High Efficiency Indoor Grow Laboratory Study

SDG&E expects significant load growth in the indoor agriculture sector, primarily driven by the legalization of recreational cannabis use as well as increased interest and growth in indoor agriculture development opportunities at large. In line with efforts to encourage producers and trade allies to adopt more efficient indoor agriculture technologies, SDG&E’s ET team collaborated with the Salk Institute for Biological Sciences to develop an indoor lighting technology test laboratory, hosted at the Salk Institute’s facility in La Jolla, CA. SDG&E and the Salk Institute jointly funded the fabrication and installation of two indoor agriculture grow chamber laboratories out of standard shipping containers. Once installed, the grow chambers were used to test the performance of new adjustable spectrum light emitting diode (LED) luminaires. The luminaires were tested by comparing the crop yield from tomato plants grown in one container with the test technology lighting to the yield from a control crop grown in a control chamber using conventional High Pressure Sodium (HPS) lighting, an industry standard lighting fixture at the time of the study.

The crop comparison study was impaired due to delays in the fabrication of the grow containers, followed by the COVID-19 pandemic beginning in February 2020, which restricted access to the grow chambers by the researchers at key points in the tomato growth cycles. These delays, along with unexpected crop failures due to software issues, impaired the results of the study. Although the study showed qualitative improvements in the crop yields from test technology compared to the control technology, much of these improvements could be attributed to the more efficient LED lighting technology. Further research is needed to thoroughly assess the impacts of the variable spectrum benefits of the test technology.

The test technology was marketed as a fully automated crop growing system. However, there were crop failures, and a lack of alarms to the operator to prompt intervention, which indicates the test technology system requires further development before it can be considered market ready.
The test technology vendor claims that the spectrally specific lighting source provides superior lighting, resulting in increased crop yields. However, since the spectral output for the product is currently manually controlled, and not measured by any standard (e.g., light wavelength) these specific claims cannot be supported or refuted based on this Study.

The Study therefore determined that further investigation of spectrally specific lighting growth characteristics is required to substantiate the test technology vendor’s claims. A future study should include a measure of light output by wavelength of both the test product and the industry standard control system.

The test technology vendor used HPS lamps, which use electric resistance lighting as the baseline system. In the five years since this Study was initially proposed, the indoor agriculture market has made significant progress towards replacing electric resistance lighting with LED luminaires as the standard for indoor agriculture. As a result, a more appropriate baseline fixture for future studies of this type may consist of LED luminaires.