Biomimetics and Biomimicry in Engineering

A sunflower-inspired solar tracker to improve harvesting of energy

In Info on 2011/09/13 at 11:18 am

[Nicolas Salort has finished his MSc project in Renewable Energies at Heriot-Watt University. This is a snapshot of his work]

Some plants, for example the sunflower, have an extraordinary ability: they can follow the sun during daylight hours to enhance their photosynthesis ratio.

This was the idea that inspired us. We wanted to investigate if sunflower-inspired solar trackers would enhance the energy collected by a solar panel during the day.

During the survey stage we learnt three things:

–       Heliotropism: plants can control the angle of their leaves relative to the sun, control light absorption, and rate of photosynthesis. [This is different from phototropism, which is their ability to orientate themselves towards the light during growth].

–       Heliotropism is not exclusive of sunflowers. Alfalfa, cotton, soybean, bean and lupine also show that feature. The movements of the plant are caused by an organ, the pulvinus, situated at the base of the leaf. It contains motor cells that can change their inner volume by the action of turgot and thus allow the leaf to move.

–       It is not the sunflower head that moves following the sun, but the leaves!. And the perception of the light is a vector. This means that the leaves are able to sense if the light beams are normal to the lamina of the leaf or oblique to it. They show a 3-axis rotation that allows them to reposition so they remain perpendicular to sunrays at all times.

The design and construction of a prototype gave us great insight in order to assess what a sunflower could bring to the design of a solar tracker.

The 3-axis rotation and the perception of light as a vector were features incorporated into the design of our mechanical device.

The program adjusts the panel so that each photodiode receives the same amount of light.

To enable solar tracking ability, Nicolas used a quadrant photodiode with a two-fold purpose: 1) Obtain information about orientation of the light beam (whether this was parallel or not to the optical axis); and 2) to inform the system which direction the device should move to reinstall a parallel position.

You can watch the video here:  Sunflower-inspired solar tracker. The prototype follows a beam of light moving in an arc above it.

The system has proven effective at tracking light and reposition itself in order to stay always aligned with the light vector. This is certainly a great success in the biomimetics front!

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