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Emerald Group Publishing Limited
Copyright © 2001, MCB UP Limited
Batteries not included
Batteries not included
The theme of this issue is "Energy conversion/transduction" and represents a small but significant departure from our normal fare.
These days sensors are being applied in places that even just a few years ago would have been considered impossible or impractical. Many are remote or located in hazardous or hard-to-get-at environments and this implies difficulties associated with the powering of the devices themselves and the communication of the resultant data.
If the sensor can obtain its power from the very environment that it has been positioned to monitor, then that is one less problem for the sensor engineer to worry about.
Solar power is likely to see a much broader application in the future, as the problems associated with burning fossil fuels increasingly favour this environmentally friendly option. The good thing about sunlight is that there is a lot of it about, and at about 1kW/m2 it is well worth the effort, although at the moment we can only manage 30 per cent conversion efficiency at best. But, even allowing for the inconvenience of nights, the amount of power is still considerable.
Some areas of the world are clearly more suited than others, and looking outside at the moment with grey skies and snow falling you do need a certain optimism. However, it is not beyond the bounds of possibility that sunlight could be the "oil" of the twenty-first century. There are vast tracts of the world thinly populated with people struggling to make a living that could benefit enormously from the new source of revenue that being able to export solar generated electricity could provide. The areas are so vast that it would not even matter too much if only low efficiencies were obtained and, given that the bulk of solar panels are made from silicon, which by some happy coincidence is the most common element on the planet, then the future is bright indeed.
This journal is not concerned with global electricity generation, so we should perhaps restrict ourselves to sensor application. If you add into the equation the reducing power consumption of sensors as they become ever more miniaturised, and the improved efficiency of radio transmitters, then self-contained solar powered sensors become very attractive, especially when you consider the very high costs associated with laying cables to inaccessible locations.
Almost any environment in which some change is occurring has the ability to power a sensor. This energy can take many forms. Light can come from the sun or artificial lighting or the process itself if it is hot enough. Mechanical vibrations can be converted directly by piezoelectric films or indirectly by coils moving in a magnetic field.
The possibilities for self-powered sensors are considerable and I consider that this makes the whole area of energy conversion a very worthwhile field for sensor engineers. One of the delights of engineering is when neat solutions present themselves and simplify the processes concerned. What can be more satisfying than a system powered by the very process it was designed to measure? Mr Heisenberg may be uncertain of the merits of such an idea but it sounds good to me.