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Silicon anodes for improved capacity lithium-ion batteries

Imperial Innovations, Nexeon

Improving energy-storage capacity of lithium-ion batteries is a key target for meeting the energy demands of many types of electronic devices such as laptops and electric vehicles. Currently, graphite anodes are used in lithium-ion cells, but the demands of technology have advanced to the point where carbon is operating near its theoretical limit. In order to meet rising power demand while keeping batteries small, Imperial

College spin-out Nexeon has been investigating the properties of silicon as an anode material.

Silicon has long been known to have a higher power capacity limit than graphite, but when used as an anode it expands dramatically during battery discharge and contracts during recharging, which quickly pulverises the material and destroys its conductivity.

Nexeon has been building on the work of its founder, Prof Milo Green, to develop a method of configuring the structure of silicon to avoid this problem.

It has developed a silicon anode that survived 500 full charge/discharge cycles without losing conductivity, with the anode handling four times the power capacity that would be achievable using a conventional carbon anode. This technology, the company says, could lead to more powerful, compact batteries, capable of longer running times: a goal it is aiming for as part of a UK consortium with £1m funding from the Technology Strategy Board.

Fuel cell-powered black cab

Intelligent Energy, Lotus Engineering, LTI, TRW Conekt, Technology Strategy Board

It is impossible to imagine London without its iconic fleet of 22,000 black taxis, but their diesel engines are heavy contributors to the city’s air pollution; it’s estimated that up to a third of the particulates are down to black cabs.

With the 2012 Olympics providing a showcase for London as a ’green city’, Intelligent Energy pulled together a consortium to develop a zero-emissions-in-use electric taxi, powered by IE’s proprietary hydrogen fuel cell.

The fuel cell provides 30kW of power for the cab’s drive train, which was developed by Lotus Engineering. TRW Conekt led the safety part of the project, developing steering and braking systems, while TRI provided TX4 taxis to assist with the structural modifications of the chassis.

As well as providing the fuel cells, Intelligent Energy assisted with the integration of the system into the vehicle.

The result is a taxi that produces no emissions on the road, can cover 250 miles on a single tank of hydrogen, can be refuelled in less than five minutes, and has as much baggage and passenger space as a conventional cab.

A small fleet will be on the road during the 2012 Olympics, but the partners say that it’s an important step on the way to an entirely fuel-cell-powered taxi fleet for the capital, and the technologies are immediately transferrable to other automotive applications.

AIRPOWER - rapid production of offshore wind turbine blades

University of Nottingham, BAW, Hexcel Composites, Gamesa, Moog Insensys, Magnum Venus Plastech, NaREC

Offshore wind turbines are huge structures that have to withstand harsh environments.

The turbine blades in particular have to combine many seemingly contradictory criteria - they have to be strong but light, they have to catch the wind but not be damaged by it and they must be made to high tolerances but in large numbers and as rapidly as possible.

This consortium, led by Nottingham University, aims to bring advanced manufacturing techniques from aerospace into the wind-turbine sector to develop a new way of making turbine blades.

The system is based on automated tape laying (ATL), commonly used to build up the structure of composite aircraft wings and very well suited to making mainly flat, gently contoured shapes. This forms the structure of the blade and is the matrix onto which the resin portion of the composite blade is cast, using a liquid-resin transfer-moulding (LRTM) process.

The blades incorporate optical-fibre strain sensors. None of these processes had previously been used in this combination and with these materials for turbine-blade manufacture.

The consortium used a BAE Systems aircraft manufacturing facility to develop and test the process, adapting it to handle the materials used for turbine blade manufacture.

Each of the members contributed to the production of a 7m section of a full-scale turbine blade to showcase the systems and the members are now employing the expertise gained from the project in their own sectors of the wind-turbine market.

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