High Power Energy Harvesting (HPEH) is a term beginning to be used for creation of electricity where it is needed using ambient "free" energy. That zero-pollution, high-energy conversion typically captures light (photovoltaics), heat difference (thermoelectrics and heat pumps) and movement (electrodynamics). Most dramatically it is seen in aircraft flying just on sunshine such as the Solar Impulse traversing the world at up to 80 kph entirely on solar and the faster, smaller Elektra One Solar that has criss-crossed the Alps recently with 500 km range, up to 100kph, 100kg payload using 30% solar. The rest came from its pre-charged 11.5-kWh lithium-ion battery pack. There are plenty of boats and land vehicles that use nothing but sunshine and clearly adding other harvesting modes and improving efficiencies will enable such vehicles to carry heavier payloads for longer and accelerate faster to higher speeds still without ever plugging in or refuelling.
In many countries the AC grid is neglected and trillions of dollars are needed to replace these rusting anachronisms. There is a huge pent up demand for alternatives. The considerable success with ground heat pumps, wind turbines and photovoltaics on buildings reducing grid load is only a beginning. Worries about electric vehicles overloading the grid will be replaced by them not using it at all.
New magic is appearing with extra ways of energy harvesting for static structures not just boats, ships, aircraft and land vehicles. Indeed, static harvesting includes charging those vehicles when they are not in use. It will lead to buildings currently on-grid going off-grid using "solar power + battery" kits newly announced from companies such as Kleenspeed, particularly when they add many complementary forms of capture of free energy that are available or imminent.
Beyond wind turbines
There are plenty of suppliers of small wind turbines creating kilowatts off-grid but tens and hundreds of kilowatts are being demonstrated from autonomous tethered drones currently under development at Enerkite, Twingtec, Kitemill and others that will be more affordable and consistent than a giant wind turbine of similar power. This is because winds at 300 meters or more are stronger and more continuous. They call it airborne wind energy (AWE) and it involves self-launching and self-landing.
The science of autonomy goes way beyond the hyped autonomous car. It drives AWE and Boeing autonomous aircraft planned to be at 60,000 feet for five years on sunshine alone. It applies to autonomous giant mining vehicles that Caterpillar has deployed and that may become part of off-grid mining communities that never use diesel again. This would be thanks to high-power energy harvesting charging the swapped 350 kWh batteries in zero pollution mining community as appraised by Deloitte Touche, their isolated micro-grid being served by photovoltaics, wind turbines and so on. Autonomous ships with 1 MWh batteries are being studied with HPEH to be added later. See the IDTechEx report, Autonomous Vehicles: Land, Water, Air 2015-2035
3D motion and electrostriction
There are many announcements of electrodynamic harvesting in newly efficient forms. Experimentally, Caterpillar and Witt Energy capture all movement in three dimensions - from vehicle motion to sea waves. As if that were not enough, physical phenomena previously thought to be useless for high power capture are returning from the dead such as Oscilla Power creating hundreds of kilowatts from wave power using electrostriction.
University of Wisconsin-Madison UWM engineers and a collaborator from China have developed a generator that harvests energy from a car's rolling tire friction. An innovative method of using energy currently wasted as heat, the generator ultimately could provide automobile manufacturers a new way to squeeze greater efficiency out of their vehicles. The researchers reported their development, which is the first of its kind, in a paper published May 6, 2015, in the journal Nano Energy.
Xudong Wang, the Harvey D. Spangler fellow and an associate professor of materials science and engineering at UW-Madison, and Yanchao Mao have been working on this device since 2014. It relies on the triboelectric effect to harness energy from the changing electric potential between the road surface and a vehicle's wheels; rubbing together of two dissimilar objects.
The UWM generator relies on an electrode integrated into a segment of the tire. Friction between those two surfaces produces an electrical charge. Wang used a toy car with LED lights to demonstrate the concept by attaching an electrode to the wheels of the car. As it rolled across the ground, the LED lights flashed demonstrating that energy lost to friction can actually be collected and reused. Those tens of milliwatts would only scale to tens of watts on a full sized car so there is work to be done but the potential is there.
"Regardless of the energy being wasted, we can reclaim it, and this makes things more efficient," Wang says. "I think that's the most exciting part of this, and is something I'm always looking for: how to save the energy from consumption. There's big potential with this type of energy. I think the impact could be huge."
The amount of energy harnessed is directly related to the weight of a car, as well as its speed. Wang estimates a 10% increase in the average vehicle's gas mileage given 50% friction energy conversion efficiency. Usually HPEH gains multiply so that 10% combined with say 10% from the promised conformal solar panels on vehicles and 10% from the planned energy harvesting shock absorbers - a form of "regenerative active suspension" - could mean approaching 33% increase in range if weight increase is minimal. There are at least twenty possibilities being worked on according to IDTechEx analysts.
$50 billion market and longest range vehicles
Dr Peter Harrop of analysts IDTechEx appraises all the options in a new report, High Power Energy Harvesting: Off-Grid 10W-100kW 2016-2026. He says, "Wang seems to imply that an electric car might garner at least 500 watts from the phenomenon. Affecting the ride and the tire life and cost-effectiveness issues may need attention but this is an exciting new development. It may add to the co-ordinated toolkit of multi-mode energy harvesting that will power vehicles day and night under all conditions with free energy and no compromises. The greater the number of modes of energy harvesting, the smaller the load-balancing battery can become and the more secure the supply."
He sees a market of about $50 billion in 2026 for high power energy harvesting i.e. off-grid for static and vehicle applications. That is when the transducers, power conditioning circuits, controls, battery management systems and batteries such as the Tesla Powerwall™ when off-grid are included.
"Expect vehicles to have longer range on free energy when compared with fuelled vehicles today, let alone plugged in ones" says Harrop, referring to a more distant future.
Energy Harvesting: Off-grid Renewable Power for Devices, Vehicles, Structures 2015-2025. provides detailed market forecasts and technology and market appraisal. It is based almost entirely on interviews, conferences, visits and searches conducted by IDTechEx Research.
The IDTechEx Energy Harvesting & Storage event on November 18-19 in Santa Clara, CA, will cover both high power and low power energy harvesting. Speakers include Witt Energy, Evident Technologies, Kitemill, National Institute of Aerospace and many more. To learn more about the event see www.EnergyHarvestingUSA.com .