In a nutshell, we produce vehicles inspired by biology. We look at how birds and insects fly and how fish swim, to investigate what nature can teach us about effective and energy efficient movement.
The aim is to understand the underlying physics of motion and discover how evolution produced such elegant solutions to high performance locomotion, and then implement those solutions in an engineering context. That doesn’t mean mimicking biology, it means taking advantage of 4.5 billion years of evolution, identifying the recurring themes that have evolved convergently in many different animal groups (where evolution has come up with the same answer from different starting points), and designing vehicles that exploit the same principles to move more efficiently.
For example, we are studying the skin surface of fish that live in strong currents, their body shape, and the design of their fins to discover how they swim without being swept away. We then build vehicles based on the underlying principles, but using conventional carbon fibre composite structures. Muscle and bone are remarkable materials and serve their purpose effectively, but biology has evolved structural materials based on what was easily available – and we can do better using modern composites, at least where strength to weight ratio is what matters.
We are applying these lessons to the development of vehicles for use on water, in the air and on land, but our human powered hydrofoil is the most developed vehicle we have. We are on to the third generation of prototypes and are planning to break the human powered water speed record next year. The current record is 18.5 knots and set by MIT, so obviously we want to record to Oxford!
We are using flapping foils, emulating fish or whales, to propel the hydrofoil. This sort of propulsion has several advantages over propellors. One major advantage, important for the record attempt, is that our hydrofoils are loaded efficiently across the whole surface, whereas with a propeller the hub at the centre moves too slowly while the tips move too fast. Propellor designers can solve this by twisting the blades from root to tip, but then they only work efficiently at a very narrow range of speeds, and suffer cavitation when the hard-working tips literally boil the water.
Our 'Lighthill-drive’ hydrofoil propulsion system treats the water far more gently, spreading the loading evenly across the whole hydrofoil and flapping it in an undulating waveform that matches the pattern of motion that has been evolved independently by whales, dolphins, tuna and sharks (and, in fact, all fast swimming animals). The other advantage of the ‘Lighthill drive’ is that once you get up to speed you can glide and if you glide down a wave you can surf. Our vehicle has a glide angle that is more than five times as efficient as a surfboard so you don’t have to surf steep breaking waves, ocean waves and ship wakes are steep enough. Once the sea warms up next summer we plan to test out the long-range surfing abilities of our hydrofoil by riding the Atlantic swells across the Irish Sea.
We haven’t yet finalised locations for the record attempt, but one idea is to use a container port because the water is calm which helps with speed, and there would be a nice contrast between the industrial setting and the sleek hydrofoil. Or perhaps Coniston Water because of its history and the smooth water. Of course, the Serpentine in Hyde Park might be a nice public place to do it.
Of course the human powered hydrofoil is really just a technology demonstrator. We think it will be great fun, and will be commercially viable as a watersports vehicle alongside paddleboards, windsurfers and kayaks, but long term we think the real impact of the 'Lighthill drive’ technology will be in more efficient propulsion systems for large ships and in its driven alternative for energy generation. The pollution generated by large ships is much more severe than that produced by cars, particularly since they burn very dirty fuel. Our technology would make ships more efficient and reduce their impact on the environment. There is an economic benefit too because companies will be able to save money if their vessels are more efficient. However, it could take two decades for this technology to be adopted by shipping.
This technology can also be used for generating hydroelectricity; unlike turbines, which have very fast tip speeds and can severely injure marine mammals and fish as they swim past. The hydropower version of the ‘Lighthill drive’ operates at much lower speeds. It doesn’t move much faster than the flow of the water, but the gearing is high so we can generate a lot of power from slow movement. It also works in shallow water and that high gearing allows it to generate significant power from slower flows than underwater turbines can economically exploit.
The other big advantage of the ‘Lighthill drive’ hydropower system is that you need much less infrastructure on the sea floor to hold these foils in place, and the system is completely scalable. You could use it for a single house next to a shallow stream or to power the light on a bouy. I like the idea that everyone could generate their own power locally. We’re running lab trials at the moment and are hoping to start field trials in 2017.