Lighting for the 21st century

bjb42 — Sat, 01 Aug 2009 14:41:07 +0000

A revolution in lighting is under way. Thanks to advances in the technology, efficiency and cost of light-emitting diodes (LEDs), these devices are ready to take over in the very near future from conventional forms of incandescent lighting. ̽��ֱ��potential energy savings are huge: statistics from the US Department of Energy estimate that, by 2025, solid-state lighting such as LEDs could reduce the global amount of electricity used for lighting by 50% and, in the US alone, could eliminate 258 million metric tons of carbon emission, alleviate the need for 133 new power stations, and result in cumulative financial savings of over a hundred billion dollars. At the forefront of research underpinning this new lighting paradigm is a focus on the semiconductor gallium nitride (GaN) at the Cambridge Centre for Gallium Nitride in the Department of Materials Science and Metallurgy.

Why use GaN for LEDs?

LEDs based on GaN, which emits brilliant light when electricity is passed through it, are extremely energy efficient and long lasting. Traditional incandescent light bulbs are only 5% efficient at converting the electricity they consume into light, and, although low-energy light bulbs are 20% efficient, they contain hazardous mercury. Compare this with white GaN LEDs, which are already 30% efficient and have a target efficiency of 60%. GaN LEDs are also incredibly long lasting: an LED can burn for 100,000 hours. In practical terms, this means it only needs replacing after 60 years of typical household use.

In the UK, lighting consumes over a fifth of all the electricity generated at power stations, and GaN LEDs have the potential to reduce this figure by at least 50% and possibly by 75%.

̽��ֱ��Holy Grail for GaN is home and office lighting. Research directed at reducing manufacturing costs and improving the quality of light is bringing this goal closer.

Materials and devices

Research at the Cambridge Centre for Gallium Nitride, directed by Professor Colin Humphreys, the Director of Research in the Department of Materials Science and Metallurgy, stretches from fundamental materials studies through to applications and devices.

̽��ֱ��Centre has world-class GaN growth and characterisation facilities and has recently developed an innovative technique for growing GaN on large silicon wafers, instead of the more expensive sapphire wafers; this could deliver a tenfold reduction in LED manufacturing costs. ̽��ֱ��Centre is also working on improving the quality of light by coating blue LEDs with phosphors to produce white light. This will be improved still further through the use of novel phosphors produced by Professor Tony Cheetham in the Department of Materials Science and Metallurgy.

̽��ֱ��future

GaN LEDs have hit the market rapidly and are already widely used in flashlights and front bicycle lights, as backlighting for mobile phones and interior lighting in cars and aeroplanes, and even to light up landmarks such as the façade of Buckingham Palace and the length of the Severn Bridge. Looking ahead, the timescale for the widespread adoption of GaN LEDs in homes and offices is probably as short as 5–10 years.

Other applications also look promising. Research at the Centre is investigating the possibility of using GaN LEDs to mimic sunlight, which could have important benefits for sufferers of seasonal affective disorder (SAD). And other studies are investigating how UV LEDs, created by adding aluminium to GaN, could be used for killing bacteria and stopping viruses from reproducing, either to purify water in the developing world or to ‘sweep’ hospital wards to eradicate superbugs.

For more information, please contact the author Professor Colin Humphreys (colin.humphreys@msm.cam.ac.uk) at the Cambridge Centre for Gallium Nitride. ̽��ֱ��Centre’s research is funded by the Engineering and Physical Sciences Research Council (EPSRC), the Technology Strategy Board (TSB), Aixtron Ltd, Sharp Electronics Europe, QinetiQ, Forge Europa, Philips, Imago Scientific Instruments and RFMD (UK) Ltd, and is performed in collaboration with the ̽��ֱ�� of Manchester and Sheffield Hallam ̽��ֱ��.

A remarkable light-emitting material, gallium nitride, could slash electricity consumption, purify water and kill superbugs.

In the UK, lighting consumes over a fifth of all the electricity generated at power stations, and GaN LEDs have the potential to reduce this figure by at least 50% and possibly by 75%.

Colin Humphreys

Green LEDs

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Yes

Cleaning up contaminated land

ns480 — Thu, 01 May 2008 09:45:15 +0000

Dr Abir Al-Tabbaa, Reader in Geotechnical Engineering at the Department of Engineering, provides the academic lead on a £1.24 million initiative that aims to develop a new technology for cleaning up the legacy of industrial contamination left in soil: heavy metals, petrol, tar, asbestos and other noxious waste. Remediation is needed both to protect the wider environment and to meet ever-increasing demands for housing and commercial developments on brownfield sites.

Project SMiRT (Soil Mix Remediation Technology) is the largest project funded by the Technology Strategy Board (TSB) on contaminated land remediation technologies to date. Leading the industrial component of the project is geotechnical contractor Bachy Soletanche, with the additional involvement of engineering consultancies, trade associations and materials suppliers.

‘Making previously developed sites safe for new development is an important but costly process, with government targets set at building 72% of new housing on brownfield sites and upwards of £400 million per year spent on remediation,’ explained Dr Al-Tabbaa. ‘ ̽��ֱ��technology that we are working on with Bachy Soletanche aims to achieve significant technical advances that will reduce the cost and time involved in this necessary process.’

Over the course of three years, the project will develop an integrated advanced Soil Mix Technology by designing and manufacturing novel equipment and employing suitable materials that can simultaneously improve land quality and deal with pollutants. An important element of the project will be to take this technology forward through consultation meetings with stakeholders and a dissemination programme. ‘This project is a unique opportunity to further develop soil mixing equipment in close parallel with materials technology,’ said Peter Barker of Bachy Soletanche. ‘ ̽��ֱ��aim is to provide new, cost-effective solutions for both the contaminated land and ground improvement sectors.’

For more information, please contact Dr Abir Al-Tabbaa (aa22@eng.cam.ac.uk).

A recently launched project that unites academia with industry is addressing the need to decontaminate ‘brownfield’ sites for redevelopment.

̽��ֱ��technology that we are working on with Bachy Soletanche aims to achieve significant technical advances that will reduce the cost and time involved in this necessary process.

Dr Al-Tabbaa

Magnus Franklin on Flickr

Contamination