Following last blog post of explaining the basics of biomimicry, in this part 2 we will show you the process of how we apply biomimicry thinking to the design of our turbine.
When we started this project we wanted to develop a new kind of hydropower technology that could meet the following requirements:
- Using an operational head of only 1.5 meters and high flows to generate energy.
- Being fish friendly.
- Requiring simple components for scalable production and ease of repair.
This was the definition of our turbine design challenge. Next thing we did was to identify the needed functions and translate them to biological terms.
So our required functions turned out to be:
- A mechanism or organism converting energy with low pressure differences.
- A natural mechanism that can be found in every fluid flow and doesn’t harm fish or other organisms.
- Something that can happen in nearly every location, under any circumstance. Something that was based on simple principles.
Then we started to look for a natural mechanism that could fit the natural principles and these function requirements. After a study of nature, we found a process that is scalable, that can be easily found in nature and in every stream, and that never harmed fish in its natural occurring state. Besides, it could work in things as small as a blood vessel to flows as large as a whole ocean. As a result, we found the natural mechanism of a whirlpool, aka the vortex.
The next step was thoroughly analyzing the vortex. We saw that there are several guiding rules for the creation of a whirlpool and that its shape is defined by a set of input values, combined with some physical laws. We started experimenting in the lab to get to the root of this mechanism.
Nature is indeed the best teacher, and by submerging us in the matter and being able to touch the mechanism itself, we obtained a good understanding of the vortex. We then started to emulate the mechanism and simulate it with CFD (Computational Fluid Dynamics).
This process was largely based on iterations of simulations, alternated by validations with the prototype. We developed a digital model to design our turbines. We also found out that, any hydraulic model we tried to distil from the vortex mechanism, was too complicated regarding the calculation time, and too simple to describe the mechanism correctly. So we decided not to define the whole mechanism in engineering formulas, but rather follow an iterative approach to design our turbines: we applied the mechanism of evolution.
We started with our CFD model of the vortex and first created a shape for the vortex basin that would allow the largest amount of flow for a head of 1,5 meters. We based most of our designs on the principles of the vortex. One of these principles was the well-known golden ratio. We were skeptical at the beginning, thinking this might only be useful for artwork, so we started off with a quick test. First we built a prototype with a basin conforming to an Archimedean spiral. Next we inserted an extra section of basin wall that followed the progression of a logarithmic spiral. This immediately increased the flow through our turbine prototype from 8l/s to 12 l/s, an increase of 70% that was not to be ignored. Considering this golden ratio seemed to work, we started applying it to more parts of the turbine.
We then designed a first turbine rotor which turned out to be inefficient. This rotor was used as a seeding design. We applied our evolutionary methodology to it and quickly improved it with our iterations.
In these simulations we modelled the vortex, instead of designing the rotor blades ourselves, we let the vortex design them for us. In a way, this was using the genius of nature to show us the best shape for our turbine.
Have you got inspired by this post? We hope that now you have an idea on biomimicry and its application. Now it’s your turn to try out this exciting new way of thinking! Open the book of nature and start looking for solutions to the challenges around you. Feel free to share your thoughts with us below.