Issue #181 | Feb. 27, 2009 | by Dr. Peter Harrop
The environmental benefits of energy harvesting are proving to be greater and more widespread than originally realised. Most importantly, the runaway use of small batteries is leading to uncontrolled disposal of poisons such as lithium and highly alkaline electrolytes.
In industry, replacing the increasingly vast number of batteries is extremely expensive in both labor cost and materials. Energy harvesting is increasingly the only way forward.
More than ten years of extra life
Energy harvesting is providing at least ten years longer life than batteries used on their own. Indeed, batteries in electronic products rarely last longer than two years and there are many applications where they are thrown away in weeks or months, which is why they hang from the check-out rack at seemingly every store with a cash register.
With 15 to 20 years life frequently offered for all the leading forms of energy harvesting, the environmental savings from less batteries being disposed is considerable. Avoiding recharging batteries every few months also saves on the cost, energy and pollution involved in visiting devices.
North America leads the world in energy harvesting in aerospace and military applications, from piezoelectric vibration harvesting for sensors in helicopters to all those photovoltaic panels on satellites. Europe leads in industrial applications, using thermoelectrics, electrodynamics, photovoltaics and piezoelectrics.
East Asia works with photovoltaics, which will undoubtedly end up preventing dead batteries in the four billion mobile phones worldwide. There, many people have two and replacing them every six months is commonplace. They are also working on affordable, compact, renewable power for those troublesome laptops. The first offerings are underwhelming; but the ergonomics will be improved.
An elephant in the room
Energy harvesting for small electronic and electrical products can clearly become a business of tens of billions of dollars yearly. However, there is an elephant in the room.
The materials contained in some energy harvesting devices employ toxic substances or rare elements subject to price hikes. Most thermoelectrics use bismuth as bismuth telluride. Some proposed alternatives use lead.
The most efficient, lightest weight solar cells employ arsenic as gallium arsenide. Arsenic also may be used for photovoltaics, which also variously employ substances like cadmium as cadmium telluride; lead zirconate titanate; highly corrosive electrolyte dye; copper indium gallium; cadmium sulfide; and other nasty sounding brews. Silver, used in energy harvesting, is both a precious metal and a biocide.
The good news concerning the poisonous elements is that they are so tightly bound in compounds such as cadmium telluride and cadmium selenide that they are highly unlikely to be released in use or disposal. They are also encapsulated.
More development, more growth in usage
Fortunately, there is massive market potential for what is available already, with no risk to humans. And about 500 organisations, half of them academic, have major programs to develop improvements in energy harvesting. In addition, 650 organisations are developing photovoltaics beyond silicon that can be used for both energy harvesting and general production of power.
IDTechEx forecasts that, despite the concerns about certain materials in certain forms of energy harvesting, the consumer applications will remain in the ascendant over the next ten years, even moving to toys, labels and packaging at the end of that period. Industrial, military and aerospace applications will grow, with industrial applications becoming particularly important and widespread from wireless sensor networks to building controls. The number of energy harvesting devices will therefore grow as follows.
This will be assisted by the advent of energy harvesting with more affordable, acceptable materials. For example, in stark contrast to traditional silicon, organic photovoltaics has the advantage of working optimally with only 15 nanometers thickness of semiconductor and it can be printed at high speed, which can keep cost well down. The thinness and flexibility opens up ten times the market potential. It can even turn a broader spectrum of light into electricity than the conventional forms of photovoltaics.
Lifetime is a problem, with barrier layers to extend life being rather expensive as yet. At least they consist of harmless inorganic oxides and nitrides alternating with harmless polymers. This will be solved within a few years with energy harvesting for disposable, low cost products of limited life being feasible in a few years, with little or no use of rare elements and no toxic materials. Use of the new electroactive polymers, zinc oxide and organic piezoelectrics, carbon nanowire semiconductors, harmless compounds as quantum dot semiconductors and other options also promise further safety and environmental dividends.
Dr. Peter Harrop is Chairman of IDTechEx. This topic and others will be addressed at IDTechEx's conference Energy Harvesting and Storage in Cambridge, UK on 3rd - 4th June. www.idtechex.com/eh for more details. IDTechEx has also released a report on this topic, Energy Harvesting and Storage for Electronic Devices 2009-2019. For more on this report, see Energy Harvesting and Storage for Electronic Devices 2009-2019: IDTechEx.
