Design Article
Zigbee-based demand-response systems reduce home energy usage
Bob Gohn, VP Marketing, Ember
11/25/2008 10:32 AM EST
Demand response systems for managing energy usage in homes are among the most promising of these new technologies. Households consume one-fifth of the nation's energy each year, with 60 percent of that consumption in the form of electricity. At the same time, utilities are struggling to manage the peak energy demand dilemma, where about 10 percent of electric generating capacity exists only to be used less than one percent of the time. If energy demand can respond dynamically to the available energy supply, huge cost, reliability and energy efficiency gains can be achieved within homes and the energy grid, without having to build additional power plants. In fact, it's no longer an option. The U.S. Federal Energy Policy Act of 2005, California's Title 24, and similar initiatives across North America and Europe, are driving requirements for demand response systems to be implemented in the grid and in homes.
Consequently, demand response needs are helping forge unlikely partnerships between homeowners and the electric utilities. Utilities are deploying Advanced Metering Infrastructure (AMI) networks to provide two-way communications between the home and the utilities back office via wireless smart meters. Homeowners are beginning to adopt wireless home area networks (HANs) to gain not just whole-house entertainment control but also the ability to better manage their energy consumption and this without the expense of traditional wired home automation systems.
Figure 1: A HAN includes home automation functions and can connect with a smart meter in a demand-response application.
(Click this image to view a larger, more detailed version)
Tying these two networking technologies together is ZigBee, a global low-power wireless networking standard designed specifically for control and monitoring applications. ZigBee-based HANs for energy management come at a time when standards based wireless home automation products that control entertainment, lighting, climate and security systems are taking hold. ZigBee is driving this new wave of affordable home automation, so it's natural that ZigBee would dovetail perfectly into HAN energy management applications as well.
ZigBee-enables smart appliances and devices in the home to communicate with the utility through ZigBee-enabled smart-meter gateways. These HAN/AMI networks let homeowners and utilities communicate in real time and collaboratively manage energy consumption, especially during times of peak demand. They enable the collection and distribution of information to consumers and the utilities for things such as time-of-day pricing information, demand-response actions, or remote service disconnects. During periods of peak demand, for example, the AMI system and HAN can work together for better communication between consumers, businesses and utilities and even automatically manage high-load devices in participating homes, such as changing the thermostat setting of the HVAC system. Utilities save big by not having to build new power plants, which also cuts CO2 emissions. Homeowners save money through lower bills and attractive rebates. And communities avoid the ravages of rolling blackouts.
In the quest to urgently solve the nation's energy dilemma, demand response systems stand out for being here now. It's proven rather than futuristic technology, on the advent of wide scale deployment. For instance, smart meter manufacturer Itron has already announced AMI implementation plans with Southern California Edison, San Diego Gas & Electric, Detroit Edison and CenterPoint Energy in Houston, totaling more than 14 million ZigBee-enabled smart meters. On the consumer side, GE recently announced energy management-enabled appliances that can be controlled remotely by the local utility, with customers of the Louisville Gas and Electric Company. Similarly, LG Electronics Inc. has incorporated ZigBee technology from Ember in its HomNet system for controlling home energy efficiency, security, appliances and other devices. And Boulder, CO-based Tendril launched a new Web-based dashboard that records a homeowner's electricity use and tracks individual appliances to enable utilities and homeowners alike to more efficiently manage power-consuming devices.
Comments
HAN1
11/28/2008 12:16 PM EST
Zigbee may be a nice idea however the Zigbee Alliance warns in their own documents:
No assurances can be made that a ZigBee Home Automation system will interoperate at all with other ZigBee devices, even if they are ZigBee certified
Sounds like just another major headache waiting for consumers.
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NickJ2008
11/29/2008 12:57 PM EST
Zigbee should definitely bring costs down - especially installation costs - but in reality not as much as one might think. I have a "wired" Brayden demand control system in our home and it lowered our power bill 30% creating a payback of about 2 years. The reason I said wireless technology doesn't drop costs as much as you might think is that "many" of the loads controlled (water heaters, dryers, etc.) are controlled by relays installed adjacent to their breakers in your electrical panel. My demand control system is installed adjacent to that panel. The only long runs of wire are to the HVAC units and in our case to several sub-panels. Bryaden offers a wireless link for those remote control points but we did not use it in our home since wireless devices sometimes have problems due to thick brick walls, etc. I'm sure it would have probably worked but I personally just don't trust wireless
on anything that "has to work". I look forward to Zigbee changing my mind on that but our WiFi network only reaches a tiny fraction of our house. Unless Zigbee has a MUCH wider range it won't be likely to work here.
An of course the other thing is that most of us aren't going to change out our appliances to buy Zigbee controlled models. I assume Zigbee controlled "swithes" will be available to plug existing appliances into but consider how you will plug in a water heater. Most are wired in so if an electrician must install the wireless switch why not install a relay adjacent to its circuit breaker? And while he's in your panel box installing a relay for your water heaters why not have him install one for your clothes dryer (breaking only one leg leaving the 120 volt leg that powers the motor and electronics intact so the heating element can be turned off while the clothes are tumbling).
My point is that you don't need to wait for wide acceptance of Zigbee (although I think it will be a great benefit when it comes) to get the advantage of demand control electric tariffs now.
Our incremental cost of electricity (SCE&G Rate 7) is 5.3 to 6.7 cents per KWh (off and on peak periods)compared to the previous 10.5 cents so even though the demand charge is $10.50 and $6.44 (summer and winter) it is fairly easy to achieve a reduction in our power bill by constraining peak demand. We have not experienced any compromise in our home environment for that 30% savings. The only bad thing about these demand limiting incentives is that it makes the justification of other "actual energy reduction" investments such as higher efficiency HVAC much more difficult since the incremental energy cost is now half of what it was. That is, any investment I now make to save energy is saving 5.3 or 6.7 cents per KWh energy instead of 10.5. I have to make myself invest the 30% we are saving on our power bill in "actual energy reduction" since it is the responsible thing to do.
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NickJ2008
11/29/2008 1:40 PM EST
Zigbee should definitely bring costs down - especially installation costs - but in reality not as much as one might think. I have a "wired" Brayden demand control system in our home and it lowered our power bill 30% creating a payback of about 2 years. The reason I said wireless technology doesn't drop costs as much as you might think is that "many" of the loads controlled (water heaters, dryers, etc.) are controlled by relays installed adjacent to their breakers in your electrical panel. My demand control system is installed adjacent to that panel. The only long runs of wire are to the HVAC units and in our case to several sub-panels. Bryaden offers a wireless link for those remote control points but we did not use it in our home since wireless devices sometimes have problems due to thick brick walls, etc. I'm sure it would have probably worked but I personally just don't trust wireless
on anything that "has to work". I look forward to Zigbee changing my mind on that but our WiFi network only reaches a tiny fraction of our house. Unless Zigbee has a MUCH wider range it won't be likely to work here.
An of course the other thing is that most of us aren't going to change out our appliances to buy Zigbee controlled models. I assume Zigbee controlled "swithes" will be available to plug existing appliances into but consider how you will plug in a water heater. Most are wired in so if an electrician must install the wireless switch why not install a relay adjacent to its circuit breaker? And while he's in your panel box installing a relay for your water heaters why not have him install one for your clothes dryer (breaking only one leg leaving the 120 volt leg that powers the motor and electronics intact so the heating element can be turned off while the clothes are tumbling).
My point is that you don't need to wait for wide acceptance of Zigbee (although I think it will be a great benefit when it comes) to get the advantage of demand control electric tariffs now.
Our incremental cost of electricity (SCE&G Rate 7) is 5.3 to 6.7 cents per KWh (off and on peak periods)compared to the previous 10.5 cents so even though the demand charge is $10.50 and $6.44 (summer and winter) it is fairly easy to achieve a reduction in our power bill by constraining peak demand. We have not experienced any compromise in our home environment for that 30% savings. The only bad thing about these demand limiting incentives is that it makes the justification of other "actual energy reduction" investments such as higher efficiency HVAC much more difficult since the incremental energy cost is now half of what it was. That is, any investment I now make to save energy is saving 5.3 or 6.7 cents per KWh energy instead of 10.5. I have to make myself invest the 30% we are saving on our power bill in "actual energy reduction" since it is the responsible thing to do.
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ZigSkip
12/3/2008 2:34 PM EST
It is a bit of a stretch to state that this sounds like a headache for consumers because a standards body states interoperability cannot be assured. ZigBee has a certification and testing program for published specifications to ensure interoperability. However, equipment manufacturers can chose to use private messaging which is then not interoperable.
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Ispeakfrench
2/12/2009 12:21 PM EST
And considering the Enron debacle, one could see Oh! So many ways for "people who know better" to make a killing $$$.
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