Energy Harvesting & Storage Tech Digest - December 2016

Get with the flow: new potential material for redox flow batteries

Batteries have 2 key criteria, (1) store electrons, (2) allow and participate in electron transfer; properties, which recent work by Buffalo University has shown a fluorescent liquid dye called boron-dipyrromethene (BODIPY), has – and it has them in abundance. Experiments on BODIPY-based batteries were still running well after 100 charge/discharge cycles. And generated an estimated 2.3 volts of electricity. 
BODIPY is a potential material for what are called ‘redox flow batteries’. These work by having two tanks of fluid. Electrons are harvested from one tank and moved to the other, generating current – which theoretically could power a lightbulb or even a house. Solar or wind power could be used to recharge the battery by forcing the electrons back to their original tank. 
This type of battery is safer than a Li-ion battery as it is not volatile. Moreover, it is easy to scale-up; hence a redox flow battery could allow for enough solar energy storage to power a house overnight. 

Programming language overcomes energy harvesting computer crashing problem

Energy harvesting computers get their power requirements from ambient energy sources such as radio waves, solar energy, heat or vibrations. As a result of using these power sources, the energy harvesting computer will be unreliable and prone to power cuts. A team at Carnegie Mellon University has created the first programming language which enables reliability from software used on energy harvesting computers. 
They have invented a programming language called Chain. Chain makes an application developer define a set of tasks which are memorised by the computer in a ‘channel’. Consequently, even with power failures the computer will still be able to reload the software without data loss. The speed of Chain is another benefit, there is virtually no load time after a crash as Chain doesn’t use conventional memory checkpointing.
According to the team areas where this has potential are the IoT and ingestibles or implantables where power outage could lead to a serious problem, or loss of vital data. 

Dyke walking

With 2/3 of the Netherlands susceptible to flooding, dykes and consequently dyke inspection rank high on Dutch to-worry-about lists. Today, highly autonomous teams of robots inspect dykes. The problem here is that their batteries soon run out and need recharging. It would be impractical to build numerous charging stations on remote dykes. Douwe Dresscher from the University of Twente believes he has come up with a way to allow the robots more autonomy and longer working hours. He overcame some issues:
1.    Movement: tracks, wheels or legs. Wheels aren’t good on muddy dykes. Tracks damage dykes. According to Dresscher’s idea walking is just right, a nice mix between mobility and energy usage requirements.
2.    Motors or mechanical storage: Electromotors use too much energy. However, by storing some of that energy in a mechanical way it can then be reused. Mechanical energy can be stored well in a spring, then this input can drive a transmission system of gears to enable the robot to move, only using the electromotor to compensate for mechanical loss. As proof for his theory Dresscher has built robots that demonstrate the validity of his ideas.

Stinking Power: Lithium Sulphur batteries

Lithium-sulphur (Li-S) batteries are a potential replacement for Lithium-ion (Li-ion) batteries. Compared to Li-ion, Li-S batteries weigh less and have a higher energy density. However, the problem is that Li-S composed batteries can unexpectedly lose charge due to a reaction inside the battery. This is known as the ‘Shuttle effect’. A team at the University of Texas have come up with a way to significantly lower this effect. Through using flexible and conductive polypyrrole-manganese dioxide (PPy-MnO2) nanotubes to contain the sulphur they inhibit the interaction of polysulphides responsible for ‘shuttling’ by binding them to MnO2. This process results in increased cyclic stability (meaning less fluctuation in charge/discharge speed and quality).

Body charged batteries 

A group of scientists at the Texas A&M University has developed a new concept of electrical storage: a heat charged solid-state supercapacitor. 
By converting thermal energy into electrical energy while also storing it, the solid-state supercapacitor can be charged by anything which creates heat differences with its surroundings i.e. a human body. This phenomenon is known as the Soret effect – in a solid-state polymer electrolyte ions move from hot to cold sides, generating a thermally induced voltage. 
This supercapacitor is flexible meaning it has potential applications in wearables, and integration in IoT wireless data transmission systems as an operator for sensors.

 

Ingestible battery wins inventor $100,000

In the 2016 Siemens competition in Math, Science and Technology 1st prize of $100,000 has been given to Vineet Edupuganti, a senior at Oregon Episcopal School in Portland, Oregon. Vineet developed a bio-degradable battery which he believed could be used in conjunction with ingestible medical devices such as organ monitors or diagnostic devices. The biologically safe battery dissolves in the body after the device has done its job. Competition judge Dr. David Crouse, professor of Electrical and Computer Engineering at Clarkson University, Potsdam, NY, emphasised what he sees as the importance of this invention: “Vineet’s project doesn’t just incrementally improve upon current capabilities – it represents a truly transforming step in creating a device that is both degradable and compatible with the body.”

Power to gas technology could provide answer to electrical storage

Chicago University developed technology that converts electricity into methane gas for more efficient and highly scalable storage, and that is now being commercialised by Electrochaea. Since it was set up 2 years ago, Electrochaea has built a large-scale demonstration wastewater treatment plant outside Danish capital, Copenhagen, called Biocat which provides natural gas to Denmark and the Danish gas grid. The gas is created by converting electricity and carbon dioxide into pipeline-grade renewable gas. This is done by using some of the electrical power to break water into its constituent parts and adding the resultant hydrogen to waste carbon dioxide in a bioreactor containing microorganisms that catalyse the mixture into methane and water. The gas can be stored easily and when needed later can be converted back into electricity. But this is just one of the potential power-uses of the gas. It could also be used as a renewable fuel, for example, in transportation, or for heating homes and industry. 
How this is done is by utilizing a microbe called methanogenic archaea which can be found in extreme environments around the globe. Electrochaea say their archaea exhibit some unique characteristics including high mass conversion efficiency, tolerance to contaminants, high selectivity and very fast reaction kinetics; all of which make them a good micro-organism for scaling up to commercial applications. 

Jumpers could be giving a lot more than static soon

University of Central Florida scientists have developed a ribbon-like device which can store and harvest solar energy. Composed of supercapacitors and solar cells, the ribbon is flexible enough to be woven into a fabric, so it offers potential for charging wearables, drones, and electric vehicles. When the ribbon is illuminated using simulated solar light, the supercapacitor has been shown to hold 1.15mWh cm-3 and have a power density of 243 Mw CM-3.

Smart pavements

Pavegen, a company based near Kings Cross, London, has just set up an energy harvesting pavement in Washington DC. Pavegen’s technology works by capturing the push-energy from peoples’ feet as they walk over its special flooring – triangular slabs covered in slip-resistant vinyl placed onto pressure sensitive energy harvesters. The energy so collected can be used to power integrated lighting systems, advertising billboards, or sold back to the power grid. In the future, Pavegen hope that through this system the energy generated by footfall could be converted into digital currency which could then be donated to charity. Pavegen also say that information can be gleaned from the tiles by local government about footfall and directional flow, to enable analysis of movement patterns, peak times and hotspots.

Charging ahead 4 Qualcomm speed charger

Qualcomm have revealed their new speed charger for mobile phones, Quick Charge 4, which will be available to buy in the 1st half of 2017. Compared to the Quickcharge 3 this is up to 20% faster, 30% more efficient, and charges 5 degrees Celsius cooler. The strapline ‘5 for 5’ is certainly compelling, Qualcomm are offering 5 hours of battery life for 5 minutes of charging. They claim that it can charge an average smartphone from 0 to 50% in 15 minutes.  

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