Cambridge | Jan-14 | Lighting, Power Electronics, Communications & Health
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Gallium Nitride (GaN) is a transformative material with significant potential for off-grid villages, especially in low-energy lighting, health (water purification), and efficient power electronics. The document emphasizes the need for cost-effective GaN LED technology to enable widespread adoption in developing countries, alongside promising applications in UV water purification and Li-Fi technology for improved internet access. It calls for increased research funding and collaboration to harness GaN's capabilities and address critical issues like energy efficiency, clean water access, and sustainable development.
Cambridge | Jan-14 | Lighting, Power Electronics, Communications & Health
- 1. Colin Humphreys Department of Materials University of Cambridge, UK Lighting, power electronics, communications and health New Technologies for off-grid villages – a look ahead Cambridge Workshop, Moller Centre, 15 January 2014
- 2. Gallium nitride (GaN) and off-grid villages • GaN is a new manmade material. • Important for off-grid: • Low-energy lighting (now + next 10 years) • Health: water purification (2-10 years) • Low-energy power electronics (3-10 years) • Communications (3-10 years) • Also for super-efficient solar cells (5-10 years)
- 4. How to make white light
- 5. US DoE Report • By 2025 Solid-State Lighting using GaN-based LEDs could reduce the global amount of electricity used for lighting by 50% • No other consumer of electricity has such a large energy-savings potential as LED lighting
- 6. LEDs • Light emitting diodes (d) • Made from solids (e.g. GaN) that emit light • LEDs last 100,000 hours (electronics 50,000) • Light bulbs (incandescent) last 1,000 hours • LEDs fail by slow intensity decrease • Light bulbs fail totally and suddenly
- 7. Efficiency of light sources Incandescent light bulb = 5% (15 lm/W) Fluorescent tube (long) = 25% (80 lm/W) Fluorescent lamp (CFL) = 20% (60 lm/W) White LEDs (350 mA) = 30% (100 lm/W) White LEDs (in lab) = 60% (200 lm/W) Sodium lamp (high P) = 40% (130 lm/W)
- 8. Lighting in the Developing World • White LED + solar cell + battery • Off-grid -- No electricity costs • Light to study when it is dark • Light to work when it is dark • Help people get out of poverty • Take care with choice of LED – no standards yet
- 9. Off-grid lighting • GaN LEDs have been available for several years for off-grid lighting (+ solar panel + battery) • LEDs recently become so efficient can be used for off-grid street lighting (+ solar + battery) • LED efficiency will continue to increase for next 10 years
- 10. What is preventing widespread use of LED lighting in developing countries • Problem: Cost • Low-power LEDs cheap: a few pence • High-power LEDs for lighting: expensive • Philips 60 W equivalent LED costs £15
- 11. Solving the GaN LED cost problem • All commercial GaN LEDs grown on small- diameter (2”, 3”, 4”) sapphire or SiC wafers • Reduce costs: grow on large-diameter Si wafers • Will substantially reduce cost of LEDs • Will enable LED lighting in homes and offices • In UK, save £2 billion pa electricity costs • Close (or not build) 8 large power stations • My group (Dandan Zhu) pioneered growth of GaN LEDs on 6-inch Silicon
- 12. Why grow GaN on 6-inch Si? • Compatibility with Si processing techniques using a Si foundry – Should give improved automation and yield – Compare with “hand” processing with sapphire • Cost substrates (6” Si costs 30x < sapphire) • Growing on 6”, 8” and larger substrates will offer increasing cost reductions • Ease of removal of Si substrate • Lower cost LEDs and other devices
- 13. Commercial Exploitation • My group set up CamGaN (2010) and Intellec (2011) to exploit Cambridge GaN on 6” Si LEDs • Plessey acquired both companies in February 2012. Hired 3 post-docs from my group • Plessey is now manufacturing low-cost GaN on 6” Si LEDs at their factory in Plymouth, UK (d) • The first manufacture of LEDs in the UK • First order: 20 million LEDs from China • Will enable widespread GaN LED lighting
- 14. Plessey exhibit with Lewis Liu, Barry Dennington and Vince Cable
- 15. Lack of Drinkable Water • Over half of the hospital beds in the developing world are occupied by people with water related diseases (BMJ) • 3 million die each year from impure water (WHO) – Mainly Africa, India • Probably more people will die this century from the lack of drinking water than from any other cause
- 16. A Scientific Approach to Purifying Water • Need to destroy bacteria, viruses, mosquito larvae, etc., in water • Preferably without chemicals – Giardia resistant to chlorine – Chlorine reacts with organic acids in soil to produce carcinogens • Earth’s atmosphere completely blocks deep- UV radiation from the Sun • Biological organisms on Earth never developed a tolerance for deep-UV radiation
- 17. Effects of Deep-UV Radiation • Deep-UV radiation damages nucleic acids in DNA, RNA • Bacteria, viruses, unicellular organisms, cannot reproduce • Fungi, mosquito larvae, etc., killed • Deep-UV radiation purifies water • WHO states that UV light is best treatment to purify water
- 18. Deep-UV for water purification • Mercury (Hg) vapour lamp used today. – Emits 254 nm deep-UV – Purifies water – Needs high voltage supply, hence grid electricity • UV LED AlGaN-based – Wavelength flexible – 280 nm the best: kills every micro-organism – Power off-grid with solar + battery – Point-of-use the best treatment (WHO)
- 19. AlGaN LEDs for Water Purification • Emission at 280 nm achievable now • BUT efficiency is too low to purify flowing water • More research required: 2-10 years timescale • Needs specific research funding • If we can achieve we will help to solve the major problem in the developing world and save millions of lives
- 20. GaN power electronics • Power electronic devices in power supplies for mobile phones, computers, power inverters for photovoltaics • GaN has low power consumption for both lighting and electronics: very energy efficient • GaN power electronics 40% more efficient than Si • Power electronics: replace Si devices by GaN – grow GaN on large-area Si to reduce the cost • Enable easier off-grid charging and use of mobile phones, computers, etc., using solar plus batteries
- 21. Li-Fi for Wi-Fi in developing world • Two-thirds of world lacks good Internet access • Wi-Fi equipment expensive and energy inefficient • Use light as carrier instead of radio frequencies • Use LEDs for Wi-Fi, videos, data communication • Li-Fi in every room in house, office, street lights • Li-Fi for off-grid low-cost energy-efficient Wi-Fi in developing countries • Details to be worked out (3-10 years)
- 22. InGaN for super-efficient solar cells • Most solar cells made from Si – Bandgap 1.1 eV -- in the infra-red – About 20% efficient (theoretical max. ~ 25%) • Organic solar cells ~ 10% efficient (max) • Bandgap of InN is 0.7 eV and of GaN is 3.4 eV – Covers most of the solar spectrum • Multi-junction InGaN solar cells in theory can be 80% efficient. Difficult (5-10 years)
- 23. How do we get to where we want to be? • GaN LEDs for lighting – Important for developed world – it will pay research – Some extra research needed for optimising LED design for off-grid power by battery/solar cell? • UV AlGaN LEDs for water purification – Research funding needed to accelerate research • GaN power electronic devices – Important for developed world – it will pay research – Extra research needed for optimising for solar power
- 24. How do we get there (2) • Li-Fi using GaN LEDs – Useful for developed world. It will fund research – Extra research needed for optimising using solar • Super-efficient InGaN solar cells – Difficult long-term project – Needs specific funding to accelerate progress
- 25. What is needed (tentative!) • New Research Centre, or network of Centres, focussed on specific problems • Strongly linked to developing countries • Funded for 10 years • Go from basic research through to real prototype devices • To solve the GaN problems (purifying water, etc) need, say, £5 m start plus £2 m pa + building
- 26. Funding source(s) • Would the Department for International Development (DFID) fund this out of its existing resources? • Or in partnership with EPSRC, etc?
- 27. Conclusions • The new material GaN has huge potential for use in developing countries • Bring light to the world • Purify water: save millions of lives • Save energy in charging computers, mobile phones • Bring Wi-Fi with LED Lighting (Li-Fi) • Promises ultra-efficient solar cells