US (MN): Year-long study of LED greenhouse lighting yields illuminating results

Two groups, Outsourced Innovations, a lighting consulting firm, and Tangletown Gardens, a greenhouse nursery and garden business, recently finished a one-year Conservation, Applied Research & Development (CARD) grant project funded by the Minnesota Department of Commerce.

The research project, LED Lighting to Improve Energy Efficiency in Controlled Environment Agriculture, aimed to show reductions in energy use from greenhouse-specific LED lamps compared to the traditional use of high pressure sodium (HPS) lamps in a controlled crop environment.
Lessons from this research project answered three primary questions: 
  • Whether LED lighting could be used in controlled environments to grow leafy greens, basil, chard and cucumbers to save energy in contrast to high pressure sodium?
  • How to assess the value of solid-state lighting technology as fundamentally different compared to conventional filament lighting?
  • What non-energy outcomes could be expected from experimental plants grown under LED lighting?
The results? 
  • The research project demonstrated it was possible to grow leafy greens, basil, chard, and cucumbers under 100% greenhouse LED lighting with no negative outcomes, meaning all plants were of salable quality. The project also found that a change in plant growth was caused by light intensity, whether LED or HPS lamps.
  • Although they have a higher upfront cost, greenhouse LEDs provided a projected net present savings of $5,745 in energy and maintenance costs over the five-year life of the LED lamps compared to conventional HPS lighting. Energy savings payback was estimated at an attractive 2.2 years.
  • The evidence related to plant growth suggested need for further research. Greenhouse LEDs offer the promise of new business opportunities for greenhouses, urban agriculture, and vertical farming in Minnesota. 

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