If our future is to have a house increasingly full of sensors and tools that automate the behavior of the lighting, heating, cooling and water distribution system, we must understand that this population does not occur with zero balance in terms of energy and that often, due For example, each light that becomes smart to reduce consumption corresponds to a constantly on wireless radio which represents a fixed consumption.
For this reason, while being able to manage any type of communication between device and gateway via Wi-Fi, the smartest and most complex home automation systems resort to less voracious wireless transmission protocols of energy resources such as Zigbee, Z-wave, Bluetooth, etc. that do not have the need to manage continuous data streams to and from the router and do not crowd its ports by entering the communication traffic with our smartphone, smartwatch, smartTV etc etc ..
In reality, the protocol historically less expensive in terms of energy in the history of modern home automation was ed Enocean but some initial device management problems within complex systems with IP and licensing costs have slowed its spread: Enocean devices were among the first to support what is called Energy Harvesting and that is the possibility of collecting energy from the environment to do without batteries and continuous power.
Enocean today, while not giving up on spreading its products in many unique ways, has made its experience available to other protocols for projects that stand out for their high level of sustainability: let's see how.
How Energy Harvesting is achieved
The trick to obtaining energy from the environment is to collect not only the potential of the sun's rays as it can happen with very small photovoltaic panels placed in correspondence with the sensors (we have been using them for some time in calculators, in garden lamps and they have already been found in some Enocean sensors) but also to capitalize on the temperature delta with micro-generators that exploit thermal gradients: this results in thermo-electric generators at very low voltage. Then there is the possibility of exploiting the electromagnetic emissions that can be collected by a sensor a bit like the external power supply of the RFID identifiers.
Finally, and certainly the simplest system for collecting energy for switches and mechanically operated devices, the mechanical motion itself can be converted with piezoelectric crystals which under deformation generate small electrical potentials capable of feeding low absorption circuits (see the Tap Philips Hue).
And what happens in many of these small objects, sensors, switches that populate our home more and more smart: their evolution will lead on the one hand to require less and less energy and on the other to exploit the energy potential of the elements and fields in which they are immersed.
Zigbee and Green Power 1.1
If unfortunately Enocean alone has found it difficult to become a widespread commercial protocol (but has interesting uses in the professional field in different European countries), the same cannot be said of Zigbee which, although with some effort from the point of view of agreement on the rules by of the different actors (unlike Z-wave here there is not a single manufacturer of the main chip) is certainly establishing itself among the most used low-consumption protocols thanks to the tide of manufacturers in play and the enormous impact that Philips had and has with the its Hue series followed by Osram and the introduction of new home automation hub manufacturers such as Amazon who have introduced Echo Plus and Echo shows directly compatible with Zigbee.
As we said at the beginning, Zigbee was already born as a low consumption communication protocol: the aim is to change the battery as little as possible in the sensors that you place around the house and that cannot be connected to the electrical network: presence sensors, opening the window, lighting sensors, temperature, atmospheric pressure etc. Changing the battery is certainly one of the most uncomfortable operations to carry out, especially if you have a heavily sensorized home.
Here then that the Zigbee Alliance in mid-2018 has developed, with the collaboration of Enocean, a new standard called Green Power 1.1 that allows you to produce electrical switches that do not require the use of any battery.In reality, behind this step forward is the collaboration of Enocean which has made its Know How available to both the Zigbee Alliance and Bluetooth SIG.
The energy required to manually operate the switch is collected and used instantly to transmit the data to the device that must receive them: a lamp, a gateway that manages the scenes, a shutter closing system connected to the electricity network etc.
If on the one hand for GreenPower 1.1 we worked on the power supply with Energy Harvesting technologies, on the other hand we studied a lesser passage of data to reduce consumption as much as possible and this was achieved in three ways:
– Normal Zigbee devices are based on 64-bit MAC addresses, Green Power uses 32-bit Source ID addresses that identify the devices
– Green Power 1.1 uses some cross-layer optimizations to avoid overloading the package structure. For example, it combines reports from different clusters within a single package.
– Green Power 1.1 divides the functionality of the devices compatible with the infrastructure nodes in an asymmetrical way. The devices are kept as simple as possible while the intelligence required for routing is downloaded to the support infrastructure (Zigbee 3.0 routing devices) and this reduces the size of the necessary packet headers.
Returning to the individual devices: as we have seen the small mechanical actuation of the switchers capable of providing the reduced electrical power to manage the transmission.
Friends of Hue the first commercial application of wide impact
The first practical application of great commercial impact certainly that of the switches that are part of the Friends of Hue system shown to the public in autumn 2018: many civil series manufacturers all over the world have joined the program and have been able, since the end of 2018, to offer to the public smart switches that do not need to be connected to the electricity network and that do not need batteries to operate.
On the other side they will have a Philips Hub based on Zigbee and lamps (up to 50) for outdoors and indoors with which to communicate to manage not only the switching on or off or even the fine adjustment of the intensity of a single lamp but also the manual activation of a complex lighting scene or (through additional systems such as Homekit) of scenarios involving other types of devices (such as thermostats, roller shutters, opening windows, water and gas supply etc).
The technology with the switches are branded carries in some cases the Enocean brand and in some cases the generic Zigbee.
In factthe savings in terms of sustainability with a switch equipped with Energy Harvesting are as follows
- The switch does not require connection with copper wires, holes in the wall, energy necessary to obtain wires, to cut plasterboard or brick and reconstruct the plaster of both the box (saving in the plastic for the box) and the wall traces
- No need to buy batteries and no need to think about their supply and disposal
- No energy is required from the network to manage the internal radio that transmits the data
- The intelligent use of the connected lamps, the possibility of automatic shutdown or ignition in the case of the only indirect presence of the most general automation or "home automation" of the house that the simplicity of installing a switch with energy harvesting makes it more immediate.
A first example of a switch with Energy Harvesting with wide commercial diffusion on the Italian market is that of Smart control by Vimar, part of the Friends of Hue series. We talk about it on this macitynet.it page.