February 2020 Management, Structures & Equipment

Creating Efficient Greenhouse Designs By Christopher Machnich

Never are operational shortcomings more apparent than in the colder months. While most operations can get through the traditional growing season with relative ease, maintaining a profitable operation during the winter can challenge even the most experienced growers. One of the most basic and effective ways to improve profitability throughout the year — but especially during the winter — is to improve a greenhouse’s overall efficiency. By doing this, operations can benefit from a more profitable winter and a greenhouse that is environmentally friendly year-round.

As heating costs soar and electricity continues to be a financial burden, maximizing a greenhouse’s efficiency will help lower operating costs, leading to more successful harvests. When first addressing efficiency, growers should look into optimizing their heating system and improving their lighting plans and then integrating automation to ensure all the greenhouse’s systems are working in harmony.

START WITH CLADDING

Heating is consistently one of the more expensive aspects of greenhouse growing. Optimizing heating efficiency is a balancing act between cladding, design and the heating systems themselves, and choosing the right cladding is an effective start to reducing heat loss. A good cladding to consider first is twin wall polycarbonate, as it provides the strength to withstand harsh winters but, more importantly, it provides excellent insulation.

The best way to judge a cladding’s heat retaining abilities is with its R-value. The R-value is a number directly correlated to a material’s insulation; the higher the number, the better insulation it provides. Twin wall polycarbonate has air pockets built in, and this factor boosts its R-value, since air is a great insulator. The R-value of twin wall polycarbonate is an impressive 1.72, so it’s clear that twin-wall polycarb is a great heat retainer.

While cladding is a good starting point, growers will still have to check for air leaks and consider further insulation, depending on their region. When properly installed, leaks should be minimal with polycarbonate, but it’s still a good idea to check before the cold weather settles in. After this, insulation can be added to the foundation and sidewalls. Integrating foundation insulation has the potential to boost soil temperatures up to 10 degrees, which is substantial during the winter. On the sidewalls, adding insulation from the ground to approximately bench height can further improve heat retention and lower heating costs.

SELECTING THE RIGHT HEATING SYSTEM

Efficient heating systems will further help by consuming less fuel. A high efficiency, condensing unit heater can be a good starting point. Today growers can purchase heaters that provide up to 93% efficiency, which can be further offset by setting up bench heating.

Bench heating functions similarly to residential radiant heating systems. Tubing is installed under the bench, and warm water is then run through the tubing. These systems supply heat directly to the root zone and ensure that soil temperature stay within the desired range. They are incredibly efficient and, best of all, they can actually offset the air temperature. Air temperature can be set 5 to 10 degrees lower, providing further savings.

Even with the proper cladding and an efficient heating system, pockets of cool air commonly form within a greenhouse. Maintaining an even and uniform temperature throughout the entire structure is essential, so installing horizontal air flow (HAF) fans will keep air moving and eliminate potentially hazardous cool pockets, ensuring that crops are all kept at the same temperature.

INVEST IN LIGHTING

Another major expense in greenhouse production is lighting. It’s true that greenhouses are a great tool for maintaining environmental control while still using the sun’s natural light, but greenhouse operations still depend on artificial lighting. Integrating efficient lighting can make a big difference when managing operating expenses, and the go-to option for many is LED lighting. There are other options to improve efficiency, but LEDs require little energy and ensure a long life. On average LED fixtures can use up to 75% less energy and last up to 25 times longer than traditional lighting options.

LED technology is still evolving, and the prices continue to fall, making it easier to get a return on the investment. While they use less energy, LEDs still allow crops to meet their daily light integral (DLI). On top of this, some LED fixtures provide even more lighting control. Programmable LED fixtures allow growers to create custom lighting plans that best complement the crop they’re growing and the region they’re in. Programmable fixtures can provide different spectrums, and are commonly used to mimic the natural changes in daylight during a crop’s lifecycle. The changes in light cycle can trigger different growth stages, so these fixtures allow growers to meet the unique needs of their plants without having to change bulbs or fixtures.

LED fixtures are also a good choice because, other than lighting, they have little effect on the growing environment. Other lighting options put off heat, and often growers need to alter their heating or cooling systems to account for this. LEDs emit little heat, so this isn’t a factor. LED fixtures also generally feature a compact design, so they take up very little space inside the structure itself and block much less of the sun’s natural light.

INTEGRATE AUTOMATION

After heating and lighting have been addressed, automation is a great way to further improve efficiency. Automation relies on sensors to take different environmental readings and then adjusts the environment accordingly. Integrating automation is especially helpful for heating and lighting, because it makes sure that they are turned off when they’re no longer needed and turned on when they are. Besides heating and lighting, operations can easily automate irrigation, air exchange, fertilizer application, and much more.

All greenhouse automation can be run through a smart controller, which allows all the systems to work seamlessly together. Smart controllers feature a user-friendly interface that makes organizing and managing greenhouses of any scale much easier. An added benefit of using a smart controller is that greenhouses can be monitored and managed remotely via a smartphone or laptop, so operations always know that their operation is functioning at its peak efficiency.