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 the uncontrolled disposal of poisons (lithium and highly alkaline electrolytes) and the exposure of children to these chemicals, as they are used in everyday items such as toys and disposables like talking gift cards. In industry, replacing the increasingly vast number of batteries is extremely expensive in both labor costs and materials--energy harvesting seems to be the only way forward.
 
Different Priorities
 
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. In the UK, the Freeplay wind-up radios for Third World countries need no battery. (Most wind up torches from East Asia have a battery that stays in for life, but this adds cost and limits life.) Freeplay radios also use photovoltaics.
 
East Asia leads in consumer applications, wristwatches with photovoltaics and electrodynamics being particularly successful, as well as the huge number of calculators, toys and so on with photovoltaics and bicycles with dynamos. Next they will learn how to prevent flat batteries in all the four billion mobile phones worldwide. Many people have two and, in East Asia, replacing them every six months is commonplace.

Much work is also directed towards affordable, compact renewable power for those troublesome laptops. The first offerings are underwhelming. As the  ergonomics are improved, it is interesting that the Massachusetts Institute of Technology One Laptop Per Child project for Africa has concluded that a ripcord is better than a crank for generating the electricity. Another step forward will be tightly rolled photovoltaics for portable electronics that pulls out and springs back as required.
 
The 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 because some energy harvesting devices employ toxic or rare materials subject to price hikes. Most thermoelectrics use bismuth as bismuth telluride. Some proposed alternatives use lead. Most piezoelectrics use lead as lead zirconate titanate. The most efficient, lightest weight solar cells on all those satellites employ arsenic as gallium arsenide, and arsenic may be used as a dopant in nanosilicon inks for photovoltaics.

Other forms of the new photovoltaics variously employ highly corrosive electrolyte dye sensitised solar cells (DSSC). In production, carcinogens are often used to make polymers employed as substrates and as the semiconductor in organic photovoltaics. Cadmium is used as cadmium telluride (CdTe) semiconductor in that form of photovoltaics and it is an element also used in copper indium gallium diselenide photovoltaics. Here it is in the form of cadmium sulfide buffer layers.
 
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. Cadmium telluride photovoltaics, based on by products of zinc and copper mining, uses only 1-2% of the amount of semiconductor used by traditional photovoltaics and its lower resulting cost and better temperature tolerance has already resulted in billions of dollars of orders being placed. The European Commission Joint Research Center concluded, "...CdTe used in PV is in an environmental stable form that does not leak into the environment during normal use or unforeseen accidents, and therefore can be considered the environmental safest current use of cadmium."

First Solar PV Modules constitute one of the safest manners of deploying cadmium mining waste. They are even classified as "waste for recovery" and non-hazardous in accordance with the German Waste Code, European Waste Legislation and U.S. Environmental Protection Agency standards. Indeed, First Solar is able to argue that it binds up toxic waste to replace power stations and batteries and it is therefore doubly environmental. Huge orders from France and the USA have resulted. Arsenic dopant in semiconductors is only at trace levels.