In time of increase of energy consumption and pollution of environment, many efforts are being made to switch to green energy sources. These sources are all around us, they just need to be harvested.
Most people instantly think about solar energy. It is a good energy source, but has some disadvantages. It gives power only during day time, and it depends on whether there will be sunlight or not. In some specific applications this could be a problem. For example if you need sensor network inside cave, solar energy is not an option.
Great trend today is development of wearable electronics. Future predictions say that in few decades, or less we will be all wearing small sensor network all over our body. In this way we will be constantly monitoring our health and many other parameters.
For these applications solar energy is also not an option, since we are constantly changing our location. The solution is very simple - we could use our body heat to produce power supply for electronics.
This kind of energy is heating up air around us and is not being used for any purpose. Concept is very simple, and it is possible to implement it already today!
Thanks to our dear friend Francesca and Newark Electronics/ Element 14 we have obtained ECT 310 which is a low-cost ultra-low-voltage DC/DC converter for powering battery-less modules by Thermal Energy.
All you need is one low-cost Peltier element and ECT 310. When temperature difference of few degrees Celsius is obtained between two sides of Peltier element, it generates very small voltage on its connector. Normally these components are used to generate temperature difference in its sides when power supply is connected to it, but what is great about Peltier element is that this process also works in reverse direction. Make sure you read article about Peltier element and check out cool video about experiment we made.
This generated voltage on Peltier element is very low (less than 200mV) and cannot be used for powering up any microcontroller. For this purpose we need to use voltage step-up converter (boost converter). Unfortunately common boost converters cannot work with such small voltages at their inputs. This is where ECT 310 shows its superiority. ECT 310 operation starts at typically 20 mV relating to a 2 Kelvin temperature difference at a standard low-cost Peltier element. This is very small temperature difference that can be found almost everywhere.
Here are just few ideas: body heat vs. surrounding air temperature, temperature inside soil vs. temperature above ground, temperature inside house vs. outside temperature, temperature of water vs. temperature of air above it… These are just few examples, but as you can see potential thermal energy harvesting sources are all around us.
Currently power supplies for these applications are not very powerful. One that we used can give you just few hundreds of micro watts, but this is enough for many applications. Sensor nodes are usually extremely low power, and we do not have to use this energy all the time continually. We can collect energy in small battery or better yet one miniature supercapacitor for two minutes, and then use it all in one second for measurement and sending measured data to central unit for further processing and display.
Make sure you check out ECT310 performance test.
Special tnx to http://www.newark.com/ for their contribution for this article
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