IoT Hacks #2: Solar-powered sensors in IoT devices

Today we will focus on a specific example of how to obtain energy. We will tell you how to get extra energy for an intelligent, battery-powered IoT sensor which is responsible for bluetooth communication, temperature and pressure measurement.

Energy harvesting — sources of obtaining energy

First, a reminder of what energy harvesting is. This concept covers various types of solutions that enable us to obtain energy from the surrounding environment. As it turns out, there are many sources of energy:

Each of these solutions has its advantages and disadvantages, and not all solutions work everywhere.

You can find more information on this in the first article of the IoT Hacks series.
The use of alternative energy sources in (inherently energy efficient) battery-powered devices makes them maintenance-free. Moreover, it also allows you to implement new features.

An example of powering the IoT sensor with solar energy

The most efficient source of energy is solar energy. Consider the following case scenario. We have a battery-powered IoT smart sensor with components responsible for Bluetooth communication, pressure and temperature measurement.

How much energy will be consumed by the sensor depends on many factors, but for our purposes, let’s assume that communication between the sensor and the data aggregation device (transmitter — receiver) occurs:

• for a 10-second interval,
• within a distance of up to 10m,
• in an office environment.

And so, in such conditions, our smart sensor consumes an average of about 0.1mA, which, using a CR2032 battery under ideal conditions gives us 2000 hours of work time. Using a small solar panel with an area of ​​​​about 7 cm x 7 cm, on which light shines with an intensity of 1000 lx, in about 80 minutes we can accumulate an average of 1.7 J of energy. This power allows the device to operate for about 76 minutes (with an average current consumption of 0.1mA).

So the good news is that for every 80 minutes of device activity, we get an extra 76 “free” minutes. Notice that the amount of energy expended is roughly equal to the amount of energy produced. As a result, our equipment is almost completely autonomous!

Of course, as we all know, in the real world the light intensity is unstable, and at night in offices, the lights do not stay on, so during this time, the system has to draw energy from the battery.

However, if we estimate that the workplace will be occupied for 16 hours each day, contributing to the appropriate light intensity, our system will run for free for 2/3 of the day, giving it a working time of 6000 hours on a single battery!

Summing it up

All of the aforementioned evidence makes it quite evident that power harvesting has the potential to change our systems. Therefore, it is definitely worthwhile to take use of the technical advancements that our modern civilization offers. So, the question that must be asked is: what are you going to do about it?

If you have any questions about extending the battery life of your Internet of Things device, or if you need a technological partner to build a custom IoT solution — drop us a line and schedule a free consultation.

We have successfully completed several projects that required energy harvesting. We will be happy to provide you with advice on how to to do it.