Green PowerWhite Paper
Author: Cam Williams, Strategy Committee Chair, Zigbee Alliance andLead Architect of IoT Connectivity, Schneider Electric
The pain points of “wireless (not wireless)”
Almost all wireless products require wires for power – or they must rely on batteries tofunction. Both options are costly and limit the usefulness of these devices today. When wethink of wireless technology, we often don’t consider the amount of labor, energy, battery
waste and other costs associated with small and large deployments. First, think of a smart
home environment. If there are 60 wireless/IoT products in your home, and each device’sbattery lasts five years, that averages to one battery change a month. If you aren’t home andcan’t change the battery, the device will fail. This makes your home automation system (andyour life) more complicated.

On the commercial side, these pain points and costs can be significant depending on thetype of deployment and scope of coverage. Commercial office space floor layouts change

on average every five years, and having to rewire each time can be a huge cost and resource

drain. Some venues – such as hotel room settings – might include 10+ potential sensors. Eachcomponent will require a battery change at some point.

Batteries constitute one of the most toxic waste streams on Earth. Ethical disposal andrecycling of batteries is costly. Why purchase, transport, install, and dispose of a battery
when the energy already exists where it is needed?
Simplifying power, streamlining design, saving the planet
Technology innovators from around the world have been working together for years

through organizations like the Zigbee Alliance to solve the power obstacles that burden andhinder the potential around the Internet of Things. An open, standardized technology isCopyright© 2016-2017, all rights reserved.

Page 1

Zigbee Green Power | White Paper
available now to support smart devices that don’t require battery changes. It’s called ‘Zigbee
Green Power’ and is already being built into millions of smart devices.

The benefits of this innovative wireless device platform go beyond installation, energy andcost savings: Zigbee Green Power products can be put anywhere, especially in places thatare hard to wire. The more sensors you can put in a controlled space, the better thefeedback and the better the control.

Zigbee Green Power devices are much simpler than full-fledged network devices. They

usually have a lower cost of components, and a lower cost for development. With Zigbee

Green Power devices, you set them and forget them. The network handles the complexity ofrouting messages and keeps the Zigbee Green Power devices connected.
The complete technology
The complete technology is actually a number of technologies combined into one global
standard:••

Energy harvesting capabilities

Ultra-low power RF silicon that uses many orders of magnitude less power than required
for a sleepy or fully networked wireless connection•

An open global standard network technology that saves even more energy by reducing

packet length, round-trips, connection rediscovery, and on-network time for devices that
may be offline for extended periods of time•

An open global standard application layer protocol that supports compressed messages
and limited transactions

Energy harvesting
The energy from dropping a needle to the ground, by cooling a drop of sweat, or a single LED

flash is sufficient to transmit several radio messages. Likewise, a solar cell the size of yourfingertip can provide enough energy to transmit a radio message every minute when exposed
to indoor light – light you can’t even read by. Harvesting energy from local sources like heat,kinetic or light allows the sensors and actuators for automation systems to go where they areneeded without wires, batteries or costly installation.

Copyright © 2016-2017, all rights reserved.

Page 2

Zigbee Green Power | White Paper
Ultra-low-power silicon
Energy harvesting technologies are not new. What is new, and getting better every day, ishighly power-optimized silicon – from a variety of vendors – designed to run on
microamperes of energy. Most power savings come from the silicon’s ability to shut off power

to unused components and optimize power up from a cold start. Further savings comes fromreducing the power for each message transaction.

These chips support IEEE 802.15.4, a mature protocol with a long list of suppliers and morethan one billion units sold as of today. IEEE 802.15.4 was designed for ultra-low-power andconstrained devices. Other technologies, like Wi-Fi and Bluetooth, were not designed forautomation systems, nor low power.
Network integration
The Zigbee mesh network standard runs over IEEE 802.15.4, and green power has been partof Zigbee for more than 10 years. The Zigbee Green Power protocol defines compressed,

secure, and highly optimized message traffic for ultra-low-power devices. It allows thesedevices to send messages, in a reliable way, to destinations in the mesh network that may
be well beyond the range of these ultra-low power devices. The Zigbee network is always
on, and can receive and forward Zigbee Green Power messages at any time.

Mains-powered devices like smart bulbs, smart power outlets, window shades, appliances,etc., serve a dual purpose. Besides their primary functionality of providing light or controlling
power to attached devices, they also serve as routers – forwarding data packets on behalfof other devices in the network. This allows coverage of even large buildings with nosignificant limitations on the number of simultaneously active routers in a network. Local
traffic does not affect the entire network. Instead of using excessive transmit power,

devices that need to talk to each other but are out of direct communication range can rely
on intermediary routers to forward their data.

The mesh structure has additional advantages beyond extending the nominal range

determined by link budget alone. In contrast to simple star networks, which only provide

point-to-point connectivity, mesh networks are resilient to indoor radio propagation effects

Copyright © 2016-2017, all rights reserved.

Page 3

Zigbee Green Power | White Paper– such as multipath fading and local interference – because there are always multiple

redundant paths (routes) in the network should a specific link not (or no longer) be available.
A Zigbee network, including green power devices, is self-organizing and self-healing andquickly adapts to changes in network topology – effectively avoiding a single point offailure. Network topology can change as people walk by, furniture is relocated, and doors
are opened or closed. Because Zigbee networks are self-organizing, there is no need toconsider placement of devices, avoiding any planning overhead.

Once a Zigbee Green Power device is securely commissioned, any mesh device in theZigbee network will forward a green power message to its destination. This amplifies thepower and usefulness of these simple devices and provides a rock-solid reliable solution thatis extremely robust against the hostile effects of indoor radio propagation, potential
bottlenecks, or just some router simply being offline for a while (e.g., a smart bulb
disconnected from mains using a conventional switch).

Zigbee devices do not rely on internet connections to function. Local control is always

possible even if your internet connection is temporarily unavailable. At home, your ZigbeeGreen Power switches can still directly control your shades and lights, even if the internet isgone, or the gateway is offline for whatever reason.
Application layerZigbee Green Power uses Dotdot, the universal language for smart objects. This is the same
application layer as Zigbee, but with a compressed and optimized message structure.

Commissioning and pairing is the same as Zigbee. Simple push button commissioning, orautomatic commissioning when a button is not available, makes it easy to connect lights toswitches, or heaters to thermostats and temperature sensors. Advanced commissioning andpairing using a smart phone or a remote control is also supported.
Mature and sustainable
There are many proprietary solutions on the market with proprietary applications over IEEE
802.15.4 or even lower layers that are proprietary. These are single-company solutions, andCopyright © 2016-2017, all rights reserved.

Page 4

Zigbee Green Power | White Paper
usually only for a single market. What our industry needs today, to realize the full potential

the IoT can offer to us all, is a universal standard for all global sensing and control markets
that supports all kinds of self-powered products.

As an industry consortium of more than 400 member companies from all points on theglobe, the Zigbee Alliance brings together innovative organizations to collaborate andcreate open wireless standards. Zigbee standards enjoy the largest market share of certified

and deployed products in the IoT, numbering in the hundreds of millions. For 15 years, Zigbee
Alliance members – product manufacturers and domain experts – have spent more than
100,000 hours participating in an ongoing rigorous standardization process to develop

consensus, resolve conflicts and continue to evolve the network and application layer sothat interoperability and backwards compatibility are enforced. Many of the device andobject models have already gone through many iterations of updates and enhancements –and Zigbee Green Power is part of this investment, which includes test tools, certified test
houses, and many silicon and stack providers. This broad and deep market of suppliersmeans there will always be silicon and stack vendors to upgrade your solutions.

The non-negotiable rule in the Zigbee Alliance is interoperability and backwards

compatibility. This means that your deployed Zigbee Green Power products will still beinteroperable in 20 years.
Simple and secure
Where wireless mesh nodes are typically equipped with at least 256K bytes of program and16K bytes of data, a Zigbee Green Power device typically needs less than 32K for theprogram and 1K for data. Because Zigbee Green Power devices are not directly exposed to
the wider internet, they are inherently protected against some of the more challenging

internet security concerns, including Distributed Denial-of-Service (DDoS) attacks. Even oneway simplex devices are secure with a random factory security key. Bi-directional devices

are able to store a generated key from the network, that is different from the network key,
thus adding another layer of security for the application.

Copyright © 2016-2017, all rights reserved.

Page 5

Zigbee Green Power | White Paper
Details on power savings
The amount of energy required for message transmission is also a substantial part of theoverall power consumption. This directly affects the lifetime of battery-powered devices
and thereby the user experience.

A single Zigbee mesh network transmission takes as little as 500uJ of energy. Zigbee GreenPower technology reduces this by factor 5 or more in many standard use cases. Transmissionof a green power message, identifying the status of a light switch, can be accomplishedusing as little as 50uJ of energy. This outstanding level of efficiency enables using the kinetic
energy of the button press itself to power Green Power radio transmissions. This makes itpractical for energy harvesting wireless switch products. These are fully maintenance-freeand can therefore be deployed into almost any environment.
A simplified wireless experience
Zigbee Green Power is a device platform for applications that monitor and control our home
to make sure it is comfortable and safe for our loved ones. Advanced control and innovative
application are only possible when there is a reliable and integrated sensing and control

network in the home. Zigbee Green Power does this for a low cost, without any effect on
your electric bill, except for the savings realized by running your home more efficiently. It

also does this with the added benefit of being environmentally friendly and progressive as
our connected culture evolves toward a battery-less, simplified wireless experience.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(SIDEBAR: Real use cases)
The following use cases and devices described below represent actual products being usedby Zigbee Green Power customers today.
•Leveraging Self Power: Kinetically powered generic switch sensors can be integrated

directly into products, like light switches, doors, desk drawers, windows and window
handles. They generate energy solely from the user’s normal, everyday hand

movements of pressing a button, opening something, or rotating a handle – and they
Copyright © 2016-2017, all rights reserved.

Page 6

Zigbee Green Power | White Paper
work for the entire lifetime of the product. These sensors can automatically control
lighting and ventilation, or alert the user about unexpected conditions such as theposition of a window latch or intrusion. There is virtually no limit to the number ofapplication use cases for user-operated mechanical products.
•Smart Breakers: Circuit breakers have a constrained and standard form factor. Making

a smart breaker by converting and using the live mains AC power is not alwayspossible because of limited space. By harvesting the energy flowing through thebreaker, it isolates the breaker logic, takes less space, and is less costly to produce.
Smart circuit breakers monitor energy use and can detect uncharacteristic
consumption which can lead to equipment failure.
•Industrial Connections: In the industrial space, on assembly line fabrication machines,

vibration, movement and other factors make wiring difficult and costly. Being able toplace a wireless button in an effective location for the operator of the machine, isimportant, especially when safety is critical – thus, the case for a completely electrokinetic industrial switch that you can place anywhere. It does not need a battery orwires of any kind.
•Independent Living Support: Peace of mind is a key promise of the smart home and is

especially important for elderly people that might need assistance in their daily life.
The above devices and specialized sensors can make life easier for seniors, and for
those that care for them. Such specialized sensors can be installed in mattresses(detecting if a person leaves the bed), in floors (detecting movement and providing

visual guidance), or as a wearable. These products may help people stay in their own
home for 5 – 10 years longer than would be possible without them. Cloudconnectivity and analytics can alert care givers of exceptional situations and patterns.
Absolute reliability, without battery changes, is a key requirement for this application.
The combination of the robust Zigbee mesh network with the ultra-low-power

requirements of Zigbee Green Power provides the basis to meet these requirements.

Copyright © 2016-2017, all rights reserved.

Page 7