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Designing Intelligent Appliances for the Smart Grid



The Smart Grid promises to be a game changer, but the rules of the new game are still being written. The burgeoning Smart Grid infrastructure promises to reduce costs and enable a wide range of innovative consumer, industrial, and embedded devices.


The Smart Grid promises to be a game-changer across the entire electronics industry, including consumer, industrial, and embedded devices of all types. Innovation is driven by value, either because a new product reduces the cost of an existing technology or because it offers new features and capabilities that users are willing to pay for. While it isn’t always predictable whether consumers will be willing to pay a premium for new features, the prospect of reduced operating cost is always attractive.

Consider the lighting automation industry. Controlling every light in a house remotely has been possible for over a decade. High-end systems offer features every consumer would love to have, just not at a price most can afford or are willing to pay. X10 technology provided a cost-effective approach to lighting automation, but its unreliability has left consumers unexcited. As a result, the home lighting automation market has experienced limited growth.

With the development of Smart Grid technology, the focus is first and foremost on enabling significant cost savings by intelligently monitoring and managing power consumption. For a few dollars more, appliances will be able to accurately measure power consumption and turn themselves on and off based on power availability and time based pricing tiers. As the Smart Grid is deployed, however, it will also bring with it an infrastructure that will readily support a wide range of automation capabilities.

The best candidates for intelligent power management are those appliances which consume a lot of power and are fairly discretionary as to when they are used. The primary consumer of power within the home and business is typically the HVAC (Heating Ventilation A/C) system, followed by appliances with motors and power supplies such as washers and dryers. Items like refrigerators and stoves may consume power but are not discretionary in their use, so the need for them to be smart is much less pertinent.

Other key trends driving the adoption of Smart Grid technologies include:

  • More efficient management of power on the grid:
    Power capacity continues to be outpaced by increases in power consumption. Building new power sources is extremely expensive and something the utility companies want to postpone for as long as possible. The alternative is to better manage the peak power load. This can be accomplished through various load shedding and demand response programs; for example, today consumers receive a rebate or price break if they allow their utility company to control their thermostat during peak usage times.
  • Bringing power awareness to consumers through visibility:
    For most people, power consumption is a single number that arrives once a month in the mail. It is difficult to attempt to be more responsible with one’s usage when one has no idea when or how power is being used. By providing real-time visibility into home and business usage patterns, consumers can actively analyze and reduce their consumption.
  • Enabling appliances to monitor their usage and support remote management: For consumers to have access to energy information, it first has to be collected. While many power meters now track usage and time-of-day, they can only see aggregate power consumption (see Figure 1). As particular appliances are not being tracked, a consumer cannot tell if a usage spike is coming from a refrigerator, hot tub, dryer, or A/C unit.
Figure 1: With no spinning wheel, smart meters can track usage and time-of-day. However, they are limited to measuring only aggregate power usage unless appliances support intelligent power tracking and self-monitoring.
  • Sharing of energy information throughout the home and beyond: When users can track power usage throughout their home, they can make wiser choices (i.e., shift time of usage to when lower pricing tiers are in place). Two primary hurdles exist: how to share information throughout the home and how to get this information out onto the Internet cloud.
  • Managing the increasing load as electric vehicles come onto the grid: Electric vehicles require a great deal of power, and most drivers will plug their cars in when they return home from work. The problem is one on the neighborhood level: the presence of several vehicles simultaneously charging on the same transformer could create many problems for the utility companies. Rather than upgrade equipment, charging load can be spread across the evening when usage tends to be lowest.
Tracking and self-monitoring

Accurately tracking power usage and patterns requires that energy consumption be measured at the appliance itself. Metrology ICs step down appliance current to measure energy consumption and provide this information to the appliance’s main processor. One of the primary cost drivers of metrology devices is how much accuracy is required. For some devices, like the smart meter itself, dynamic range impacts accuracy and so a higher resolution ADC is needed. For systems that operate within a well-defined range, a lower resolution ADC may be sufficient.

One side benefit of self-monitoring is the ability to profile appliance operation. With enough accuracy, an appliance can identify that it is exhibiting degraded behavior and alert the owner that servicing is required to avoid system failure. Major Smart Grid players such as Microchip, STMicroelectronics, and Texas Instruments offer a variety of metrology ICs to support their extensive offerings of Smart Grid components. ICs start at $1 for low-end applications and can run up to $20 for higher current and precision applications.

To improve efficiency, appliances also need to support demand response events and actively assist consumers in making usage choices based on tiered rates. Traditionally, the home HVAC system must be adjusted manually to reflect pricing tiers. When the thermostat is connected to a smart meter, it becomes possible to download real-time rate schedules and adjust usage automatically. When peak demand is high, the thermostat can be adjusted to a higher temperature and even turned off directly by the utility companies. Note that appliances such as refrigerators, communication devices (phones, routers, computers), and especially medical equipment cannot be arbitrarily shut down. Only devices that are connected to the Smart Grid can be managed in this way.

Self-monitoring also enables more granular control. Rather than supporting only control of weekday or weekend settings to keep programming complexity low, smart thermostats (see Figure 2) can allow consumers to program more complex schedules or even analyze power usage to determine if someone is currently in the house or building.

Figure 2: Smart thermostats allow intelligent management of heating and air conditioning systems, such as allowing utility companies to adjust usage during peak demand periods.

Designers also need to take into account the fact that some appliances need to be managed with more grace than simply being shut down. For example, consider a washer that is shut down mid-cycle as part of a demand response event. Unless the meter can also tell the washer to turn itself back on, the clothes will sit in water for hours. Preferably, the washer could drain before shutting off. The washer should also have a bleach indicator so that the washer can decline to shut down to prevent clothes from being destroyed in the hours it takes a consumer to return home. Alternatively, a person may be cleaning a shirt for an important meeting and needs to be able to override the demand response mechanism. These are the sorts of issues manufacturers need to anticipate.

Connection

Part of the philosophy behind tracking power usage in real-time is to increase consumer awareness of consumption, both by amount and by time-of-day. The current billing system provides consumers with a single consumption number, once a month, making it difficult to identify even simple inefficiencies such as a stereo left on or a parasitic wall charger that uses power even when it isn’t charging. Real-time tracking allows consumers to uncover such energy drains by profiling the use of major power appliances in the home. If the total unaccounted for usage — i.e., all of the other appliances and electronics in the house — is high, this will alert consumers to potential areas for improvement through a change in usage habits.

To provide remote access and other automation features, appliances need to have a link to the home network and out to the Internet. Candidates to serve as the home network gateway include the smart meter, a separately purchased energy monitor, or the thermostat (because it is already connected to the largest power consuming appliance in the home).

The home network requires a connectivity technology that is inexpensive, simple to use, scalable, and power efficient. Those most commonly associated with Smart Grid applications include:

ZigBee: ZigBee has positioned itself as the defacto smart meter standard, claiming to be present in an overwhelming majority of deployed smart meters. Offering its Smart Energy and Home Automation Profiles which define how appliances communicate to the meter and each other (see Figure 3), ZigBee simplifies integration into the home network.

Figure 3: ZigBee’s Smart Energy Profile provides an efficient way of connecting appliances within the home through the smart meter and allowing consolidation of energy data by utility companies.

Wi-Fi: As a wireless technology, Wi-Fi has a huge installed based, is readily available in most homes as an Internet connection, and is familiar to consumers. Connecting to a Wi-Fi-enabled appliance is about as complicated as configuring a wireless printer. In some circles, however, this is thought to be too complicated and a technology is desired that requires no configuration.

Power line Communications (PLC): PLC provides a wired connection for appliances. Since it runs over power lines, all major appliances are already connected to the smart meter.

Proprietary: Proprietary wireless connections tend to support automatic configuration and can be less risky to introduce to market. However, they require more hardware, cost more than standard technologies, and tend to have limited extensibility.

From a technology perspective, there is no obvious winning technology. Many of today’s silicon vendors offer a variety of connectivity interfaces off-the-shelf. All of the required software, hardware, and features (such as encryption) are available. These vendors don’t support one standard over another because they sell several of them. Depending upon the protocols, developers can even migrate between interfaces with minimal changes to system design. This allows manufacturers to support different connectivity options based on the cost and complexity the end product can tolerate.

There is also a good likelihood that all of these technologies will serve in the same home or business to connect the variety of appliances. ZigBee appears to have a clear lead from being integrated into many smart meter architectures. However, there are concerns that there may be appliances which are too far from the meter or another ZigBee node for reliable connectivity. PLC, in contrast, guarantees a connection. A likely scenario is to have ZigBee and PLC PHYs in the meter.

Access to the meter, however, is proving to be a tremendous challenge for appliances manufacturers. This is because of the great variety of implementations used throughout each country. Utility companies use different types of meter and require a different set of APIs to connect with them. In addition, many utility companies have yet to activate and open their communications link for use by appliances, thus preventing the meter from being used as the energy gateway. While independent energy gateways are available, these too support a wide range of protocols. From this perspective, the wariness of manufacturers to integrate Smart Grid technology into their appliances is understandable since there is no clear target yet at which to aim. Most appliances have an extended lifetime, and providing a dead-end implementation can damage a brand.

Regardless of the technology used, appliances will need to be able to operate when connectivity is disrupted. Ideally, appliances will track time on their own and be able to call up the last energy rate profile received. They may also be able to forecast demand response events to warn users during potentially expensive time slots. These are important considerations as well since it is the appliance manufacturers who will be held responsible for the robustness of energy management systems.

Consolidation

One of the major design considerations for utilities and manufacturers is managing and consolidating the flow of energy information. Moving from a single data point per month to several data points per half hour represents a tremendous amount of data to collect and correlate. As more appliances incorporate displays, they will be able to provide an accounting of their own consumption. However, much of the value of energy tracking comes from being able to coordinate all of the appliances in a home or business from a central point. While a thermostat, smart meter, or central energy monitor can serve as the data gateway for connected appliances, these devices may have limited display capabilities that prevent them from effectively conveying information about all of the devices within a home.

One approach is to support access to a PC or smart phone which can provide full configuration and UI functionality over a wireless link. Ideally, consumers would like to have remote access to energy information, requiring that information be passed out to the Internet cloud. This approach, however, requires that information be collected on a back-end server. Supporting such a server potentially introduces additional complexity and expense to appliance design. In addition, to be the most useful to consumers, energy information for the entire home needs to be consolidated onto a single management platform so that consumers don’t have to manually track individual devices. Consolidating energy savings is also likely to improve consumer responsiveness to energy conservation. For example, a dryer stating that it saves $5/month may not impress consumers as much as seeing that overall home savings are $40/month.

Some utility and energy monitor companies have chosen to use Google Power Meter as an alternative to investing in building their own energy management platform. Google Power Meter supports consumers and businesses either directly through their utility company or through a gateway device that can be purchased separately. As a standardized platform, Google Power Meter will potentially facilitate a smoother transition to consumer energy awareness by providing a common and readily available API upon which to base smart energy designs. It also eliminates the need for utility or appliance companies to develop their own proprietary management platform.

The ability to track da ta raises many concerns: energy data can be used to determine what people do in their houses (privacy) as well as whether or not they are currently home (security). One of the more sticky issues yet to be resolved is who owns energy consumption data once it has been collected. Within the home, the meter or energy monitor can use standard security protocols and certificates to protect home network communications. Similar mechanisms will need to be in place between the gateway and back-end management platform. To support security, appliances will also need a simple and intuitive way to pair to the energy gateway. Pairing can be done through the use of a PIN provided by the gateway which is typed in on the appliance.

Smart Grid technology is still in its early stages. Fortunately, the base technologies required to implement intelligent energy management are themselves mature and already proven in the market. The challenge for manufacturers lies in determining which technologies to integrate and when to release them. Already products are coming to market that support energy awareness and as appliance manufacturers continue their trials and testing, more shall be added to store floors. With the advantages of intelligent energy management so high, especially with the promise of increased automation capabilities, it shouldn’t be long before the details of how to connect appliances are clear.

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