Energy Harvesting & Storage Tech Digest - June 2017

Flywheel energy storage project

As part of the Energy 2050 project a hybrid battery / flywheel energy storage solution will be installed at the University of Sheffield’s energy storage facility in the UK. The result of the EUR4 million project will be connected to the Irish and UK grids to help respond to energy demand. Flywheels work by accelerating a rotor to high speeds using electrical energy which effectively becomes stored in there as rotational energy. It can then be converted back to electrical energy when demand requires. Flywheels have a longer life span than batteries. This flywheel battery combination will produce 1MW of power and store 10kWh of energy. 

Kite wind energy system

Kite Power Systems, a TU Delft spin-off, is developing a 100kW airborne wind energy system to work with diesel generators in remote locations. The Kitepower system uses kites at high altitudes to harvest energy from high speed winds. The kites fly in a circular loop achieving speeds of over 100 mph from a 20 mph wind. Tension in a tether attaching the kite to a ground based station causes spooled cable – which can be 100 to 200 metres long - in a rotating drum to spool out. This motion powers a generator which creates electricity. To retract the tether the angle of the kite’s wing is robotically altered to offer minimum aerodynamic resistance, and the loose cable can then be respooled. The system generates more energy in the unspooling motion than is required to respool creating a net energy gain.

STENG: a device powered by skin

Scientists at Georgia Institute of Technology have improved the flexibility of triboelectric nanogenerators (TENGs), creating what they have named skin-like triboelectric nanogenerators (STENGs). A STENG is composed of an elastomer (which acts as electrification layer) and an ionic hydrogel (which acts as an electrode) that can then be attached to skin. TENGs are able to generate electricity from contact between two materials, and as such the scientists think that their material could be used to make self-powered electronic skin for self-powered soft robots. The STENG material can be stretched to ratios of over 1000 percent according to the scientists. It is also very transparent, allowing over 95% percent of visible light to pass through it. It can cope with temperatures of 30° Celsius. 

Coating bacteria increases microbial fuel cell potential

Scientists at Nanyang Technological University have created an anode for microbial fuel cells (MFCs) by coating live, electroactive bacteria with an electrically conductive polymer. The coated bacteria showed 23 times less electrical resistance than uncoated bacteria, a fivefold increase in electricity generation, and 14 times the power density in a MFC’s anode. 

Self-powering pacemaker

Rice University researchers have developed a battery-less, wireless pacemaker that can be implanted directly into a patient’s heart. The pacemaker harvests power from radio frequency radiation from an external battery pack – which in the prototype is functional when a few centimetres from the pacemaker. The device’s chip is 4mm wide and includes a receiving antenna, an AC to DC rectifier, a power management unit and a pacing activation signaller. The device has been tested in a pig to tune its heartrate from 100 to 172 beats per minute. 

Turning ambient moisture into hydrogen

Researchers at RMIT University have developed a solar ‘paint’ that can absorb water vapour and split it to generate hydrogen – which can then be used as an energy source. This is made possible by the paint – ink – containing synthetic molybdenum-sulphide which acts as a semi-conductor and moisture absorber and that also catalyses the splitting of water – found in the air – into its constituent parts. This is combined with titanium oxide particles to absorb solar energy, thus providing the power needed for the splitting. The ink could be applied to insulating surfaces such as glass or could be incorporated into future solar cell design.

Flexible energy harvester

North Carolina State University scientists have designed a proof of concept of a flexible thermoelectric energy harvester. The device uses a liquid metal of gallium and indium – known as EGaln – a non-toxic alloy that exhibits low resistance to connect the thermoelectric harvesters. Low resistance means more power. Liquid metal also enables the device to self-heal: if a connection is broken the liquid metal will reconnect. Future work will focus on improving the device’s efficiency by further reducing the resistance. 

Urine as a power source

Pee Power uses technology developed by scientists at the Bristol Bioenergy Centre (BBiC) to use urine as a power source for things such as lights and mobile phones. Pee Power is being installed at British music festival Glastonbury where there will be a 40-person Pee Power urinal. The technology uses a microbial fuel cell, the bacteria inside of which consume the urine and produce electrons in the process. These electrons are then sent through an electrical circuit where it can be used to power electronic devices. At the festival Pee Power will use the 1000 litres of urine produced per day to power 10 information panels.   

Japanese company creates several devices that can scavenge heat to make electricity 

Japanese company KELK plans to launch three thermoelectric energy harvesting products in June 2017. These are:

1) Thermoelectric EH*1 Device – this generates electricity by being placed on a heat-emitting machine. It uses the electricity to power its sensors and wireless module for on-site monitoring. 

2) Stand-Alone Thermoelectric Generation Power Source Unit – this is capable of generating electricity from being placed near a camp fire or stove and can charge mobile devices.

3) Waste Heat Recovery Unit – recovers waste heat from industrial machine such as furnaces. 

Phone that uses ambient energy to power itself

Scientists at the University of Washington, USA, have developed a cellular phone that harvests ambient radio signals or energy from light to power itself. The battery-free cell phone is able to power itself with only a few microwatts of power, the scientists claim. To show its ability to transmit and receive audio a Skype call was made on the prototype – made of commercial, off the shelf components. To reduce the power needed to run the phone the scientists altered how the phone converts analogue signals into digital data. The battery-less phone converts vibrations in the microphone or speaker into standard analogue radio signals emitted by a cellular base station. The team plans to increase the phone’s operating range and add encryption to conversations.  

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