It seems obvious; energy harvesting is intermittent, so combine different types to make it continuous and therefore much more useful.
Coordinated multi-mode energy harvesting (EH) could largely overcome intermittency and increase power density and cost-effectiveness with less or no energy storage required. Indeed we see it in a crude way with the combination of photovoltaics and wind turbines on both road furniture and seagoing boats. Add to that buoys at sea and autonomous underwater vehicles that garner both wave and solar power. Again one works in bad weather and the other in good.
So what became of the dream of something the size of a cigarette packet providing three or four types of energy harvesting for general use? It has proved tougher to do as a commercial offering than had at first been realised. Acceptable broadband piezoelectric vibration harvesters have not been forthcoming for mass usage. Thermoelectrics are also designed to purpose rather than for general-purpose use in a universal product. For providing the most useful power, photovoltaics need to have greater area than that available on a cigarette-sized package, so it’s back to the drawing board.
Indeed, charging mobile phones on the move now looks like succeeding not with energy harvesting but with ubiquitous contactless charging stations to the widely adopted Qi standards. That is planned to be embedded in Starbucks tables and recently started to appear in new cars for charging mobile phones and the like.
Multi-mode energy harvesting is not yet getting major commercial traction but the need is so strong and it is so feasible that success surely awaits. For example, the different modes can work alternately as with an electric car charging its battery by photovoltaics and wind turbine when parked, by energy harvesting shock absorbers and photovoltaics when moving along and by electrodynamic regenerative braking when slowing down. Sometimes these can be optimally matched. Electrodynamic energy harvesting is the most fertile technological option in its scope, such as energy range, versatility, price and options for shape. The variations are proliferating.
The end game for multi-mode harvesting in one package could be smart materials exhibiting several EH properties. The University of Bolton in the UK is developing flexible plastic film layered to create hybrid piezo photovoltaic harvesting (HPP). This can blend into many forms of structure such as curtains, airships and sails.
Upping the power ante
High-power energy harvesting (HPEH) is the clean part of off-grid renewable energy and its main potential lies at kilowatts to megawatts. Few things are genuinely new in this world but newly important aspects of energy harvesting really matter. Unfortunately, they are expressed in unfamiliar acronyms. You have to know your TARA from your RAS and your EIV from your BIPV. But it is worth the effort, as this next round of technological advance will be transformative for all of us.
Over 30 years ago we were correctly told that computing would disappear into the fabric of society: now we see electricity production doing the same. Structural electronics, as explained in the IDTechEx report, ‘Structural Electronics 2015-2025’, is replacing components-in-a-box with smart load-bearing materials taking no extra space at all because they replace dumb structures.
For example, following a solar boat and a solar plane going around the world, many boats, aircraft and land vehicles are being offered or proposed with ‘unlimited’ speeds of up to 70 km/h – providing the sun is out. Their solar cells replace dumb structure just as they do in the new building integrated photovoltaics (BIPV). Both will benefit even further from conformal, rollable and spray-on solar panels now being developed.
Solar power is beginning to be complemented in many ways, by replacing brakes in a vehicle with kinetic energy recovery systems (KERS), conventional shock absorbers with energy harvesting ones and with regenerative active suspension (RAS) for example. In addition, the external capture of ambient energy just got cleverer with boats creating electricity by capturing wave, tide and wind power, not just sunshine.
Affordable energy independent vehicles (EIV) will run in bad weather and good, at night and in the day. That is of profound impact on all of us, including the Third World and remote regions. This technology even feeds back into modernising the traditional vehicle with torque assist reversing alternators (TARA), thermoelectrics on the exhaust and RAS.
In addition, whether it is houses, vehicles or other facilities, the possibilities are being widened greatly by old technologies reinvented, such as wind turbines potentially replaced by kites, tethered drones and turbines in balloons that use one tenth of the materials while accessing the much stronger and more consistent winds just above the noisy and expensive rotating blades we see today. Such technologies can together be classified as airborne wind energy (AWE).
IDTechEx analyst, Franco Gonzalez comments, “Of the host of new HPEH technologies now arriving, we like the idea of magnetostrictive 1 MW wave power from Oscilla Power with virtually no moving parts. If they pull that off it will be in sharp contrast to what goes on in most electrodynamic wave power devices. We are a bit sceptical that the work on triboelectric power from car tyres will produce viable energy at the 500 Watt level. However, reversing propellers for boats and small ships already capture tide when moored or in motion when under sail, giving up to 3 kW. Optimising designs and compromises will certainly take that further.
“The miracles with woven smart fibre planned for sails, kites, balloons and so on will take longer. They include combined piezo and solar fibre from the University of Bolton in the UK and the combined solar harvesting and supercapacitor storage in the fibres being developed by the European Powerweave project. They are impressive nonetheless. We travel intensively to learn and interpret what is going on but it is a sheer pleasure to see such progress. Unusually, Europe is doing most in many aspects of HPEH, from AWE to KERS, but remarkable advances are being announced all over the world”.
The table lists some of the energy harvesting technologies and the interesting companies, power targets and systems involved.
For more information visit www.IDTechEx.com
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