Indoor farming startups are known to grow crops using efficient LED light bulbs with custom “light recipes” that adjust the color of the LEDs to help plants grow faster. With that said, all these lighting systems using LED bulbs still use a huge amount of energy, which is why scientists have developed a new technology so traditional greenhouses can manipulate sunlight in a similar way, without any use of electricity at all.

The idea behind the new technology is quite simple, according to Hunter McDaniel, founder of UbiQD, the advanced materials startup that makes the new greenhouse tech. “Our approach is, basically, let’s just tweak sunlight—let’s improve sunlight.”

To do this, the startup uses quantum dots, the same nano-size crystals that are used to emit color in TVs and monitors. On greenhouse roofs, a film filled with quantum dots shifts UV light from the blue portion of the spectrum to red. The orange glow that the film emits helps plants grow faster.

Modern greenhouses already grow food more efficiently than growing in a field; a greenhouse in the Netherlands growing tomatoes might grow more than 30 times more pounds of food per square meter than a traditional farm because watering, temperature, CO2, and other factors are optimized. But controlling the color of the light can help even more. In tests in greenhouses growing tomatoes, the new film helped farmers produce crops that were 20% larger. The product also helped in tests with lettuce, cannabis, and cucumbers.

The design can be adjusted for different crops to help each perform best, although only one option is available now. Some greenhouses with glass roofs use additional lighting to help extend short winter days. The film could achieve the same result for growers who want to save energy or who haven’t been able to afford supplemental lighting in the past. It might also convince some indoor farming companies to shift from fully controlled warehouses to less costly greenhouses with natural light.