Gold in Solar & Glass
Gold has optical properties that range from use in photovoltaics, blocking heat in buildings and infrared radiation in telescopes, and as an anti-fog coating in eyeglasses. In traditional photovoltaics (PV), residential solar panels are able to achieve around 15% efficiency. Newer commercial PV solar panels are reaching about 20-25% efficiency and military and space PV solar panels are capable for up to 30% efficiency or slightly higher. Researchers at Hokkaido University in Japan claim to have designed gold-embedded solar panels that can reach 85% energy efficiency.
The team of scientists led by Professor Hiroaki Misawa, have developed an experimental setup cell that uses a very thin gold nanometer layer loaded on a thin 30-nanometer layer of titanium dioxide sandwiched between a 100 nanometer-thick layer of gold The gold sandwich layers act as a mirror to trap light in the cavity between the gold layer and the gold nanoparticle layer, allowing them to absorb more energy over a larger spectrum of light than traditional PV solar panels. The gold nanoparticle absorbs photon energy from the sun which triggers excitation of gold electrons and transfers those electrons to the titanium dioxide semiconductor layer.
Using gold as a major component in the production of these solar panels would not ordinarily reduce the cost of utilizing solar energy although, the small amounts of gold used to create nanoparticles should not impose a significant cost as one might think. The original goal of the Misawa group was to create a photo electrode that uses solar energy to convert water to hydrogen and oxygen-a synthetic photosynthesis process. This project is totally dependent on gold as a major component in the process and has the potential to yield a source of clean energy from the sun.
In aerospace, NASA uses gold in many different ways-it is used to reflect infrared radiation, as a lubricant, and in its circuitry. As it relates to optical properties, gold is used as a film to reflect infrared radiation that would absorb significant amounts of heat. In fact, many parts of space vehicles are fitted with a gold-coated polyester film. In an astronaut’s helmet visor, the glass is coated with a thin coat of gold to protect skin and eyes from intense solar radiation. Furthermore, gold has a very low shear strength and the gold molecules slip past each other under frictional forces. For this reason, gold is used as a lubricant between mechanical parts that organic lubricants would not be able to hold up against which the vacuum and intense radiation of space would volatize.
NASA’s James Webb Telescope is a space telescope made of 18 gold- coated [25) ultra-lightweight beryllium, hexagonal-shaped mirror segments After its launch in space, the segments of mirrors unfold and adjust to shape The microscopically-thin gold coating reflects infrared light and is said to greatly improve resolution and sensitivity over the Hubble space telescope.
In glassmaking, gold has a basic use as pigment and also keeps buildings cool when it is combined with glass. When a small amount of gold is suspended in annealing glass, it will produce a rich ruby colour. A small amount of gold coated on the surface or dispersed within the glass will reflect solar radiation and keep buildings cool during the summer. It will also reflect heat inward during the winter to keep buildings warm. The two Royal Bank Plaza towers in Canada have 14,000 windows and are all coated with a layer of 24-karat gold. The bank building required a total of 2,500 ounces of gold to coat all their windows-this adds up to about $3.2 million dollars’ worth of gold in today’s prices.
A sudden drop in temperature or an increase in humidity can cause the surface of eyeglasses. Windshields and camera lenses to accumulate fog. Researchers at FTH Zurich, fielded by Professor Dimos Poulikakos, have developed a technology that can combat this problem. They have developed a transparent material coating that is made of gold nanoparticles embedded in non-conductive titanium oxide. The coating is only a few Nanometres thick, but it greatly reduces the effect of glass fogging by converting light into heat. By absorbing a Small part of visible sunlight, the surface is heated up by 5 to 4 degrees Celsius-the difference prevents fogging.