How much power is there?
State-of-the-art and 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.
Ambient energy sources include light, heat differentials, vibrating beams, transmitted RF signals, or just about any other source that can produce an electrical charge through a transducer. Table 1
below illustrates the amount of energy that can be produced from different energy sources.
Table 1: Energy sources and the amount of energy they can produce
There are a plethora of applications where these power levels make sense for a system deployment. Here are just a few examples:
1) Aircraft corrosion sensors
2) Auto dimming windows
3) Bridge monitors
4) Building automation
5) Electricity usage meters
6) Gas sensors
7) Health monitors
8) HVAC controls
9) Light switches
10) Remote pipeline monitors
12) Water meters
Opportunities for energy harvesting for use in Green Power alternative energies are abundant and plentiful. An excellent example of these opportunities is presented by the market for solar-powered electronic devices. It continues to grow as companies look for ways to reduce energy consumption. Consider smart meters for instance. These are deployed on the smart grid and would like to be powered by an ambient energy source in order to reduce operating energy costs. And one viable and abundant source of energy comes from solar power. However, because solar power is variable and unreliable, nearly all solar-powered devices feature rechargeable batteries. Thus, an important goal would be to extract as much solar power as possible to charge these batteries quickly and to maintain their state of charge for use as an energy source when solar power is not available.
Conversely, if smart meters used batteries as their primary power sources, then the power conversion and management electronics would need to have very low quiescent currents in a standby mode in order to extend battery life. Linear Technology offers a broad range of ICs, which have quiescent current levels typically less than 25uA.
About the author:
Tony Armstrong is director of product marketing, Power Products, Linear Technology Corporation
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