The photo is sourced from Scoltech
When a washing machine, an iron or other domestic appliances are used at night, the consumer can save on utility charges, while the energy company can cut daytime load and thereby reduce infrastructure maintenance expenses. But can this solution be applied in agriculture without damaging the plants, especially in countries where vegetables can only be grown in greenhouses because of low temperatures and insufficient natural light?
Seeking an answer to this question, Skolkovo researchers conducted an experiment with different varieties of lettuce and leaved chicory: similar plants were grown in parallel in two identical greenhouses with all other conditions equal except for the lighting regime. “In both greenhouses the plants were exposed to 16 hours of light of prescribed intensity. The only difference was that in the control group, the eight dark hours were uninterrupted and more or less coincided with natural darkness at night, while in the test group the dark intervals could be dispersed over the 24-hour period, depending on when the electricity rates were highest. No measurable growth differences were identified in any of the varieties,” says Javier Penuela, PhD student of the Engineering Systems program, as cited by Skoltech.
A similar experiment was performed in a four-tier vertical farm setup, and the result was the same. Comparison between lettuce cultures grown on two test tiers and those harvested from control tiers did not reveal any meaningful differences in weight or leaf count. The saving associated with the use of artificial lighting during the experiments was between 17% and 23%, resulting from the application of hourly rates as well as participation in long-term demand management programs where the supplier has the discretion to set the “dark” (i.e. “cheap”) rates several times a month.
According to the authors, it will be difficult to achieve similar savings for cucumbers, tomatoes and strawberries without affecting the harvest. Leafy green vegetables are cut “off the bed” before bloom, while cucumbers, tomatoes and strawberries spend more than half of their lifecycle flowering and fruiting, and for them natural light cycles are more important.