Paybacks from energy harvesting

The IDTechEx report 'Energy Harvesting and Storage for Electronic Devices 2009–2019' identifies potentially significant commercial benefits of energy harvesting for both industrial and consumer markets.

Energy harvesting is the process by which ambient energy is captured, converted into electricity and used to drive small autonomous electronic and electrical devices. Globally, about 500 organisations are developing or applying energy harvesting other than photovoltaics.

As more energy-harvesting products hit the market, we can move forward from the technical issues to look at more commercial considerations such as payback.

Choices

Electrodynamics, piezoelectrics, photovoltaics and thermoelectrics are popular forms of energy harvesting. From the huge temperature differences in engines and exhausts, for example, thermoelectrics can produce watts per cubic centimetre, while piezoelectrics in actuators and vibration harvesters can exhibit 60% efficiency. Electrodynamics and photovoltaics exhibit a good compromise of both parameters.

Huge environmental and cost benefits

As much as 38% of energy is consumed in buildings, so long life and more affordable building controls are the focus of most of the 70+ companies in the EnOcean energy harvesting alliance which provides interoperable wireless sensors and controls that never need a battery. For example, EnOcean installed 4200 wireless and battery-less light switches, occupancy sensors and daylight sensors in a new building in Madrid, Spain. These are powered by energy harvesters and embedded in the building. This installation saved 32 km in cables, 42,000 batteries (projected over 25 years) and most of the cost of retrofitting, while saving 40% of lighting energy costs by automatically controlling the lighting in the building.

In similar applications, the value proposition for the Lightning Switch wireless switch technology from PulseSwitch Systems in the US emphasises the saving in construction costs. In one case, a 6600 m² industrial facility needed 21 banks of lighting with associated control. The contractor originally bid US$63,000 based mostly on the labour and overhead costs of installing more than 1600 m of conduit and switch wire. He then bid again and won, using various Lightning products to complete the job for US$10,000 for materials and 10 hours of labour.

This technology has applications in remodelling and renovation projects, since Lightning Switches — unlike re-wired switches — require no new wires, no demolition, no patching and no re-painting. Dividing walls supporting switches can be moved without rewiring. Another contractor wrote, “We tried your [PulseSwitch] product and saved the customer time, hundreds of dollars and the hassle of breaking into the drywall [plaster] and repairing the wall.”

Long life span

The long life expectancy of these alternatives is now a strong selling point for energy harvesting. Some electrodynamic vibration harvesters have an expected system life of 20 years, while the Lightning Switch piezoelectric light switches mentioned above have no battery and are reported to have a 20-year life span. Suppliers of the EnOcean piezoelectric light switches and allied controllers using various forms of energy harvesting claim a 25-year life, with over 500,000 installed already. A pattern therefore emerges by which the life of energy-harvesting devices without batteries is at least 10 years longer than the life of battery-driven wireless devices and this alone gives valuable paybacks.

Industrial and consumer applications lead the way

In the past, aerospace and military energy harvesting have attracted huge investment, but consumer applications of energy harvesting are rapidly increasing. They will remain dominant with industrial applications coming in to rival them. IDTechEx forecasts huge numbers of energy-harvesting devices to be sold into electronic medical disposables, e-labels, e-packaging and e-posters. Whereas today most calculators have energy harvesting, in future most torches, lanterns, wristwatches, mobile phones and other electronic items sold in billions may have it too.

Key enablers of the next generation

The next generation of energy-harvesting devices will be smaller, lower in cost and have lives exceeding 20 years in many cases. The energy density will improve but there is probably more scope for the efficiency to improve and that will also expand the addressable market. Many devices will be announced that work within the human body without need of further intrusive surgery. Many others will be embedded in apparel. Energy harvesting will power many of the billions of medical disposables needed for self-diagnostics and drug delivery as the demographic timebomb — too many old people — hits.

*Dr Peter Harrop, IDTechEx.