home network to an access point now needs to traverse to a concentration point as part of smart grid. Data traversal is indeed bi-directional. However, the volume of data from a concentration point to a device will be lower than the volume of data from the consumer side flowing to the utility. A concentration point can be a substation, a utility pole-mounted device such as a transformer, or a communications tower. Bandwidth requirements are in the 10-100 kbps range per device from the home or office. However, if appliance-level data points as opposed to whole-home data are transmitted to the concentration point, the bandwidth requirement will bump up.
Initial solution installations relied on power line carrier (PLC). PLC transmits data from a device, meter, or command to a device or meter over existing power lines. PLC is the most common conduit. It is cost effective for utilities, especially in low-density areas where deploying wireless technology is not viable yet power lines are ubiquitous. Deploying wireless technology makes an appealing business case when expensive equipment installation can be shared. Deploying exclusive wireless technology across dispersed premises is cost prohibitive. However, at certain circumstances, PLC is susceptible to interference and PLC offers extremely low bandwidth – less than ~20 kbps. Real-time-data-intensive AMI requires bandwidth up to 100 kbps per device. In dense cities, AMI deployments use 900 MHz wireless mesh network for data transmission. In wireless mesh networks, connectivity between meters and collection endpoints is obtained via a dedicated network using unlicensed radio spectrum, run by the utility or a subcontractor. Stat network is another wireless alternative. It uses fixed points to a multipoint RF network using licensed spectrum and communication towers. More bandwidth supportive broadband communications, such as the IEEE 802.16e, mobile WiMAX, broadband PLC, next-generation cellular technologies, and satellite technologies, are other possible choices. With growing data and big data buzz, bandwidth requirements tend to go up.
Utility Data Center
Information flow from concentration points to the utility typically functions over a private network. A variety of technologies are available: fiber optic cable, T1 cable, microwave networks, or star networks can be used to send data from the hub to the utility. Sophisticated smart grid applications supporting two-way and frequent communication seek bandwidth in the range of at least 500 kbps to dispatch data from a concentration point to a utility. Currently, many AMI networks support intermittent connectivity to the utility – data gets aggregated at a neighborhood node and is only sent to the utility periodically. More bandwidth may be needed to support more functionalities or more real-time connectivity.
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