Use of chillers in cannabis greenhouses

The legalisation of medical cannabis in several states in the US involves the development of new techniques to manage temperatures while reducing production costs.

Since 2011, the therapeutic use of cannabis has been authorised in the US State of New Jersey. On July 2, 2019, a new measure (1) made it possible to extend this use: for example, until then doctors could prescribe approximately 56 grams of cannabis per month (2 ounces). Since July, the limitation has been around 85 grams (3 ounces). In 2020 the use of recreational cannabis might even be allowed in this state.

Therapeutic cannabis plants are generally grown in a greenhouse, so they enjoy optimal growth conditions:

  • sufficient light (at least 18 hours a day),
  • stable temperature, between 21 and 29 °C,
  • good control of relative humidity, which can vary between 30 and 70% depending on the plant lifetime.

The lighting systems generate significant heat which can compromise plant growth.

Evaporative cooling is generally used in greenhouses, but since 2017, there are also chillers powered by natural gas.

For instance three such chillers will be supplied in the course of 2020 by the company Tecogen, in the State of New Jersey. The heat lost by the coolers will be used to dehumidify the greenhouses.

This type of system should reduce operating costs of farm by 50%, while reducing the carbon footprint of the installation compared to the use of conventional electric coolers.