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A Slightly Non-Technical Introduction to the Zigbee Smart Energy Profile | Print |
Written by Akiba   
Wednesday, 09 July 2008

The Zigbee Smart Energy Profile has been getting a lot of attention recently, however there seems to be a lack of information on what the spec actually is. The info that I'm seeing in the press mostly deals with products that are coming out such as smart thermostats or perhaps the marketing research firms discussing the potential market size. There's no doubt that the smart energy market is potentially a very large market for Zigbee, but what exactly is it?

I should probably start with a small blurb on why smart energy seems to have such a large uptake in the US. The move to smart grids probably gained a lot of momentum from the Smart Grid Facilitation Act of 2007. The bill has passed through the committees and its currently on the legislative calendar. Here's a summary:

Smart Grid Facilitation Act of 2007 - Declares it is the policy of the United States:(1) to support the modernization of the electricity transmission and distribution system to incorporate digital information and controls technology and to share real-time pricing information with electricity customers; and (2) that electricity purchasers are entitled to receive information about the varying value of electricity at different times and places, and that states shall not prohibit or erect unreasonable barriers to the provision of such information flows to end users.

The implication of having some form of communications within the meters is that new applications can also be enabled. On the utilities side, automatic meter reading has the potential to save huge amounts since you won't need people to come by your house monthly and check your meter for usage data. All of this information would be available instantaneously via metering networks that the utilities could theoretically set up.

On the consumer side, it would be possible to get instantaneous pricing information on the electricity that is being used and to scale electricity consumption accordingly. I think if most people knew that their 500W PC that they leave on all the time is costing them an additional $100/month, they would be somewhat persuaded to turn it off every so often.

Basically, the Congressional bill, the recent focus on energy efficiency, and the buzz over wireless communication and wireless sensor networks has come together and made smart energy somewhat of a trendy thing. And in the middle of that is the Zigbee Alliance who is surfing the smart energy wave by coming out with the Smart Energy Profile to standardize wireless communications over 802.15.4 networks.

But probably most of you already know all about that. So let's dig into the details of the Zigbee Smart Energy Profile…

The Smart Energy Profile envisions two types of networks: the home area network and the neighborhood area network. They call it the HAN and the NAN (isn't that what you get at Indian restaurants?) but I'll just call it the home network and the meter network.

The meter network is something that the utilities industries are interested in because it could potentially save them large amounts of money. The idea is that for a neighborhood, all the meters would be fitted with a wireless radio that would allow them to join a network that funnels individual metering data to a gateway that communicates with the utility's home office. This would allow the utilities to avoid the cost of dispatching meter readers since the data is now coming to them in real time. The cost savings of this alone would be huge, however the utilities could then slice and dice that energy consumption data to more accurately estimate demand, pricing, and all the other wonderful things that statistical analysis allows you to do. The painful part about this is that America's metering infrastructure would need to be retrofitted with "smart meters" which is a huge investment. So most utilities aren't taking this drastic step yet. They're dipping their toes in the water with optional load control devices, which we'll talk about in a minute.

The home network, in the energy sense, is a wireless sensor network composed of a device that can communicate with the utility and other devices that can communicate with that device. In the Smart Energy Profile language, its composed of an "Energy Service Portal" and "Smart Energy Devices". Since I've arrived in California, I've already heard from my non-Zigbee friends that Southern California Edison is already introducing the smart Thermostat which gives the utilities the power to control the home's A/C and other HVAC equipment during peak load times in exchange for a reduction in electricity pricing. Using it is voluntary among the electricity customers, and I assume that most customers would probably be suspicious of allowing the utilities to control something as private as your home settings. Hey, I would and I'm a tech geek.

The Smart Energy Profile actually defines many other types of devices as well, but before we get into that, let me define a couple of the features in the Smart Energy Profile:
  • Demand Response and Load Control - Actually, this feature should just be called Load Control, however I guess the words "Demand Response" adds a bit of  oomph to the name. As the name implies, this feature allows the utilities to control the electrical load of the device that supports this feature. Load control events can be as simple as turn on/off or temperature values can be assigned that will set off a load control event when they get crossed. This is the principal feature in the smart thermostats that I mentioned earlier. Actually, there is an opt-in and opt-out feature defined the load control cluster (that's a Zigbee term) where users can choose to opt-out of the load control event if they want to. But most likely you won't see this from the utility's devices. Ha ha ha…evil.
  • Simple Metering - This feature provides a mechanism to get the information from a variety of metering devices including electric, gas, water, and thermal meters. I'm not exactly sure what a thermal meter is, but maybe its lucrative to sell heat or the lack of it (cold?). The reason it's called simple metering is that it provides the formatting for a limited set of devices. More advanced metering control features will be introduced into the Complex Metering feature that is currently being worked on by the Alliance.
  • Pricing - This is probably one that most users would be interested in. This feature communicates the real time pricing to a device and defines two ways of sending the pricing data. It can send it via secured messages or anonymous (unsecured) messages. The unsecured pricing data may create new types of appliances that can communicate with the home energy network and adjust their electricity usage according to the current pricing (ie: refrigerators).
  • Messaging - No, this will not allow your AIM client to communicate with the utility, although its similar. It provides a mechanism to allow the exchange of text messages between smart energy devices. This would probably be used to broadcast warnings to users ie: "Your AC will be turned off in 3…2…1…".
  • There are also two more feature sets that are in the works and at the time of this post are not yet available publicly. Those feature sets are Complex Metering and Pre-Payment. Both of those will probably take a while. Complex metering will extend the functionality of the simple metering feature set to specific types of meters, and the implementation will be very dependent on how the Alliance works with meter manufacturers and utilities. The pre-payment feature set will require extremely robust security so they're going to need to do extensive testing to make sure everything is hack-proof. On the other hand, someday you may be able to purchase Amazon books through your electricity meter.

Okay, now that we got that out of the way, lets talk about the types of devices that are envisioned in the Smart Energy Profile specification.

  • Energy Service Portal - This device connects the utility's network to the smart energy devices within the home. Basically, it’s a gateway to the utility and probably only these types of devices will be able to communicate directly with the utility. Most likely these will end up being on the actual meter itself.
    • Mandatory Features
      • Messaging
      • Pricing
      • Demand Response/Load Control
    • Optional Features
      • Simple Metering
      • Pricing
      • Complex Metering (TBD)
      • Prepayment (TBD)
  • Metering Device - These devices will be meters that are able to join a Zigbee network wirelessly. As I mentioned, in most cases, they will end up being combined with the Energy Service Portal, however its possible to have one portal and multiple metering devices in one location (ie: a factory).
    • Mandatory Features
      • Simple Metering
    • Optional Features
      • Pricing
      • Messaging
      • Prepayment (I'm going to drop the TBD from now)
  • In-Premise Display Device - This can be a simple LCD device that just passes information to the user. The image I have is a wall clock that can show electricity usage, pricing, and temperature. Oh, and I forgot…the time.
    • Mandatory Features
      • None
    • Optional Features
      • Pricing
      • Simple Metering
      • Messaging
      • Prepayment
  • Load Control Device - This device can receive load control events from the energy services portal to manage consumption of a device. These can be fitted on things like pool water pumps, water heaters, lighting, PCs (just kidding…nobody touches my computers).
    • Mandatory Features
      • Demand Response and Load Control
    • Optional Features
      • Pricing
  • Smart Appliance - These devices are the most promising for creating a new market. They will be able to get real-time information from the utilities and make decisions based on that information. The obvious applications are price-aware refrigerators, laundry machines (washers or dryers), lighting controllers, HVAC (heating, ventilation, and cooling) equipment, etc…and wall clocks, I guess.
    •  Mandatory Features
      • Pricing
    • Optional Features
      • Demand Response and Load Control
      • Messaging

Well, I guess that about does it for my slightly non-technical introduction to the Smart Energy Profile. I guess the final question would be "Is it ready for prime time?". I'm also interested in the answer.

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Thanks!
written by eouiwer, February 10, 2009
Thanks for the clear and easy to read information! Very useful! smilies/smiley.gif
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Optional/Mandatory Services
written by Josh, May 06, 2009
This is a great article, but there are some errors in the mandatory and optional features for the device types. For example, "Pricing" is listed as mandatory and optional for the energy service portal. The in-premise display device shows no mandatory features, but I imagine "Messaging" would be mandatory. Also, how does "simple metering" apply to smart appliances?

Thanks,

-Josh
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written by Akiba, May 06, 2009
Yeah, I should have clarified that. Actually, any Zigbee device supports both server and client functionality. I didn't really want to get into it too much because I wanted to keep things simple. However these devices are actually specified in the Zigbee Smart Energy Device Profile and you can more detailed info by checking the device descriptions there.

For the energy service portal, pricing must be supported on the server side. That means that if it gets a request for pricing, it will need to answer it or at least provide a response that has the NOT SUPPORTED status in it.

An energy service portal optionally can support the client side of the pricing cluster. This means that it can generate a pricing request to another device and process the pricing response. I don't think it would get used too much since the ESP is supposed to be the provider of pricing info, not a consumer of it. That's probably why it's optional on the client side.

For the in-premise display device, this is mostly just an LCD that shows different attributes. The best example of this is that weird refrigerator magnet that was announced by SoCal Edison a while back. It would display the real time pricing of the electricity and (I think) the energy consumption. This device is just a display that dumps attribute info, hence everything is optional and on the client side.

You brought up a good point though. This article was just written as an intro and anyone that wants to get deeper into it should check the Zigbee smart energy spec for themselves. The section that describes Smart Energy devices is not too dense and can provide much more detail. The rest of it is pretty dense and has a lot of protocol, security, and cryptography discussion.
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Richard Hansel. Sweden
A Slightly Non-Technical Introduction to the Zigbee Smart Energy Profile
Feb 20 2010 15:31:39
This thread discusses the Content article: A Slightly Non-Technical Introduction to the Zigbee Smart Energy Profile

We are using Zigbee network (Zigbit Bit Cloude Atmel) for warm water usage measuring based on an Energy Harvesting method. As the building owner want to use one and the same Zigbee network for different metering I m looking for a Zigbee profile standard allowing meters from different factories to be able to join one and the same network. [email protected]
#1784

Akiba
Re:A Slightly Non-Technical Introduction to the Zigbee Smart Energy Profile
Feb 21 2010 11:46:03
I doubt you're going to find it. The Zigbee Smart Energy Profile has pretty heavy security. In the US, you need a certificate from a trusted authority in order to gain access to the network. That would probably be the utility or the encryption library provider. I don't think you can buy an off-the-shelf meter with Zigbee/802.15.4 in it and install it yourself. If the utility installs it, you can be pretty sure that the meter would be on their private network.
#1788


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