Taking a close look at new resources and new technologies is key, as is finding out what other growers are up to.
All greenhouse operators have taken steps to cut energy consumption, but deciding which steps to take next to further boost efficiency isn’t always easy. Help is here – in the form of new video and print resources developed by Dr. Erik Runkle, an associate professor in the Michigan State University Department of Horticulture and Dr. A.J. Both, an associate extension specialist in Bioresource Engineering in the Department of Environmental Sciences at Rutgers University in New Jersey.
In their 16-page pdf booklet ‘Greenhouse Energy Conservation Strategies,’ they investigate 13 approaches and technologies growers can use to maximize energy efficiency. And – from front-line interviews – Runkle has also produced 42 short videos relating to best energy conservation practices. “Many of the concepts apply to any greenhouse operation, but the focus of the resources is on floriculture in controlled greenhouse environments located in temperate climates,” says Runkle.
The booklet and videos were developed over nine months in 2011, with support from and in collaboration with the United States Department of Agriculture, the Michigan Floriculture Growers Council, the Agricultural Counselor’s Office of the Royal Embassy of the Netherlands in Washington, D.C., and private company Ferguson Caras.
“We visited several operations in Holland, which was helpful, but much of the researching and writing had been done before the visits,” says Runkle. “We kept the typical U.S. floriculture crop grower in mind when writing the booklet. Some of the suggestions wouldn’t typically be applicable to floriculture operations in the Netherlands, and vice-versa, nor applicable to vegetable crops.”
Several of the videos focus on lighting, an aspect of greenhouse operation that is changing swiftly. “A lot of growers are interested in LED lighting, and there are a few videos that show them being used in the Netherlands,” he says. As part of a multi-institutional, multi-disciplinary team researching LEDs for specialty crop production, Runkle manages a site with reports and resources (see bottom of page).
“The efficiency of LEDs continues to increase, and prices are coming down,” he notes. “I think it’s only a matter of time before they replace high-intensity discharge (HID) lights such as high-pressure sodium lamps.” Growers often rely on HID lighting for supplemental lighting required at many stages of the growing process, but much of the energy used to power these lights is wasted in their production of light that plants do not require to grow, and in heat. They also come with negative environmental impacts. LED lights solve all these problems, as well as providing longer lamp life, potentially smaller fixture size, tailored light spectrum, and more.
The 13 strategies outlined in the booklet relate to lighting, heating and air circulation systems, temperature management, insulation, and ventilation. When asked what growers should tackle first in their quest to ramp up energy efficiency, Runkle says it depends very much on specific greenhouse characteristics and what crops are being grown.
“If, for example, we were to talk to a year-round floriculture crop grower with a double-polyethylene greenhouse who had not implemented any of the strategies in the booklet, I would recommend the immediate installation of infrared anti-condensate polyethylene film,” he says. “Doing this would probably have the quickest return on investment in terms of energy saved.” Runkle’s second recommended action for a person in this situation would most likely be to reduce air leaks, and keep the space between two plastic layers properly inflated. “This insulation cuts down on the extremely large amount of potential heat loss,” he notes. “The costs of keeping the space inflated are very low and the potential energy savings are very high.”
Because deciding on which energy-saving practices and technologies are most appropriate depends so much on the specifics of a particular operation, Runkle believes it’s very useful to first have an energy audit performed by someone with greenhouse experience. “A trained and experienced energy auditor will provide a cost/benefit analysis of different scenarios, so that growers invest in things that make the most financial sense,” he says. “I would ask the auditor for references on greenhouse jobs, and give them a call. My concern is that if an auditor doesn’t know the intricacies of how a greenhouse works, the different lighting systems and so on, you won’t get as much value from the audit.”
(Energy audits provide customized recommendations such as energy curtains, above.)
Getting references from auditing companies, as well as talking with other greenhouse operators is also recommended by Michelle Vieira, sales, operations and member relations manager at Ag Energy Co-operative in Guelph, Ontario. Ag Energy was formed in 1988 by Ontario greenhouse operators to leverage member purchasing power in securing better energy rates; the organization now includes all ag sectors. The organization completed a ‘Greenhouse Energy Audit Project’ in 2006, involving 22 greenhouse (flower and veggie) operations. “We reviewed energy consumption, energy distribution, control systems, system balance, system efficiencies and problems identified by the growers, and produced a booklet of tips,” says Vieira. Check out Greenhouse Canada Magazine and our ‘Energy Edge’ website for an upcoming in-depth look at audits.
One simple strategy in the booklet involves transplanting larger plugs and liners to shorten finish crop time and therefore total heating inputs necessary for producing the crop. But other energy-saving concepts that Runkle and Both describe are much more complex.
“The concept of managing your greenhouse temperature based on the crop and finish date is one that’s tough to implement,” Runkle notes. “It requires a lot of time and effort to determine optimum temperatures, where one has to consider the lighting that’s best for crop timing at the same time one must look at energy consumption for heating. Many growers also have production constraints where it’s not possible to optimize temperature since they grow many, even of hundreds, of different kinds of crops in the same greenhouse environment.”
Runkle points to the free software program ‘Virtual Grower’ (developed by Jonathan Frantz of the United States Department of Agriculture – Agricultural Research Service) as a good tool. “It allows growers to predict heating costs for their greenhouses, and provides help in deciding growing temperature set points, use of alternative fuels and energy-saving investments.” One of the most powerful features of the program in Runkle’s view is its ability to predict the amount of energy needed to maintain a desired temperature at different times of the year for a greenhouse with user-defined characteristics. “When you combine this with information on temperature’s effects on crop timing, you can identify the most energy-efficient growing temperatures,” he notes.
In terms of the technologies and/or energy options that are on the horizon to boost efficiency in North American greenhouses, Runkle says that there are technologies being used in the Netherlands today that have the potential to be cost effective here. “Some of these are discussed in the sustainability videos, such as combined heat and power systems,” he says. “Re-use of water or more efficient use of water is also receiving increasing attention as water concerns continue, especially for growers located in arid climates and those who live in regions with abnormally low rainfall the past decade.”
By Treena Hein, Energy Edge editor
Energy Efficiency links
The pdf booklet ‘Greenhouse Energy Conservation Strategies’ and other resources are available at Michigan State’s energy website for floriculture operations.
Virtual Grower software is produced by the US Department of Agriculture ‘Agricultural Research Service’ and available for free download here.
An MSU multi-partner website with resources on using LEDs for specialty crop production is here.
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