Mechanical device harvests energy from random and chaotic motion

Harvesting energy from random and chaotic motion has led to the development of an innovative mechanical device that has far reaching potential application. Justin Cunningham finds out more.

While energy can't be created or destroyed, it can certainly be captured or lost. Indeed, people, like nature, all expend an extraordinary amount of energy everyday that has the potential to be recovered. It was this concept of capturing and using random and chaotic movements that saw engineer Martin Wickett embark on an eight year journey of invention and development that led to the aptly named WITT, that's the Whatever Input to Torsion Transfer device. At the time a keen cyclist, Wicketts set out with the idea of capturing acceleration forces from every direction acting on a bicycle and turning that energy in to something useful. He started by thinking about the mechanisms used in automatic watches. These use a counterweight with two separate one-way clutches. This type of mechanism takes inputs from two directions on a single axis and turns them in to a single rotational movement. The rotating shaft lends itself to electricity production, as it can be easily connected to a generator. The brainwave However, the watch mechanism only takes one-axis of motion, so movements in other directions are not able to be captured. Keeping to the same elegant principle, Wickett had a brainwave; the idea of adding another stage to the mechanism, essentially making it three dimensional. By using a double pendulum arrangement, a weight swings freely on one axis while an attached shaft allows rotation in another. While this captures lateral movements, the swinging nature of the pendulum captures vertical motion, enabling energy to be harnessed on all six axes. Wickett was sure the principle in the watch could now be modified and applied to his new layout and allow the resultant output to be a rotating shaft. So, like any good inventor, Wickett locked himself in the shed and began to tinker. After sometime, the inner mechanics of gears and clutches were devised in such a way that a working prototype was build and an application for a patent was soon granted. "We were initially surprised at quite how effective it was," says Will Boult, product and development manager at the since formed WITT Energy. "You imagine having two sets of gears is going to produce a fair amount of resistance and slow everything down because of the interference between the two inputs. But actually, the way it works, with the clutches, is incredibly effective. Any movement results in some fairly rapid acceleration of the attached flywheel." The flywheel is important as it keeps the momentum in the rotating shaft and also helps to iron out some of the random inputs that can be experienced. The device needs chaotic motion to operate as the mechanism is unable to transfer purely vertical inputs. After the initial proof of concept, funding from the Technology Strategy Board (TSB) soon followed and a more robust demo unit was built. "Once we had a demo unit we could see the power it could produce, and that has been our calling card since," says Boult. "Every time we go somewhere people ask us if we have considered using it for this or that application. There are potential uses are everywhere." However, in an effort to develop a commercial product and establish the technology, WITT Energy partnered with a number of other companies and universities to get a production ready and fit for purpose device. Together the consortium is targeting the marine industry, specifically for use on navigational buoys. The potential to convert wave energy to electricity would allow the buoys to perform scientific measurement, have sensors and navigational aids integrated, as well as the potential for mounting lights on top. Its partners helped WITT get the device ready for production. Gearbox manufacturer MCT Reman helped in design for manufacture while marine power electronics company, Triskel Marine Services looked at reducing energy consumption of systems to be mounted on the buoys. "Marine is an obvious area for WITT as there is a lot of random motion from waves," says Boult. "There are lots of marine based applications where they would like to have continuous power but it's difficult to carry that many batteries and renewable generation is sometimes not practical. As well as navigational buoys, yachts and even sea kayaks look like they could easily have a unit retrofitted. "Our device is standalone, produces zero emissions and is self contained. You don't need to see it or hear it. You plug it in and get free power out. It's not heavy and is only about the size of a shoebox." With computer models predicting the shoebox sized marine WITT device should be able to produce up to 15W. Tests are being carried out to verify these predictions, with its first commercial product to be launched early next year. However, there is still room for optimisation and the team is busy making sure the gearbox, the pendulum length and weight, the flywheel size and weight, the generator type and output, along with the control electronics are all well matched to capture and convert as much energy from waves as possible. Far reaching applications Such is the enthusiasm from potential end users that WITT Energy is looking at scaling the device both larger and smaller. At the larger end of the spectrum is the possibility of using it as a tuned mass damper, a device often used on tall buildings to stop swaying. These devices, at the moment, are energy negative meaning they absorb energy but are not able to re-use it. A large WITT device offers the potential to capture the energy of the swaying buildings and convert it in to electricity. The obvious large scale application for the WITT device is a wave energy renewable power generator. However, the company is all too aware about the long route to market. While many wave energy devices are still being trialled, no significant sites are under development despite calls for the technology for more than 20 years. "It is a great opportunity," says Boult, "But it is a much bigger nut to crack and a lot of the devices in this market have had a rocky road. A majority need direct contact with the sea. You need really effective seals to keep water away from the moving parts and they are susceptible to damage by the harsh nature of the environment. We can seal our device off almost completely, so that is a real advantage. But, first of all, we need to establish the technology and get a good understanding of how it operates in the marine environment." While this is perhaps further away in terms of development, WITT Energy has received more grants from Innovate UK for nearer term developments. One project with ANT Scientific, a specialist in miniaturisation, is looking to assess if the mechanism can be scaled down so it could be worn. The feasibility study is to assess whether peoples movements could be used to effectively charge a small device like a tablet or smartphone. "We are looking at how much power is useful for something like a phone, and therefore how big does our unit have to be to produce that." says Boult. "It's a really exciting time, exploring all the potential applications and it's not long until we get some products in the market place next year. And of course, we are always looking to develop opportunities with new partners."