Success of energy harvesting depends on collaboration between industry and academics

A mobile phone charged from your body heat. Pavements that scavenge energy from your footsteps. Less than 10 years ago these were fanciful academic dreams, blue sky ideas floated at university conferences. Today energy harvesting is serious business and an emerging industry potentially worth billions with European developers at the forefront. However, for European companies to develop this market successfully, they must start to embed metrological principles and standards into their products and performance claims, argues Paul Weaver, the UK representative in the EU-funded Metrology for Energy Harvesting Project. Without such standards, the market will not take off.

Green pavement generates electricity (c) Environmentteam.com

Anyone who has had a laptop or PC overheat, watched their old washing machine vibrate across the kitchen floor or burnt their hand changing the oil in their car will know that our daily appliances produce a lot of excess energy.

In fact anything that overheats, shakes, rattles or rolls is a sign that energy, generated at an environmental cost, is being wasted. This is an even bigger issue in industry. Step inside a power station, manufacturing plant or refinery and the first thing that hits you is the heat and noise generated by their machines.

The good news is that much of this free energy might be turned to use. If this were to happen, it would boost European industry, improve its green credentials and create a multibillion market all of its own.

Killer app

In the past decade a race to harvest excess energy has been led by a strong European academic base, which has been in the forefront developing tiny devices that scavenge such waste energy. Known as energy harvesters, they come in a variety of forms. There are two types that have by now made the step up to commercially viable products.

Thermoelectric harvesters, which look like small grey square tiles, often only a couple of centres in diameter, turn temperature differences across their two surfaces into electrical energy. Piezoelectric harvesters, equally small, contain crystals or fibres that generate a small voltage of electrical energy whenever they are mechanically deformed by vibrations or strain.

The principles of harvesting waste energy can be traced right back to the first windmills and waterwheels. However, the origins of modern thermoelectric and piezoelectric harvesters date back to a few academic papers published around 2006. These built on research primarily undertaken in the military, which wanted to reduce the need for military personnel to carry heavy power packs in their equipment. These papers described a near limitless source of free, zero carbon low power energy, which are today being incorporated into all manner of devices.

For example, in cars, where more than 70% of the energy produced by an engine is lost, mostly in the form of heat, prototype thermoelectric generators are being developed by the likes of Volkswagen and BMW to recover some of that heat back from the exhaust to power the electronics of the cars. In 2009, Volkswagen demonstrated a prototype car that gained about 600W from running on a highway, reducing fuel consumption by 5%.

Also in the research stage we have seen prototypes for training equipment that absorbs power from the pounding of a foot, based on a ‘heel-strike generator’, a piezoelectric harvester in the boot heel that generates a battery-charging current when crushed by the wearer's weight. Energy harvesting paving slabs have also been demonstrated at Japanese train stations, harvesting the energy of the crowd’s footsteps to power ticket gates and display systems. There has also been a lot of interest in the replacement of mobile phone batteries with harvesters that scavenge your body heat as you walk, though many of these more headline grabbing applications are still predominantly in the research and development prototype phase.

However, there is one application which above all others is driving academic interest and billions of investment: wireless sensors. It is expected that millions of tiny information gathering sensors will be deployed around the world in the coming decade by academics and industry alike, to continuously

It is expected that millions of tiny information gathering sensors will be deployed around the world in the coming decade by academics and industry alike
monitor everything from the effects of climate change on our oceans to mechanical stress in industrial machinery and the functioning of offshore wind turbines to avoid failures and fractures. Powering these sensors, especially those deployed in hard to reach locations, through batteries, is expensive and often difficult. The potential to attach a tiny energy harvester to each sensor and power it from ambient energy would be a huge improvement. In fact, energy harvesting could give us the power to monitor the world around us continuously and from a large distance.

Common language

With all these applications, it not surprising that we are seeing headline grabbing predictions over the future value of this market. Earlier this year IDTechEx, an independent market researcher specialising in energy harvesting, published its latest Energy Harvesting and Storage Market Forecast, which predicted the value of the energy harvesting market to rise from $0.7 billion in 2012, to over $5 billion by 2022.

There is however, one significant problem, a hurdle which must be overcome in order to realise the true potential of these tiny harvesting machines. At present there is no internationally agreed set of measurement standards or verification tools around energy harvesters. This leaves potential customers, whether they are Rolls Royce manufacturers, power plant owners or climate change scientists, with no common language to gauge the power a harvester could generate in their car engine, power plant or field locality and whether that is sufficient to power their devices.

Without such standards, developers are unable to provide meaningful product specifications for commercially available energy harvesting devices, and customers are forced to conduct their own trials, often at great expense and time. With many of the potential markets for this technology up for grabs, and increasing competition from new developers in Asia and the US, the race is on to provide reliable standards for energy harvesters underpinned by traceable claims around energy output.

It was for this reason that in 2010 the European Commission funded a group of measurement

Timing is of the essence. The next decade will be crucial to realising the potential value of energy harvesting for European industry
scientists and metrology experts from across Europe to investigate the standardisation required to maintain and develop Europe’s position in the energy harvesting market. The Metrology for Energy Harvesting Project brings together seven national research centres in the UK, Germany, France, Italy, Slovenia, Finland, and the Czech Republic. It is the first initiative that is trying to apply the principles of metrology (measurement science) to energy harvesting products and materials.

However as a predominantly academic initiative, it cannot alone achieve the progress required to fulfil the technology potential in energy harvesting. The Project needs significant industrial buy-in and greater collaboration between the measurement community and product developers. This is currently lacking. Hence, project leaders are calling on European developers to work with them to not only verify the potential output of their products but utilise a world leading European metrology community who can help them develop the next generation of high performance harvesters.

Timing is of the essence. The next decade will be crucial to realising the potential value of energy harvesting for European industry. Without metrology, the potential growth of this sector will be severely limited. With it, we can take advantage of the wealth of knowledge and range of interdisciplinary skills held within our national measurement institutes, leap ahead of our competitors, and turn the European energy harvesting sector into a global leader.

 

Dr Paul Weaver leads the National Physical Laboratory's activity as the UK representative in the Metrology for Energy Harvesting Project. The project is part of the European Metrology Research Programme and is jointly funded by the EMRP participating countries within EURAMET and the European Union.