As a concept, the idea of energy harvesting is hardly new. It comes from many similar ideas about other human needs – like food. Of course it is not feasible that everyone grows their own food because of the shortage of arable land. However, in the case of energy, we can get at least a partial amount of energy from our own backyards.
The good thing about harvesting energy at the small scale is that you can have thousands of energy harvesters in parallel and you can add more of them as and when you see fit. Thus if a household finds it profitable and have the necessary cash or financing options, they can expand the array of harvesters they use. This is quite unlike installing a solar or wind energy harvester on your rooftop.
On a larger scale of a neighborhood, town or city, if these devices become feasible, they can be employed in a number of different places. For example, traffic lights can power themselves, and so can street lights. This would be a significant saving in energy.
Also, since these energy harvesters will be placed usually very near to the place where the energy is being consumed, the transmission losses can be greatly minimized. This is a boon for efficiency and also helps energy become greener.
So how can we harvest energy at this small scale? And what energy can we tap into? Most of the research in this area is being done in tapping solar energy. In fact, at this small scale, it wouldn’t be right to just talk about solar energy – it is tapping into the energy spectrum. For example, a small device placed in the path of car headlights will be able to tap into this energy, though very small. The trick is to use plenty of these so that the total energy can add up.
The way the whole harvesting technique works is by connecting energy collectors in huge numbers in parallel, so that they can together become a significant energy source. This can be done on a large scale if the devices become more efficient. Part of the efficiency of using them comes from reduction of transmission losses, but new research in this area is increasingly showing promise of an efficiency on par with other solar energy harvesting techniques. If this efficiency is achieved, it can be fabricated on a much larger scale, like an energy farm.
Since these energy collectors are small, they can be placed practically anywhere. The Design and Development of Infrared Rectennas for Energy Harvesting, called DARPA works in the infrared region of the energy spectrum and aims to create micron-sized antennas. These are vanishingly small and thus can practically be used to coat a house without any visible difference. The advantages of their small size are all too apparent.
The ability to harvest energy at a small scale empowers homeowners and small businesses that can decide to produce their own energy using convenient methods. In addition, one can expand the array of collectors as and when the need arises. If the price of renewable energy is good, we can see ordinary homeowners using energy harvesting sell it to the grid, so that they can make some money while going green. There is a huge potential if this becomes economically and technologically feasible, which I suspect isn’t very far away.