Ceravision
Ceravision is a privately owned lighting company based in Bletchley Park, UK. Ceravision is the inventor of a range of electrodeless lamps and integrated luminaires under the trade name Alvara, the world's first High Efficiency Plasma (HEP) lamp.[1][2] The Alvara range uses half the power and has half the total cost of ownership of competing ceramic metal halide lamps. Thus far, the lamp is not produced in styles suitable for the home and small business markets, but is marketed as bay lighting for large warehouse spaces, and as street lighting.
Electrodeless lamp
Electrodeless lamps have been recognized, since Nikola Tesla filed a patent in 1894, as having a number of advantages:
- No electrodes to break - so potentially very long life
- No chemical degradation of the electrodes - so much lower lumen loss and discoloration during life
- No reactive metal inside the bulb - so the ability to use much more efficient fill materials
The main problems have been constraining the radio waves within the lamp, and generating RF power at low cost.
Developments
Earlier incarnations, such as the sulfur lamp, had been very large. The invention took advantage of the high dielectric constant of ceramic to create a very small waveguide to constrain and focus the radio waves. Though the resulting lamp was small and produced a large number of lumens per watt at the bulb, the lamp efficiency was low since 80-85% of the light generated is trapped inside the opaque ceramic waveguide.
Ceravision's invention was a clear quartz waveguide and integrated lamp, which forms a single piece construction. The generated light can now be collected because the waveguide is optically clear, giving excellent lamp lumens per watt. The integrated burner and waveguide, which is source of light, is very small meaning that it is possible to design exceptionally efficient luminaires. HID (high intensity discharge) luminaires have typical utilization efficiencies of 75%. Fluorescent lamp luminaires have efficiencies of 70% - meaning that 25% and 30% respectively of the light produced by the lamp is wasted. The Alvara(TM) range has utilization efficiencies of more than 90%. The burner is integrated into the thick walled quartz waveguide, high powers from 100 - 5000W's are possible without damage to the lamp.
The second issue - long life, low cost RF generation has been solved using a combination of a magnetron with a specialized controller. Magnetrons are manufactured in large volumes for use in microwave ovens. They are able to produce RF power at a cost of less than $0.02/W(RF). This is far below any expected solid state chip price for the foreseeable future.
Historically, the problem with magnetrons has been their short life. A microwave magnetron has a typical life of approximately 2,000 hours. In cooperation with Dipolar of Sweden, Ceravision has developed a method of extending the life of magnetrons to over 40,000 hours. Ceravision recently announced an agreement with Toshiba to develop high efficiency magnetrons.[3]
The benefits of Ceravision's High Efficiency Plasma range are:
- High efficiency lamp system
- High luminaire coefficient of utilization
- Highest luminaire efficacy rating
- Fast turn-on
- Hot re-strike (<60 seconds)
- Dimmable to 20%
- CRI between 60 and 90
- Remote software control and monitoring
- Full-spectrum light
- Lumen maintenance 90% through life
- Color stability
- Extremely long life
- 80% recyclable - no specific disposal requirements
- Lowest cost of ownership compared to existing solutions
The lamp consists of four integrated elements; a quartz RF resonator and integral plasma burner (lamp), a transition unit (the system which couples the RF source to the resonator), a magnetron, and an AC power supply. The resonator and integrated burner contain an inert gas and metal halide salts. Microwave energy ionizes the gas to form the plasma which combines with the metal halide to vaporize the metal halide salts and produce the light.