Zeta develops LED lamp with UK funding

After winning a UK government funding competition last year, Zeta LED has built an LED lamp with a unique approach to thermal management.

Sep 16th, 2011
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Zeta LED, a UK-based technology company, has unveiled the LifeBulb, which it developed after winning a funding competition from the UK Technology Strategy Board (TSB).

The 8W lamp, which Zeta describes as the “world’s first true replacement for the 60W incandescent bulb,” is currently going undergoing extensive testing. A limited production run is planned for later this year.

Zeta principals
The unique design of the LifeBulb provides omnidirectional illumination similar to a conventional incandescent lamp. Unlike many LED-based designs, it does not have a large finned heat sink or other obvious thermal-management features. It is also unusual in that the LEDs can be directly viewed on the exterior of the lamp.

The development of a 60W-replacement is timely considering that production of 60W incandescent lamps is now banned in Europe.

Development funding

Zeta LED is part of Zeta Controls, which has experience in developing controls for solar and LED systems. In 2010, Zeta won a development contract for GBP450,000 (around USD700,000) from the UK Department for Environment, Food and Rural Affairs (Defra) and the UK Technology Strategy Board (TSB) to develop an ultra-efficient lighting prototype for domestic use. The contract was part of the Small Business Research Initiative (SBRI), which invests in cutting-edge UK projects.

Phil Shadbolt, Managing Director of Zeta Controls, explained that a number of companies each received GBP 40,000 in July 2010 to conduct feasibility studies of their SSL concepts. In November of last year, Zeta LED and Juice Technology were selected as the two winners, both in the non-directional lighting section of the competition. Each received GBP450,000 to develop their prototypes and produce 50 fully-functional, tested demonstration units.

Lamp design

A central feature of Zeta LED’s lamp design is an aluminum cage on which the LEDs are mounted. Air flow through the lamp’s body and around the aluminum cage provides passive cooling. This removes the need for a heat sink of the type often seen near the base of LED lamps. The design was also crucial in enabling the lamp to meet the TSB’s stringent design criteria. “The lamp had to fit in the exact same envelope as a conventional lamp,” said Shadbolt.

The thermal design enables a life span of 25 years when used for four hours a day, says Zeta, which equates to 36,500 hours. The lamp has an overall efficiency of 76%, a power factor of 0.9, a CRI in excess of 80 and a color temperature of 3200K. Zeta’s experience in building control systems for solar- and LED-based systems allowed it to develop driver circuitry that enables to the lamp to be dimmed down to 1% with most conventional wall dimmers. This circuitry is positioned within the aluminum cage.

The lamp uses 10 LED arrays mounted on the cage, with 5 each in the upper and lower hemispheres. Shadbolt says that the nine-chip arrays are custom-made in China and have a unique shape to fit the lamp design. The chip-on-board LEDs are coated in phosphor but have no other optics. This approach reduces glare, which could be an issue if power-LED packages were used instead of the arrays.

Shadbolt says that the light output is 720 lm – which falls short of the level of 806 lm required to claim equivalence to a 60W incandescent lamp – although further testing is being carried out. This puts the efficacy at 90 lm/W, which was another of the stringent requirements set by the TSB.

From prototype to production

As part of the funded development project, Zeta manufactured 100 units, of which 50 were submitted to the TSB to undergo further testing. The others will be sent to potential interested parties (retailers, prominent people) for evaluation.

Shadbolt says that the company plans to manufacture 1000 units by the end of this year, and these will go on sale with a retail price of around GBP 20. “Our target is for the price to be below GBP 10 in volume production,” he said, meaning a volume in excess of half a million units annually. To achieve this, Zeta is looking for potential investors or partners with manufacturing expertise.

It’s not clear whether the TSB will support further product development. This is in contrast with the L Prize in the US, a key component of which is the promotion of the winning product and its utilization by partners such as energy-efficiency organizations.

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