Report
Teaser, summary, work performed and final results
Periodic Reporting for period 1 - NextGEnergy (Next Generation Power Sources for Self-sustainable Devices – Integrated Multi-source Energy Harvesters)
Teaser
In recent years, various energy harvesting techniques have been realised to overcome shortcomings of batteries in terms of lifespan, overall cost-effectiveness and chemically safe electronics. Energy harvesters convert different forms of environmental energies into electricity...
Summary
In recent years, various energy harvesting techniques have been realised to overcome shortcomings of batteries in terms of lifespan, overall cost-effectiveness and chemically safe electronics. Energy harvesters convert different forms of environmental energies into electricity thus making devices self-powered. However, with over a decade’s development, energy harvesters have not been able to overtake batteries yet, although academia and industry are keen to apply it for wide range of emerging IoT solutions with multibillion markets. One of the reasons is that the power level provided by single-source energy harvester, which most research has been focused on, is not high or stable enough.
This project sought solution for this by researching multi-source energy harvesting and developing first known single piece of material able to convert three ambient energy sources to electricity (light, heat fluctuation and kinetic energies). The project generated a breakthrough in the development of self-sustainable devices and other opto-ferroelectric devices. These discoveries are expected to lead further new scientific findings and have significant impact in energy harvesting, IoT and other applications to be applied for smart human societies.
Work performed
Ceramic powders and bulk discs of KBNNO ((K,Ba)(Nb,Ni)O3) and KNBNNO ((K,Na,Ba)(Nb,Ni)O3) have been successfully fabricated using solid-state reaction. The physical properties and microstructure have been characterised. Dielectric, ferroelectric, piezoelectric, pyroelectric and photovoltaic properties of the ceramic samples have been measured. A perovskite-structured photo-ferroelectric composition, (K0.49Na0.49Ba0.02)(Ni0.01Nb0.99)O2.995, has been discovered for the first time ever. Such a composition is able to co-exhibit a narrow band gap and strong ferroelectricity. Conventionally, these two properties were not found to exist simultaneously. The combination of Ni ions and oxygen vacancies has been proved crucial for obtaining narrow band gap and strong ferroelectricity simultaneously. The concentration of the combination of Ni ions and oxygen vacancies should be kept as small as possible, in order to maintain the strong ferroelectricity.
A series of optoelectric and opto-ferroelectric measurements, including the ferroelectric characterisation with illumination, attempt of poling the KNBNNO sample solely by illumination (in absence of an external electric field) and investigation of the influence of polarization on photovoltaic performance have been carried out. A time-dependent, photo-induced domain switching phenomenon has been observed for the first time. Using the KNBNNO, the phenomena of all-optical domain control under illumination, visible-range light-tunable photo-diode/transistor phenomena and opto-electrically tunable photovoltaic properties have also been demonstrated for the first time. As most of the conventional photo-ferroelectrics have wide band gaps, these phenomena were not observed earlier. With the KNBNNO monolithic material, tuning of the electric conductivity independent of ferroelectricity has been achieved, which previously could only be achieved in organic phase-separate blends. Guided by these discoveries, a boost of 5 orders of magnitude in the photovoltaic output power and energy conversion efficiency has been achieved via optical and electrical control of ferroelectric domains in an energy harvesting circuit.
KBNNO and KNBNNO thick-films have been made via laser machining. The thick-films have been attached on stainless steel substrates providing cantilever-structured multi-source energy harvesters. A comprehensive evaluation system has been built, consisting of vibration, heat and light sources as well as data acquisition equipment. The fabricated multi-source energy harvesters have been tested with individual and multiple energy sources. The influence of strain on photovoltaic performance has also been investigated. Neither recognisable effect of strain on photovoltaic output nor degrade between different energy conversion schemes has been observed. Therefore, the KNBNNO ceramics have been proven to be able to simultaneously convert kinetic (e.g. vibration), thermal (e.g. temperature fluctuation) and solar (visible light) energy into electricity. This makes the KNBNNO truly feasible for multi-source energy harvesting applications based on only one piece of material. Such a route is fundamentally new compared to the conventional approaches or even recently developed hybrid energy harvesters.
In terms of the exploitation, the research results obtained in this project has gained many opportunities for both further scientific study and industrial application. Based on the results, two other research proposals which are competitive in higher-level international or national research funding applications have been drafted. The results will also be developed to commercial energy harvesting solutions with industrial partners focusing on smart wearable devices and/or smart infrastructures.
Final results
The outcomes of the project, including publications, scientific achievements and personal development of the Researcher, have gone well beyond the expectation in the proposal.
The dissemination of the research results was doubled from the expectations. By the end of this project, 4 papers have been published, 2 of which are on a top-level journal (Advanced Materials) and the others on leading journals in the field (Applied Physics Letter and Ceramics International). Another 4 manuscripts have been submitted, one of which is very likely to be on a top-level journal while the others are likely to be on leading journals in the field. In addition, 2 manuscripts are to be drafted. The number of finally published papers with the project funding may reach up to 10, of which half are considered ground-breaking and the others high-quality. Only 2-4 ground-breaking papers were planned in the proposal.
Beside the two public engagement events, an open lecture and a talk on the European Researcher’s Night, the results of the project have reached the general public by far more extensively and frequently than planned in the proposal. The ground-breaking research has been reported by over 125 online or mainstream media (even in radio channel in Finland) in many languages around the world reaching ~94 million audience and 57 000 share getting known about the project and its results. The Researcher has also been invited to give a talk on a seminar with the topic of Energy Efficient Design in September organised by IEEE and IOP (two of the world’s largest research communities). The talk will be based on the results of the project and will be delivered to the wide public once again.
By the end of this project, the Researcher has attended 7 international conferences with 4 invited talks and 2 as organisers and session chairs. This is well beyond the expected 3 international conferences. All of these 7 conferences are either established or well recognised in the field. An internal seminar has also been organised according to the proposal. In addition, the Researcher was just invited to give a talk on the 2nd Energy Harvesting Society Meeting in USA. This society is extended and developed from a former energy harvesting community, and is now the world’s largest energy harvesting network.
In summary, the project has been implemented above expectations. All the expected impacts and more have been achieved.