Energy Harvesting: A Wireless New World

by Victoria Haykin

In April, the world looked on once again as its leaders convened in New York City for the historic signing of the Paris Climate Agreement, adopted in Paris during the 21st Conference of the Parties. Nevertheless, many questions regarding the Agreement’s implementation remain unanswered, and critics, such as leading climate scientists James Hansen and Piers Forster, argue that it is still too little, too late.

As scientists and politicians continue to debate the efficacy of the Agreement, researchers and engineers are actively seeking to identify cost-effective and easily implemented means by which to assist the global switch from fossil fuels to renewable-energy generation. When it comes to jumpstarting humankind’s divestment from carbon-intensive energy sources, however, no “one-size-fits-all” solution exists.

On a regional basis, each country is better suited to a different method of clean-energy generation. Even then, the unimpeded availability of solar and wind energy, for example, cannot be guaranteed, and long-term storage for widespread distribution remains an issue. New technological developments in the area of small-scale energy harvesting can therefore assist both developed and developing nations in the coming decades as they seek to transition from centralized power generation to distributed energy networks adapted to fit the needs of each consumer.

“Energy harvesting” refers to the process whereby energy sources widely available in the ambient, such as mechanical and electromagnetic energy or thermal gradients, are captured and stored for later use. Energy-harvesting technologies are therefore specifically designed to transfer ambient energy into useable electricity, thereby augmenting the lifetime of a battery or replacing it entirely.

Such devices have long been applied in extremely niche industries, such as space-based technologies, and in certain medical devices where previously high material costs and low device efficiencies were no great cause for concern. In recent years, however, energy-harvesting devices have garnered increased interest from entrepreneurs and policymakers alike. Earlier this year, the Electronic Engineering Times reported that the market for energy-harvesting devices will reach USD 3 billion by 2020 and notes that sectors of application will widen significantly in the coming years.

In 2014, the European Commission’s “Business Innovation Observatory” commissioned a study of energy-harvesting market potential. In addition to corroborating external analyses that market value is expected to increase dramatically over the next five years, the report documents several successful energy-harvesting companies and their products and highlights many of energy harvesting’s numerous benefits.

First and foremost, perhaps, is energy harvesting’s ability to harness and reclaim, in the case of waste heat, ambient energy that would otherwise be lost to the environment. Energy-harvesting devices can therefore enhance the efficiency of industries and households. Energy harvesters can likewise reduce material and installation costs as direct connection to a wall-socket is no longer required, and battery replacement and disposal costs are either minimized or non-existent.

Currently, energy-harvesting technologies are utilized primarily in industry to power Wireless Sensor Networks (WSNs). According to EnOcean, one of Europe’s leading suppliers of energy-harvesting solutions, harvester-powered wireless sensors “enable unlimited data-capturing where cables or batteries fail.” These sensors can then monitor machine performance in harsh or infrequently visited locations and identify malfunctions before they occur.

Slowly but surely WSNs are making their way into the European “Smart Home.” In the household, WSNs can monitor temperature and indoor illumination in order to reduce over-consumption of energy. In the near future, as device efficiencies improve, energy harvesters will also be used to power advanced medical sensor networks that can monitor a patient’s vitals anywhere and at any time. Energy-harvesting technologies will likewise be able to capture and store mechanical energy from laptop keystrokes or the energy from footsteps to power mobile phones for use after the battery has failed or when access to an external power source is limited.

Laurence Kemball-Cook, CEO of UK-based company Pavegen, has already patented floor tiles that convert the mechanical energy of pedestrian footfalls into electricity. Pavegen’s website states that harvested energy can be used to charge mobile devices, power way-finding signage and stoplights, and monitor pedestrian traffic and congestion. In a 2011 interview with CNN, Kemball-Cook acknowledged the role such technology could play in developing countries, providing off-grid power in remote areas and urban slums during blackouts.

In spite of their innumerable benefits, however, energy-harvesting devices have a long way to go before widespread adoption. Even Pavegen’s ground-breaking floor tile currently outputs only 5 Watts from continuous footfalls, hardly enough to power a single LED street light for a mere thirty seconds. Regardless, recent market trends and new R&D initiatives all confirm that it is only a matter of time before wireless harvesting devices overtake and replace their outdated wire- and battery-dependent counterparts.

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