Do we need to build nuclear power stations to cope with the IoT Energy demand? – Part One
Bettina Rubek Slater, Pycom
As we well know, world leaders are working on managing climate change and are negotiating hard to forge treaties that reduce carbon emissions. However, as the IoT revolution kicks in the effort going into protecting the planet, may actually be counter productive if we need more energy to drive the connected living we aspire to, write Abilio Marques, a senior software engineer, and Bettina Rubek Slater, the chief operating and chief marketing officer of Pycom.Some proponents think that the power we will need to keep our smart cities smart will take energy on a nuclear scale. But is that really true? Over the last few months we’ve been assessing the evidence and the made some basic calculations that will alter the course of how we plan and consume energy in an IoT world.
What does the future look like?
The predictions range from 22 billion and 200 billion connected smart things by 2020. In the very near future it’s important that as an IoT industry we take a moment to understand what it means to be responsible connected-thing manufacturers and service providers. What does our future energy usage look like and how can we influence it positively?
So, let’s take a look at some basics.
Today
Approximately five billion machine-to-machine related devices are already connected to the internet today. Two basic devices that we now take for granted are the standard Wi-Fi router and the smartphone.
An average Wi-Fi router will use around 6Wh – that’s 6 Watts per hour. If it stays connected 24×7, by the end of the year it will have used around 53kW.
A regular smartphone with a 7.5W battery will draw around 8W per charge. That’ll round up to a total of 3kW per year if you flat discharge the battery every day.
That being said and for reference, the modem found in IoT devices will typically use less energy, as there is no screen. They are also not in constant use, perhaps only receiving or sending updates a few seconds a day. The consumption when applied in IoT would therefore be closer to a standby consumption of the router and the mobile.
But it all depends
Even when the previous examples show two power hungry devices, it’s easy to spot that on average, a regular mobile phone – as opposed to a smartphone) – will use a lot less energy (around 0.3 Wh). This tells us that devices are not created equally. It all depends on the application and the technology used.
If you own a smartphone, you may have noticed that the longest time the screen is on, the less the battery will last. If you turn the screen on for six minutes at a time every hour, that you’ve effectively kept it on 10% of the time. If you increase that to 12 minutes every hour, you’ve kept it on 20% of the time and so on. Now, if on the other hand you keep it on for 30 minutes, but this time only every 10 hours, you’ll only have kept it on for 5%. This concept is called duty cycle, and is really important when it comes to calculating IoT power consumption. I’m sure the physicist in you, will like to know that this is defined by:
D = T / P * 100%, where T is the “on” time, and P is the period of the signal (the time between repetitions)
So if you keep your screen on all the time, you’ll get a 100% duty cycle, and if you never ever use it, you’ll get 0%.
And the energy consumption is directly proportional to that value. So of course, this means your mobile phone battery will last forever if you never turn the screen on? You know it doesn’t. The reason? There are other things happening even when the screen off, like receiving and processing notifications from the different apps you have installed, and being ready to ring when someone calls.
So this idle energy consumption is important too. It will also rule how much your battery will last. In the end, the total average power consumption (known as Pavg) on any device could be calculated using the following sum:
Power when on or ‘Pon’ multiplied by the duty cycle ‘D’ / 100%, plus the power consumption when the device is idle or ‘Pidle’ multiplied by (1-Duty cycle) / 100%.
Now you have this you can start to make some genuine assessments as to how much power we really need. This will be explored further in the second part of this blog.