Q&A: Energy Trends in Vertical Farming
February 6, 2025 CEAg World recently chatted with Gretchen Schimelpfenig, senior energy engineer at Energy Resources Integration, about energy trends vertical farmers should have on their radar.
CEAg World: One of the biggest pain points in vertical farming is energy usage; it’s often cited as the sector’s Achilles’ heel. As an energy engineer, can you break that down for us?
Gretchen Schimelpfenig: The wholesale price of food and the cost of energy are the two sides of the coin that drive the profit margin of a vertical farm, so the price a consumer will pay for lettuce has a ceiling. Energy costs do not.
Every year utilities will raise their rates for electricity and natural gas, and fossil fuel prices fluctuate but generally don’t go down. So, vertical farming has the strength and the skills that no one else has (like Achilles). But if energy is not addressed, it becomes their greatest weakness, as it chips away at profits. And it affects businesses’ ability to plan.
CEAg World: What are the biggest energy users you’ve seen in vertical farming operations?
Gretchen Schimelpfenig: For indoor farms, growing food generally uses the most energy for the machines that control the climate: the chillers, fans, pumps, and dehumidifiers that keep vertical farms cool and at the proper humidity.
And since vertical farms usually grow with LED lights, lighting systems are the second largest energy user for growers. In other discussions, you might hear lighting being the biggest energy user, but that’s more common for crops like cannabis grown for longer hours with higher powered lights. Since vertical farms are often stacked, they need a lot of HVAC equipment to keep every layer cool and dry, so that’s the bigger energy user there.
CEAg World: What advice do you have for growers to make their vertical farms more energy efficient?
Gretchen Schimelpfenig: I love this question, and I think the journey is different for everyone. But I think a medicine that’s acceptable for any business is monitoring energy at the systems level. You can manage what you measure. You cannot manage what you don’t see. So identifying the systems using the most energy allows you to trim excess operating hours, and there are different ways of doing that.
For example, some growers experiment with different photo periods. They look at how long their lights are on each day to observe the impact on crop quality and yield to determine the best balance of energy use and production. I call that a tweak and peek strategy.
Another example is adjusting set points for HVAC systems to reduce cooling and dehumidification system operating hours; if you turn your air conditioning unit to 65, it’s going to be turning on more often than if you turn it to 70.
In plants, we often talk about vapor pressure deficit (VPD). That’s essentially the pressure difference between the leaf surface and the space. And it’s preferred to be a value of around 0.8 to 0.95 for leafy greens. But those conditions can actually be achieved by a lot of different set points.
In general, my recommendation would be to take a look at warmer and wetter set points that will get you the same VPD. And continue to tweak and peek. Make sure your plants are happy and your yields are good, but you might be able to reduce the operating hours of lots of equipment by changing some set points with the systems you already have.