Butterfly wings offer clues to vastly improved
solar power

By studying the structure and temperature of butterfly wings, researchers have observed physical properties that could hugely improve the efficiency of solar energy.

The humble butterfly may hold the key to unlocking new techniques to make solar energy far cheaper and more efficient, pioneering new research has shown. Experts from the University of Exeter have studied new methods for generating photovoltaic (PV) energy – or ways to convert sunlight into power. They showed that by mimicking the v-shaped posture adopted by Cabbage White butterflies to heat up their flight muscles before take-off, the amount of energy produced by solar panels could increase by almost 50 per cent. Crucially, by replicating this 'wing-like' structure, the power-to-weight ratio of the overall solar energy structure is increased 17-fold, making it vastly more efficient.

Professor Tapas Mallick, lead author of the research said: "Biomimicry in engineering is not new. However, this truly multidisciplinary research shows pathways to develop low cost solar power that have not been done before."

Cabbage White butterflies are known to take flight before other butterflies on cloudy days – which limit how quickly the insects can use the energy from the Sun to heat their flight muscles. This ability is thought to be due to the v-shaped posturing, known as reflectance basking, they adopt on such days to maximise the concentration of solar energy onto their thorax, which allows for flight. Furthermore, specific sub-structures of the butterflies' wings allow the light from the Sun to be reflected most efficiently, ensuring the flight muscles are warmed to an optimal temperature as quickly as possible.

The scientists therefore investigated how to replicate the wings to develop a new, lightweight reflective material that could be used in solar energy production. They found that the optimal angle by which the butterfly should hold its wings to increase temperature to its body was around 17°, which increased the temperature by 7.3°C compared to when held flat. They also showed that by replicating the simple mono-layer of scale cells found in the butterfly wings in solar energy producers, this could vastly improve the power-to-weight ratios of future solar concentrators, making them significantly lighter and so more efficient.

Professor Richard ffrench-Constant, who conducts world-leading research into butterfly mimicry at the University of Exeter, said: "This proves that the lowly Cabbage White is not just a pest of your cabbages, but actually an insect that is an expert at harvesting solar energy."

The paper – White butterflies as solar photovoltaic concentrators – was published in the journal Scientific Reports and is available online.