EuroWire July 2020

Transatlantic Cable

Dr Tan explained that, due to this work function contrast, “electrons can flow from the light region into the dark region, as they are being generated, in the silicon substrate.” Connecting this generator with an external circuit will convert the flow of electrons into electrical power. Each cell contains a gold film deposited on a silicon wafer. Several cells of the same size are arranged on a flexible and transparent polyethylene terephthalate film. Experiments have demonstrated that the device is sensitive to where the electrodes sit, in relation to the shadow edge and the transparency of the metal film. In 50 per cent shadow it can generate a power density of 0.14μW/cm 2 under indoor conditions (0.0001 sun illumination) – roughly twice that of a commercial silicon solar cell. However, Anita Ho-Baillie, an adjunct professor at the School of Photovoltaic and Renewable Energy Engineering department of Australia’s University of Sydney, has cast a doubt: “Commercial silicon cells are designed for respectable power generation, and deliver a reasonable amount of current. The efficiency [of the shadow effect generator] is actually really low – 0.14μW/cm 2 under 0.0001 sun corresponds to a 0.000014 per cent power conversion efficiency.” Dr Tan aims to make the device cheaper, by using a tungsten film, and plans surface modifications to boost performance. While the generated power will not be as high as that of solar cells under full illumination, Dr Tan wants to inspire others to think about shadows as “an untapped energy source” rather than a problem. The California Energy Commission has awarded $3.5mn in funding to the Lawrence Berkeley National Laboratory to develop fibre optic cables that can monitor offshore wind operations and underground natural gas storage. Yuxin Wu, head of Berkeley Lab’s geophysics department, said, “One of the most expensive components of a wind turbine is the gearbox; they also tend to be the part that’s most vulnerable to failure. Often, before they fail, they produce abnormal vibrations or excessive heat due to increased or irregular friction. We intend to use fibre optic cables to monitor the vibrational, strain and temperature signal of the gearbox in order to pinpoint where problems are happening.” The Berkeley researchers believe that fibre optic cables, wrapped around the entire gearbox, could provide a 3D map of changes. Real-time monitoring could bring greater reliability in natural gas storage and offshore wind

Research

Versatile graphene causes more excitement for the materials research community: a new, and timely, application Mining News magazine reported in early May that Graphene Solutions, based in Illinois, USA, is collaborating with the UK’s Graphene Composites (GC) and Canada’s ZEN Graphene Solutions to work on a graphene ink that could be applied to textiles. As soon as the development, testing and confirmation of the graphene ink’s properties are complete, the ink will be incorporated into fabrics used in personal protection equipment, such as masks and filters. For its part, ZEN has synthesised a silver nanoparticle functionalised graphene oxide ink at its laboratory in Guelph, Ontario, Canada, that previous researchers documented as capable of destroying earlier versions of coronavirus. COVID-19 testing of the ZEN/GC ink will be conducted at Western University’s ImPaKT facility biosafety level 3 laboratory in Ontario, and tested to kill influenza A and B viruses at biosafety level 2 laboratories in the UK and the USA. Could there be power in the shadows? Solar panels need precision placing to receive maximum sunlight, and to prevent one panel from shading another; this limits the number of panels in a given area and, as a consequence, the amount of power generated. However, a recent paper from Q Zhang et al, writing in Energy & Environmental Science , reports a device capable of generating energy in shadowy areas where solar cells are ineffective, potentially even inside the home or office. Swee Ching Tan, and his colleagues from the National University of Singapore, have developed a device that can harvest energy, even when considerably shaded. Dr Tan said, “To make this device is much cheaper and easier than silicon solar cells. [Our device] only needs a piece of silicon substrate coated with a thin piece of [gold] metal film.” It is believed the device could boost power generation indoors, as well as on solar farms, as the device is sensitive in shadows cast by even low light intensities. The team has demonstrated that optical illumination contrasts create work function contrasts on metal films coated onto a semiconductor (silicon, in this case).

Image: www.bigstockphoto.com Photographer Adrian Grosu

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July 2020