The pace of packaged LED and solid-state lighting (SSL) product announcements has certainly escalated of late, coincident with the more widespread usage of the technology in greenhouses and vertical, urban farms. Cree began the summer announcing its Photo Red packaged LED for horticultural applications and now just four months later has said that performance has increased by 21% in both the new XLamp XQ-E and XP-E High Efficiency (HE) LEDs. The improvement will enable horticultural lighting manufacturers to reduce the size of luminaires and/or cut system cost.
The Photo Red LEDs are intended to optimize the plant photosynthesis process by emitting light in the 660-nm energy band, a spectrum known for increasing chlorophyll absorption as we covered in a feature article on horticulture. More recently, horticultural experts have evolved the knowledge base to identify other spectra that are also important to various plant types.
The company is characterizing the LED performance using the Photosynthetic Photon Flux (PPF) metric. Metrics such as lumens and efficacy that target the sensitivity of the human eye have little or no significance in terms of the effectiveness of LED lighting on plant growth. The PPF metric is based on the total photons produced in the plant PAR (Photosynthetically Active Radiation) region from 400–700 nm, although other new horticultural metrics will include an even wider region from 280–800 nm or the plant biologically active radiation (PBAR) band.