The humble sunflower is forming the basis of another high tech solar energy design.
Early this year, we reported researchers at MIT and RWTH Aachen University discovered by arranging heliostats used in concentrated solar power systems (CSP) in a pattern similar to the spirals on the face of a sunflower, they could reduce the array’s footprint significantly and increase its potential electricity generation.
More recently, a UW-Madison electrical and computer engineer has found a way to mimic the “passive heliotropism” seen in sunflowers for use in creating more efficient solar-tracking based panel arrays.
Heliotropism is an adaptation used by some plants such as the sunflower that sees them rotating to follow the sun throughout the day.
Professor Hongrui Jiang’s design, published in Advanced Functional Materials, uses a combination of liquid crystalline elastomer (LCE) that undergoes a phase change and contracts in the presence of heat, with carbon nanotubes; which absorb a wide range of light wavelengths.
Direct sunlight hits a mirror beneath the solar panel, which is focused onto multiple actuators composed of LCE laced with carbon nanotubes. The carbon nanotubes heat up as they absorb light, and the heat differential between the environment and inside the actuator causes the LCE to shrink.
This results in the assembly moving in the direction of the strongest sunlight. As the sun tracks across the sky, the actuators cool and re-expand, and new ones shrink, re-positioning the panel for optimal solar harvesting over a day.
Tests so far show an improved solar efficiency of 10 percent. This is significant, particularly as being a passive system, there is no electric componentry driving the system that chews into the gains.
Professor Jiang and his team are now researching ways to refine the materials used for driving larger solar panels.
Biomimicry, where designs in nature are utilised for solving human challenges, is playing an important part in the evolution of solar power and related technologies. Aside from sunflowers, in the past we’ve covered solar designs based on butterflies, bacteria , a virus and moth eyes.
