The technology in an indoor farm provides light, water, nutrients, and climate control. Each of these elements is essential. Climate control, however, is the most challenging, particularly when uniform temperature and humidity must be maintained across large cultivation areas.

Large areas – comparable to the compartments of modern high-tech greenhouses – are therefore often required. This enables the use of proven cultivation systems developed and widely applied in horticulture over the past decades, such as ebb-and-flow tables, rockwool gutters with drip irrigation, and mobile gutter systems for lettuce and herbs.

Indoor farming becomes economically viable only when technology is applied efficiently. The Dutch horticultural sector demonstrates how this can be achieved.

Farm scale
Our ambition is to develop indoor farms at a scale that allows efficient operation and cost control. For this reason, we designed and patented a climate system that enables uniform conditions across large cultivation areas.

For crops such as tomatoes and cucumbers, this makes it possible to work with row lengths of up to 100 meters, similar to greenhouse practice, which significantly improves labor efficiency during crop maintenance and harvesting. The same principle applies to ebb-and-flow systems and mobile gutters: cultivation rooms can be designed with comparable length-to-width ratios, allowing proven horticultural systems to be applied directly. Tested, robust, and cost-effective.

Laminar airflow
Our patent covers the combination of laminar airflow and precise humidity control. The laminar airflow is generated by moving air from one side of the cultivation space through a plenum that spans the entire wall toward a plenum on the opposite wall, tens of meters away. This laminar airflow creates a predictable and linear change in temperature and humidity from the inlet plenum to the return plenum. Air circulates from the inlet to the return plenum and then through a return duct to the air-handling unit. There, moisture is removed from the air through condensation on a cold coil, after which the recovered water flows back to the irrigation reservoir. The air is then reheated using a warm coil to the desired inlet temperature before being returned to the cultivation area. In this way we impose a desired level of transpiration on the crop. Rather than removing what the plants evaporate, we set the vapor pressure deficit so that the plants transpire precisely the amount required for transporting water and nutrients from the roots to the actively growing parts of the plant.

Stable climate
As the air moves through the crop from the inlet to the return plenum, it gradually becomes more humid due to plant transpiration. To ensure that transpiration remains uniform throughout the cultivation area, the system includes controlled heating that compensates for this increase in humidity. By slightly increasing the air temperature along the airflow path, the vapor pressure deficit remains constant from inlet to return plenum despite the rising moisture content. This means that the outgoing air is a few degrees warmer than the incoming air, while the vapor pressure deficit remains identical across the entire cultivation area. To prevent any structural temperature gradient from influencing crop development, the direction of the airflow is periodically reversed. If the temperature increase remains within a few degrees, the crop responds to the average temperature, and no differences in growth or quality are observed between the outer sections and the center of the cultivation area.

System design
In this way, large indoor farms can be built using laminar airflow, a constant vapor pressure deficit throughout the cultivation space, and regular reversal of the airflow direction. Under these, any cultivation system from modern greenhouse horticulture can be applied, provided it does not block or significantly disturb the airflow. These systems can also be implemented in multiple cultivation layers.

For the avoidance of doubt: Seven Steps To Heaven grants licenses for the use of its intellectual property and knowledge but does not build or operate indoor farms itself. Through IP licenses, partners are enabled to build their own farms and to operate them as effectively as possible using our knowledge and experience.