‘Smart lighting’ might make vertical farming more affordable

Fiddling with the dimmer switch might help some indoor farmers curb one of their biggest challenges: soaring electricity costs.

Growing crops in stacked rows indoors under fixed-intensity artificial lights can produce more food per square foot while using less land and water than traditional outdoor farms. But this vertical farming technique is also energy intensive and expensive (SN: 9/26/08). Now, researchers have designed a computer program that controls lighting to optimize both photosynthesis and electric bills. Described September 24 in Frontiers in Science, the computer program adjusts the intensity of grow lights hourly based on the changing cost of electricity.

This “smart lighting” could potentially cut vertical farms’ electricity costs by up to 12 percent, says Leo Marcelis, a horticulturist at Wageningen University in the Netherlands. That could save some farms tens of thousands of dollars annually, according to the 2021 Global CEA Census Report — a survey of the indoor and controlled environment agriculture industry — and Marcellis’ own projections.

But how might indoor crops fare under dynamic lighting? Marcelis and colleagues tested how leafy greens such as basil, spinach and arugula reacted to light patterns that changed hourly. One group of plants grew under high- then low-intensity lighting intervals. Another group grew under light that was more intense in the morning and dimmer in the afternoon. Both groups’ mature weight and leaf area — which can determine a plant’s value in the supermarket — were about the same as plants grown under fixed intensity lights.

The new computer program didn’t determine the experimental lighting conditions, but the team now knows that indoor farms have room to save on electricity. Continued research that tests dynamic lighting on larger scales is needed, Marcelis says. He plans to continue experimenting with how much dynamic lighting indoor crops can handle.

The study “seems to be a very good proposal to start more research,” says Fatemeh Sheibani, a plant physiologist at Purdue University in West Lafayette, Ind. But she emphasizes that the work is preliminary, and that dynamic lighting is “not a near-term benefit for vertical farming.”