"Correctly design and operate your circulation fan system"

Jon Swain, GrowSave project manager, discusses the critical role fans play in creating uniform climates and the positive impact on crop yields, as well as their potential to reduce energy consumption.

Circulation fans have been widely used in greenhouses for many years. A well designed fan installation will benefit the greenhouse climate by helping to maintain consistent temperature and humidity throughout the growing area.

The gentle movement of air over the leaf surface is also an aid both to transpiration and the distribution and uptake of CO2. Fans also contribute to a more pleasant working environment.

Air is heavy and difficult to get moving, so persistence of air movement rather than speed is the key to achieving a uniform greenhouse environment. It is more efficient to move large amounts of air at low speed and pressures, although by no means all fans are designed with this in mind and, many, will operate at high speed with little regard to operational costs.

Designing a suitable fan system that complements rather than conflicts with the heating and ventilation systems in a greenhouse requires considerable experience. In general the objective should be to install a system that is capable of circulating the entire air volume in the greenhouse between once and twice per hour.

Saving energy
Since January 2015, fans with an electrical input of between 125W and 500W are subject to the Energy related Products (ErP) directive which sets standards for efficiency.

Growers should ensure that any fan system being considered meets the ErP criteria. Fans should be fitted with variable speed motors which can be modulated automatically and thereby save energy.

To find out more about different types of fans available and their relative benefits and advantages visit the GrowSave website www.growsave.co.uk.