Saving energy

In the summer, the biggest energy users in the greenhouse tend to be ventilation fans, irrigation pumps, and refrigerated storage spaces. There are several low-cost practices greenhouse growers can follow.
 

Tips for ventilation fans:

• Make sure your fans are clean and the belts are tight. Clean blades can improve efficiency by as much as 10 to 15 percent. Loose belts not only make annoying squeaky sounds, they are also wasting energy that should be going directly to the fans.
• Don’t block the fans. Many people don’t realize that obstructions to fan airflow – especially on the downstream side of the fan – can cut down on ventilation efficiency. Make sure that you don’t have vehicles, trees, or other obstructions in the blast of air that is exiting the greenhouse from your ventilation fans.
• Consider a bit of shade. Much of the time (especially in the northeast United States) the problem is too little daylight in the greenhouse. However, in midsummer, we often have more than we need, and that translates to extra-heat load and extra-ventilation requirements. It might be a good idea to use a shade cloth to reduce temperature, and improve ventilation energy.
  
   

For irrigation/fertigation pumps:

• Make sure your pumps are working properly. Old, corroded impellers and worn bearings translate to reduced efficiency.
• Strive for less “spaghetti.” All those elbows, bends, and fittings in an irrigation system cause resistance to flow, and that means you end up using extra energy to pump your water. Streamline your system if you can, minimizing the number of fittings.
• Stop leaks, and don’t overwater. Leaks in the irrigation system, and excess watering, are money down the drain. Usually a little attention to detail and elbow grease is all you need to eliminate this source of wasted energy.
  
   

For refrigerated storage:

• Service the system. Low refrigerant pressure and dirty coils are a common cause of excess energy use. As hot weather approaches, make sure that your system has been is in good working order.
• Check the lights. Lights in a cold room not only use energy, they also generate heat that must be removed by the refrigeration system. If you are using incandescent lights, consider switching to compact fluorescent or LED lights, and turn the lights off when not in use. If you have forgetful employees, low-cost occupancy sensors are easy to install.
• Shut it down. Many growers have a minimal need for refrigerated storage during the summer months. It might make sense to shut down the cooler and save on energy that way. Growers that have more than one cold room can often consolidate material into one cold room, and shut down the others to save energy.

Other tips

Daniel Ciolkosz, research associate in the department of agricultural and biological engineering at Penn State, and Rutgers Extension Specialist AJ Both have some additional tips: 

• Install multiple shade curtains, with different levels of shading capability. This will allow for more precise control of the solar heat load on the plants, resulting in potential energy savings. Growers may also want to explore variable frequency drives for pump and fan motors, or electronically commutated (EC) motors.
  EC motors are small motors that are much more efficient (up to 40 percent) than traditional small motors. A common application for these would be the fans inside a cold room.
• Employ “proper lighting” and catch air leaks to help reduce your energy costs. “Proper lighting” calls for efficient light sources, high efficiency fixtures, regular cleaning, and controls that turn the lights off when not needed. Neglecting any of these points means that you’ll be getting less light, or using more electricity than you need (or both).
  Growers may want to invest in LED lighting, which are now about as efficient as fluorescent lights, and tend to work well in cold temperatures.
• Catch air leaks by regularly inspecting the greenhouse structure. Many greenhouses have noticeable cracks or holes that can be easily patched. Air leak around doors can be reduced by making a double-door entry system (which may also reduce inadvertent insect entry).

Daniel Ciolkosz is a research associate in the department of agricultural and biological engineering at Penn State. AJ Both is an extension specialist at Rutgers.