Energy Harvesting & Storage Tech Digest - April 2017

Heat differential could act as a charger

University of Utah scientists have developed a new material that can convert heat energy into electricity. The material – a combination of calcium, cobalt and terbium – uses the thermoelectric effect to turn the heat differential between, for example, a gas stove flame and a pan of cooler water or food, or human skin and the air, into electricity. The scientists claim that the material is biofriendly and cheap to produce making it suitable for integration into jewellery, cooking utensils, or in cars.  Most current thermoelectric materials are built from toxic elements such as cadmium, tellurium or mercury.

Cooling batteries could improve life-cycle

University of Columbia researchers have discovered a way to extend lithium ion batteries’ life, improve safety and possibly lend batteries bendability. The technique involves ice-templating the battery – using freezing temperatures to create a desired structure within solid electrolytes of the battery. Instead of using the common liquid electrolyte lithium ion battery the team used a safer solid state lithium ion electrolyte. The team could fabricate vertically aligned structures of ceramic solid electrolytes. They cooled the electrolyte allowing ice crystals to form. This concentrated the ceramic particles into clusters that were then formed into vertical columns through the application of a vacuum to turn the ice into gas. The team plans to continue optimizing the electrolyte with the intention of including it within a working lithium ion battery. 

New screen

Scientists at Ritsumeikan University, Japan, have developed a technique to convert a luminescent solar concentrator to a display by projecting lightwaves with different intensities onto it. The scientists achieved this by creating a centimetre square screen – a sandwich of coumarin 6 (an organic luminous dye) between acrylic plates. They then fed blue laser light through a commercial projector. The screen showed clear monochrome images. A photodiode integrated into a section of the screen pulsed in unison with laser pulses. The scientists predict that a screen fully covered in the photodiodes would harvest up to 71% of the incoming laser power. The team are working on making the screen thinner – to reduce ‘photon bounce’ – which would provide a clearer picture on screen with less ghosting. 

California state investigating energy harvesting from passing traffic

According to IEEE Spectrum California Energy Commission is investing USD2 million into a series of piezoelectric systems that would be applied to the road to harvest energy from passing cars. One of the projects would see a 60 metre stretch of road to the north of Fresno equipped with 2 cm wide, stacked piezoelectric generators. The project is an experiment, but the scientist leading the work at University of California Merced, Jianqiao Sun, says the electricity generated could power local lights and signs. Another similar trial is being run by the company Pyro-E which claims that the energy generated from half a mile of highway would be enough to power 5000 homes. 

Oslo Airport’s energy recycling project

Oslo Airport in Norway has announced plans to use sewage and snow as energy sources in its new North Pier terminal. The sewage would come from northern parts of Ullensaker (where there  is a water treatment plant), Nannestad and other areas of Oslo Airport, and will be used for heating. The wastewater’s temperature rises as contaminants are broken down, which increases the amount of heat that can be recovered. Snow stored from the winter will be used to cool North Pier during the summer months. The snow is collected into a large stockpile shaped like a basin. When full it is covered with sawdust as insulation. Cold melt water is fed to the cooling system and then released into the ground. 

Phototrophic bacteria for batteries

Binghamton University in the US has developed a self-sustaining, micro-scale microbial fuel cell (MFC) that has generated power for 13 days. A symbiotic relationship between two types of bacteria led to the long lifespan. Researchers placed a mixture of phototrophic bacteria (that use sunlight, water and carbon dioxide to create energy) and heterotrophic bacteria (that eat provided organic matter or phototrophic bacteria) into a 90 microliter cell chamber. When the cell was exposed to sunlight a dose of food was provided for the heterotrophic bacteria to kickstart the symbiotic cycle, after this no more food was added and the heterotrophic bacteria consumed the other bacteria. The consumed bacteria were oxidised in the same way that bacteria commonly oxidise food to generate their own energy, releasing electrons in the process. In the experiments, the researchers created an electric current (8 microamps per centimetre squared) that was sustained for 13 days. The team sees the cell having potential future uses in low power devices such as sensors and health monitors. 

Solar powered battery

Ulsan National Institute of Science and Technology scientists in South Korea have demonstrated a single unit photorechargable portable power source using silicon solar cells and lithium-ion batteries. The device is designed to work anywhere where there is a light source – outdoors or inside. The SiPV–LIBs (silicon photovoltaic lithium-ion batteries) are fabricated by directly printing the battery onto the SiPV. The device displays rapid charging (fully charged within two minutes) and has a conversion (to storage) efficiency of 7.61%. The team sees the device having future potential as a mobile power source for smartphones, laptops, wearable devices etc. 


Supercapacitor as storage

A group of scientists from Georgia Institute of Technology, USA, and Chongqing University, China, have developed a lightweight, portable and sustainable power source that could possibly have uses in personal electronics. The device – a grid of paper strips with layers of graphite, fluorinated ethylene propylene, gold and PVA – can harvest energy from movement like walking. The TENG (triboelectric nanogenerator) device stores energy in a supercapacitor built into the outer frame of the structure made of gold- and graphite-coated sand paper. The harvested energy is capable charging the supercapacitor to around 1V and 1mF within a minute. This would make it capable of powering a remote-control temperature sensor or a watch the team claims. 

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