We’ve seen all sorts of novel materials used to create solar cells and batteries, but here’s a new one for a different component – wood as glass facing for solar panels.
Solar panel glass doesn’t get much attention in the media; but it’s a very important component of a module. Poor quality glass can discolour or become cloudy, impacting on efficiency. If glass is weak and should crack, water can seep in and damage the module.
Boffins at Stockholm’s KTH Royal Institute of Technology believe they have come up with an alternative to the conventional tempered glass used for panels – wood; transparent wood of course.
Creating the wood-based glass involves chemically removing lignin – a brown organic substance binding the cells, fibres and vessels of plant material.
“When the lignin is removed, the wood becomes beautifully white,” says Professor Lars Berglund from KTH’s Wallenberg Wood Science Center. “But because wood isn’t naturally transparent, we achieve that effect with some nanoscale tailoring.”
According to an associated paper published in the journal Biomacromolecules, after this “tailoring” the glass demonstrates a high optical haze, which diffuses the light. While hazy glass can negatively impact on panel efficiency; apparently this is a good type.
“This high haze is attractive in solar cell applications. Light will be trapped in the solar cell for longer time due to light scattering caused by the wood tissue. Longer trapping time means better interaction between light and active medium, which can lead to better solar cell efficiency,” say the paper’s authors.
High optical transmittance of 85% and haze of 71% was achieved at a transparent wood thickness of 1.2 mm.
The researchers state that transparent wood with a cellulosic wood template volume fraction of 19% showed twice as high strength and modulus as for neat Poly(methyl methacrylate) (PMMA); i.e. acrylic or acrylic glass.
Professor Berglund says wood is a good base material for solar panel glass as it is low-cost, readily available and a renewable resource.
Obviously they have some serious tweaking to do to get things just right for solar panels; but it’s certainly an interesting development. Professor Berglund says his team also intends to work further with different types of wood.