Can we measure the impact of renewable energy harvesting, asks Prof. Markys Cain? Reports show how scavenging wasted energy will boost industry and create a multibillion pound market. To ensure this happens, urgent agreement is needed on measurement standards and a new European project has been established to achieve this
Energy harvesting – also known as power harvesting or renewable energy scavenging – is the process of capturing ambient energy and converting it into renewable electricity to drive small autonomous electronic, electrical and combined devices. Basically, energy harvesting gathers energy that would otherwise be lost as heat, light, sound or vibration – and puts it to use.
Why is creating this type of renewable energy important?
Good news for those who are interested in renewable energy. Energy harvesting technology is on the up. At present there are approximately 500 organisations developing energy harvesting or applying this means of renewable energy. All round Europe, manufacturers are developing tiny devices to be fitted inside industrial machinery to capture lost heat and reduce energy wastage.
Whilst they won’t solve the looming energy crisis or convince those to switch to renewable energy, they will make everyday and industrial processes more efficient and as demand increases and new markets open up, their production could deliver economic growth across the continent. Already, trials have delivered positive results in applications from thermoelectric generators fitted to heavy duty lorries to condition monitoring sensors in oil fields.
Energy harvesting in buildings
More than a third of the energy we consume is related to buildings. In the UK alone this results in approximately half of the nation’s CO2 being produced from energy in buildings.
The EnOcean Alliance is a consortium of more than 70 companies looking to address this. It is working to develop and promote self-powered wireless monitoring and control systems for sustainable buildings by formalising the interoperable wireless standard. The EnOcean Alliance has the largest installed base of field-proven wireless building automation networks in the world.
Through this EnOcean has installed 4,200 wireless and battery-less light switches, occupancy sensors and daylight sensors in a new building construction in Madrid. These are powered by energy harvesters and embedded in the building. This saved 40 percent of lighting energy costs (by automatically controlling the lighting in the building) 20 miles in cabling, 42,000 batteries (over 25 years) and most of the cost of retrofitting.
Similarly, the Lightning Switch piezoelectric wireless switch technology from US-based company, PulseSwitch Systems can deliver significant savings in construction costs. In one case, a 71,000-square-foot industrial facility needed 21 banks of lighting with associated controls. The contractor originally bid $63,000, based mostly on the labour and overhead costs of installing more than a mile of conduit and switch wire. The contractor then bid again and won, using various Lightning products to complete the job for $10,000 for materials and 10 hours’ labour. This technology has applications in re-modelling 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 product and saved the customer hundreds of dollars, time, and the hassle of breaking into the drywall and repairing the wall.’
The future
Analysts have forecast multi-billion pound market growth in energy harvesting over the next decade and a whole range of new applications. An IDTechEx report predicted the global market would grow from $605m in 2010 to $4.4bn by 2020.
While these numbers are impressive, there are important considerations to be made. Talk to developers and investors in the energy harvesting community and there is one major part of the jigsaw missing – an agreed set of measurement standards to gauge potential savings and compare efficiency.
Measurement infrastructure
The lack of internationally recognised standards prevents the accurate prediction of improved efficiency provided by these devices under different operating conditions. Without this key information, developers are unable to provide meaningful product specifications for commercially available energy harvesting devices and potential markets are forced to buy the products and conduct their own trials – often at great expense and time.
Whilst Europe is currently a world leader in this technology and best placed to take full commercial advantage of its benefits, other regions are catching up and the lack of dialogue between closed pockets of researchers and developers is threatening our position.
It is in this context that the Metrology for Energy Harvesting project was set up last year. Made up of seven European national measurement institutes (NMIs) including the UK’s National Physical Laboratory, it aims to develop traceable (traced back to national standards) measurement methods that reduce duplication and accelerate innovation and competitiveness in energy harvesting.
Within the first year of the project, it has already developed measuring systems for quantifying the electric potential within thermoelectric materials across different temperatures. There are many of these materials, which convert temperature differences into electric potential, available on the market, so NPL has built a system for characterising and comparing the efficiency of each. For piezoelectric harvesting devices, which convert mechanical strain into electric output, the project has developed models to predict power output based on the initial force applied.
The project has also developed an ever expanding industry base of support. This group comprises 30 companies from across Europe involved in construction, automotive, transport, mobile communication, and sensors and instrumentation further highlighting the wide range of uses of energy harvesting devices. Major names such as Fiat, French electronics company, Thales and UK-based Perpetuum, a global leader in vibration energy harvesting, are helping focus direction and inform the development of new standards.
The viability and cost effectiveness of energy harvesting is widely appreciated. However there is also recognition that to take energy harvesting further and fulfil its market potential, there must be a platform for comparing products in various environments before buying them.
This is where the Metrology for Energy Harvesting project will deliver tangible benefits. The project is helping metrology meet the challenge of standardisation, taking into account perspectives from manufacturers, integrators as well as end-users, by defining measurement conditions and qualifying systems and harvesting environments.
Current research
At present, focus is on specific projects within thermoelectric and vibration energy harvesting, but the research is expected to grow with time.
Thermoelectric materials convert wasted heat into electrical energy. Thermoelectricity is regarded as one of the most promising technologies for increasing energy efficiency in industrial processes and automotive applications, which produce a large amount of waste heat. Piezoelectric materials convert electrical energy into a strain (or vice-versa). The best known use of piezoelectricity is for medical ultrasound. Current research in these fields includes:
• The Physikalisch-Technische Bundesanstalt (PTB) in Germany has installed a measuring system to determine the Seebeck coefficient of thermoelectric (TE) materials. PTB is currently testing the system and making improvements such as a calibrated thermometer to ensure that the reference temperature, which is close to the sample temperature, is traceable to National Standards. Once these improvements are complete, the group will start to investigate and characterise different TE materials as candidates for reference materials for Seebeck coefficients in the temperature range 300K–900K.
• France’s Laboratoire National d’Essais has designed first electrostatic energy harvesters based on comb-drive MEMS. The device architecture has been optimised to maximise the electrical power converted from mechanical vibrations in the frequency range 1 kHz to 4 kHz. VHDL (VHSIC hardware description language) simulations on these systems indicate that they are capable of harvesting electrical powers ranging from 6 µW to 60 µW. The harvesters are fabricated through an industrial SOI (silicon on insulator) wafer process and will be distributed to the project partners for full electromechanical characterisations.
• NPL has also undertaken work recently into piezoelectric energy harvesters. These are typically cantilevers with an inertial mass at the end. The base of the cantilever is exited by ambient vibrations and the inertial mass exerts a force on the cantilever which generates a stress in the piezoelectric (yellow). NPL has developed a model that predicts the output of the beam based on the force at the cantilever tip. In order to investigate the effect of the coverage of the beam with piezoelectric elements NPL have made a cantilever with 30 elements along its length, and measured the power output.
Industrial engagement
Achieving this will require expertise and input from all aspects of science and industry, including from leading research institutions on energy capture and storage, material science, and systems engineering as well as metrology. Yet just as importantly will be engagement with European businesses. The technology characterised through the Metrology for Energy Harvesting project has to reflect what industry wants and this requires input from companies, to find out the issues they currently have, and how the project can address them.
Europe is a world leader in energy harvesting R&D, and this project will both keep it there and service the needs of industry across the continent.
Prof Markys Cain is Knowledge Leader at NPL, and an IOP member. To find out more about the Metrology for Energy Harvesting project please contact markys.cain@npl.co.uk
The Metrology for Energy Harvesting project is funded by the European Metrology Research Programme (EMRP) and national metrology research programmes.
