Free energy is all around, but how do you get it?
There is plenty of “free” ambient energy all around us; however, harnessing it as an alternative power source is not for free. The conventional approach for energy harvesting has been through solar panels and wind generators.
However, new harvesting tools allow us to produce electrical energy from a wide variety of ambient sources, including light, heat differentials, vibrating beams, transmitted RF signals, or just about any other source that can produce an electrical charge through a transducer.
For instance, thermoelectric generators convert heat to electricity, piezo elements convert mechanical vibration, photovoltaics convert sunlight (or any photon source) and galvanism converts energy from moisture. This makes it possible to power remote sensors, or to charge a storage device such as supercapacitors or thin film batteries, so that a microprocessor, sensor and transceiver can be powered from a remote location without the need for a wired power source
Off-the-shelf energy harvesting technologies, for example in vibration energy harvesting and indoor photovoltaic cells, yield power levels in the order of milliwatts under typical operating conditions.
While such power levels may appear restrictive, the operation of harvesting elements over a number of years can mean that the technologies are broadly comparable to long-life primary batteries, both in terms of energy provision and the cost per energy unit provided.
Furthermore, systems incorporating energy harvesting will typically be capable of recharging after depletion, something that systems powered by primary batteries cannot do. Nevertheless, most implementations will use an ambient energy source as the primary power source, but will supplement it with a primary battery that can be switched in if the ambient energy source goes away or is disrupted.
As a result, any products targeted toward green energy or energy harvesting will see growth opportunities during the next decade. Energy costs and environmental concerns have resulted in a focus on power optimisation for a broad range of applications.
Furthermore, the current crop of energy-efficient conversion ICs enable customers to convert power more efficiently, consume less power and extend battery life.
All of these factors enable designers to develop and implement WSNs without wires and in some case, without batteries. This will truly make use of the abundant “free” ambient energy around us.
Author is Tony Armstrong, director of product marketing power products at Linear Technology