- for super-efficient PV’s
The Attraction of iridescent Blue
The Blue Morpho Didius butterfly uses the striking colour on the top of its wings to improve its chances of mating (the underside is dull brown and covered in 14 fake eyes to put off predators). However, the colour comes from cone-shaped structures that scatter light to create a vivid shade of iridescent blue, rather than any pigmentation. (Global Construction Review)
Now scientists at the Australian National University (ANU) have discovered that the nano-cones which cover the 150mm-wide wings of Morpho Didius could be uses the to control the sunlight striking the surface of a solar panel. Niraj Lal, the lead researchers at ANU’s School of Engineering, said: “There’s a whole bunch of potential applications using our light-control technique, including next-generation solar cell, architectural and stealth technologies.” The research paper is published in ACS Photonics, with co-authors Kevin Le, Andrew Thomson, Maureen Brauers, Tom White and Kylie Catchpole
Niraj Lal giving a TED talk on sunlight and butterflies (YouTube)
In 2009 it was discovered that Perovskite, a mineral that contains calcium titanium oxide, has photovoltaic properties. Development of perovskite as one of the most efficient possible solar cell is one of the main prizes in the solar industry. The Australian research seeks a way to absorb the blue, green and ultraviolet wavelengths in the perovskite layer of a “tandem” design of solar cell, whereas the longer red, orange and yellow light would be directed to the silicon layer.
Limits to Efficiency
The greatest theoretical efficiency of a solar panel is 33% – this is the Shockley-Queisser limit, which was discovered in 1961. The greatest practical efficiency is thought to be 29%, and the photovoltaic industry is racing to produce panels that get as close as possible to it. The problem is that the degree of effort and innovation required for each additional fraction of a percentage point increases as the limit approaches.
The Race is On
Researchers at ANU recently produced a cell with an efficiency of 26.4% using stacked configuration of perovskite and silicon, a figure that was beaten in March by Japanese solar panel maker Kaneka Corporation which achieved 26.6%. Niraj Lal of ANU claims that “Using our approach, a window could be designed to be transparent to some colours, non-see through and matt textured for others – so there are very cool potential applications in architecture” Scientists at Kaneka estimate that the ability to control the way light strikes the surface of a PV cell would add one point to its efficiency. This may not seem like a large amount in absolute terms, but it would be a significant step towards producing the perfect solar panel.
The Butterfly Advantage
The advantage of scattering light at the surface of the cell is that each photon hits the surface at a shallow angle and moves sideways through the PV layer, thereby increasing the length of its path, and making it more likely that it will interact with an electron.
Disappear and Dim
According to Lal, the ability to control light could have other applications besides PV manufacturing. For example, it could be used to make opaque objects appear to disappear when lit by certain wavelengths. It could also be used to modify the transparency of glass, which may allow the production of windows that could be “dimmed”.
New Type of Window
Lal suggests that using their approach, a window could be designed to be transparent to some colours, non-see through and matt textured for others – so there are very cool potential applications in architecture.
One factor that may help the technology to reach market is that it is not inherently expensive: “These intricate nanostructures grow and assemble themselves – it’s not by precise control with a tiny laser or electrons,” said Lal.
Delivering Low Energy Buildings & Components
Timber has the lowest embodied energy of any building material. Having low thermal conductivity. It is also one of the best materials to sue in the design and building of any low energy structure. That said, we believe it is also incumbent on our architectural designers and technicians, individually and in concert with other construction professional, to seek out and incorporate the best ‘low energy’ components for each and every project, both as manufacturers, builders and suppliers.
Progressively our industry is adopting processes familiar in the automotive and aeronautical sectors. The search for Continuous Product Improvement is as challenging as designing buildings for factory sub-assembly. It introduces further discipline into the construction process and provides greater opportunity for the delivery of more accurate, higher quality, more energy efficient components and eventual on site assembled buildings. The procedures and processes involved tends to be more controlled and considered. ‘Safety’ of assembly, along with Energy Efficiency becomes an essential and integral part of the design process. Pre-planning of what components are to be selected and how works are to be executed has to be considered in detail before any element is actually sent to the factory for fabrication. Plans for moving, delivering, unloading, site storage and site handling all form part of the ‘off-site’ manufacturer’s tasks.
Call us to discuss how our approach to ‘Off-Site’ can help improve your projects