However, just as the cost and carbon footprint of electricity are becoming less of a hurdle for indoor farms, the LED situation is also evolving quickly.
An idea that’s become a modern certainty is that technology gets cheaper over time. As the environmental economist William Nordhaus studied in the 1990s, the declining cost of light
over the centuries – from candles, to oil lamps, to ever-more-efficient light bulbs – has been changing the world and fueling innovation for millennia.
Something similar is happening with LEDs – up to a point. Moore’s Law famously predicted computing power doubling every year, and Haitz’s Law now forecasts
that the cost per lumen for LED light will fall by a factor of 10 each decade
, while the light produced increases 20-fold.
However, as Van der Feltz points out, this cannot continue forever, and is more limited by the laws of physics than Moore’s Law. Currently, a well-designed horticultural LED system can be up to about 55% efficient
– meaning 55% of the energy put in becomes photons, which plants use to grow, and 45% becomes heat. Fifty-five percent efficiency is already impressive when compared with incandescent light bulbs, for example, where energy input produces 5% light and 95% heat.
But still, for the purpose of CEA and especially in vertical farms, the remaining 45% of the energy that becomes heat is often – though not always – useless.
“In greenhouses,” Van der Feltz explains, “the additional heat is typically not all bad. Especially since auxiliary greenhouse lighting is mostly used in the darker and cooler winter months, and there are usually plenty of options for ventilation in case it gets too warm.”But vertical farms heat up quickly, and as closed systems where opening a window is not an option, any extra heat from LEDs must be balanced with air conditioning or creatively repurposed.
Van der Feltz says some indoor farms have been designed to divert excess heat to warm an adjacent building, for example.
So LED performance can still improve marginally, but not exponentially. Van der Feltz says experts estimate that another 25% efficiency improvement is possible, but LEDs will never be able to produce light energy out of thin air.
Whatever the limits of Haitz’s Law, it’s still true that while electricity and LED light bulbs are the most expensive part of a vertical farm today, they’re also the area where improvement is most imminent.
(Innovation, and the laws of supply and demand, are constantly bringing down the costs of both, regardless of how much efficiency improvement is still technologically possible.) So operating a vertical farm should still become increasingly affordable over time.
Improved technology and reduced costs for LEDs are especially good news for the potential to grow even more crops in vertical farms, as different plants use different parts of the light spectrum.
iFarm is already a leader in the industry when it comes to research and development for expanding the crop selection available to vertical farmers. As LED technology improves, we’ll be able to take those efforts even further.