With this in mind, researchers from the Green Design Institute at Carnegie Mellon University, US, have taken apart three commercial solid-state lighting devices designed to fit in conventional screw-type light bulb sockets. Their aim was to investigate strategies for dealing with the products once they are no longer usable.
"As far as we know, our current paper is the first to consider solid-state lighting design for end-of-life material recovery and component re-use," Chris Hendrickson of Carnegie Mellon told environmentalresearchweb.
According to Hendrickson, designing products carefully can reduce their overall lifecycle energy consumption and minimize disposal of key materials. "Other products have achieved significant savings from this approach," he said. "For example, I studied re-manufacturing of power tools over a decade ago and this re-manufacturing market is now widespread."
Light-emitting diodes are expected to have lifetimes of from 10,000 to more than 25,000 hours – around 7–15 years at a usage rate of four hours per day. The devices typically produce 50–70 lumens of light per Watt, compared to 10–20 lumens per Watt for traditional filament light bulbs. But they're currently around three or four times more expensive to manufacture than other lighting technologies.
Of the three lamps analysed, one contained only 83 g of material, whereas the other two contained 250 and 287 g, respectively. In all three products the aluminium heat sink was the heaviest component, while the housing and optics contained a range of different plastics and glass. Each lamp contained 10–15 materials or components; the researchers say disassembly spanned from easy to difficult.
Hendrickson and colleagues recommend that lamp designs use standardized part connections such as screws or snap-fits rather than welds to make taking them apart easier – only one of the lamps they studied used screws, so that in some cases the disassembly was destructive.
Designs should also employ fewer types of materials in structural components to aid materials recovery, for example using only one type and colour of plastic, and labelling its composition clearly. Materials recovery is particularly viable for aluminium and plastics, but may also become feasible for gallium in future.
Finally, designing standardized replaceable parts would make remanufacturing easier. This would enable replacement of failed LED arrays and drivers, while using similar heat sink components in several lamp designs would enable remanufacturing of the heat sink from a failed lamp into several other products.
"The lighting industry should also start now to develop effective product take-back systems to collect future end-of-life products," write the researchers in Environmental Research Letters (ERL).
The researchers believe that good design can reduce end-of-life waste and reduce costs, in turn promoting more rapid adoption of solid-state lighting. Because the industry is in the early stages of development it should be relatively easy to introduce new standards.
"Manufacturers have the opportunity to factor in end-of-life issues at the design stage now, so as to make recovery simpler later, avoiding issues that other lighting technologies have seen," said Hendrickson.
But the team's research hasn't been straightforward. "This work is slowed by manufacturers concerned about releasing proprietary information and the rapid changes in solid-state lighting technology, but we think we can get some reasonable bounds on the savings that such lighting might provide," said Hendrickson.
The researchers reported their results in ERL.