Large industrial greenhouse at sunset. | v_sot via Adobe Stock
Consider that energy accounts for 20%-30% of total greenhouse expenses. To address this, there is a growing focus on achieving near-zero energy consumption in greenhouses by minimizing energy usage for operations like heating and cooling while maintaining optimal growing conditions.
Advances in technology are making this balance more achievable. Energy curtains are one of the more practical solutions for minimizing energy losses and creating uniform growing conditions in adverse environments.
What Are Energy Curtains?
Energy curtains act as both shading during hot weather and as a thermal barrier in cold climates, minimizing heat loss. They can reduce heat loss by 20% to 75% and provide shade anywhere from 15% to nearly 100%.
According to one estimate, some growers have saved up to 50% on their heating bills using energy curtains, while others have significantly cut their electricity consumption due to reduced cooling needs. When used on greenhouse walls, energy curtains can provide an ROI of about 30%.
In addition to temperature control, energy curtains help manage humidity levels. Condensation is a common issue in greenhouses when outside temperatures are cold. The droplets can drip on plants and cause disease. Energy screens serve a dual purpose in this situation, providing both a protective barrier over plants when condensation occurs and helping to stabilize humidity levels. For climate control, greenhouse operators can use energy curtains in combination with other solutions such as insulated blankets or reflective sheeting.
Adding to these benefits, the installation of energy curtains and the resulting improved energy efficiency often qualify for rebates, further improving the ROI.
Types of Energy Curtains
Energy curtains are made of various materials, including polyethylene, PVC, or fiberglass, and can be hung from the ceiling or walls. Curtains can also be combined with other heating and cooling systems, including insulating blankets and reflective sheets.
Types of curtains include blackout, diffusion, shade, thermal, and light abatement.
Various screens are available to help greenhouse operators achieve optimal growing conditions while reducing energy consumption. Energy curtains can be affixed to walls or trusses. Additionally, some curtains may be more transparent to allow for more light transmission during the winter, while others have shading properties to minimize light exposure in the hotter months.
Energy Curtain Selection and Installation Considerations
Selecting the type of greenhouse energy curtain is dependent upon specific circumstances. Light, temperature, and humidity criteria for different crops will dictate the proper selection of curtain material and its characteristics.
For instance, blackout curtains provide photoperiodic control and may be needed for greenhouses using supplemental lighting due to local regulations against light pollution. Transparent curtains are typically preferable for vegetable crops in northern climates, while energy curtains with moderate to high shade value are used for ornamentals and lettuce in moderate and warm climates.
In the northern climates, for instance, you want higher light transmission, but heat savings in cold times of the year. Lettuce and ornamentals will require lower light, but blocking out the solar gain will help with peak heat problems.
Regional differences also influence the type of material selected. Screens with a closed weave and aluminum strips provide shading during the day and energy conservation at night, holding warmth during night down at the crop level. Greenhouse operators can crack the screen sections to allow excess moisture to escape. In hotter climates, open-weave materials are often more suitable as they allow unwanted heat and humidity to rise and escape through roof vents.
Another consideration is whether to use a sliding or suspended shading system. In suspended greenhouse curtain systems, hooks are attached to reinforced portions of the screen and suspended from support wires. These systems typically offer better wind resistance, making them ideal for open-roof, sawtooth vent designs, and exposed greenhouses.
For additional installation and maintenance tips for greenhouse energy curtains, please read the original article found on the LLK Greenhouse Solutions website.