When you leave home in the morning and you realize it’s raining, often it is seen as an inconvenience. But what if this same rain could contribute to powering your home? Researchers in China have been working on a new kind of solar cell which can produce energy from raindrops, thanks to the addition of graphene.
For those of us who haven’t heard of it, graphene is simply a single layer of graphite – like you find in a pencil. At just one atom thick it is the thinnest (yet strongest) compound known to man with extraordinary properties for heat and energy conductivity and light absorption. Although graphene was first isolated in 2004, it has taken several years to be able to take advantage of these properties, integrate it or devise new technology in the electronics, battery energy or composite industries.
In this case, scientists in have discovered that since rainwater is not “pure” and contains various salts and minerals, graphene can be used to split the various positively charged atoms from the negative. A solar cell is coated with a layer of graphene which then binds the positive ions, forming a double layer with the electrons already present, known as a pseudocapacitor. As we remember from school science class, electrons are negatively charged and thanks to this potential energy difference an electric current can be generated. Although still in the early stages of development, tests have been positive with a promising solar-to-electric conversion efficiency.
Another way graphene is being used in solar is as the solar panel itself. Researchers in the UK have been looking into how graphene’s heat and light absorption properties can be harnessed to allow for the generation of electricity from ambient light and heat within the home. As the material is so thin, only absorbing a small percentage of light which falls on it, researchers have had to take cues from nature in order to solve this problem. Moth eyes are microscopically patterned, allowing light to be channeled to the middle of the eye, minimizing reflections. Using a similar texture to this they have been able to significantly improve the collection of light, as the nanotexturing works almost like sets of tiny mirrors, gathering and focusing the light. Previously a normal graphene sheet would absorb only 2-3% of light. By using nanotexturing this has been increased to 95%, over a broad spectrum of UV to infrared light.
Since graphene is so versatile and flexible, these panels could be used as “smart wallpaper” or “smart windows” inside the home and hooked up or integrated into an Internet of Things system. Adding this technology to new or existing optical devices will allow simple and unobtrusive energy generation from ambient heat and light we have previously thought there was no use for. The good news is that graphene isn’t too expensive either at $0.10 per gram down from $1,000 per gram only a few years ago. As the technology for creating it improves and demand increases we will hopefully see the price fall even more.
This technology is vital to those of us who long for solar panels yet live in areas where inclement weather is prevalent. No longer will solar just be for those of us fortunate enough to live in sunny climates with predictable weather patterns and direct sunlight. Although still early in development, it’s a glimmer of hope that fully sustainable living could be just around the corner and our reliance on fossil fuels could be coming to an end.